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diff --git a/.gitattributes b/.gitattributes new file mode 100644 index 0000000..d7b82bc --- /dev/null +++ b/.gitattributes @@ -0,0 +1,4 @@ +*.txt text eol=lf +*.htm text eol=lf +*.html text eol=lf +*.md text eol=lf diff --git a/LICENSE.txt b/LICENSE.txt new file mode 100644 index 0000000..6312041 --- /dev/null +++ b/LICENSE.txt @@ -0,0 +1,11 @@ +This eBook, including all associated images, markup, improvements, +metadata, and any other content or labor, has been confirmed to be +in the PUBLIC DOMAIN IN THE UNITED STATES. + +Procedures for determining public domain status are described in +the "Copyright How-To" at https://www.gutenberg.org. + +No investigation has been made concerning possible copyrights in +jurisdictions other than the United States. Anyone seeking to utilize +this eBook outside of the United States should confirm copyright +status under the laws that apply to them. diff --git a/README.md b/README.md new file mode 100644 index 0000000..5f971d9 --- /dev/null +++ b/README.md @@ -0,0 +1,2 @@ +Project Gutenberg (https://www.gutenberg.org) public repository for +eBook #51021 (https://www.gutenberg.org/ebooks/51021) diff --git a/old/51021-8.txt b/old/51021-8.txt deleted file mode 100644 index 49ea758..0000000 --- a/old/51021-8.txt +++ /dev/null @@ -1,10520 +0,0 @@ -The Project Gutenberg EBook of The Geological History of Plants, by -Sir J. William Dawson - -This eBook is for the use of anyone anywhere in the United States and most -other parts of the world at no cost and with almost no restrictions -whatsoever. You may copy it, give it away or re-use it under the terms of -the Project Gutenberg License included with this eBook or online at -www.gutenberg.org. If you are not located in the United States, you'll have -to check the laws of the country where you are located before using this ebook. - -Title: The Geological History of Plants - -Author: Sir J. William Dawson - -Release Date: January 23, 2016 [EBook #51021] - -Language: English - -Character set encoding: ISO-8859-1 - -*** START OF THIS PROJECT GUTENBERG EBOOK THE GEOLOGICAL HISTORY OF PLANTS *** - - - - -Produced by Tom Cosmas compiled from files made available -at The Internet Archive. - - - - - - - - - - - -Transcriber Notes - -Text emphasis displayed as _Italics_ and =Bold=. Whole and fractional -parts displayed as 19-4/12. - - - THE INTERNATIONAL SCIENTIFIC SERIES - - VOLUME LXI - - - THE - - INTERNATIONAL SCIENTIFIC SERIES. - - ------------------- - =Each book complete in One Volume, 12mo, and bound in Cloth.= - ------------------- - - - 1. FORMS OF WATER: A Familiar Exposition of the Origin and - Phenomena of Glaciers. By J. Tyndall, LL. D., F. R. S. 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By Alfred Binet and Charles Féré, Assistant - Physician at the Salpêtrière. - - - * * * * * - - -[Illustration: DIAGRAM OF THE HISTORY OF PLANTS IN GEOLOGICAL TIME. -(Adapted from Ward.)] - - - - - THE INTERNATIONAL SCIENTIFIC SERIES - - - THE - - GEOLOGICAL HISTORY - - OF PLANTS - - - BY - - - SIR J. WILLIAM DAWSON C. M. G., LL. D., F. R. S., &c. - - - _WITH ILLUSTRATIONS_ - - - NEW YORK APPLETON AND COMPANY 1888 - - - Copyright, 1888, By D. APPLETON AND COMPANY. - - - - -PREFACE. - - -The object of this work is to give, in a connected form, a summary of the -development of the vegetable kingdom in geological time. - -To the geologist and botanist the subject is one of importance with -reference to their special pursuits, and one on which it has not been -easy to find any convenient manual of information. It is hoped that its -treatment in the present volume will also be found sufficiently simple -and popular to be attractive to the general reader. - -In a work of so limited dimensions, detailed descriptions cannot be -given, except occasionally by way of illustration; but references to -authorities will be made in foot-notes, and certain details, which may be -useful to collectors and students, will be placed in notes appended to -the chapters, so as not to encumber the text. - -The illustrations of this work are for the most part original; but some -of them have previously appeared in special papers of the author. - - J. W. D. - -_February, 1888._ - - - - -CONTENTS. - - - PAGE - -CHAPTER I. - - Preliminary Ideas of Geological Chronology and of the - Classification of Plants 1 - - -CHAPTER II. - - Vegetation of the Laurentian and Early Paleozoic--Questions - as to Algæ 8 - - -CHAPTER III. - - The Erian or Devonian Forests--Origin of Petroleum--The - Age of Acrogens and Gymnosperms 45 - - -CHAPTER IV. - - The Carboniferous Flora--Culmination of the - Acrogens--Formation of Coal 110 - - -CHAPTER V. - - The Flora of the Early Mesozoic--Reign of Pines and Cycads 175 - - -CHAPTER VI. - - The Reign of Angiosperms in the Later Cretaceous and Early - Tertiary or Kainozoic 191 - - -CHAPTER VII. - - Plants from the Tertiary to the Modern Period 219 - - -CHAPTER VIII. - - General Laws of Origin and Migrations of Plants--Relations - of Recent and Fossil Floras 237 - - -APPENDIX. - - I. Comparative View of Paleozoic Floras 273 - - II. Heer's Latest Statements on the Greenland Flora 281 - - III. Mineralisation of Fossil Plants 284 - - IV. General Works on Palæobotany 286 - - - - -LIST OF ILLUSTRATIONS. - - - PAGE - - Table of Chronology of Plants (Frontispiece.) - Protannularia Harknessii 21 - Nematophyton Logani (three Figures) 22, 23 - Trail of King-Crab 28 - Trail of Carboniferous Crustacean 28 - Rusichnites 29 - Palæophycus 30 - Astropolithon 31 - Carboniferous Rill-mark 33 - Cast of Shrinkage Cracks 34 - Cone-in-cone 36 - Buthotrephis 37 - Silurian Vegetation 40 - Erian Plants 49 - Protosalvinia 54 - Ptilophyton (two Figures) 62, 63 - Psilophyton (two Figures) 64, 66 - Sphenophyllum 65 - Lepidodendron 66 - Various Ferns 72, 73 - Archæopteris 74 - Caulopteris 75 - Megalopteris 76 - Calamites 77 - Asterophyllites 78 - Dadoxylon 79 - Cordaites 81 - Erian Fruits 82 - Foliage from the Coal-formation 111 - Sigillariæ (five Figures) 112-114 - Stigmariæ (two Figures) 115 - Vegetable Tissues 117 - Coals and Erect Trees (two Figures) 118, 119 - Lepidodendron 120 - Lepidophloios 121 - Asterophyllites, &c. 122 - Calamites (five Figures) 123-125 - Ferns of the Coal-formation (six Figures) 126-129 - Noeggerathia dispar 130 - Cordaites 131 - Fruits of Cordaites, &c. 132 - Conifers of the Coal-formation (four Species) 135 - Trigonocarpum 136 - Sternbergia 137 - Walchia imbricatula 138 - Foliage of the Jurassic Period 177 - Podozamites 178 - Salisburia 180 - Sequoia 181 - Populus primæva 191 - Stercalia and Laurophyllum 194 - Vegetation of the Cretaceous Period 195 - Platanus 198 - Protophyllum 199 - Magnolia 200 - Liriodendron (two Figures) 201 - Brasenia 207 - Gaylussaccia resinosa 228 - Populus balsamifera 229 - Fucus 230 - - - - -THE - -GEOLOGICAL HISTORY OF PLANTS. - - - - -CHAPTER I. - - PRELIMINARY IDEAS OF GEOLOGICAL CHRONOLOGY AND - OF THE CLASSIFICATION OF PLANTS. - - -The knowledge of fossil plants and of the history of the vegetable -kingdom has, until recently, been so fragmentary that it seemed hopeless -to attempt a detailed treatment of the subject of this little book. Our -stores of knowledge have, however, been rapidly accumulating in recent -years, and we have now arrived at a stage when every new discovery serves -to render useful and intelligible a vast number of facts previously -fragmentary and of uncertain import. - -The writer of this work, born in a district rich in fossil plants, began -to collect and work at these as a boy, in connection with botanical and -geological pursuits. He has thus been engaged in the study of fossil -plants for nearly half a century, and, while he has published much -on the subject, has endeavoured carefully to keep within the sphere -of ascertained facts, and has made it a specialty to collect, as far -as possible, what has been published by others. He has also enjoyed -opportunities of correspondence or personal intercourse with most of the -more eminent workers in the subject. Now, in the evening of his days, he -thinks it right to endeavour to place before the world a summary of facts -and of his own matured conclusions--feeling, however, that nothing can -be final in this matter; and that he can only hope to sketch the present -aspect of the subject, and to point the way to new developments, which -must go on long after he shall have passed away. - -The subject is one which has the disadvantage of presupposing -some knowledge of the geological history of the earth, and of the -classification and structures of modern plants; and in order that all -who may please to read the following pages may be placed, as nearly as -possible, on the same level, this introductory chapter will be devoted to -a short statement of the general facts of geological chronology, and of -the natural divisions of the vegetable kingdom in their relations to that -chronology. - -The crust of the earth, as we somewhat modestly term that portion of -its outer shell which is open to our observation, consists of many beds -of rock superimposed on each other, and which must have been deposited -successively, beginning with the lowest. This is proved by the structure -of the beds themselves, by the markings on their surfaces, and by the -remains of animals and plants which they contain; all these appearances -indicating that each successive bed must have been the surface before it -was covered by the next. - -As these beds of rock were mostly formed under water, and of material -derived from the waste of land, they are not universal, but occur -in those places where there were extensive areas of water receiving -detritus from the land. Further, as the distinction of land and water -arises primarily from the shrinkage of the mass of the earth, and from -the consequent collapse of the crust in some places and ridging of it -up in others, it follows that there have, from the earliest geological -periods, been deep ocean-basins, ridges of elevated land, and broad -plateaus intervening between the ridges, and which were at some times -under water, and at other times land, with many intermediate phases. -The settlement and crumpling of the crust were not continuous, but took -place at intervals; and each such settlement produced not only a ridging -up along certain lines, but also an emergence of the plains or plateaus. -Thus at all times there have been ridges of folded rock constituting -mountain-ranges, flat expansions of continental plateau, sometimes dry -and sometimes submerged, and deep ocean-basins, never except in some of -their shallower portions elevated into land. - -By the study of the successive beds, more especially of those deposited -in the times of continental submergence, we obtain a table of geological -chronology which expresses the several stages of the formation of the -earth's crust, from that early time when a solid shell first formed on -our nascent planet to the present day. By collecting the fossil remains -embedded in the several layers and placing these in chronological order, -we obtain in like manner histories of animal and plant life parallel to -the physical changes indicated by the beds themselves. The facts as to -the sequence we obtain from the study of exposures in cliffs, cuttings, -quarries, and mines; and by correlating these local sections in a great -number of places, we obtain our general table of succession; though it is -to be observed that in some single exposures or series of exposures, like -those in the great canons of Colorado, or on the coasts of Great Britain, -we can often in one locality see nearly the whole sequence of beds. Let -us observe here also that, though we can trace these series of deposits -over the whole of the surfaces of the continents, yet if the series could -be seen in one spot, say in one shaft sunk through the whole thickness of -the earth's crust, this would be sufficient for our purpose, so far as -the history of life is concerned. - -The evidence is similar to that obtained by Schliemann on the site of -Troy, where, in digging through successive layers of _débris_, he found -the objects deposited by successive occupants of the site, from the time -of the Roman Empire back to the earliest tribes, whose flint weapons and -the ashes of their fires rest on the original surface of the ground. - -Let us now tabulate the whole geological succession with the history of -animals and plants associated with it: - - - ANIMALS. SYSTEMS OF FORMATIONS. PLANTS. - - Age of Man and Mammalia. - - Kainozoic. { Modern, - { Pleistocene, Angiosperms and - { Pliocene, Palms dominant. - { Miocene, - { Eocene. - - Age of Reptiles. - - Mesozoic. { Cretaceous, Cycads and Pines - { Jurassic, dominant. - { Triassic. - - Age of Amphibians and Fishes. - Age of Invertebrates. - - Palæozoic. { Permian, Acrogens and - { Carboniferous, Gymnosperms - { Erian, dominant. - { Silurian, - { Ordovician, - { Cambrian, - { Huronian (Upper). - - Age of Protozoa. - - Eozoic. { Huronian (Lower), Protogens and Algæ. - { Upper Laurentian, - { Middle Laurentian, - { Lower Laurentian. - -It will be observed, since only the latest of the systems of formations -in this table belongs to the period of human history, that the whole -lapse of time embraced in the table must be enormous. If we suppose the -modern period to have continued for say ten thousand years, and each -of the others to have been equal to it, we shall require two hundred -thousand years for the whole. There is, however, reason to believe, -from the great thickness of the formations and the slowness of the -deposition of many of them in the older systems, that they must have -required vastly greater time. Taking these criteria into account, it has -been estimated that the time-ratios for the first three great ages may -be as one for the Kainozoic to three for the Mesozoic and twelve for -the Palæozoic, with as much for the Eozoic as for the Palæozoic. This -is Dana's estimate. Another, by Hull and Houghton, gives the following -ratios: Azoic, 34·3 per cent.; Palæozoic, 42·5 per cent.; Mesozoic and -Kainozoic, 23·2 per cent. It is further held that the modern period -is much shorter than the other periods of the Kainozoic, so that our -geological table may have to be measured by millions of years instead of -thousands. - -We cannot, however, attach any certain and definite value in years to -geological time, but must content ourselves with the general statement -that it has been vastly long in comparison to that covered by human -history. - -Bearing in mind this great duration of geological time, and the fact that -it probably extends from a period when the earth was intensely heated, -its crust thin, and its continents as yet unformed, it will be evident -that the conditions of life in the earlier geologic periods may have been -very different from those which obtained later. When we further take -into account the vicissitudes of land and water which have occurred, we -shall see that such changes must have produced very great differences of -climate. The warm equatorial waters have in all periods, as superficial -oceanic currents, been main agents in the diffusion of heat over the -surface of the earth, and their distribution to north and south must have -been determined mainly by the extent and direction of land, though it -may also have been modified by the changes in the astronomical relations -and period of the earth, and the form of its orbit.[A] We know by the -evidence of fossil plants that changes of this kind have occurred -so great as, on the one hand, to permit the plants of warm temperate -regions to exist within the Arctic Circle; and, on the other, to drive -these plants into the tropics and to replace them by Arctic forms. It -is evident also that in those periods when the continental areas were -largely submerged, there might be an excessive amount of moisture in -the atmosphere, greatly modifying the climate, in so far as plants are -concerned. - -[A] Croll, "Climate and Time." - -Let us now consider the history of the vegetable kingdom as indicated in -the few notes in the right-hand column of the table. - -The most general subdivision of plants is into the two great series of -Cryptogams, or those which have no manifest flowers, and produce minute -spores instead of seeds; and Phænogams, or those which possess flowers -and produce seeds containing an embryo of the future plant. - -The Cryptogams may be subdivided into the following three groups: - -1. _Thallogens_, cellular plants not distinctly distinguishable into stem -and leaf. These are the Fungi, the Lichens, and the Algæ, or sea-weeds. - -2. _Anogens_, having stem and foliage, but wholly cellular. These are the -Mosses and Liverworts. - -3. Acrogens, which have long tubular fibres as well as cells in -their composition, and thus have the capacity of attaining a more -considerable magnitude. These are the Ferns (_Filices_), the Mare's-tails -(_Equisetaceæ_), and the Club-mosses (_Lycopodiaceæ_), and a curious -little group of aquatic plants called Rhizocarps (_Rhizocarpeæ_). - -The Phænogams are all vascular, but they differ much in the simplicity -or complexity of their flowers or seeds. On this ground they admit of a -twofold division: - -1. _Gymnosperms_, or those which bear naked seeds not enclosed in fruits. -They are the Pines and their allies, and the Cycads. - -2. _Angiosperms_, which produce true fruits enclosing the seeds. In this -group there are two well-marked subdivisions differing in the structure -of the seed and stem. They are the _Endogens_, or inside growers, with -seeds having one seed-leaf only, as the grasses and the palms; and -the _Exogens_, having outside-growing woody stems, and seeds with two -seed-leaves. Most of the ordinary forest-trees of temperate climates -belong to this group. - -On referring to the geological table, it will be seen that there is a -certain rough correspondence between the order of rank of plants and the -order of their appearance in time. The oldest plants that we certainly -know are Algæ, and with these there are plants apparently with the -structures of Thallophytes but the habit of trees, and which, for want -of a better name, I may call _Protogens_. Plants akin to the Rhizocarps -also appear very early. Next in order we find forests in which gigantic -Ferns and Lycopods and Mare's-tails predominate, and are associated -with pines. Succeeding these we have a reign of Gymnosperms, and in the -later formations we find the higher Phænogams dominant. Thus there is an -advance in elevation and complexity along with the advance in geological -time, but connected with the remarkable fact that in earlier times low -groups attain to an elevation unexampled in later times, when their -places are occupied with plants of higher type. - -It is this historical development that we have to trace in the following -pages, and it will be the most simple and at the same time the most -instructive method to consider it in the order of time. - - - - -CHAPTER II. - -VEGETATION OF THE LAURENTIAN AND EARLY PALÆOZOIC--QUESTIONS AS TO ALGÆ. - - -Oldest of all the formations known to geologists, and representing -perhaps the earliest rocks produced after our earth had ceased to be a -molten mass, are the hard, crystalline, and much-contorted rocks named -by the late Sir W. E. Logan Laurentian, and which are largely developed -in the northern parts of North America and Europe, and in many other -regions. So numerous and extensive, indeed, are the exposures of these -rocks, that we have good reason to believe that they underlie all the -other formations of our continents, and are even world-wide in their -distribution. In the lower part of this great system of rocks which, in -some places at least, is thirty thousand feet in thickness, we find no -traces of the existence of any living thing on the earth. But, in the -middle portion of the Laurentian, rocks are found which indicate that -there were already land and water, and that the waters and possibly the -land were already tenanted by living beings. The great beds of limestone -which exist in this part of the system furnish one indication of this. In -the later geological formations the limestones are mostly organic--that -is, they consist of accumulated remains of shells, corals, and other -hard parts of marine animals, which are composed of calcium carbonate, -which the animals obtain directly from their food, and indirectly from -the calcareous matter dissolved in the sea-water. In like manner great -beds of iron-ore exist in the Laurentian; but in later formations the -determining cause of the accumulation of such beds is the partial -deoxidation and solution of the peroxide of iron by the agency of -organic matter. Besides this, certain forms known as _Eozoon Canadense_ -have been recognised in the Laurentian limestones, which indicate the -presence at least of one of the lower types of marine animals. Where -animal life is, we may fairly infer the existence of vegetable life as -well, since the plant is the only producer of food for the animal. But -we are not left merely to this inference. Great quantities of carbon -or charcoal in the form of the substance known as graphite or plumbago -exist in the Laurentian. Now, in more recent formations we have deposits -of coal and bituminous matter, and we know that these have arisen from -the accumulation and slow putrefaction of masses of vegetable matter. -Further, in places where igneous action has affected the beds, we find -that ordinary coal has been changed into anthracite and graphite, that -bituminous shales have been converted into graphitic shales, and that -cracks filled with soft bituminous matter have ultimately become changed -into veins of graphite. When, therefore, we find in the Laurentian thick -beds of graphite and beds of limestone charged with detached grains and -crystals of this substance, and graphitic gneisses and schists and veins -of graphite traversing the beds, we recognise the same phenomena that are -apparent in later formations containing vegetable _débris_. - -The carbon thus occurring in the Laurentian is not to be regarded as -exceptional or rare, but is widely distributed and of large amount. In -Canada more especially the deposits are very considerable. - -The graphite of the Laurentian of Canada occurs both in beds and in -veins, and in such a manner as to show that its origin and deposition -are contemporaneous with those of the containing rock. Sir William -Logan states[B] that "the deposits of plumbago generally occur in the -limestones or in their immediate vicinity, and granular varieties of the -rock often contain large crystalline plates of plumbago. At other times -this mineral is so finely disseminated as to give a bluish-grey colour -to the limestone, and the distribution of bands thus coloured seems to -mark the stratification of the rock." He further states: "The plumbago -is not confined to the limestones; large crystalline scales of it are -occasionally disseminated in pyroxene rock, and sometimes in quartzite -and in feldspathic rocks, or even in magnetic oxide of iron." In addition -to these bedded forms, there are also true veins in which graphite -occurs associated with calcite, quartz, orthoclase, or pyroxene, and -either in disseminated scales, in detached masses, or in bands or layers -"separated from each other and from the wall-rock by feldspar, pyroxene, -and quartz." Dr. Hunt also mentions the occurrence of finely granular -varieties, and of that peculiarly waved and corrugated variety simulating -fossil wood, though really a mere form of laminated structure, which also -occurs at Warrensburg, New York, and at the Marinski mine in Siberia. -Many of the veins are not true fissures, but rather constitute a network -of shrinkage cracks or segregation veins traversing in countless numbers -the containing rock, and most irregular in their dimensions, so that they -often resemble strings of nodular masses. It is most probable that the -graphite of the veins was originally introduced as a liquid or plastic -hydrocarbon; but in whatever way introduced, the character of the veins -indicates that in the case of the greater number of them the carbonaceous -material must have been derived from the bedded rocks traversed by these -veins, to which it bears the same relation with the veins of bitumen -found in the bituminous shales of the Carboniferous and Silurian rocks. -Nor can there be any doubt that the graphite found in the beds has been -deposited along with the calcareous matter or muddy and sandy sediment of -which these beds were originally composed.[C] - -[B] "Geology of Canada," 1863. - -[C] Paper by the author on Laurentian Graphite, "Journal of London -Geological Society," 1876. - -The quantity of graphite in the Lower Laurentian series is enormous. Some -years ago, in the township of Buckingham, on the Ottawa River, I examined -a band of limestone believed to be a continuation of that described by -Sir W. E. Logan as the Green Lake limestone. It was estimated to amount, -with some thin interstratified bands of gneiss, to a thickness of six -hundred feet or more, and was found to be filled with disseminated -crystals of graphite and veins of the mineral to such an extent as to -constitute in some places one-fourth of the whole; and, making every -allowance for the poorer portions, this band cannot contain in all a less -vertical thickness of pure graphite than from twenty to thirty feet. In -the adjoining township of Lochaber Sir W. E. Logan notices a band from -twenty-five to thirty feet thick, reticulated with graphite veins to such -an extent as to be mined with profit for the mineral. At another place -in the same district a bed of graphite from ten to twelve feet thick, -and yielding 20 per cent, of the pure material, is worked. As it appears -in the excavation made by the quarrymen, it resembled a bed of coal; and -a block from this bed, about four feet thick, was a prominent object in -the Canadian department of the Colonial Exhibition of 1886. When it is -considered that graphite occurs in similar abundance at several other -horizons, in beds of limestone which have been ascertained by Sir W. E. -Logan to have an aggregate thickness of thirty-five hundred feet, it -is scarcely an exaggeration to maintain that the quantity of carbon in -the Laurentian is equal to that in similar areas of the Carboniferous -system. It is also to be observed that an immense area in Canada appears -to be occupied by these graphitic and _Eozoon_ limestones, and that rich -graphitic deposits exist in the continuation of this system in the State -of New York, while in rocks believed to be of this age near St. John, -New Brunswick, there is a very thick bed of graphitic limestone, and -associated with it three regular beds of graphite, having an aggregate -thickness of about five feet.[D] - -[D] Matthew in "Quarterly Journal of the Geological Society," vol. xxi., -p. 423. "Acadian Geology," p. 662. - -It may fairly be assumed that in the present world, and in those -geological periods with whose organic remains we are more familiar than -with those of the Laurentian, there is no other source of unoxidized -carbon in rocks than that furnished by organic matter, and that this -has obtained its carbon in all cases, in the first instance, from the -deoxidation of carbonic acid by living plants. No other source of carbon -can, I believe, be imagined in the Laurentian period. We may, however, -suppose either that the graphitic matter of the Laurentian has been -accumulated in beds like those of coal, or that it has consisted of -diffused bituminous matter similar to that in more modern bituminous -shales and bituminous and oil-bearing limestones. The beds of graphite -near St. John, some of those in the gneiss at Ticonderoga in New York, -and at Lochaber and Buckingham, and elsewhere in Canada, are so pure and -regular that one might fairly compare them with the graphitic coal of -Rhode Island. These instances, however, are exceptional, and the greater -part of the disseminated and vein graphite might rather be likened in -its mode of occurrence to the bituminous matter in bituminous shales and -limestones. - -We may compare the disseminated graphite to that which we find in those -districts of Canada in which Silurian and Devonian bituminous shales -and limestones have been metamorphosed and converted into graphitic -rocks not very dissimilar to those in the less altered portions of -the Laurentian.[E] In like manner it seems probable that the numerous -reticulating veins of graphite may have been formed by the segregation -of bituminous matter into fissures and planes of least resistance, in -the manner in which such veins occur in modern bituminous limestones -and shales. Such bituminous veins occur in the Lower Carboniferous -limestone and shale of Dorchester and Hillsborough, New Brunswick, with -an arrangement very similar to that of the veins of graphite; and in -the Quebec rocks of Point Levi, veins attaining to a thickness of more -than a foot, are filled with a coaly matter having a transverse columnar -structure, and regarded by Logan and Hunt as an altered bitumen. These -palæozoic analogies would lead us to infer that the larger part of the -Laurentian graphite falls under the second class of deposits above -mentioned, and that, if of vegetable origin, the organic matter must have -been thoroughly disintegrated and bituminised before it was changed into -graphite. This would also give a probability that the vegetation implied -was aquatic, or at least that it was accumulated under water. - -[E] Granby, Melbourne, Owl's Head, &c., "Geology of Canada," 1863, p. 599. - -Dr. Hunt has, however, observed an indication of terrestrial vegetation, -or at least of subaërial decay, in the great beds of Laurentian iron-ore. -These, if formed in the same manner as more modern deposits of this kind, -would imply the reducing and solvent action of substances produced in the -decay of plants. In this case such great ore-beds as that of Hull, on the -Ottawa, seventy feet thick, or that near Newborough, two hundred feet -thick,[F] must represent a corresponding quantity of vegetable matter -which has totally disappeared. It may be added that similar demands on -vegetable matter as a deoxidising agent are made by the beds and veins of -metallic sulphides of the Laurentian, though some of the latter are no -doubt of later date than the Laurentian rocks themselves. - -[F] "Geology of Canada," 1863. - -It would be very desirable to confirm such conclusions as those above -deduced by the evidence of actual microscopic structure. It is to be -observed, however, that when, in more modern sediments, Algæ have been -converted into bituminous matter, we cannot ordinarily obtain any -structural evidence of the origin of such bitumen, and in the graphitic -slates and limestones derived from the metamorphosis of such rocks -no organic structure remains. It is true that, in certain bituminous -shales and limestones of the Silurian system, shreds of organic -tissue can sometimes be detected, and in some cases, as in the Lower -Silurian limestone of the La Cloche Mountains in Canada, the pores -of brachiopodous shells and the cells of corals have been penetrated -by black bituminous matter, forming what may be regarded as natural -injections, sometimes of much beauty. In correspondence with this, while -in some Laurentian graphitic rocks, as, for instance, in the compact -graphite of Clarendon, the carbon presents a curdled appearance due to -segregation, and precisely similar to that of the bitumen in more modern -bituminous rocks, I can detect in the graphitic limestones occasional -fibrous structures which may be remains of plants, and in some specimens -vermicular lines, which I believe to be tubes of Eozoon penetrated by -matter once bituminous, but now in the state of graphite. - -When palæozoic land-plants have been converted into graphite, they -sometimes perfectly retain their structure. Mineral charcoal, with -structure, exists in the graphitic coal of Rhode Island. The fronds of -ferns, with their minutest veins perfect, are preserved in the Devonian -shales of St. John, in the state of graphite; and in the same formation -there are trunks of Conifers (_Dadoxylon Ouangondianum_) in which the -material of the cell-walls has been converted into graphite, while -their cavities have been filled with calcareous spar and quartz, the -finest structures being preserved quite as well as in comparatively -unaltered specimens from the coal-formation.[G] No structures so perfect -have as yet been detected in the Laurentian, though in the largest -of the three graphitic beds at St. John there appear to be fibrous -structures, which I believe may indicate the existence of land-plants. -This graphite is composed of contorted and slickensided laminæ, much -like those of some bituminous shales and coarse coals; and in these are -occasional small pyritous masses which show hollow carbonaceous fibres, -in some cases presenting obscure indications of lateral pores. I regard -these indications, however, as uncertain; and it is not as yet fully -ascertained that these beds at St. John are on the same geological -horizon with the Lower Laurentian of Canada, though they certainly -underlie the Primordial series of the Acadian group, and are separated -from it by beds having the character of the Huronian. - -[G] "Acadian Geology," p. 535. In calcined specimens the structures -remain in the graphite after decalcification by an acid. - -There is thus no absolute impossibility that distinct organic tissues -may be found in the Laurentian graphite, if formed from land-plants, -more especially if any plants existed at that time having true woody or -vascular tissues; but it cannot with certainty be affirmed that such -tissues have been found. It is possible, however, that in the Laurentian -period the vegetation of the land may have consisted wholly of cellular -plants, as, for example, mosses and lichens; and if so, there would be -comparatively little hope of the distinct preservation of their forms or -tissues, or of our being able to distinguish the remains of land-plants -from those of Algæ. - -We may sum up these facts and considerations in the following statements: -First, that somewhat obscure traces of organic structure can be detected -in the Laurentian graphite; secondly, that the general arrangement and -microscopic structure of the substance corresponds with that of the -carbonaceous and bituminous matters in marine formations of more modern -date; thirdly, that if the Laurentian graphite has been derived from -vegetable matter, it has only undergone a metamorphosis similar in kind -to that which organic matter in metamorphosed sediments of later age -has experienced; fourthly, that the association of the graphitic matter -with organic limestone, beds of iron-ore, and metallic sulphides greatly -strengthens the probability of its vegetable origin; fifthly, that -when we consider the immense thickness and extent of the Eozoonal and -graphitic limestones and iron-ore deposits of the Laurentian, if we admit -the organic origin of the limestone and graphite, we must be prepared to -believe that the life of that early period, though it may have existed -under low forms, was most copiously developed, and that it equalled, -perhaps surpassed, in its results, in the way of geological accumulation, -that of any subsequent period. - -Many years ago, at the meeting of the American Association in Albany, the -writer was carrying into the room of the Geological Section a mass of -fossil wood from the Devonian of Gaspé, when he met the late Professor -Agassiz, and remarked that the specimen was the remains of a Devonian -tree contemporaneous with his fishes of that age. "How I wish I could -sit under its shade!" was the smiling reply of the great zoölogist; and -when we think of the great accumulations of Laurentian carbon, and that -we are entirely ignorant of the forms and structures of the vegetation -which produced it, we can scarcely suppress a feeling of disappointment. -Some things, however, we can safely infer from the facts that are known, -and these it may be well to mention. - -The climate and atmosphere of the Laurentian may have been well adapted -for the sustenance of vegetable life. We can scarcely doubt that the -internal heat of the earth still warmed the waters of the sea, and these -warm waters must have diffused great quantities of mists and vapours over -the land, giving a moist and equable if not a very clear atmosphere. The -vast quantities of carbon dioxide afterwards sealed up in limestones and -carbonaceous beds must also have still floated in the atmosphere and must -have supplied abundance of the carbon, which constitutes the largest -ingredient in vegetable tissues. Under these circumstances the whole -world must have resembled a damp, warm greenhouse, and plants loving such -an atmosphere could have grown luxuriantly. In these circumstances the -lower forms of aquatic vegetation and those that love damp, warm air and -wet soil would have been at home. - -If we ask more particularly what kinds of plants might be expected to be -introduced in such circumstances, we may obtain some information from the -vegetation of the succeeding Palæozoic age, when such conditions still -continued to a modified extent. In this period the club-mosses, ferns, -and mare's-tails engrossed the world and grew to sizes and attained -degrees of complexity of structure not known in modern times. In the -previous Laurentian age something similar may have happened to Algæ, to -Fungi, to Lichens, to Liverworts, and Mosses. The Algæ may have attained -to gigantic dimensions, and may have even ascended out of the water in -some of their forms. These comparatively simple cellular and tubular -structures, now degraded to the humble position of flat lichens or soft -or corky fungi, or slender cellular mosses, may have been so strengthened -and modified as to constitute forest-trees. This would be quite in -harmony with what is observed in the development of other plants in -primitive geological times; and a little later in this history we shall -see that there is evidence in the flora of the Silurian of a survival of -such forms. - -It may be that no geologist or botanist will ever be able to realise -these dreams of the past. But, on the other hand, it is quite possible -that some fortunate chance may have somewhere preserved specimens of -Laurentian plants showing their structure. - -In any case we have here presented to us the strange and startling fact -that the remarkable arrangement of protoplasmic matter and chlorophyll, -which enables the vegetable cell to perform, with the aid of solar -light, the miracle of decomposing carbon dioxide and water, and forming -with them woody and corky tissues, had already been introduced upon the -earth. It has been well said that no amount of study of inorganic nature -would ever have enabled any one to anticipate the possibility of the -construction of an apparatus having the chemical powers of the living -vegetable cell. Yet this most marvellous structure seems to have been -introduced in the full plenitude of its powers in the Laurentian age. - -Whether this early Laurentian vegetation was the means of sustaining -any animal life other than marine Protozoa, we do not know. It may -have existed for its own sake alone, or merely as a purifier of the -atmosphere, in preparation for the future introduction of land-animals. -The fact that there have existed, even in modern times, oceanic islands -rich in vegetation, yet untenanted by the higher forms of animal life, -prepares us to believe that such conditions may have been general or -universal in the primeval times we are here considering. - -If we ask to what extent the carbon extracted from the atmosphere and -stored up in the earth has been, or is likely to be, useful to man, the -answer must be that it is not in a state to enable it to be used as -mineral fuel. It has, however, important uses in the arts, though at -present the supply seems rather in excess of the demand, and it may well -be that there are uses of graphite still undiscovered, and to which it -will yet be applied. - -Finally, it is deserving of notice that, if Laurentian graphite indicates -vegetable life, it indicates this in vast profusion. That incalculable -quantities of vegetable matter have been oxidised and have disappeared we -may believe on the evidence of the vast beds of iron-ore; and, in regard -to that preserved as graphite, it is certain that every inch of that -mineral must indicate many feet of crude vegetable matter. - -It is remarkable that, in ascending from the Laurentian, we do not at -first appear to advance in evidences of plant-life. The Huronian age, -which succeeded the Laurentian, seems to have been a disturbed and -unquiet time, and, except in certain bands of iron-ore and some dark -slates coloured with carbonaceous matter, we find in it no evidence -of vegetation. In the Cambrian a great subsidence of our continents -began, which went on, though with local intermissions and reversals, all -through the Siluro-Cambrian or Ordovician time. These times were, for -this reason, remarkable for the great abundance and increase of marine -animals rather than of land-plants. Still, there are some traces of land -vegetation, and we may sketch first the facts of this kind which are -known, and then advert to some points relating to the earlier Algæ, or -sea-weeds. - -An eminent Swedish geologist, Linnarsson, has described, under the name -of _Eophyton_, certain impressions on old Cambrian rocks in Sweden, and -which certainly present very plant-like forms. They want, however, any -trace of carbonaceous matter, and seem rather to be grooves or marks cut -in clay by the limbs or tails of some aquatic animal, and afterwards -filled up and preserved by succeeding deposits. After examining large -series of these specimens from Sweden, and from rocks of similar age in -Canada, I confess that I have no faith in their vegetable nature. - -The oldest plants known to me, and likely to have been of higher grade -than Algæ, are specimens kindly presented to me by Dr. Alleyne Nicholson, -of Aberdeen, and which he had named _Buthotrephis Harknessii_[H] and _B. -radiata_. They are from the Skiddaw rocks of Cumberland. On examining -these specimens, and others subsequently collected in the same locality -by Dr. Gr. M. Dawson, while convinced by their form and carbonaceous -character that they are really plants, I am inclined to refer them not -to Algæ, but probably to Rhizocarps. They consist of slender branching -stems, with whorls of elongate and pointed leaves, resembling the genus -_Annularia_ of the coal formation. I am inclined to believe that both -of Nicholson's species are parts of one plant, and for this I have -proposed the generic name _Protannularia_ (Fig. 1). Somewhat higher in -the Siluro-Cambrian, in the Cincinnati group of America, Lesquereux -has found some minute radiated leaves, referred by him to the genus -_Sphenophyllum_,[I] which is also allied to Rhizocarps. Still more -remarkable is the discovery in the same beds of a stem with rhombic -areoles or leaf-bases, to which the name _Protostigma_ has been given.[J] -If a plant, this may have been allied to the club-mosses. This seems to -be all that we at present know of land-vegetation in the Siluro-Cambrian. -So far as the remains go, they indicate the presence of the families of -Rhizocarps and of Lycopods. - -[H] "Geological Magazine," 1869. - -[I] See figure in next chapter. - -[J] _Protostigma sigillarioides_, Lesquereux. - -[Illustration: Fig. 1.--_Protannularia Harknessii_ (Nicholson), a -probable Rhizocarp of the Ordovician period.] - -If we ascend into the Upper Silurian, or Silurian proper, the evidences -of land vegetation somewhat increase. In 1859 I described, in "The -Journal of the Geological Society" of London, a remarkable tree from the -Lower Erian of Gaspé, under the name _Prototaxites_, but for which I -now prefer the name _Nematophyton_. When in London, in 1870, I obtained -permission to examine certain specimens of spore-cases or seeds from -the Upper Ludlow (Silurian) formation of England, and which had been -described by Sir Joseph Hooker under the name _Pachytheca_. In the same -slabs with these I found fragments of fossil wood identical with those of -the Gaspé plant. Still later I recognised similar fragments associated -also with _Pachytheca_ in the Silurian of Cape Bon Ami, New Brunswick. -Lastly, Dr. Hicks has discovered similar wood, and also similar fruits, -in the Denbighshire grits, at the base of the Silurian.[K] - -[K] "Journal of the Geological Society," August, 1881. - -[Illustration: Fig. 2.--_Nematophyton Logani_ (magnified). Vertical -section.] - -[Illustration: Fig. 3.--_Nematophyton Logani_ (magnified). Horizontal -section, showing part of one of the radial spaces, with tubes passing -into it.] - -[Illustration: Fig. 4.--_Nematophyton Logani_ (magnified). -Restoration.[L]] - -[L] Figs. 2, 3, and 4 are drawn from nature by Prof. Penhallow, of McGill -College. - -From comparison of this singular wood, the structure of which is -represented in Figs. 2, 3, 4, with the _débris_ of fossil taxine woods, -mineralised after long maceration in water, I was inclined to regard -_Prototaxites_, or, as I have more recently named it, _Nematophyton_, as -a primeval gymnosperm allied to those trees which Unger had described -from the Erian of Thuringia, under the name _Aporoxylon_.[M] Later -examples of more lax tissues from branches or young stems, and the -elaborate examinations kindly undertaken for me by Professor Penhallow -and referred to in a note to this chapter, have induced me to modify -this view, and to hold that the tissues of these singular trees, which -seem to have existed from the beginning of the Silurian age and to have -finally disappeared in the early Erian, are altogether distinct from -any form of vegetation hitherto known, and are possibly survivors of -that prototypal flora to which I have already referred. They are trees -of large size, with a coaly bark and large spreading roots, having the -surface of the stem smooth or irregularly ribbed, but with a nodose or -jointed appearance. Internally, they show a tissue of long, cylindrical -tubes, traversed by a complex network of horizontal tubes thinner walled -and of smaller size. The tubes are arranged in concentric zones, which, -if annual rings, would in some specimens indicate an age of one hundred -and fifty years. There are also radiating spaces, which I was at first -disposed to regard as true medullary rays, or which at least indicate a -radiating arrangement of the tissue. They now seem to be spaces extending -from the centre towards the circumference of the stem, and to have -contained bundles of tubes gathered from the general tissue and extending -outward perhaps to organs or appendages on the surface. Carruthers has -suggested a resemblance to Algæ, and has even proposed to change the -name to _Nematophycus_, or "thread-sea-weed"; but the resemblance is -by no means clear, and it would be quite as reasonable to compare the -tissue to that of some Fungi or Lichens, or even to suppose that a plant -composed of cylindrical tubes has been penetrated by the mycelium or -spawn of a dry-rot fungus. But the tissues are too constant and too -manifestly connected with each other to justify this last supposition. -That the plant grew on land I cannot doubt, from its mode of occurrence; -that it was of durable and resisting character is shown by its state -of preservation; and the structure of the seeds called _Pachytheca_, -with their constant association with these trees, give countenance to -the belief that they are the fruit of Nematophyton. Of the foliage or -fronds of these strange plants we unfortunately know nothing. They seem, -however, to realise the idea of arboreal plants having structures akin -to those of thallophytes, but with seeds so large and complex that they -can scarcely be regarded as mere spores. They should perhaps constitute a -separate class or order to which the name _Nematodendreæ_ may be given, -and of which _Nematophyton_ will constitute one genus and _Aporoxylon_ of -Unger another.[N] - -[M] "Palæontologie des Thuringer Waldes," 1856. - -[N] See report by the author on "Erian Flora of Canada," 1871 and 1882, -for full description of these fossils. - -Another question arises as to the possible relation of these plants -to other trees known by their external forms. The _Protostigma_ of -Lesquereux has already been referred to, and Claypole has described -a tree from the Clinton group of the United States, with large ovate -leaf-bases, to which he has given the name _Glyptodendron_.[O] If the -markings on these plants are really leaf-bases, they can scarcely have -been connected with _Nematophyton_, because that tree shows no such -surface-markings, though, as we have seen, it had bundles of tubes -passing diagonally to the surface. These plants were more probably -trees with an axis of barred vessels and thick, cellular bark, like -the _Lepidodendron_ of later periods, to be noticed in the sequel. Dr. -Hicks has also described from the same series of beds which afforded -the fragments of Nematophyton certain carbonised dichotomous stems, -which he has named _Berwynia_. It is just possible that these plants may -have belonged to the Nematodendreæ. The thick and dense coaly matter -which they show resembles the bark of these trees, the longitudinal -striation in some of them may represent the fibrous structure, and the -lateral projections which have been compared to leaves or leaf-bases -may correspond with the superficial eminences of _Nematophyton_, and -the spirally arranged punctures which it shows on its surface. In -this case I should be disposed to regard the supposed stigmaria-like -roots as really stems, and the supposed rootlets as short, spine-like -rudimentary leaves. All such comparisons must, however, in the mean time -be regarded as conjectural. We seem, however, to have here a type of tree -very dissimilar to any even of the later Palæozoic age, which existed -throughout the Silurian, and probably further back, which ceased to -exist early in the Erian age, and before the appearance of the ordinary -coniferous and lepidodendroid trees. May it not have been a survivor of -an old arboreal flora extending back even to the Laurentian itself? - -[O] "American Journal of Science," 1878. - -Multitudes of markings occurring on the surfaces of the older rocks have -been referred to the Algæ or sea-weeds, and indeed this group has been -a sort of refuge for the destitute to which palæontologists have been -accustomed to refer any anomalous or inexplicable form which, while -probably organic, could not be definitely referred to the animal kingdom. -There can be no question that some of these are truly marine plants; and -that plants of this kind occur in formations older than those in which -we first find land-plants, and that they have continued to inhabit the -sea down to the present time. It is also true that the oldest of these -Algæ closely resemble in form plants of this kind still existing; and, -since their simple cellular structures and soft tissues are scarcely -ever preserved, their general forms are all that we can know, so that -their exact resemblance to or difference from modern types can rarely -be determined. For the same reasons it has proved difficult clearly to -distinguish them from mere inorganic markings or the traces of animals, -and the greatest divergence of opinion has occurred in recent times -on these subjects, as any one can readily understand who consults the -voluminous and well-illustrated memoirs of Nathorst, Williamson, Saporta, -and Delgado. - -The author of this work has given much attention to these remains, and -has not been disposed to claim for the vegetable kingdom so many of them -as some of his contemporaries.[P] The considerations which seem most -important in making such distinctions are the following: 1. The presence -or absence of carbonaceous matter. True Algæ not infrequently present at -least a thin film of carbon representing their organic matter, and this -is the more likely to occur in their case, as organic matters buried in -marine deposits and not exposed to atmospheric oxidation are very likely -to be preserved. 2. In the absence of organic matter, the staining of -the containing rock, the disappearance or deoxidation of its ferruginous -colouring matter, or the presence of iron pyrite may indicate the removal -of organic matter by decay. 3. When organic matter and indications of it -are altogether absent, and form alone remains, we have to distinguish -from Algæ, trails and burrows similar to those of aquatic animals, casts -of shrinkage-cracks, water-marks, and rill-marks widely diffused over the -surfaces of beds. 4. Markings depressed on the upper surfaces of beds, -and filled with the material of the succeeding layer, are usually mere -impressions. The cases of possible exceptions to this are very rare. On -the contrary, there are not infrequently forms in relief on the surfaces -of rocks which are not Algæ, but may be shallow burrows arched upward on -top, or castings of worms thrown up upon the surface. Sometimes, however, -they may have been left by denudation of the surrounding material, just -as footprints on dry snow remain in relief after the surrounding loose -material has been drifted away by the wind; the portion consolidated by -pressure being better able to resist the denuding agency. - -[P] "Impressions and Footprints of Aquatic Animals," "American Journal of -Science," 1873. - -[Illustration: Fig. 5.--Trail of a modern king-crab, to illustrate -imitations of plants sometimes named _Bilobites_.] - -[Illustration: Fig. 6.--Trail of Carboniferous crustacean (_Rusichnites -Acadicus_), Nova Scotia, to illustrate supposed Algæ.] - -The footprints from the Potsdam sandstone in Canada, for which the name -_Protichnites_ was proposed by Owen, and which were by him referred to -crustaceans probably resembling _Limulus_, were shown by the writer, -in 1862,[Q] to correspond precisely with those of the American Limulus -(_Polyphemus Occidentalis_) (Fig. 5). I proved by experiment with the -modern animal that the recurring series of groups of markings were -produced by the toes of the large posterior thoracic feet, the irregular -scratches seen in _Protichnites lineatus_ by the ordinary feet, and the -central furrow by the tail. It was also shown that when the Limulus uses -its swimming-feet it produces impressions of the character of those -named _Climactichnites_, from the same beds which afford _Protichnites_. -The principal difference between _Protichnites_ and their modern -representatives is that the latter have two lateral furrows produced by -the sides of the carapace, which are wanting in the former. - -[Q] "Canadian Naturalist," vol. vii. - -I subsequently applied the same explanation to several other ancient -forms now known under the general name _Bilobites_ (Figs. 6 and 7).[R] - -[R] The name Bilobites was originally proposed by De Kay for a bivalve -shell (Conocardium). Its application to supposed Algæ was an error, but -this is of the less consequence, as these are not true plants but only -animal trails. - -[Illustration: Fig. 7.--_Rusophycus_ (_Rusichnites_) _Grenvillensis_, -an animal burrow of the Siluro-Cambrian, probably of a crustacean, _a_, -Track connected with it.] - -The tuberculated impressions known as _Phymatoderma_ and _Caulerpites_ -may, as Zeiller has shown, be made by the burrowing of the mole-cricket, -and fine examples occurring in the Clinton formation of Canada are -probably the work of Crustacea. It is probable, however, that some of -the later forms referred to these genera are really Algæ related to -_Caulerpa_, or even branches of Conifers of the genus _Brachyphyllum_. - -_Nereites_ and _Planulites_ are tracks and burrows of worms, with -or without marks of setæ, and some of the markings referred to -_Palæochorda_, _Palæophycus_, and _Scolithus_ have their places here. -Many examples highly illustrative of the manner of formation of the -impressions are afforded by Canadian rocks (Fig. 8). - -Branching forms referred to _Licrophycus_ of Billings, and some of -those referred to _Buthotrephis_, Hall, as well as radiating markings -referable to _Scotolithus_, _Gyrophyllites_, and _Asterophycus_, are -explained by the branching burrows of worms illustrated by Nathorst -and the author. _Astropolithon_, a singular radiating marking of the -Canadian Cambrian,[S] seems to be something organic, but of what nature -is uncertain (Fig. 9). - -[S] Supplement to "Acadian Geology." - -[Illustration: Fig. 8.--_Palæophycus Beverlyensis_ (Billings), a supposed -Cambrian Fucoid, but probably an animal trail.] - -_Rhabdichnites_ and _Eophyton_ belong to impressions explicable by the -trails of drifting sea-weeds, the tail-markings of Crustacea, and the -ruts ploughed by bivalve mollusks, and occurring in the Silurian, Erian, -and Carboniferous rocks.[T] Among these are the singular bilobate forms -described as _Rusophycus_ by Hall, and which are probably burrows or -resting-places of crustaceans. The tracks of such animals, when walking, -are the jointed impressions known as _Arthrophycus_ and _Crusiana_. -I have shown by the mode of occurrence of these, and Nathorst has -confirmed this conclusion by elaborate experiments on living animals, -that these forms are really trails impressed on soft sediments by animals -and mostly by crustaceans. - -[T] "Canadian Naturalist," 1864. - -I agree with Dr. Williamson[U] in believing that all or nearly all the -forms referred to Crossochorda of Schimper are really animal impressions -allied to Nereites, and due either to worms or, as Nathorst has shown to -be possible, to small crustaceans. Many impressions of this kind occur in -the Silurian beds of the Clinton series in Canada and New York, and are -undoubtedly mere markings. - -[U] "Tracks from Yoredale Rocks," "Manchester Literary and Philosophical -Society," 1885. - -[Illustration: Fig. 9.--_Astropolithon Hindii_, an organism of the Lower -Cambrian of Nova Scotia, possibly vegetable.] - -It is worthy of note that these markings strikingly resemble the -so-called _Eophyton_, described by Torell from the Primordial of -Sweden, and by Billings from that of Newfoundland; and which also occur -abundantly in the Primordial of New Brunswick. After examining a series -of these markings from Sweden shown to me by Mr. Carruthers in London, -and also specimens from Newfoundland and a large number _in situ_ at St. -John, I am convinced that they cannot be plants, but must be markings of -the nature of _Rhabdichnites_. This conclusion is based on the absence of -carbonaceous matter, the intimate union of the markings with the surface -of the stone, their indefinite forms, their want of nodes or appendages, -and their markings being always of such a nature as could be produced by -scratches of a sharp instrument. Since, however, fishes are yet unknown -in beds of this age, they may possibly be referred to the feet or spinous -tails of swimming crustaceans. Salter has already suggested this origin -for some scratches of somewhat different form found in the Primordial -of Great Britain. He supposed them to have been the work of species of -_Hymenocaris_. These marks may, however, indicate the existence of some -free-swimming animals of the Primordial seas as yet unknown to us. - -Three other suggestions merit consideration in this connection. One -is that Algæ and also land-plants, drifting with tides or currents, -often make the most remarkable and fantastic trails. A marking of this -kind has been observed by Dr. G. M. Dawson to be produced by a drifted -Laminaria, and in complexity it resembled the extraordinary _Ænigmichnus -multiformis_ of Hitchcock from the Connecticut sandstones. Much more -simple markings of this kind would suffice to give species of _Eophyton_. -Another is furnished by a fact stated to the author by Prof. Morse, -namely, that Lingulæ, when dislodged from their burrows, trail themselves -over the bottom like worms, by means of their cirri. Colonies of these -creatures, so abundant in the Primordial, may, when obliged to remove, -have covered the surfaces of beds of mud with vermicular markings. The -third is that the Rhabdichnite-markings resemble some of the grooves in -Silurian rocks which have been referred to trails of Gasteropods, as, for -instance, those from the Clinton group, described by Hall. - -Another kind of markings not even organic, but altogether depending on -physical causes, are the beautiful branching rill-marks produced by the -oozing of water out of mud and sand-banks left by the tide, and which -sometimes cover great surfaces with the most elaborate tracery, on -the modern tidal shores as well as in some of the most ancient rocks. -_Dendrophycus_[V] of Lesquereux seems to be an example of rill-mark, as -well as _Aristophycus_, _Cloephycus_, and _Zygopliycus_, of Miller and -Dyer, from the Lower Silurian. - -[V] "Coal Flora of Pennsylvania," vol. iii., Plate 88. - -Rill-marks occur in very old rocks,[W] but are perhaps most beautifully -preserved in the Carboniferous shales and argillaceous sandstones, and -even more elaborately on the modern mud-banks of the Bay of Fundy.[X] -Some of these simulate ferns and fronds of Laminariæ, and others resemble -roots, fucoids allied to _Buthotrephis_, or the radiating worm-burrows -already referred to (Fig. 10). - -[W] "Journal of the Geological Society," vol. xii., p. 251. - -[X] "Acadian Geology," 2d ed., p. 26. - -[Illustration: Fig. 10.--Carboniferous rill-mark (Nova Scotia), reduced, -to illustrate pretended Algæ.] - -_Shrinkage-cracks_ are also abundant in some of the Carboniferous beds, -and are sometimes accompanied with impressions of rain-drops. When finely -reticulated they might be mistaken for the venation of leaves, and, -when complicated with little rill-marks tributary to their sides, they -precisely resemble the _Dictyolites_ of Hall from the Medina sandstone -(Fig. 11). - -[Illustration: Fig. 11.--Cast of shrinkage cracks (Carboniferous, Nova -Scotia), illustrating pretended Algæ.] - -An entirely different kind of shrinkage-crack is that which occurs in -certain carbonised and flattened plants, and which sometimes communicates -to them a marvellous resemblance to the netted under surface of an -exogenous leaf. Flattened stems of plants and layers of cortical -matter, when carbonised, shrink in such a manner as to produce minute -reticulated cracks. These become filled with mineral matter before the -coaly substance has been completely consolidated. A further compression -occurs, causing the coaly substance to collapse, leaving the little veins -of harder mineral matter projecting. These impress their form upon the -clay or shale above and below, and thus when the mass is broken open we -have a carbonaceous film or thin layer covered with a network of raised -lines, and corresponding minute depressed lines on the shale in contact -with it. The reticulations are generally irregular, but sometimes they -very closely resemble the veins of a reticulately veined leaf. One of -the most curious specimens in my possession was collected by Mr. Elder -in the Lower Carboniferous of Horton Bluff. The little veins which form -the projecting network are in this case white calcite; but at the surface -their projecting edges are blackened with a carbonaceous film. - -_Slickensided bodies_, resembling the fossil fruits described by Geinitz -as _Gulielmites_, and the objects believed by Fleming and Carruthers[Y] -to be casts of cavities filled with fluid, abound in the shales of the -Carboniferous and Devonian. They are, no doubt, in most cases the results -of the pressure and consolidation of the clay around small solid bodies, -whether organic, fragmentary, or concretionary. They are, in short, local -slickensides precisely similar to those found so plentifully in the coal -under-clays, and which, as I have elsewhere[Z] shown, resulted from the -internal giving way and slipping of the mass as the roots of Stigmaria -decayed within it. Most collectors of fossil plants in the older -formations must, I presume, be familiar with appearances of this kind in -connection with small stems, petioles, fragments of wood, and carpolites. -I have in my collection petioles of ferns and fruits of the genus -Trigonocarpum partially slickensided in this way, and which if wholly -covered by this kind of marking could scarcely have been recognised. I -have figured bodies of this kind in my report on the Devonian and Upper -Silurian plants of Canada, believing them, owing to their carbonaceous -covering, to be probably slickensided fruits, though of uncertain nature. -In every case I think these bodies must have had a solid nucleus of -some sort, as the severe pressure implied in slickensiding is quite -incompatible with a mere "fluid-cavity," even supposing this to have -existed. - -[Y] "Journal of the Geological Society," June, 1871. - -[Z] _Ibid._, vol. x., p. 14. - -Prof. Marsh has well explained another phase of the influence of hard -bodies in producing partial slickensides, in his paper on _Stylolites_, -read before the American Association in 1867, and the application -of the combined forces of concretionary action and slickensiding to -the production of the cone-in-cone concretions, which occur in the -coal-formation and as low as the Primordial. I have figured a very -perfect and beautiful form of this kind from the coal-formation of Nova -Scotia, which is described in "Acadian Geology"[AA] (Fig. 12). - -I have referred to these facts here because they are relatively more -important in that older period, which may be named the age of Algæ, and -because their settlement now will enable us to dispense with discussions -of this kind further on. The able memoirs of Nathorst and Williamson -should be studied by those who desire further information. - -[AA] Appendix, p. 676, edition of 1878. - -[Illustration: Fig. 12.--Cone-in-cone concretion (Carboniferous, Nova -Scotia), illustrating pretended Algæ.] - -But it may be asked, "Are there no real examples of fossil Algæ?" I -believe there are many such, but the difficulty is to distinguish them. -Confining ourselves to the older rocks, the following may be noted: - -The genus _Buthotrephis_ of Hall, which is characterised as having -stems, sub-cylindric or compressed, with numerous branches, which are -divaricating and sometimes leaf-like, contains some true Algæ. Hall's -_B. gracilis_, from the Siluro-Cambrian, is one of these. Similar -plants, referred to the same species, occur in the Clinton and Niagara -formations, and a beautiful species, collected by Col. Grant, of -Hamilton, and now in the McGill College collection, represents a broader -and more frondose type of distinctly carbonaceous character. It may be -described as follows: - -_Buthotrephis Grantii_, S. N. (Fig. 13).--Stems and fronds smooth and -slightly striate longitudinally, with curved and interrupted striæ. -Stem thick, bifurcating, the divisions terminating in irregularly -pinnate fronds, apparently truncate at the extremities. The quantity -of carbonaceous matter present would indicate thick, though perhaps -flattened, stems and dense fleshy fronds. - -[Illustration: Fig. 13.--_Buthotrephis Grantii_, a genuine Alga from the -Silurian, Canada.] - -The species _Buthotrephis subnodosa_ and _B. flexuosa_, from the Utica -shale, are also certainly plants, though it is possible, if their -structures and fruit were known, some of these might be referred to -different genera. All of these plants have either carbonaceous matter or -produce organic stains on the matrix. - -The organism with diverging wedge-shaped fronds, described by Hall as -_Sphenothallus angustifolius_, is also a plant. Fine specimens, in the -collection of the Geological Survey of Canada, show distinct evidence of -the organic character of the wedge-shaped fronds. It is from the Utica -shale, and elsewhere in the Siluro-Cambrian. It is just possible, as -suggested by Hall, that this plant may be of higher rank than the Algæ. - -The genus _Palæophycus_ of Hall includes a great variety of uncertain -objects, of which only a few are probably true Algæ. I have specimens of -fragments similar to his _P. virgatus_, which show distinct carbonaceous -films, and others from the Quebec group, which seem to be cylindrical -tubes now flattened, and which have contained spindle-shaped sporangia -of large size. Tortuous and curved flattened stems, or fronds, from the -Upper Silurian limestone of Gaspé, also show organic matter. - -Respecting the forms referred to _Licrophycus_ by Billings, containing -stems or semi-cylindrical markings springing from a common base, I have -been in great doubt. I have not seen any specimens containing unequivocal -organic matter, and am inclined to think that most of them, if not the -whole, are casts of worm-burrows, with trails radiating from them. - -Though I have confined myself in this notice to plants, or supposed -plants, of the Lower Palæozoic, it may be well to mention the remarkable -Cauda-Galli fucoids, referred by Hall to the genus _Spirophyton_, and -which are characteristic of the oldest Erian beds. The specimens which -I have seen from New York, from Gaspé, and from Brazil, leave no doubt -in my mind that these were really marine plants, and that the form of a -spiral frond, assigned to them by Hall, is perfectly correct. They must -have been very abundant and very graceful plants of the early Erian, -immediately after the close of the Silurian period. - -We come now to notice certain organisms referred to Algæ, and which are -either of animal origin, or are of higher grade than the sea-weeds. -We have already discussed the questions relating to _Prototaxites_. -_Drepanophycus_, of Goeppert,[AB] I suspect, is only a badly preserved -branch or stem of the Erian land-plant known as Arthrostigma. In like -manner, _Haliserites Dechenianus_,[AC] of Goeppert, is evidently -the land-plant known as _Psilophyton_. _Sphærococcites dentatus_ -and _S. serra_--the _Fucoides dentatus_ and _serra_ of Brongniart, -from Quebec--are graptolites of two species quite common there.[AD] -_Dictyophyton_ and _Uphantenia_, as described by Hall and the author, are -now known to be sponges. They have become _Dictyospongiæ_. The curious -and very ancient; fossils referred by Forbes to the genus _Oldhamia_ are -perhaps still subject to doubt, but are usually regarded as Zoöphytes, -though it is quite possible they may be plants. Though I have not seen -the specimens, I have no doubt whatever that the plants, or the greater -part of them, from the Silurian of Bohemia, described by Stur as Algæ -and Characeæ,[AE] are really land-plants, some of them of the genus -_Psilophyton_. I may say in this connection that specimens of flattened -_Psilophyton_ and _Arthrostigma_, in the Upper Silurian and Erian of -Gaspé, would probably have been referred to Algæ, but for the fact that -in some of them the axis of barred vessels is preserved. - -[AB] "Fossile Flora," 1852, p. 92, Table xli. - -[AC] _Ibid._, p. 88, Table ii. - -[AD] Brongniart, "Vegeteaux Fossiles," Plate vi., Figs. 7 to 12. - -[AE] "Proceedings of the Vienna Academy," 1881. _Hostinella_, of this -author, is almost certainly _Psilophyton_, and his _Barrandiana_ seems to -include _Arthrostigma_, and perhaps leafy branches of _Berwynia_. These -curious plants should be re-examined. - -It is not surprising that great difficulties have occurred in the -determination of fossil Algæ. Enough, however, remains certain to prove -that the old Cambrian and Silurian seas were tenanted with sea-weeds -not very dissimilar from those of the present time. It is further -probable that some of the graphitic, carbonaceous, and bituminous -shales and limestones of the Silurian owe their carbonaceous matters -to the decomposition of Algæ, though possibly some of it may have been -derived from Graptolites and other corneous Zoöphytes. In any case, -such microscopic examinations of these shales as I have made, have not -produced any evidence of the existence of plants of higher grade, while -those of the Erian and Carboniferous periods, similar to the naked eye, -abound in such evidence. It is also to be observed that, on the surfaces -of beds of sandstone in the Upper Cambrian, carbonaceous _débris_, which -seems to be the remains of either aquatic or land plants, is locally not -infrequent. - -[Illustration: Fig. 14.--Silurian vegetation restored. _Protannularia_, -_Berwynia_, _Nematophyton_, _Sphenophyllum_, _Arthrostigma_, -_Psilophyton_.] - -Referring to the land vegetation of the older rocks, it is difficult to -picture its nature and appearance. We may imagine the shallow waters -filled with aquatic or amphibious Rhizocarpean plants, vast meadows or -brakes of the delicate _Psilophyton_ and the starry _Protannularia_ and -some tall trees, perhaps looking like gigantic club-mosses, or possibly -with broad, flabby leaves, mostly cellular in texture, and resembling -Algæ transferred to the air. Imagination can, however, scarcely realise -this strange and grotesque vegetation, which, though possibly copious and -luxuriant, must have been simple and monotonous in aspect, and, though it -must have produced spores and seeds and even fruits, these were probably -all of the types seen in the modern acrogens and gymnosperms. - - "In garments green, indistinct in the twilight, - They stand like Druids of old, with voices sad and prophetic." - -Prophetic they truly were, as we shall find, of the more varied forests -of succeeding times, and they may also help us to realise the aspect -of that still older vegetation, which is fossilised in the Laurentian -graphite; though it is not impossible that this last may have been of -higher and more varied types, and that the Cambrian and Silurian may have -been times of depression in the vegetable world, as they certainly were -in the submergence of much of the land. - -These primeval woods served at least to clothe the nakedness of the -new-born land, and they may have sheltered and nourished forms of -land-life still unknown to us, as we find as yet only a few insects and -scorpions in the Silurian. They possibly also served to abstract from the -atmosphere some portion of its superabundant carbonic acid harmful to -animal life, and they stored up supplies of graphite, of petroleum, and -of illuminating gas, useful to man at the present day. We may write of -them and draw their forms with, the carbon which they themselves supplied. - - * * * * * - -NOTE TO CHAPTER II. - -Examination of Prototaxites (_Nematophyton_), by Prof. Penhallow, of -McGill University. - -Prof. Penhallow, having kindly consented to re-examine my specimens, has -furnished me with elaborate notes of his facts and conclusions, of which -the following is a summary, but which it is hoped will be published in -full: - -"1. _Concentric Layers._--The inner face of each of these is composed -of relatively large tubes, having diameters from 13·6 to 34·6 -micro-millimetres. The outer face has tubes ranging from 13·8 to 27·6 mm. -The average diameter in the lower surface approaches to 34, that in the -outer to 13·8. There is, however, no abrupt termination to the surface of -the layers, though in some specimens they separate easily, with shining -surfaces. - -"2. _Minute Structure._--In longitudinal sections the principal part of -the structure consists of longitudinal tubes of indeterminate length, -and round in cross-section. They are approximately parallel, but in some -cases may be seen to bend sinuously, and are not in direct contact. Finer -myceloid tubes, 5·33 mm. in diameter, traverse the structure in all -directions, and are believed to branch off from the larger tubes. In a -small specimen supposed to be a branch or small stem, and in which the -vertical tubes are somewhat distant from one another, this horizontal -system is very largely developed; but is less manifest in the older -stems. The tubes themselves show no structure. The ray-like openings -in the substance of the tissue are evidently original parts of the -structure, but not of the nature of medullary rays. They are radiating -spaces running outward in an interrupted manner or so tortuously that -they appear to be interrupted in their course from the centre towards -the surface. They show tubes turning into them, branching into them, -and approximately horizontal, but tortuous. On the external surface -of some specimens these radial spaces are represented by minute pits -irregularly or spirally arranged. The transverse swellings of the stem -show no difference of structure, except that the tubes or cells may be a -little more tortuous, and a transverse film of coaly matter extends from -the outer coaly envelope inwardly. This may perhaps be caused by some -accident of preservation. The outer coaly layer shows tubes similar to -those of the stem.[AF] The horizontal or oblique flexures of the large -tubes seem to be mainly in the vicinity of the radial openings, and it is -in entering these that they have been seen to branch." - -[AF] It is possible that these tubes may be merely part of the stem -attached to the bark, which seems to me to indicate the same dense -cellular structure seen in the bark of _Lepidodendra_, etc. - -The conclusions arrived at by Prof. Penhallow are as follows: - -"1. The plant was not truly exogenous, and the appearance of rings -is independent of the causes which determine the layers of growth in -exogenous plants. - -"2. The plant was possessed of no true bark. Whatever cortical layer -was present was in all probability a modification of the general -structure,[AG] - -[AG] On these points I would reserve the considerations: 1. That there -must have been some relation between the mode of growth of these great -stems and their concentric rings; and, 2. That the evidence of a bark is -as strong as in the case of any Palæozoic tree in which the bark is, as -usual, carbonised. - -"3. An intimate relation exists between the large tubular cells and the -myceloid filaments, the latter being a system of small branches from -the former; the branching being determined chiefly in certain special -openings which simulate medullary rays. - -"4. The specimens examined exhibit no evidence of special decay, and the -structure throughout is of a normal character. - -"5. The primary structure consists of large tubular cells without -apparent terminations, and devoid of structural markings, with which is -associated a secondary structure of myceloid filaments arising from the -former. - -"6. The structure of _Nematophyton_ as a whole is unique; at least there -is no plant of modern type with which it is comparable. Nevertheless, the -loose character of the entire structure; the interminable cells; their -interlacing; and, finally, their branching into a secondary series of -smaller filaments, point with considerable force to the true relationship -of the stem as being with Algæ or other Thallophytes rather than with -Grymnosperms. A more recent examination of a laminated resinous -substance found associated with the plant shows that it is wholly -amorphous, and, as indicated by distinct lines of flow, that it must -have been in a plastic state at a former period. The only evidence of -structure was found in certain well-defined mycelia, which may have been -derived from associated vegetable matter upon which they were growing, -and over which the plastic matrix flowed." - -I have only to add to this description that when we consider that -_Nematophyton Logani_ was a large tree, sometimes attaining a diameter of -more than two feet, and a stature of at least twenty before branching; -that it had great roots, and gave off large branches; that it was -an aërial plant, probably flourishing in the same swampy flats with -_Psilophyton_, _Arthrostigma_, and _Leptophleum_; that the peculiar -bodies known as Pachytheca were not unlikely its fruit--we have evidence -that there were, in the early Palæozoic period, plants scarcely dreamt -of by modern botany. Only when the appendages of these plants are more -fully known can we hope to understand them. In the mean time, I may state -that there were probably different species of these trees, indicated -more particularly by the stems I have described as _Nematoxylon_ and -_Celluloxylon_[AH] There were, I think, some indications that the plants -described by Carruthers as _Berwynia_, may also be found to have been -generically the same. The resinous matter mentioned by Prof. Penhallow is -found in great abundance in the beds containing _Nematophyton_, and must, -I think, have been an exudation from its bark. - -[AH] "Journal Geol. Society of London," 1863, 1881. - - - - -CHAPTER III. - -THE ERIAN OF DEVONIAN FORESTS--ORIGIN OF PETROLEUM--THE AGE OF ACROGENS -AND GYMNOSPERMS. - - -In the last chapter we were occupied with the comparatively few and -obscure remains of plants entombed in the oldest geological formations. -We now ascend to a higher plane, that of the Erian or Devonian period, in -which, for the first time, we find varied and widely distributed forests. - -The growth of knowledge with respect to this flora has been somewhat -rapid, and it may be interesting to note its principal stages, as -an encouragement to the hope that we may yet learn something more -satisfactory respecting the older floras we have just discussed. - -In Goeppert's memoir on the flora of the Silurian, Devonian, and Lower -Carboniferous rocks, published in 1860,[AI] he enumerates twenty species -as Silurian, but these are all admitted to be Algæ, and several of them -are remains which may be fairly claimed by the zoologists as zoophytes, -or trails of worms and mollusks. In the Lower Devonian he knows but six -species, five of which are Algæ, and the remaining one a _Sigillaria_, -but this is of very doubtful nature. In the Middle Devonian he gives but -one species, a land-plant of the genus _Lepidodendron_. In the Upper -Devonian the number rises to fifty-seven, of which all but seven are -terrestrial plants, representing a large number of the genera occurring -in the succeeding Carboniferous system. - -[AI] Jena, 1860. - -Goeppert does not include in his enumeration the plants from the -Devonian of Gaspé, described by the author in 1859,[AJ] having seen only -an abstract of the paper at the time of writing his memoir, nor does -he appear to have any knowledge of the plants of this age described -by Lesquereux in Roger's "Pennsylvania." These might have added ten -or twelve species to his list, some of them probably from the Lower -Devonian. It is further to be observed that a few additional species had -also been recognised by Peach in the Old Red Sandstone of Scotland. - -[AJ] "Journal of the Geological Society of London," also "Canadian -Naturalist." - -But from 1860 to the present time a rich harvest of specimens has -been gathered from the Gaspé sandstones, from the shales of southern -New Brunswick, from the sandstones of Perry in Maine, and from the -wide-spread Erian areas of New York, Pennsylvania, and Ohio. Nearly -all these specimens have passed through my hands, and I am now able -to catalogue about a hundred species, representing more than thirty -genera, and including all the great types of vascular Cryptogams, the -Gymnosperms, and even one (still doubtful) Angiosperm. Many new forms -have also been described from the Devonian of Scotland and of the -Continent of Europe. - -Before describing these plants in detail, we may refer to North America -for illustration of the physical conditions of the time. In a physical -point of view the northern hemisphere presented a great change in the -Erian period. There were vast foldings of the crust of the earth, and -great emissions of volcanic rock on both sides of the Atlantic. In North -America, while at one time the whole interior area of the continent, as -far north as the Great Lakes, was occupied by a vast inland sea, studded -with coral islands, the long Appalachian ridge had begun to assume, -along with the old Laurentian land, something of the form of our present -continent, and on the margins of this Appalachian belt there were wide, -swampy flats and shallow-water areas, which, under the mild climate that -seems to have characterised this period, were admirably suited to nourish -a luxuriant vegetation. Under this mild climate, also, it would seem that -new forms of plants were first introduced in the far north, where the -long continuance of summer sunlight, along with great warm th, seems to -have aided in their introduction and early extension, and thence made -their way to the southward, a process which, as Gray and others have -shown, has also occurred in later geological times. - -The America of this Erian age consisted during the greater part of the -period of a more or less extensive belt of land in the north with two -long tongues descending from it, one along the Appalachian line in the -east, the other in the region west of the Rocky Mountains. On the seaward -sides of these there were low lands covered with vegetation, while on the -inland side the great interior sea, with its verdant and wooded islands, -realised, though probably with shallower water, the conditions of the -modern archipelagoes of the Pacific. - -Europe presented conditions somewhat similar, having in the earlier and -middle portions of the period great sea areas with insular patches of -land, and later wide tracts of shallow and in part enclosed water areas, -swarming with fishes, and having an abundant vegetation on their shores. -These were the conditions of the Eifel and Devonshire limestones, and of -the Old Red Sandstone of Scotland, and the Kiltorcan beds of Ireland. In -Europe also, as in America, there were in the Erian age great ejections -of igneous rock. On both sides of the Atlantic there were somewhat varied -and changing conditions of land and water, and a mild and equable -climate, permitting the existence of a rich vegetation in high northern -latitudes. Of this latter fact a remarkable example is afforded by the -beds holding plants of this age in Spitzbergen and Bear Island, in its -vicinity. Here there seem to be two series of plant-bearing strata, -one with the vegetation of the Upper Erian, the other with that of the -Lower Carboniferous, though both have been united by Heer under his -so-called "Ursa Stage" in which he has grouped the characteristic plants -of two distinct periods. This has recently been fully established by the -researches of Nathorst, though the author had already suggested it as the -probable explanation of the strange union of species in the Ursa group of -Heer. - -In studying the vegetation of this remarkable period, we must take -merely some of the more important forms as examples, since it would be -impossible to notice all the species, and some of them may be better -treated in the Carboniferous, where they have their headquarters. (Fig. -15.) - -I may first refer to a family which seems to have culminated in the Erian -age, and ever since to have occupied a less important place. It is that -of the curious aquatic plants known as Rhizocarps,[AK] and referred to in -the last chapter. - -[AK] Or, as they have recently been named by some botanists, -"Heterosporous Filices," though they are certainly not ferns in any -ordinary sense of that term. - -My attention was first directed to these organisms by the late Sir W. -E. Logan in 1869. He had obtained from the Upper Erian shale of Kettle -Point, Lake Huron, specimens filled with minute circular discs, to which -he referred, in his report of 1863, as "microscopic orbicular bodies." -Recognising them to be macrospores, or spore-cases, I introduced them -into the report on the Erian flora, which I was then preparing, and -which was published in 1871, under the name _Sporangites Huronensis_. - -[Illustration: Fig. 15.--Vegetation of the Devonian period, restored. -_Calamites_, _Psilophyton_, _Leptophleum_, _Lepidodendron_, _Cordaites_, -_Sigillaria_, _Dadoxylon_, _Asterophyllites_, _Platyphyllum_.] - -In 1871, having occasion to write a communication to the "American -Journal of Science" on the question then raised as to the share of spores -and spore-cases in the accumulation of coal, a question to be discussed -in a subsequent chapter, these curious little bodies were again -reviewed, and were described in substance as follows: - -"The oldest bed of spore-cases known to me is that at Kettle Point, Lake -Huron. It is a bed of brown bituminous shale, burning with much flame, -and under a lens is seen to be studded with flattened disc-like bodies, -scarcely more than a hundredth of an inch in diameter, which under -the microscope are found to be spore-cases (or macrospores) slightly -papillate externally (or more properly marked with dark pores), and -sometimes showing a point of attachment on one side and a slit more or -less elongated and gaping on the other. When slices of the rock are -made, its substance is seen to be filled with these bodies, which, -viewed as transparent objects, appear yellow like amber, and show little -structure, except that the walls can be distinguished from the internal -cavity, which may sometimes be seen to enclose patches of granular -matter. In the shale containing them are also vast numbers of rounded, -translucent granules, which may be escaped spores (microspores)." The -bed containing these spores at Kettle Point was stated, in the reports -of the "Geological Survey of Canada," to be twelve or fourteen feet -in thickness, and besides these specimens it contained fossil plants -referable to the species _Calamites inornatus_ and _Lepidodendron -primævum_, and I not unnaturally supposed that the Sporangites might -be the fruit of the latter plant. I also noticed their resemblance -to the spore-cases of _L. corrugatum_ of the Lower Carboniferous (a -Lepidodendron allied to _L. primævum_), and to those from Brazil -described by Carruthers under the name _Flemingites_, as well as to those -described by Huxley from certain English coals, and to those of the -Tasmanite or white coal of Australia. The bed at Kettle Point is shown to -be marine by its holding the sea-weed known as _Spirophyton_, and shells -of _Lingula_. - -The subject did not again come under my notice till 1882, when Prof. -Orton, of Columbus, Ohio, sent me some specimens from the Erian shales -of that State, which on comparison seemed undistinguishable from -_Sporangites Huronensis_.[AL] Prof. Orton read an interesting paper on -these bodies, at the meeting of the American Association in Montreal, in -which were some new and striking facts. One of these was the occurrence -of such bodies throughout the black shales of Ohio, extending "from the -Huron River, on the shore of Lake Brie, to the mouth of the Scioto, in -the Ohio Valley, with an extent varying from ten to twenty miles in -breadth," and estimated to be three hundred and fifty feet in thickness. -I have since been informed by my friend Mr. Thomas, of Chicago, that its -thickness, in some places at least, must be three times that amount. -About the same time. Prof. Williams, of Cornell, and Prof. Clarke, of -Northampton, announced similar discoveries in the State of New York, -so that it would appear that beds of vast area and of great thickness -are replete with these little vegetable discs, usually converted into -a highly bituminous, amber-like substance, giving a more or less -inflammable character to the containing rock. - -[AL] These shales have been described, as to their chemical and -geological relations, by Dr. T. Sterry Hunt, "American Journal of -Science," 1863, and by Dr. Newberry, in the "Reports of the Geological -Survey of Ohio," vol. i., 1863, and vol. iii., 1878. - -Another fact insisted on by Prof. Orton was the absence of Lepidodendroid -cones, and the occurrence of filamentous vegetable matter, to which the -Sporangites seemed to be in some cases attached in groups. Prof. Orton -also noticed the absence of the trigonal form, which belongs to the -spores of many Lepidodendra, though this is not a constant character. In -the discussion on Prof. Orton's paper, I admitted that the facts detailed -by him shook my previous belief of the lycopodiaceous character of these -bodies, and induced me to suspect, with Prof. Orton, that they might have -belonged to some group of aquatic plants lower than the Lycopods. - -Since the publication of my paper on Rhizocarps in the Palæozoic period -above referred to, I have received two papers from Mr. Edward Wethered, -F. G. S., in one of which he describes spores of plants found in the -lower limestone shales of the Forest of Dean, and in the other discusses -more generally the structure and origin of Carboniferous coal-beds.[AM] -In both papers he refers to the occurrence in these coals and shales of -organisms essentially similar to the Erian spores. - -[AM] "Cotteswold Naturalists' Field Club," 1884; "Journal of the Royal -Microscopical Society," 1885. - -In the "Bulletin of the Chicago Academy of Science," January, 1884, Dr. -Johnson and Mr. Thomas, in their paper on the "Microscopic Organisms -of the Boulder Clay of Chicago and Vicinity," notice _Sporangites -Huronensis_ as among these organisms, and have discovered them also in -large numbers in the precipitate from Chicago city water-supply. They -refer them to the decomposition of the Erian shales, of which boulders -filled with these organisms are of frequent occurrence in the Chicago -clays. The Sporangites and their accompaniments in the boulder clay are -noticed in a paper by Dr. G. M. Dawson, in the "Bulletin of the Chicago -Academy," June, 1885. - -Prof. Clarke has also described, in the "American Journal of Science" -for April, 1885, the forms already alluded to, and which he finds to -consist of macrospores enclosed in sporocarps. He compares these with my -_Sporangites Huronensis_ and _Protosalvinia bilobata_, but I think it is -likely that one of them at least is a distinct species. - -I may add that in the "Geological Magazine" for 1875, Mr. Newton, F. -G. S., of the Geological Survey of England, published a description -of the Tasmanite and Australian white coal, in which he shows that the -organisms in these deposits are similar to my _Sporangites Huronensis_, -and to the macrospores previously described by Prof. Huxley, from the -Better-bed coal. Mr. Newton does not seem to have been aware of my -previous description of _Sporangites_, and proposes the name _Tasmanites -punctatus_ for the Australian form. - -Here we have the remarkable fact that the waste macrospores, or larger -spores of a species of Cryptogamous plant, occur dispersed in countless -millions of tons through the shales of the Erian in Canada and the United -States. - -No certain clue seemed to be afforded by all these observations as to -the precise affinities of these widely distributed bodies; but this was -furnished shortly after from an unexpected quarter. In March, 1883, Mr. -Orville Derby, of the Geological Survey of Brazil, sent me specimens -found in the Erian of that country, which seemed to throw a new light on -the whole subject. These I described and pointed out their connection -with _Sporangites_ at the meeting of the American Association at -Minneapolis, in 1883, and subsequently published my notes respecting them -in its proceedings, and in the "Canadian Record of Science." - -Mr. Derby's specimens contained the curious spiral sea-weed known as -_Spirophyton_, and also minute rounded Sporangites like those obtained -in the Erian of Ohio, and of which specimens had been sent to me some -years before by the late Prof. Hartt. But they differed in showing the -remarkable fact that these rounded bodies are enclosed in considerable -numbers in spherical and oval sacs, the walls of which are composed of -a tissue of hexagonal cells, and which resemble in every respect the -involucres or spore-sacs of the little group of modern acrogens known as -Rhizocarps, and living in shallow water. More especially they resemble -the sporocarps of the genus _Salvinia_. This fact opened up an entirely -new field of investigation, and I at once proceeded to compare the -specimens with the fructification of modern Rhizocarps, and found that -substantially these multitudinous spores embedded in the Erie shales may -be regarded as perfectly analogous to the larger spores of the modern -_Salvinia natans_ of Europe, as may be seen by the representation of them -in Fig. 16. - -[Illustration: Fig. 16.--_Sporangites_ (_Protosalvinia_). A, _Sporangites -Braziliensis_, natural size, AX, Same, magnified, B, _Sp. biloba_, -natural size, C, Detached macrospores. D, Spore-cases of Salvinia natans. -DX, Same, magnified. E, Shale with sporangites, vertical section, highly -magnified.] - -The typical macrospores from the Erian shales are perfectly circular -in outline, and in the flattened state appear as discs with rounded -edges, their ordinary diameter being from one seventy-fifth to one -one-hundredth of an inch, though they vary considerably in size. This, -however, I do not regard as an essential character. The edges, as seen -in profile, are smooth, but the flat surface often presents minute dark -spots, which at first I mistook for papillæ, but now agree with Mr. -Thomas in recognising them as minute pores traversing the wall of the -disc, and similar to those which Mr. Newton has described in Tasmanite, -and which Mr. Wethered has also recognised in the similar spores of the -Forest of Dean shales. The walls also sometimes show faint indications -of concentric lamination, as if they had been thickened by successive -deposits. - -As seen by transmitted light, and either in front or in profile, the -discs are of a rich amber colour, translucent and structureless, except -the pores above referred to. The walls are somewhat thick, or from -one-tenth to one-twentieth the diameter of the disc in thickness. They -never exhibit the triradiate marking seen in spores of Lycopods, nor -any definite point of attachment, though they sometimes show a minute -elongated spot which may be of this nature, and they are occasionally -seen to have opened by slits on the edge or front, where there would seem -to have been a natural line of dehiscence. The interior is usually quite -vacant or structureless, but in some cases there are curved internal -markings which may indicate a shrunken lining membrane, or the remains of -a prothallus or embryo. Occasionally a fine granular substance appears in -the interior, possibly remains of microspores. - -The discs are usually detached and destitute of any envelope, but -fragments of flocculent cellular matter are associated with them, and -in one specimen from the corniferous limestone of Ohio, in Mr. Thomas's -collection, I have found a group of eight or more discs partly enclosed -in a cellular sac-like membrane of similar character to that enclosing -the Brazilian specimens already referred to. - -The characters of all the specimens are essentially similar, and -there is a remarkable absence of other organisms in the shale. In one -instance only, I have observed a somewhat smaller round body with a -dark centre or nucleus, and a wide translucent margin, marked by a -slight granulation. Even this, however, may indicate nothing more than a -different state of preservation. - -It is proper to observe here that the wall or enclosing sac of these -macrospores must have been of very dense consistency, and now appears -as a highly bituminous substance, in this agreeing with that of the -spores of Lycopods, and, like them, having been when recent of a highly -carbonaceous and hydrogenous quality, very combustible and readily -admitting of change into bituminous matter. In the paper already referred -to, on spore-cases in coals, I have noticed that the relative composition -of lycopodium and cellulose is as follows: - -Cellulose, C{24}H{20}O{20}. - -Lycopodium, C{42}H{19-4/12}NO{5-6/10}. - -Thus, such spores are admirably suited for the production of highly -carbonaceous or bituminous coals, etc. - -Nothing is more remarkable in connection with these bodies than their -uniformity of structure and form over so great areas and throughout so -great thickness of rock, and the absence of any other kind of spore-case. -This is more especially noteworthy in contrast with the coarse coals and -bituminous shales of the Carboniferous, which usually contain a great -variety of spores and sporangia, indicating the presence of many species -of acrogenous plants, while the Erian shales, on the contrary, indicate -the almost exclusive predominance of one form. This contrast is well -seen in the Bedford shales overlying these beds, and I believe Lower -Carboniferous.[AN] Specimens of these have been kindly communicated to me -by Prof. Orton, and have been prepared by Mr. Thomas. In these we see the -familiar Carboniferous spores with triradiate markings called _Triletes_ -by Reinsch, and which are similar to those of Lycopodiaceous plants. -Still more abundant are those spinous and hooked spores or sporangia, -to which the names _Sporocarpon_, _Zygosporites_, and _Traquaria_ have -been given, and some of which Williamson has shown to be spores of -Lycopodiaceous plants.[AO] - -[AN] According to Newberry, lower part of Waverly group. - -[AO] _Traquaria_ is to be distinguished from the calcareous bodies found -in the corniferous limestone of Kelly's Island, which I have described -in the "Canadian Naturalist" as _Saccamina Eriana_, and believe to be -Foraminiferal tests. They have since been described by Ulrich under a -different name (_Moellerina_: contribution to "American Palæontology," -1886). See Dr. Williamson's papers in "Transactions of Royal Society of -London." - -The true "Sporangites," on the contrary, are round and smooth, with thick -bituminous walls, which are punctured with minute transverse pores. In -these respects, as already stated, they closely resemble the bodies found -in the Australian white coal and Tasmanite. The precise geological age of -this last material is not known with certainty, but it is believed to be -Palæozoic. - -With reference to the mode of occurrence of these bodies, we may note -first their great abundance and wide distribution. The horizontal range -of the bed at Kettle Point is not certainly known, but it is merely a -northern outlier of the great belt of Erian shales referred to by Prof. -Orton, and which extends, with a breadth of ten to twenty miles, and of -great thickness, across the State of Ohio, for nearly two hundred miles. -This Ohio black shale, which lies at the top of the Erian or the base of -the Carboniferous, though probably mainly of Erian age, appears to abound -throughout in these organisms, and in some beds to be replete with them. -In like manner, in Brazil, according to Mr. Derby, these organisms are -distributed over a wide area and throughout a great thickness of shale -holding _Spirophyton_, and apparently belonging to the Upper Erian. The -recurrence of similar forms in the Tasmanite and white coal of Tasmania -and Australia is another important fact of distribution. To this we -may add the appearance of these macrospores in coals and shales of the -Carboniferous period, though there in association with other forms. - -It is also to be observed that the Erian shales, and the Forest of Dean -beds described by Wethered, are marine, as shown by their contained -fossils; and, though I have no certain information as to the Tasmanite -and Australian white coal, they would seem, from the description of -Milligan, to occur in distinctly aqueous, possibly estuarine, deposits. -Wethered has shown that the discs described by Huxley and Newton in -the Better-bed coal occur in the earthy or fragmentary layers, as -distinguished from the pure coal. Those occurring in cannel coal are -in the same case, so that the general mode of occurrence implies -water-driftage, since, in the case of bodies so large and dense, -wind-driftage to great distances would be impossible. - -These facts, taken in connection with the differences between these -macrospores and those of any known land-plant of the Palæozoic, would -lead to the inference that they belonged to aquatic plants, and these -vastly abundant in the waters of the Erian and Carboniferous periods. - -It is still further to be observed that they are not, in the Erian beds, -accompanied with any remains of woody or scalariform tissues, such -as might be expected in connection with the _débris_ of terrestrial -acrogens, and that, on the other hand, we find them enclosed in cellular -sporocarps, though in the majority of cases these have been removed by -dehiscence or decay. - -These considerations, I think, all point to the probability which I -have suggested in my papers on this subject referred to above, that we -have in these objects the organs of fructification of plants belonging -to the order _Rhizocarpeæ_, or akin to it. The comparisons which I have -instituted with the sporocarps and macrospores of these plants confirm -this suggestion. Of the modern species which I have had an opportunity -to examine, _Salvinia natans_ of Europe perhaps presents the closest -resemblance. In this plant groups of round cellular sporocarps appear -at the bases of the floating fronds. They are about a line in diameter -when mature, and are of two kinds, one containing macrospores, the -other microspores or antheridia. The first, when mature, hold a number -of closely packed globular or oval sporangia of loose cellular tissue, -attached to a central placenta. Each of these sporangia contains a single -macrospore, perfectly globular and smooth, with a dense outer membrane -(exhibiting traces of lamination, and showing within an irregularly -vacuolated or cellular structure, probably a prothallus). I cannot detect -in it the peculiar pores which appear in the fossil specimens. Each -macrospore is about one-seventieth of an inch in diameter when mature. -The sporocarps of the microspores contain a vastly greater number of -minute sporangia, about one two-hundredths of an inch in diameter. These -contain disc-like antheridia, or microspores of very minute size. - -The discs from Kettle Point and from the Ohio black shale, and from the -shale boulders of the Chicago clays, are similar to the macrospores of -_Salvinia_, except that they have a thicker wall and are a little less in -diameter, being about one-eightieth of an inch. The Brazilian sporocarps -are considerably larger than those of the modern _Salvinia_, and the -macrospores approach in size to those of the modern species, being one -seventy-fifth of an inch in diameter. They also seem, like the modern -species, to have thinner walls than those from Canada, Ohio, and Chicago. -No distinct indication has been observed in the fossil species of the -inner Sporangium of _Salvinia_. Possibly it was altogether absent, but -more probably it is not preserved as a distinct structure. - -With reference to the microspores of _Salvinia_, it is to be observed -that the sporocarps, and the contained spores or antheridia, are very -delicate and destitute of the dense outer wall of the macrospores. -Hence such parts are little likely to have been preserved in a fossil -state; and in the Erian shales, if present, they probably appear merely -as flocculent carbonaceous matter not distinctly marked, or as minute -granules not well defined, of which there are great quantities in some of -the shales. - -The vegetation appertaining to the Sporangites has not been distinctly -recognised. I have, however, found in one of the Brazilian specimens two -sporocarps attached to what seems a fragment of a cellular frond, and -numerous specimens of the supposed Algæ, named _Spirophyton_, are found -in the shales, but there is no evidence of any connection of this plant -with the _Protosalvinia_. - -Modern Rhizocarps present considerable differences as to their vegetative -parts. Some, like _Pilularia_, have simple linear leaves; others, like -_Marsilea_, have leaves in whorls, and cuneate in form; while others, -like _Azolla_ and _Salvinia_, have frondose leaves, more or less pinnate -in their arrangement. If we inquire as to fossils representing these -forms of vegetation, we shall find that some of the plants to be noticed -in the immediate sequel may have been nearly allied to the Rhizocarps. -In the mean time I may state that I have proposed the generic name -_Protosalvinia_ for these curious macrospores and their coverings, and -have described in the paper in the "Bulletin of the Chicago Academy of -Sciences," already quoted, five species which may be referred to this -genus. - -These facts lead to inquiries as to the origin of the bituminous matter -which naturally escapes from the rocks of the earth as petroleum and -inflammable gas, or which may be obtained from certain shales in -these forms by distillation. These products are compounds of carbon -and hydrogen, and may be procured from recent vegetable substances by -destructive distillation. Some vegetable matters, also, are much richer -in carbon and hydrogen than others, and it is a remarkable fact that -the spores of certain cryptogamous plants are of this kind, as we see in -the inflammable character of the dry spores of Lycopodium; and we know -that the slow putrefaction of such material underground effects chemical -changes by which bituminous matter can be produced. There is, therefore, -nothing unreasonable in the supposition advanced by Prof. Orton, that the -spores so abundantly contained in the Ohio black shales are important -or principal sources of the bituminous matter which they contain. -Microscopic sections of this shale show that much of its material -consists of the rich bituminous matter of these spores (Fig. 16). At the -same time, while we may trace the bitumen of these shales, and of some -beds of coal, to this cause, we must bear in mind that there are other -kinds of bituminous rocks which show no such structures, and may have -derived their combustible material from other kinds of vegetable matter, -whether of marine or of land plants. We shall better understand this when -we have considered the origin of coal. - -The macrospores above referred to may have belonged to humble aquatic -plants mantling the surfaces of water or growing up from the bottom, and -presenting little aërial vegetation. But there are other Erian plants, -as already mentioned, which, while of higher structure, may be of -Rhizocarpean affinities. - -One of these is the beautiful plant with whorls of wedge-shaped leaves, -to which the name _Sphenophyllum_ (see Fig. 20) has been given. Plants -referred to this genus have been described by Lesquereux from the upper -part of the Siluro-Cambrian,[AP] and a beautiful little species occurs -in the Erian shales of St. John, New Brunswick.[AQ] The genus is also -continued, and is still more abundant, in the Carboniferous. Many years -ago I observed, in a beautiful specimen collected by Sir W. E. Logan, in -New Brunswick, that the stem of this plant had an axis of reticulated and -scalariform vessels, and an outer bark.[AR] Renault and Williamson have -more recently obtained more perfect specimens, and the former has figured -a remarkably complex triangular axis, containing punctate and barred -vessels, and larger punctate vessels filling in its angles. Outside of -this there is a cellular inner bark, and this is surrounded by a thick -fibrous envelope. That a structure so complex should belong to a plant so -humble in its affinities is one of the strange anomalies presented by the -old world, and of which we shall find many similar instances. The fruit -of _Sphenophyllum_ was borne in spikes, with little whorls of bracts or -rudimentary leaves bearing round sporocarps. - -[AP] "American Journal of Science." - -[AQ] Dawson, "Report on Devonian Plants," 1870. - -[AR] "Journal of the Geological Society," 1865. - -[Illustration: Fig. 17.--_Ptilophyton plumosum_ (Lower Carboniferous, -Nova Scotia). Natural size and magnified.] - -A second type of plant, which may have been Rhizocarpean in its -affinities, is that to which I have given the name _Ptilophyton_.[AS] -It consists of beautiful feathery fronds, apparently bearing on parts -of the main stem or petiole small rounded sporocarps. They are found -abundantly in the Middle Erian of the State of New York, and also occur -in Scotland, while one species appears to occur in Nova Scotia, as high -as the Lower Carboniferous (Figs. 17, 18). - -[AS] _Plumalina_ of Hall. - -[Illustration: Fig. 18.--_Ptilophyton Thomsoni_ (Scotland), _a_, -Impression of plant in vernation, _b_, Branches conjecturally restored, -_c_, Branches of _Lycopodites Milleri_, on same slab.] - -These organisms have been variously referred to Lycopods, to Algæ, or to -Zoöphytes, but an extended comparison of American and Scottish specimens -has led me to the belief that they were aquatic plants, more likely to -have been allied to Rhizocarps than to any other group. Some evidence of -this will be given in a note appended to this chapter. - -[Illustration: Fig. 19.--_Psilophyton princeps_, restored (Lower -Erian, Gaspé). _a_, Fruit, natural size. _b_, stem, natural size, _c_, -Scalariform tissue of the axis, highly magnified. In the restoration, one -side is represented in vernation and the other in fruit.] - -Another genus, which I have named _Psilophyton_[AT] (Figs. 19, 21), may -be regarded as a connecting link between the Rhizocarps and the Lycopods. -It is so named from its resemblance, in some respects, to the curious -parasitic Lycopods placed in the modern genus _Psilotum_. Several species -have been described, and they are eminently characteristic of the Lower -Erian, in which they were first discovered in Gaspé. The typical species, -_Psilophyton princeps_, which fills many beds of shale and sandstone in -Gaspé Bay and the head of the neighbouring Bay des Chaleurs with its -slender stems and creeping, cord-like rhizomes, may be thus described: - -[AT] "Journal of the Geological Society," vols, xv., xviii., and xix., -"Report on Devonian Plants of Canada," 1871. - -Stems branching dichotomously, and covered with interrupted ridges. -Leaves rudimentary, or short, rigid, and pointed; in barren stems, -numerous and spirally arranged; in fertile stems and branchlets, sparsely -scattered or absent; in decorticated specimens, represented by a minute -punctate scars. Young branches circinate; rhizomata cylindrical, covered -with hairs or ramenta, and having circular areoles irregularly disposed, -giving origin to slender cylindrical rootlets. Internal structure--an -axis of scalariform vessels, surrounded by a cylinder of parenchymatous -cells, and by an outer cylinder of elongated woody cells. Fructification -consisting of naked oval spore-cases, borne usually in pairs on slender, -curved pedicels, either lateral or terminal. - -[Illustration: Fig. 20.--_Sphenophyllum antiquum_ (Erian, New -Brunswick). See pp. 61, 67.] - -This species was fully described by me in the papers referred to above, -from specimens obtained from the rich exposures at Gaspé Bay, and which -enabled me to illustrate its parts more fully, perhaps, than those of any -other species of so great antiquity. In the specimens I had obtained I -was able to recognise the forms of the rhizomata, stems, branches, and -rudimentary leaves, and also the internal structure of the stems and -rhizomata, and to illustrate the remarkable resemblance of the forms and -structures to those of the modern _Psilotum_. The fructification was, -however, altogether peculiar, consisting of narrowly ovate sporangia, -borne usually in pairs, on curved and apparently rigid petioles. Under -the microscope these sporangia show indications of cellular structure, -and appear to have been membranous in character. In some specimens -dehiscence appears to have taken place by a slit in one side, and, clay -having entered into the interior, both walls of the spore-case can be -seen. In other instances, being flattened, they might be mistaken for -scales. No spores could be observed in any of the specimens, though in -some the surface was marked by slight, rounded prominences, possibly the -impressions of the spores within. This peculiar and very simple style -of spore-case is also characteristic of other species, and gives to -_Psilophyton_ a very distinct generic character. These naked spore-cases -may be compared to those of such lycopodiaceous plants as _Psilotum_, -in which the scales are rudimentary. They also bear some resemblance, -though on a much larger scale, to the spore-cases of some Erian ferns -(_Archæopteris_), to be mentioned in the sequel. On the whole, however, -they seem most nearly related to the sporocarps of the Rhizocarpeæ. - -[Illustration: Fig. 21.--_Lepidodendron_ and _Psilophyton_ (Erian, New -Brunswick). A, _Lepidodendron Gaspianum_. B, C, _Psilophyton elegans_.] - -_Arthrostigma_, which is found in the same beds with Psilophyton, was a -plant of more robust growth, with better-developed, narrow, and pointed -leaves, borne in a verticillate or spiral manner, and bearing at the -ends of its branches spikes of naked sporocarps, apparently similar to -those of _Psilophyton_ but more rounded in form. The two genera must -have been nearly related, and the slender branchlets of _Arthrostigma_ -are, unless well preserved, scarcely distinguishable from the stems of -_Psilophyton_.[AU] - -[AU] Reports of the author on "Devonian Plants," "Geological Survey of -Canada," which see for details as to Erian Flora of northeastern America. - -If, now, we compare the vegetation of these and similar ancient plants -with that of modern Rhizocarps, we shall find that the latter still -present, though in a depauperated and diminished form, some of the -characteristics of their predecessors. Some, like _Pilularia_, have -simple linear leaves; others, like _Marsilea_, have leaves in verticils -and cuneate in form; while others, like Azolla and Salvinia, have -frondose leaves, more or less pinnate in their arrangement. The first -type presents little that is characteristic, but there are in the -Erian sandstones and shales great quantities of filamentous and linear -objects which it has been impossible to refer to any genus, and which -might have belonged to plants of the type of _Pilularia_. It is quite -possible, also, that such plants as _Psilophyton glabrum_ and _Cordaites -angustifolia_, of which the fructification is quite unknown, may have -been allied to Rhizocarps. With regard to the verticillate type, we are -at once reminded of _Sphenophyllum_ (Fig. 20), which many palæobotanists -have referred to the _Marsiliacæ_, though, like other Palæozoic Acrogens, -it presents complexities not seen in its modern representatives. _S. -primævum_ of Lesquereux is found in the Hudson River group, and my -_S. antiquum_ in the Middle Erian. Besides these, there are in the -Silurian and Erian beds plants with verticillate leaves which have -been placed with the Annulariæ, but which may have differed from them -in fructification. _Annularia laxa_, of the Erian, and _Protannularia -Harknessii_, of the Siluro-Cambrian, may be given as examples, and must -have been aquatic plants, probably allied to Rhizocarps. It is deserving -of notice, also, that the two best-known species of _Psilophyton_ -(_P. princeps_ and _P. robustius_), while allied to Lycopods by the -structure of the stem and such rudimentary foliage as they possess, are -also allied, by the form of their fructification, to the Rhizocarps, -and not to ferns, as some palæobotanists have incorrectly supposed. A -similar remark applies to _Arthrostigma_; and the beautiful pinnately -leaved _Ptilophyton_ may be taken to represent that type of foliage as -seen in modern Rhizocarps, while the allied forms of the Carboniferous -which Lesquereux has named _Trochophyllum_, seem to have had sporocarps -attached to the stem in the manner of _Azolla_. - -The whole of this evidence, I think, goes to show that in the Erian -period there were vast quantities of aquatic plants, allied to the modern -Rhizocarps, and that the so-called _Sporangites_ referred to in this -paper were probably the drifted sporocarps and macrospores of some of -these plants, or of plants allied to them in structure and habit, of -which the vegetative organs have perished. I have shown that in the Erian -period there were vast swampy flats covered with _Psilophyton_, and in -similar submerged tracts near to the sea the _Protosalvinia_ may have -filled the waters and have given off the vast multitudes of macrospores -which, drifted by currents, have settled in the mud of the black shales. -We have thus a remarkable example of a group of plants reduced in modern -times to a few insignificant forms, but which played a great role in the -ancient Palæozoic world. - -Leaving the Rhizocarps, we may now turn to certain other families of -Erian plants. The first to attract our attention in this age would -naturally be the Lycopods, the club-mosses or ground-pines, which in -Canada and the Eastern States carpet the ground in many parts of our -woods, and are so available for the winter decoration of our houses -and public buildings. If we fancy one of these humble but graceful -plants enlarged to the dimensions of a tree, we shall have an idea of -a _Lepidodendron_, or of any of its allies (Figs. 15, 21). These large -lycopodiaceous trees, which in different specific and generic forms were -probably dominant in the Erian woods, resembled in general those of -modern times in their fruit and foliage, except that their cones were -large, and probably in most cases with two kinds of spores, and their -leaves were also often very long, thus bearing a due proportion to the -trees which they clothed. Their thick stems required, however, more -strength than is necessary in their diminutive successors, and to meet -this want some remarkable structures were introduced similar to those -now found only in the stems of plants of higher rank. The cells and -vessels of all plants consist of thin walls of woody matter, enclosing -the sap and other contents of these sacs and tubes, and when strength is -required it is obtained by lining their interior with successive coats -of the hardest form of woody matter, usually known as lignin. But while -the walls remain thin, they afford free passage to the sap to nourish -every part. If thickened all over, they would become impervious to sap, -and therefore unsuited to one of their most important functions. These -two ends of strength and permeability are secured by partial linings of -lignin, leaving portions of the original wall uncovered. But this may be -done in a great variety of ways. - -The most ancient of these contrivances, and one still continued in the -world of plants, is that of the barred or scalariform vessel. This may -be either square or hexagonal, so as to admit of being packed without -leaving vacancies. It is strengthened by a thick bar of ligneous matter -up each angle, and these are connected by cross-bars so as to form a -framework resembling several ladders fastened together. Hence the name -_scalariform_, or ladder-like. Now, in a modern Lycopod there is a -central axis of such barred vessels associated with simpler fibres or -elongated cells. Even in _Sphenophyllum_ and _Psilophyton_, already -referred to as allied to Rhizocarps,[AV] there is such a central axis, -and in the former rigidity is given to this by the vascular and woody -elements being arranged in the form of a three-sided prism or three-rayed -star. But such arrangements would not suffice for a tree, and hence -in the arboreal Lycopods of the Erian age a more complex structure is -introduced. The barred vessels were expanded in the first instance into -a hollow cylinder filled in with pith or cellular tissue, and the outer -rind was strengthened with greatly thickened cells. But even this was not -sufficient, and in the older stems wedge-shaped bundles of barred tissue -were run out from the interior, forming an external woody cylinder, and -inside of the rind were placed bundles of tough bast fibres. Thus, a stem -was constructed having pith, wood, and bark, and capable of additions to -the exterior of the woody wedges by a true exogenous growth. The plan -is, in short, the same with that of the stems of the exogenous trees of -modern times, except that the tissues employed are less complicated. -The structures of these remarkable trees, and the manner in which -they anticipate those of the true exogens of modern times, have been -admirably illustrated by Dr. Williamson, of Manchester. His papers, it -is true, refer to these plants as existing in the Carboniferous age, but -there is every reason to believe that they were of the same character -in the Erian. The plan is the same with that now seen in the stems of -exogenous phænogams, and which has long ceased to be used in those of the -Lycopods. In this way, however, large and graceful lycopodiaceous trees -were constructed in the Erian period, and constituted the staple of its -forests. - -[AV] First noticed by the author, "Journal of Geological Society," 1865; -but more completely by Renault, "Comptes Rendus," 1870. - -The roots of these trees were equally remarkable with their stems, and -so dissimilar to any now existing that botanists were long disposed to -regard them as independent plants rather than roots. They were similar -in general structure to the stems to which they belonged, but are -remarkable for branching in a very regular manner by bifurcation like -the stems above, and for the fact that their long, cylindrical rootlets -were arranged in a spiral manner and distinctly articulated to the root -after the manner of leaves rather than of rootlets, and fitting them for -growing in homogeneous mud or vegetable muck. They are the so-called -_Stigmaria_ roots, which, though found in the Erian and belonging to -its lycopodiaceous plants, attained to far greater importance in the -Carboniferous period, where we shall meet with them again. - -There were different types of lycopodiaceous plants in the Erian. In -addition to humble Lycopods like those of our modern woods and great -Lepidodendra, which were exaggerated Lycopods, there were thick-stemmed -and less graceful species with broad rhombic scars (_Leptophleum_), and -others with the leaf-scars in vertical rows (_Sigillaria_), and others, -again, with rounded leaf-scars, looking like the marks on Stigmaria, and -belonging to the genus _Cyclostigma_. Thus some variety was given to the -arboreal club-mosses of these early forests. (See Fig. 15.) - -[Illustration: Fig. 22.--Erian ferns (New Brunswick), A, _Aneimites -obtusa_. C, _Neuropteris polymorpha_. F, _Sphenopteris pilosa_. N, -_Hymenophyllites subfurcatus_.] - -Another group of plants which attained to great development in the Erian -age is that of the Ferns or Brackens. The oldest of these yet known -are found in the Middle Erian. The _Eopteris_ of Saporta, from the -Silurian, at one time supposed to carry this type much further back, -has unfortunately been found to be a mere imitative form, consisting of -films of pyrites of leaf-like shapes, and produced by crystallisation. -In the Middle Erian, however, more especially in North America, many -species have been found (Figs. 22 to 24).[AW] I have myself recorded -more than thirty species from the Middle Erian of Canada, and these -belong to several of the genera found in the Carboniferous, though -some are peculiar to the Erian. Of the latter, the best known are -perhaps those of the genus _Archæopteris_ (Fig. 24), so abundant in the -plant-beds of Kiltorcan in Ireland, as well as in North America. In this -genus the fronds are large and luxuriant, with broad obovate pinnules -decurrent, on the leaf-stalk, and with simple sac-like spore-cases -borne on modified pinnæ. Another very beautiful fern found with -_Archæopteris_ is that which I have named _Platyphyllum_, and which grew -on a creeping stem or parasitically on stems of other plants, and had -marginal fructification.[AX] Another very remarkable fern, which some -botanists have supposed may belong to a higher group than the ferns, is -Megalopteris (Fig. 26). - -[AW] For descriptions of these ferns, see reports cited above. - -[AX] "Reports on Fossil Plants of the Devonian and Upper Silurian of -Canada," 1871, &c. - -[Illustration: Fig. 23.--Erian ferns (New Brunswick), B, _Cyclopteris -valida_, and pinnule enlarged, D, _Sphenopteris marginata_, and portion -enlarged. E, _Sphenopteris Harttii_. G, _Hymenophyllites curtilobus_. H, -_Hymenophyllites Gersdorffii_, and portion enlarged. I, _Alethopteris -discrepans_, K, _Pecopteris serrulata_, L, _Pecopteris preciosa_. M, -_Alethopteris Perleyi_.] - -[Illustration: Fig. 24.--_Archæopteris Jacksoni_, Dawson (Maine). An -Upper Erian fern, _a_, _b_, Pinnules showing venation.] - -[Illustration: Fig. 25.--An Erian tree-fern. _Caulopteris Lockwoodi_, -Dawson, reduced. (From a specimen from Gilboa, New York.)] - -Some of the Erian ferns attained to the dimensions of tree-ferns. Large -stems of these, which must have floated out far from land, have been -found by Newberry in the marine limestone of Ohio (_Caulopteris antiqua_ -and _C. peregrina_, Newberry),[AY] and Prof. Hall has found in the Upper -Devonian of Gilboa, New York, the remains of a forest of tree-ferns -standing _in situ_ with their great masses of aërial roots attached to -the soil in which they grew (_Caulopteris Lockwoodi_, Dn.).[AZ] - -[AY] "Journal of the Geological Society," 1871. - -[AZ] _Ibid._ - -[Illustration: Fig. 26.--_Megalopteris Dawsoni_, Hartt (Erian, New -Brunswick), _a_, Fragment of pinna. _b_, Point of pinnule, _c_, Venation, -(The midrib is not accurately given in this figure.)] - -These aërial roots introduce us to a new contrivance for strengthening -the stems of plants by sending out into the soil multitudes of cord-like -cylindrical roots from various heights on the stem, and which form -a series of stays like the cordage of a ship. This method of support -still continues in the modern tree-ferns of the tropics and the southern -hemisphere. In one kind of tree-fern stem from the Erian of New York, -there is also a special arrangement for support, consisting of a -series of peculiarly arranged radiating plates of scalariform vessels, -not exactly like those of an exogenous stem, but doing duty for it -(_Asteropteris_)[BA] Similar plants have been described from the Erian of -Falkenberg, in Germany, and of Saalfeld, in Thuringia, by Goeppert and -Unger, and are referred to ferns by the former, but treated as doubtful -by the latter,[BB] This peculiar type of tree-fern is apparently a -precursor of the more exogenous type of _Heterangium_, recently described -and referred to ferns by Williamson. Here, again, we have a mechanical -contrivance now restricted to higher plants appropriated by these old -cryptogams. - -[BA] "Journal of the Geological Society," London, 1881. - -[BB] "Sphenopteris Refracta," Goeppert; "Flora des Uebergangsgebirges." -"Cladoxylon Mirabile," Unger; "Palæontologie des Thuringer Waldes." - -[Illustration: Fig. 27.--_Calamites radiatus_ (Erian, New Brunswick).] - -The history of the ferns in geological time is remarkably different -from that of the Lycopods; for while the latter have long ago descended -from their pristine eminence to a very humble place in nature, the -former still, in the southern hemisphere at least, retain their arboreal -dimensions and ancient dominance. - -[Illustration: Fig. 28.--Asterophyllites (Erian, New Brunswick), A, -Asterophyllites latifolia. B, Do., apex of stem (?) fruit, C, -C^1, _A. scutigera_. D, _A. latifolia_, larger whorl of leaves. D^1, -Leaf.] - -The family of the _Equisetaceæ_, or mare's-tails, was also represented -by large species of _Calamites_ and by _Asterophyllites_ in the Erian; -but, as its headquarters are in the Carboniferous, we may defer its -consideration till the next chapter. (Figs. 27, 28.) - -Passing over these for the present, we find that the flowering plants are -represented in the Erian forests by at least two types of Gymnosperms, -that of _Taxineæ_ or yews, and an extinct family, that of the _Cordaites_ -(Figs. 30, 31). The yew-trees are closely allied to the pines and -spruces, and are often included with them in the family of _Coniferæ_. -They differ, however, in the habit of producing berries or drupe-like -fruits instead of cones, and there is some reason to believe that this -was the habit of the Erian trees of this group, though their wood in -some instances resembles rather that of the Araucaria, or Norfolk -Island pine, than that of the modern yews. These trees are chiefly -known to us by their mineralised trunks, which are often found like -drift-wood on modern sand-banks embedded in the Erian sandstones or -limestones. It often shows its structure in the most perfect manner in -specimens penetrated by calcite or silica, or by pyrite, and in which -the original woody matter has been resolved into anthracite or even into -graphite. These trees have true woody tissues presenting that beautiful -arrangement of pores or thin parts enclosed in cup-like discs, which is -characteristic of the coniferous trees, and which is a great improvement -on the barred tissue already referred to, affording a far more strong, -tough, and durable wood, such as we have in our modern pines and yews -(Fig. 29). - -[Illustration: Fig. 29.--_Dadoxylon Ouangondianum_, an Erian conifer, A, -Fragment showing Sternberg pith and wood; _a_, medullary sheath; _b_, -pith; _c_, wood; _d_, section of pith, B, Wood-cell; _a_, hexagonal -areole; _b_, pore, _c_, Longitudinal section of wood, showing, _a_, -areolation, and _b_, medullary rays, D, Transverse section, showing, -_a_, wood-cells, and _b_, limit of layer of growth, (B, C, D, highly -magnified.)] - -These primitive pines make their appearance in the Middle Erian, in -various parts of America, as well as in Scotland and Germany, and they -are represented by wood indicating the presence of several species. I -have myself indicated and described five species from the Erian of Canada -and the United States. From the fact that these trees are represented -by drifted trunks embedded in sandstones and marine limestones, we may, -perhaps, infer that they grew on the rising grounds of the Erian land, -and that their trunks were carried by river-floods into the sea. No -instance has yet certainly occurred of the discovery of their foliage or -fruit, though there are some fan-shaped leaves usually regarded as ferns -which may have belonged to such trees. These in that case would have -resembled the modern _Gingko_ of China, and some of the fruits referred -to the genus _Cardiocarpum_ may have been produced by them. Various -names have been given to these trees. I have preferred that given by -Unger, _Dadoxylon_, as being more non-committal as to affinities than the -others.[BC] Many of these trees had very long internal pith-cylinders, -with curious transverse tubulæ, and which, when preserved separately, -have been named _Sternbergia_. - -[BC] _Araucarites_, Goeppert; _Araucarioxylon_, Kraus. - -Allied to these trees, and perhaps intermediate between them and the -_Cycads_, were those known as _Cordaites_ (Fig. 30), which had trunks -resembling those of _Dadoxylon_, but with still larger _Sternbergia_ -piths and an internal axis of scalariform vessels, surrounded by a -comparatively thin woody cylinder. Some of them have leaves over a -foot in length, reminding one of the leaves of broad-leaved grasses or -iridaceous plants. Yet their flowers and fruit seem to have been more -nearly allied to the yews than to any other plants (Fig. 31). Their stems -were less woody and their piths larger than in the true pines, and some -of the larger-leaved species must have had thick, stiff branches. They -are regarded as constituting a separate family, intermediate between -pines and cycads, and, beginning in the Middle Devonian, they terminate -in the Permian, where, however, some of the most gigantic species occur. -In so far as the form and structure of the leaves, stems, and fruit are -concerned, there is marvellously little difference between the species -found in the Erian and the Permian. They culminated, however, in the -Carboniferous period, and the coal-fields of southern France have proved -so far the richest in their remains. - -[Illustration: Fig. 30.--_Cordaites Robbii_ (Erian, New Brunswick), -_a_, Group of young leaves. _b_, Point of leaf, _c_, Base of leaf, _d_. -Venation, magnified.] - -[Illustration: Fig. 31.--Erian fruits, &c., some gymnospermous, and -probably of _Cordaites_ and Taxine trees (St. John, New Brunswick), A, -_Cardiocarpum cornutum_. B, _Cardiocarpum acutum_. C, _Cardiocarpum -Crampii_. D, _Cardiocarpum Baileyi_. E, _Trigonocarpum racemosum_. -E^1, E^2, Fruits enlarged, F, _Antholithes Devonicus_. G, Annularia -acuminata, H, _Asterophyllites acicularis_. H^2, Fruit of the same, K, -_Cardiocarpum_ (? young of _A._), L, _Pinnularia dispalans_ (probably a -root).] - -Lastly, a single specimen, collected by Prof. James Hall, of Albany, -at Eighteen-mile Creek, Lake Erie, has the structure of an ordinary -angiospermous exogen, and has been described by me as _Syringoxylon -mirabile_.[BD] This unique example is sufficient to establish the fact -of the existence of such plants at this early date, unless some accident -may have carried a specimen from a later formation to be mixed with -Erian fossils. It is to be observed, however, that the non-occurrence of -any similar wood in all the formations between the Upper Erian and the -Middle Cretaceous suggests very grave doubt as to the authenticity of the -specimen. I record the fact, waiting further discoveries to confirm it. -Of the character of the specimen which I have described I entertain no -doubt. - -[BD] "Journal of the Geological Society," vol. xviii. - -We shall be better able to realise the significance and relations of this -ancient flora when we have studied that of the succeeding Carboniferous. -We may merely remark here on the fact that, in these forests of the -Devonian and in the marshes on their margins, we find a wonderful -expansion of the now modest groups of Rhizocarps and Lycopods, and that -the flora as a whole belongs to the highest group of Cryptogams and the -lowest of Phænogams, so that it has about it a remarkable aspect of -mediocrity. Further, while there is evidence of some variety of station, -there is also evidence of much equality of climate, and of a condition -of things more resembling that of the insular climates of the temperate -portions of the southern hemisphere than that of North America or Europe -at present. - -The only animal inhabitants of these Devonian woods, so far as known, -were a few species of insects, discovered by Hartt in New Brunswick, and -described by Dr. Scudder. Since, however, we now know that scorpions as -well as insects existed in the Silurian, it is probable that these also -occurred in the Erian, though their remains have not yet been discovered. -All the known insects of the Erian woods are allies of the shad-flies and -grasshoppers (_Neuroptera_ and _Orthoptera_), or intermediate between -the two. It is probable that the larvæ of most of them lived in water -and fed upon the abundant vegetable matter there, or on the numerous -minute crustaceans and worms. There were no land vertebrates, so far as -known, but there were fishes (_Dipterus_, etc.), allied to the modern -Barramunda or _Ceratodus_ of Australia, and with teeth suited for -grinding vegetable food. It is also possible that some of the smaller -plate-covered fishes (Placoganoids, like _Pterichthys_) might have fed -on vegetable matter, and, in any case, if they fed on lower animals, the -latter must have subsisted on plants. I mention these facts to show that -the superabundant vegetation of this age, whether aquatic or terrestrial, -was not wholly useless to animals. It is quite likely, also, that we have -yet much to learn of the animal life of the Erian swamps and woods. - - -NOTES TO CHAPTER III. - -I.--Classification of Sporangites. - -It is, of course, very unsatisfactory to give names to mere fragments of -plants, yet it seems very desirable to have some means of arranging them. -With respect to the organisms described above, which were originally -called by me _Sporangites_, under the supposition that they were -Sporangia rather than spores, this name has so far been vindicated by the -discovery of the spore-cases belonging to them, so that I think it may -still be retained as a provisional name; but I would designate the whole -as _Protosalviniæ_, meaning thereby plants with rhizocarpean affinities, -though possibly when better understood belonging to different genera. We -may under these names speak of their detached discs as macrospores and of -their cellular envelopes as sporocarps. The following may be recognized -as distinct forms: - -1. _Protosalvinia Huronensis_, Dawson, _Syn._, _Sporangites Huronensis_, -"Report on Erian Flora of Canada," 1871.--Macrospores, in the form of -discs or globes, smooth and thick-walled, the walls penetrated by minute -radiating pores. Diameter about one one-hundredth of an inch, or a little -more, When in situ several macrospores are contained in a thin cellular -sporocarp, probably globular in form. From the Upper Erian, and perhaps -Lower Carboniferous shales of Kettle Point, Lake Huron, of various places -in the State of Ohio, and in the shale boulders of the boulder clay of -Chicago and vicinity. First collected at Kettle Point by Sir W. E. Logan, -and in Ohio by Prof. Edward Orton, and at Chicago by Dr. H. A. Johnson -and Mr. B. W. Thomas, also in New York by Prof. J. M. Clarke. - -The macrospores collected by Mr. Thomas from the Chicago clays and shales -conform closely to those of Kettle Point, and probably belong to the -same species. Some of them are thicker in the outer wall, and show the -pores much more distinctly. These have been called by Mr. Thomas _S. -Chicagoensis_, and may be regarded as a varietal form. Specimens isolated -from the shale and mounted dry, show what seems to have been the hilum or -scar of attachment better than those in balsam. - -Sections of the Kettle Point shale show, in addition to the macrospores, -wider and thinner shreds of vegetable matter, which I am inclined to -suppose to be remains of the sporocarps. - -2. _Protosalvinia_ (_Sporangites_) _Braziliensis_, Dawson, "Canadian -Record of Science," 1883.--Macrospores, round, smooth, a little longer -than those of the last species, or about one seventy-fifth of an inch -in diameter, enclosed in round, oval, or slightly reniform sporocarps, -each containing from four to twenty-four macrospores. Longest diameter -of sporocarps three to six millimetres. Structure of wall of sporocarps -hexagonal cellular. Some sporocarps show no macrospores, and may possibly -contain microspores. The specimens are from the Erian of Brazil. -Discovered by Mr. Orville Derby. The formation, according to Mr. Derby, -consists of black shales below, about three hundred feet thick, and -containing the fucoid known as Spirophyton, and probably decomposed -vegetable matter. Above this is chocolate and reddish shale, in which -the well-preserved specimens of Protosalvinia occur. These beds are very -widely distributed, and abound in _Protosalvinia_ and _Spirophyton_. - -3. _Protosalvinia_ (_Sporangites_) _bilobata_, Dawson, "Canadian -Record of Science," 1883.--Sporocarps, oval or reniform, three to six -millimetres in diameter, each showing two rounded prominences at the -ends, with a depression in the middle, and sometimes a raised neck or -isthmus at one side connecting the prominences. Structure of sporocarp -cellular. Some of the specimens indicate that each prominence or tubercle -contained several macrospores. At first sight it would be easy to mistake -these bodies for valves of _Beyrichia_. - -Found in the same formations with the last species, though, in so far as -the specimens indicate, not precisely in the same beds. Collected by Mr. -Derby. - -4. _Protosalvinia Clarkei_, Dawson, _P. bilobata_, Clarke, "American -Journal of Science."--Macrospores two-thirds to one millimetre in -diameter. One, two, or three contained in each sporocarp, which is -cellular. The macrospores have very thick walls with radiating tortuous -tubes. Unless this structure is a result of mineral crystallisation, -these macrospores must have had very thick walls and must have resembled -in structure the thickened cells of stone fruits and of the core of the -pear, or the tests of the Silurian and Erian seeds known as _Pachytheca_, -though on a smaller scale. - -It is to be observed that bodies similar to these occur in the Boghead -earthy bitumen, and have been described by Credner. - -I have found similar bodies in the so-called "Stellar coal" of the coal -district of Pictou, Nova Scotia, some layers of which are filled with -them. They occur in groups or patches, which seem to be enclosed in a -smooth and thin membrane or sporocarp. It is quite likely that these -bodies are generically distinct from _Protosalvinia_. - -5. _Protosalvinia punctata_, Newton, "Geological Magazine," New Series, -December 2d, vol. ii.--Mr. Newton has named the discs found in the -white coal and Tasmanite, _Tasmanites_, the species being _Tasmanites -punctatus_, but as my name _Sporangites_ had priority, I do not think it -necessary to adopt this term, though there can be little doubt that these -organisms are of similar character. The same remark may be made with -reference to the bodies described by Huxley and Newton as occurring in -the Better-bed coal. - -In Witham's "Internal Structure of Fossil Vegetables," 1833, Plate XI, -are figures of Lancashire cannel which shows _Sporangites_ of the type of -those in the Erian shales. Quekett, in his "Report on the Torbane Hill -Mineral," 1854, has very well figured similar structures from the Methel -coal and the Lesmahagow cannel coal. These are the earliest publications -on the subject known to me; and Quekett, though not understanding the -nature of the bodies he observed, holds that they are a usual ingredient -in cannel coals. - - -II.--The Nature and Affinities of Ptilophyton. - -(_Lycopodites Vanuxemii_ of "Report on Devonian and Upper Silurian -Plants," Part I., page 35, _L. plumula_ of "Report on Lower Carboniferous -Plants," page 24, Plate I., Figs. 7, 8, 9.) In the reports above referred -to, these remarkable pinnate, frond-like objects were referred to the -genus _Lycopodites_, as had been done by Goeppert in his description -of the European species _Lycopodites pennæformis_, which is very near -to the American Erian form. Since 1871, however, there have been many -new specimens obtained, and very various opinions expressed as to their -affinities. While Hall has named some of them _Plumalina_, and has -regarded them as animal structures, allied to hydroids, Lesquereux -has described some of the Carboniferous forms under the generic name -_Trochophyllum_, which is, however, more appropriate to plants with -verticillate leaves which are included in this genus. Before I had seen -the publications of Hall and Lesquereux on the subject, I had in a paper -on "Scottish Devonian Plants"[BE] separated this group from the genus -_Lycopodites_, and formed for it the genus _Ptilophyton_, in allusion -to the feather-like aspect of the species. My reasons for this, and my -present information as to the nature of these plants, may be stated -as follows: Schimper, in his "Palæontologie Vegetale" (possibly from -inattention to the descriptions or want of access to specimens), doubts -the lycopodiaceous character of species of _Lycopodites_ described in my -published papers on plants of the Devonian of America and in my Report of -1871. Of these, _L. Richardsoni_ and _L. Matthewi_ are undoubtedly very -near to the modern genus _Lycopodium_. _L. Vanuxemii_ is, I admit, more -problematical; but Schimper could scarcely have supposed it to be a fern -or a fucoid allied to _Caulerpa_ had he observed that both in my species -and the allied _L. pennæformis_ of Goeppert, which he does not appear to -notice, the pinnules are articulated upon the stem, and leave scars where -they have fallen off. When in Belfast in 1870, my attention was again -directed to the affinities of these plants by finding in Prof. Thomson's -collection a specimen from Caithness, which shows a plant apparently -of this kind, with the same long narrow pinna? or leaflets, attached, -however, to thicker stems, and rolled up in a circinate manner. It seems -to be a plant in vernation, and the parts are too much crowded and -pressed together to admit of being accurately figured or described; but -I think I can scarcely be deceived as to its true nature. The circinate -arrangement in this case would favour a relationship to ferns; but some -lycopodiaceous plants also roll themselves in this way, and so do the -branches of the plants of the genus _Psilophyton_. (Fig. 17, _supra_.) - -[BE] "Canadian Naturalist," 1878. - -The specimen consists of a short, erect stem, on which are placed -somewhat stout alternate branches, extending obliquely outward and then -curving inward in a circinate manner. The lower ones appear to produce -on their inner sides short lateral branchlets, and upon these, and also -upon the curved extremities of the branches, are long, narrow, linear -leaves placed in a crowded manner. The specimen is thus not a spike of -fructification, but a young stem or branch in vernation, and which when -unrolled would be of the form of those peculiar pinnate _Lycopodites_ -of which _L. Vanuxemii_ of the American Devonian and _L. pennæformis_ of -the European Lower Carboniferous are the types, and it shows, what might -have been anticipated from other specimens, that they were low, tufted -plants, circinate in vernation. The short stem of this plant is simply -furrowed, and bears no resemblance to a detached branch of Lycopodites -Milleri which lies at right angles to it on the same slab. As to the -affinities of the singular type of plants to which this specimen belongs, -I may quote from my "Report on the Lower Carboniferous Plants of Canada," -in which I have described an allied species, _L. plumula_: - -"The botanical relations of these plants must remain subject to doubt, -until either their internal structure or their fructification can be -discovered. In the mean time I follow Goeppert in placing them in what -we must regard as the provisional genus _Lycopodites_. On the one hand, -they are not unlike the slender twigs of _Taxodium_ and similar Conifers, -and the highly carbonaceous character of the stems gives some colour to -the supposition that they may have been woody plants. On the other hand, -they might, so far as form is concerned, be placed with Algæ of the type -of Brongniart's _Chondrites obtusus_, or the modern _Caulerpa plumaria_. -Again, in a plant of this type from the Devonian of Caithness to which -I have referred in a former memoir, the vernation seems to have been -circinate, and Schimper has conjectured that these plants may be ferns, -which seems also to have been the view of Shumard." - -On the whole, these plants are allied to Lycopods rather than to ferns; -and as they constitute a small but distinct group, known only, so far -as I am aware, in the Lower Carboniferous and Erian or Devonian, they -deserve a generic name, and I proposed for them in my "Paper on Scottish -Devonian Plants," 1878, that of _Ptilophyton_, a name sufficiently -distinct in sound from Psilophyton, and expressing very well their -peculiar feather-like habit of growth. The genus was defined as follows: - -"Branching plants, the branches bearing long, slender leaves in two or -more ranks, giving them a feathered appearance; vernation circinate. -Fruit unknown, but analogy would indicate that it was borne on the bases -of the leaves or on modified branches with shorter leaves." - -The Scottish specimen above referred to was named _Pt. Thomsoni_, and was -characterised by its densely tufted form and thick branches. The other -species known are: _Pt. pennæformis_, Goeppert, L. Carboniferous; _Pt. -Vanuxemii_, Dawson, Devonian; _Pt. plumula_, Dawson, L. Carboniferous. - -Shumard's _Filicites gracilis_, from the Devonian of Ohio, and Stur's -_Pinites antecedens_, from the Lower Carboniferous of Silesia, may -possibly belong to the same genus. The Scottish specimen referred to is -apparently the first appearance of this form in the Devonian of Europe. - -I have at a still later date had opportunities of studying considerable -series of these plants collected by Prof. Williams, of Cornell -University, and prepared a note in reference to them for the American -Association, of which, however, only an abstract has been published. -I have also been favoured by Prof. Lesquereux and Mr. Lacoe, of -Pittston, with the opportunity of studying the specimens referred to -_Trochophyllum_. - -Prof. Williams's specimens occur in a dark shale associated with -remains of land-plants of the genera _Psilophyton_. _Rhodea_, &c., -and also marine shells, of which a small species of _Rhynchonella_ is -often attached to the stems of the _Ptilophyton_. Thus these organisms -have evidently been deposited in marine beds, but in association with -land-plants. - -The study of the specimens collected by Prof. Williams develops the -following facts: (1) The plants are not continuous fronds, but slender -stems or petioles, with narrow, linear leaflets attached in a pinnate -manner. (2) The pinnules are so articulated that they break off, leaving -delicate transverse scars, and the lower parts of the stems are often -thus denuded of pinnæ for the length of one or more inches. (3) The -stems curve in such a manner as to indicate a circinate vernation. (4) -In a few instances the fronds were observed to divide dichotomously -toward the top; but this is rare. (5) There are no indications of cells -in the pinnules; but, on the other hand, there is no appearance of -fructification unless the minute granules which roughen some of the -sterns are of this nature. (6) The stems seem to have been lax and -flexuous, and in some instances they seem to have grown on the petioles -of ferns preserved with them in the same beds. (7) The frequency of the -attachment of small brachiopods to the specimens of _Ptilophyton_ would -seem to indicate that the plant stood erect in the water. (8) Some of -the specimens show so much carbonaceous matter as to indicate that the -pinnules were of considerable consistency. All these characters are those -rather of an aquatic plant than of an animal organism or of a land-plant. - -The specimens communicated by Prof. Lesquereux and Mr. Lacoe are from the -Lower Carboniferous, and evidently represent a different species with -similar slender pitted stems, often partially denuded of pinnules below; -but the pinnules are much broader and more distant. They are attached -by very narrow bases, and apparently tend to lie on a plane, though they -may possibly have been spirally arranged. On the same slabs are rounded -sporangia or macrospores like those of _Lepidodendron_, but there is no -evidence that these belonged to _Trochophyllum_. On the stems of this -plant, however, there are small, rounded bodies apparently taking the -places of some of the pinnules. These may possibly be spore-cases; but -they may be merely imperfectly developed pinnules. Still the fact that -similar small granules appear on the stems of the Devonian species, -favours the idea that they may be organs of fructification. - -The most interesting discovery, however, which results from the study -of Mr. Lacoe's specimens, is that the pinnules were cylindrical and -hollow, and probably served to float the plant. This would account for -many of the peculiarities in the appearance and mode of occurrence of the -Devonian _Ptilophyton_, which are readily explained if it is supposed to -be an aquatic plant, attaching itself to the stems of submerged vegetable -remains and standing erect in the water by virtue of its hollow leaves. -It may well, however, have been a plant of higher organisation than the -Algæ, though no doubt cryptogamous. - -The species of _Ptilophyton_ will thus constitute a peculiar group -of aquatic plants, belonging to the Devonian and Lower Carboniferous -periods, and perhaps allied to Lycopods and Pillworts in their -organisation and fruit, but specially distinguished by their linear -leaves serving as floats and arranged pinnately on slender stems. The -only species yet found within the limits of Canada is _Pt. plumula_, -found by Dr. Honeyman in the Lower Carboniferous of Nova Scotia; but as -_Pt. Vanuxemii_ abounds in the Erian of New York, it will no doubt be -found in Canada also. - - -III.--Tree-Ferns of the Erian Period. - -As the fact of the occurrence of true tree-ferns in rocks so old as the -Middle Erian or Devonian has been doubted in some quarters, the following -summary is given from descriptions published in the "Journal of the -Geological Society of London" (1871 and 1881), where figures of the -species will be found: - -Of the numerous ferns now known in the Middle and Upper Devonian of -North America, a great number are small and delicate species, which were -probably herbaceous; but there are other species which may have been -tree-ferns. Little definite information, however, has, until recently, -been obtained with regard to their habit of growth. - -The only species known to me in the Devonian of Europe is the -_Caulopteris Peachii_ of Salter, figured in the "Quarterly Journal of -the Geological Society" for 1858. The original specimen of this I had an -opportunity of seeing in London, through the kindness of Mr. Etheridge, -and have no doubt that it is the stem of a small arborescent fern, allied -to the genus _Caulopteris_, of the coal formation. - -In my paper on the Devonian of Eastern America ("Quarterly Journal -of the Geological Society," 1862), I mentioned a plant found by Mr. -Richardson at Perry, as possibly a species of _Megaphyton_, using that -term to denote those stems of tree-ferns which have the leaf-scars in -two vertical series; but the specimen was obscure, and I have not yet -obtained any other. - -More recently, in 1869, Prof. Hall placed in my hands an interesting -collection from Gilboa, New York, and Madison County, New York, including -two trunks surrounded by aërial roots, which I have described as -_Psaronius textilis_ and _P. Erianus_, in my "Revision of the Devonian -Flora," read before the Royal Society.[BF] In the same collection were -two very large petioles, _Rhachiopteris gigantea_ and _R. palmata_, which -I have suggested may have belonged to tree-ferns. - -[BF] Abstract in "Proceedings of the Royal Society," May, 1870; also -"Report on Erian Plants of Canada," 1871. - -My determination of the species of _Psaronius_, above mentioned, has -recently been completely confirmed by the discovery on the part of Mr. -Lockwood, of Gilboa, of the upper part of one of these stems, with its -leaf-scars preserved and petioles attached, and also by some remarkable -specimens obtained by Prof. Newberry, of New York, from the Corniferous -limestone of Ohio, which indicate the existence there of three species of -tree-ferns, one of them with aërial roots similar to those of the Gilboa -specimens. The whole of these specimens Dr. Newberry has kindly allowed -me to examine, and has permitted me to describe the Gilboa specimen, -as connected with those which I formerly studied in Prof. Hall's -collections. The specimens from Ohio he has himself named, but allows me -to notice them here by way of comparison with the others. I shall add -some notes on specimens found with the Gilboa ferns. - -It may be further observed that the Gilboa specimens are from a bed -containing erect stumps of tree-ferns, in the Chemung group of the Upper -Devonian, while those from Ohio are from a marine limestone, belonging to -the lower part of the Middle Devonian. - -1. _Caulopteris Lockwoodi_, Dawson.--Trunk from two to three inches in -diameter, rugose longitudinally. Leaf-scars broad, rounded above, and -radiatingly rugose, with an irregular scar below, arranged spirally in -about five ranks; vascular bundles not distinctly preserved. Petioles -slender, much expanded at the base, dividing at first in a pinnate -manner, and afterwards dichotomously. Ultimate pinnæ with remains of -numerous, apparently narrow pinnules. - -This stem is probably the upper part of one or other of the species -of _Psaronius_ found in the same bed (_P. Erianus_, Dawson, and _P. -textilis_, Dawson).[BG] It appears to have been an erect stem embedded -in situ in sandstone, and preserved as a cast. The stem is small, being -only two inches, or a little more, in diameter. It is coarsely wrinkled -longitudinally, and covered with large leaf-scars, each an inch in -diameter, of a horseshoe-shape. The petioles, five of which remain, -separate from these scars with a distinct articulation, except at one -point near the base, where probably a bundle or bundles of vessels passed -into the petiole. They retain their form at the attachment to the stem, -but a little distance from it they are flattened. They are inflated -at the base, and somewhat rapidly diminish in size. The leaf-scars -vary in form, and are not very distinct, but they appear to present -a semicircular row of pits above, largest in the middle. From these -there proceed downward a series of irregular furrows, converging to a -second and more obscure semicircle of pits, within or below which is the -irregular scar or break above referred to. The attitude and form of the -petioles will be seen from Fig. 24, _supra_. - -[BG] Memoir on Devonian Flora, "Proceedings of the Royal Society," May, -1870. - -The petioles are broken off within a few inches of the stem; but other -fragments found in the same beds appear to show their continuation, and -some remains of their foliage. One specimen shows a series of processes -at the sides, which seem to be the remains of small pinnæ, or possibly -of spines on the margin of the petiole. Other fragments show the -division of the frond, at first in a pinnate manner, and subsequently by -bifurcation; and some fragments show remains of pinnules, possibly of -fertile pinnules. These are very indistinct, but would seem to show that -the plant approached, in the form of its fronds and the arrangement of -its fructification, to the Cyclopterids of the sub-genus _Aneimites_, -one of which (_Aneimites Acadica_), from the Lower Carboniferous of Nova -Scotia, I have elsewhere described as probably a tree-fern,[BH] The -fronds were evidently different from those of _Archæopteris_[BI] a genus -characteristic of the same beds, but of very different habit of growth. -This accords with the fact that there is in Prof. Hall's collection a -mass of fronds of _Cyclopteris_ (_Archæopteris_) Jacksoni, so arranged -as to make it probable that the plant was an herbaceous fern, producing -tufts of fronds on short stems in the ordinary way. The obscurity of -the leaf-scars may render it doubtful whether the plant above described -should be placed in the genus _Caulopteris_ or in _Stemmatopteris_; but -it appears most nearly allied to the former. The genus is at present, -of course, a provisional one; but I have thought it only justice to the -diligent labours of Mr. Lockwood to name this curious and interesting -fossil _Caulopteris Lockwoodi_. - -[BH] "Quarterly Journal of the Geological Society," 1860. - -[BI] The genus to which the well-known _Cyclopteris_ (_Adiantites_) -_Hibernicus_ of the Devonian of Ireland belongs. - -I have elsewhere remarked on the fact that trunks, and petioles, and -pinnules of ferns are curiously dissociated in the Devonian beds--an -effect of water-sorting, characteristic of a period in which the -conditions of deposition were so varied. Another example of this is, -that in the sandstones of Gaspé Bay, which have not as yet afforded -any example of fronds of ferns, there are compressed trunks, which Mr. -Lockwood's specimens allow me at least to conjecture may have belonged -to tree-ferns, although none of them are sufficiently perfect for -description. - -Mr. Lockwood's collection includes specimens of _Psaronius textilis_; and -in addition to these there are remains of erect stems somewhat different -in character, yet possibly belonging to the higher parts of the same -species of tree-fern. One of these is a stem crushed in such a manner -that it does not exhibit its form with any distinctness, but surrounded -by smooth, cylindrical roots, radiating from it in bundles, proceeding at -first horizontally, and then curving downward, and sometimes terminating -in rounded ends. They resemble in form and size the aërial roots of -_Psaronius Erianus_; and I believe them to be similar roots from a higher -part of the stem, and some of them young and not prolonged sufficiently -far to reach the ground. This specimen would thus represent the stem -of _P. Erianus_ at a higher level than those previously found. We can -thus in imagination restore the trunk and crown of this once graceful -tree-fern, though we have not the detail of its fronds. Mr. Lockwood's -collections also contain a specimen of the large fern-petiole which I -have named _Rhachiopteris punctata_. My original specimen was obtained by -Prof. Hall from the same horizon in New York. That of Mr. Lockwood is of -larger size, but retains no remains of the frond. It must have belonged -to a species quite distinct from _Caulopteris Lockwoodi_, but which may, -like it, have been a tree-fern. - -2. _Caulopteris antiqua_, Newberry.--This is a flattened stem, on a slab -of limestone, containing Brachiopods, Trilobites, &c., of the Corniferous -limestone. It is about eighteen inches in length, and three and a half -inches in average breadth. The exposed side shows about twenty-two large -leaf-scars arranged spirally. Each leaf, where broken off, has left -a rough fracture; and above this is a semicircular impression of the -petiole against the stem, which, as well as the surface of the bases of -the petioles, is longitudinally striated or tuberculated. The structures -are not preserved, but merely the outer epidermis, as a coaly film. The -stem altogether much resembles _Caulopteris Peachii_, but is of larger -size. It differs from _C. Lockwoodi_ in the more elongated leaf-bases, -and in the leaves being more remotely placed; but it is evidently of the -same general character with that species. - -3. _Caulopteris_ (_Protopteris_) _peregrina_, Newberry.--This is a much -more interesting species than the last, as belonging to a generic or -subgeneric form not hitherto recognised below the Carboniferous, and -having its minute structure in part preserved. - -The specimens are, like the last, on slabs of marine limestone of the -Corniferous formation, and flattened. One represents an upper portion -of the stem with leaf-scars and remains of petioles; another a lower -portion, with aërial roots. The upper part is three inches in diameter, -and about a foot in length, and shows thirty leaf-scars which are about -three-fourths of an inch wide, and rather less in depth. The upper part -presents a distinct rounded and sometimes double marginal line, sometimes -with a slight depression in the middle. The lower part is irregular, -and when most perfect shows seven slender vascular bundles, passing -obliquely downward into the stem. The more perfect leaf-bases have the -structure preserved, and show a delicate, thin-walled, oval parenchyma, -while the vascular bundles show scalariform vessels with short bars in -several rows, in the manner of many modern ferns. Some of the scars show -traces of the hippocrepian mark characteristic of _Protopteris_; and the -arrangement of the vascular bundles at the base of the scars is the same -as in that genus, as are also the general form and arrangement of the -scars. On careful examination, the species is indeed very near to the -typical _P. Sternbergii_, as figured by Corda and Schimper.[BJ] - -[BJ] Corda, "Beiträge," Pl. 48, copied by Schimper, Pl. 52. - -The genus _Protopteris_ of Sternberg, though the original species (_P. -punctata_) appears as a _Lepidodendron_ in his earlier plate (Plate 4), -and as a _Sigillaria_ (_S. punctata_) in Brongniart's great work, is a -true tree-fern; and the structure of one species (_P. Cottai_) has been -beautifully figured by Corda. The species hitherto described are from the -Carboniferous and Permian. - -The second specimen of this species represents a lower part of the stem. -It is thirteen inches long and about four inches in diameter, and is -covered with a mass of flattened aërial roots lying parallel to each -other, in the manner of the _Psaronites_ of the coal-formation and of _P. -Erianus_ of the Upper Erian or Devonian. - -4. _Asteropteris noveboracensis_, gen. and sp. n.--The genus -_Asteropteris_ is established for stems of ferns having the axial portion -composed of vertical radiating plates of scalariform tissue embedded in -parenchyma, and having the outer cylinder composed of elongated cells -traversed by leaf-bundles of the type of those of _Zygopteris_. - -The only species known to me is represented by a stem 2·5 centimetres in -diameter, slightly wrinkled and pitted externally, perhaps by traces of -aërial roots which have perished. The transverse section shows in the -centre four vertical plates of scalariform or imperfectly reticulated -tissue, placed at right angles to each other, and united in the middle -of the stem. At a short distance from the centre, each of these plates -divides into two or three, so as to form an axis of from ten to twelve -radiating plates, with remains of cellular tissue filling the angular -interspaces. The greatest diameter of this axis is about 1·5 centimetre. -Exterior to the axis the stem consists of elongated cells, with somewhat -thick walls, and more dense toward the circumference. The walls of -these cells present a curious reticulated appearance, apparently caused -by the cracking of the ligneous lining in consequence of contraction -in the process of carbonization. Embedded in this outer cylinder are -about twelve vascular bundles, each with a dumb-bell-shaped group of -scalariform vessels enclosed in a sheath of thick-walled fibres. Each -bundle is opposite to one of the rays of the central axis. The specimen -shows about two inches of the length of the stem, and is somewhat bent, -apparently by pressure, at one end. - -This stem is evidently that of a small tree-fern of a type, so far as -known to me, not before described,[BK] and constituting a very complex -and symmetrical form of the group of Palæozoic ferns allied to the -genus _Zygopteris_ of Schimper. The central axis alone has a curious -resemblance to the peculiar stem described by Unger ("Devonian Flora -of Thuringia") under the name of _Cladoxylon mirabile_; and it is just -possible that this latter stem may be the axis of some allied plant. The -large aërial roots of some modern tree-ferns of the genus _Angiopteris_ -have, however, an analogous radiating structure. - -[BK] Prof. Williamson, to whom I have sent a tracing of the structure, -agrees with me that it is new. - -The specimen is from the collection of Berlin H. Wright, Esq., of Penn -Yan, New York, and was found in the Portage group (Upper Erian) of Milo, -New York, where it was associated with large petioles of ferns and trunks -of _Lepidodendra_, probably _L. Chemungense_ and _L. primævum_. - -The occurrence of this and other stems of tree-ferns in marine beds -has recently been illustrated by the observation of Prof. A. Agassiz -that considerable quantities of vegetable matter can be dredged from -great depths in the sea on the leeward side of the Caribbean Islands. -The occurrence of these trunks further connects itself with the great -abundance of large petioles (_Rhachiopteris_) in the same beds, while the -rarity of well-preserved fronds is explained by the coarseness of the -beds, and also by the probably long maceration of the plant-remains in -the sea-water. - -In connection with this I may refer to the remarkable facts recently -stated by Williamson[BL] respecting the stems known as Heterangium and -_Lyginodendron_. It would seem that these, while having strong exogenous -peculiarities, are really stems of tree-ferns, thus placing this family -in the same position of advancement with the Lycopods and Equisetaceæ of -the Coal period. - -[BL] "Proceedings of the Royal Society," January 6, 1887. - - -IV.--On Erian Trees of the Genus Dadoxylon, Unger. (_Araucarites_ of -Goeppert, _Araucarioxylon_ of Kraus.) - -Large woody trunks, carbonised or silicified, and showing wood-cells with -hexagonal areoles having oval pores inscribed in them, occur abundantly -in some beds of the Middle Erian of America, and constitute the most -common kind of fossil wood all the way to the Trias. They have in the -older formations, generally, several rows of pores on each fibre, and -medullary rays composed of two or more series of cells, but become more -simple in these respects in the Permian and Triassic series. The names -_Araucarites_ and _Araucarioxylon_ are perhaps objectionable, inasmuch -as they suppose affinities to _Araucaria_ which may not exist. Unger's -name, which is non-committal, is therefore, I think, to be preferred. In -my "Acadian Geology," and in my "Report on the Geology of Prince Edward -Island," I have given reasons for believing that the foliage of some at -least of these trees was that known as _Walchia_, and that they may have -borne nutlets in the manner of Taxine trees (_Trigonocarpum_, &c). Grand -d'Eury has recently suggested that some of them may have belonged to -_Cordaites_, or to plants included in that somewhat varied and probably -artificial group. - -The earliest discovery of trees of this kind in the Erian of America was -that of Matthew and Hartt, who found large trunks, which I afterwards -described as _Dadoxylon Ouangondianum_, in the Erian sandstone of St. -John, New Brunswick, hence named by those geologists the "Dadoxylon -sandstone." A little later, similar wood was found by Prof. Hall and -Prof. Newberry in the Hamilton group of New York and Ohio, and the allied -wood of the genus _Ormoxylon_ was obtained by Prof. Hall in the Portage -group of the former State. These woods proved to be specifically distinct -from that of St. John, and were named by me _D. Halli_, _D. Newberryi_, -and _Ormoxylon Erianum_. The three species of _Dadoxylon_ agreed in -having composite medullary rays, and would thus belong to the group -_Palæoxylon_ of Brongniart. In the case of _Ormoxylon_ this character -could not be very distinctly ascertained, but the medullary rays appeared -to be simple. - -I am indebted to Prof. J. M. Clarke, of Amherst College, Massachusetts, -for some well-preserved specimens of another species from the Genesee -shale of Canandaigua, New York. They show small steins or branches, with -a cellular pith surrounded with wood of coniferous type, showing two -to three rows of slit-formed, bordered pores in hexagonal borders. The -medullary sheath consists of pseudo-scalariform and reticulated fibres; -but the most remarkable feature of this wood is the structure of the -medullary rays, which are very frequent, but short and simple, sometimes -having as few as four cells superimposed. This is a character not before -observed in coniferous trees of so great age, and allies this Middle -Erian form with some Carboniferous woods which have been supposed to -belong to _Cordaites_ or _Sigillaria_. In any case this structure is new, -and I have named the species _Dadoxylon Clarkii_, after its discoverer. -The specimens occur, according to Prof. Clarke, in a calcareous layer -which is filled with the minute shells of _Styliola fissurella_ of Hall, -believed to be a Pteropod; and containing also shells of _Goniatites_ and -_Gyroceras_. The stems found are only a few inches in diameter, but may -be branches of larger trees. - -It thus appears that we already know five species of Coniferous trees -of the genus _Dadoxylon_ in the Middle Erian of America, an interesting -confirmation of the facts otherwise known as to the great richness and -variety of this ancient flora. The late Prof. Goeppert informed me that -he had recognised similar wood in the Devonian of Germany, and there -can be no doubt that the fossil wood discovered by Hugh Miller in the -Old Red Sandstone of Scotland, and described by Salter and McNab, is of -similar character, and probably belongs to the genus _Dadoxylon_. Thus -this type of Coniferous tree seems to have been as well established and -differentiated into species in the Middle Devonian as in the succeeding -Carboniferous. - -I may here refer to the fact that the lower limit of the trees of -this group coincides, in America, with the upper limit of those -problematical trees which in the previous chapter I have named Protogens -(_Nematophyton_, _Celluloxlyon_,[BM] _Nematoxylon_[BN]), though -_Aporoxylon_ of Unger extends, in Thuringia, up to the Upper Devonian -(Cypridina schists). - -[BM] "Journal of the Geological Society," May, 1881. - -[BN] _Ibid._, vol. xix, 1863. - - -V.--Scottish Devonian Plants of Hugh Miller and others. (Edinburgh -Geological Society, 1877.) - -Previously to the appearance of my descriptions of Devonian plants -from North America, Hugh Miller had described forms from the Devonian -of Scotland, similar to those for which I proposed the generic name -_Psilophyton_; and I referred to these in this connection in my earliest -description of that genus.[BO] He had also recognised what seemed to be -plants allied to Lycopods and Conifers. Mr. Peach and Mr. Duncan had made -additional discoveries of this kind, and Sir J. Hooker and Mr. Salter had -described some of these remains. More recently Messrs. Peach, Carruthers, -and McNab have worked in this field, and still later[BP] Messrs. Jack and -Etheridge have summed up the facts and have added some that are new. - -[BO] "Journal of the Geological Society," London, 1859. - -[BP] _Ibid._, 1877. - -The first point to which I shall refer, and which will lead to the -other matters to be discussed, is the relation of the characteristic -_Lepidodendron_ of the Devonian of eastern America, _L. Gaspianum_, to -_L. nothum_ of Unger and of Salter. At the time when I described this -species I had not access to Scottish specimens of _Lepidodendron_ from -the Devonian, but these had been well figured and described by Salter, -and had been identified with _L. nothum_ of Unger, a species evidently -distinct from mine, as was also that figured and described by Salter, -whether identical or not with Unger's species. In 1870 I had for the -first time an opportunity to study Scottish specimens in the collection -of Mr. Peach; and on the evidence thus afforded I stated confidently -that these specimens represented a species distinct from _L. Gaspianum_, -perhaps even generically so.[BQ] It differs from _L. Gaspianum_ in -its habit of growth by developing small lateral branches instead of -bifurcating, and in its foliage by the absence or obsolete character of -the leaf-bases and the closely placed and somewhat appressed leaves. If -an appearance of swelling at the end of a lateral branch in one specimen -indicates a strobile of fructification, then its fruit was not dissimilar -from that of the Canadian species in its position and general form, -though it may have differed in details. On these grounds I declined to -identify the Scottish species with _L. Gaspianum_. The Lepidodendron -from the Devonian of Belgium described and figured by Crepin,[BR] has -a better claim to such identification, and would seem to prove that -this species existed in Europe as well as in America. I also saw in Mr. -Peach's collection in 1870 some fragments which seemed to me distinct -from Salter's species, and possibly belonging to _L. Gaspianum_.[BS] - -[BQ] "Report on Devonian Plants of Canada," 1871. - -[BR] "Observations sur quelques Plantes Fossiles des dépôts Devoniens." - -[BS] "Proceedings of the Geological Society of London," March, 1871. - -In the earliest description of _Psilophyton_ I recognised its probable -generic affinity with Miller's "dichotomous plants," with Salter's -"rootlets," and with Goeppert's _Haliserites Dechenianus_, and stated -that I had "little doubt that materials exist in the Old Red Sandstone of -Scotland for the reconstruction of at least one species of this genus." -Since, however, Miller's plants had been referred to coniferous roots, -and to fucoids, and Goeppert's _Haliserites_ was a name applicable only -to fucoids, and since the structure and fruit of my plants placed them -near to Lycopods, I was under the necessity of giving them a special -generic name, nor could I with certainty affirm their specific identity -with any European species. The comparison of the Scottish specimens with -woody rootlets, though incorrect, is in one respect creditable to the -acumen of Salter, as in almost any state of preservation an experienced -eye can readily perceive that branchlets of _Psilophyton_ must have been -woody rather than herbaceous, and their appearance is quite different -from that of any true Algæ. - -The type of _Psilophyton_ is my _P. princeps_, of which the whole of the -parts and structures are well known, the entire plant being furnished in -abundance and in situ in the rich plant-beds of Gaspé. A second species, -_P. robustius_, has also afforded well-characterised fructification. _P. -elegans_, whose fruit appears as "oval scales," no doubt bore sac-like -spore-cases resembling those of the other species, but in a different -position, and perfectly flattened in the specimens procured. The only -other Canadian species, _P. glabrum_, being somewhat different in -appearance from the others, and not having afforded any fructification, -must be regarded as uncertain. - -The generic characters of the first three species may be stated as -follows: - -Stems dichotomous, with rudimentary subulate leaves, sometimes obsolete -in terminal branchlets and fertile branches; and in decorticated -specimens represented only by punctiform scars. Young branches circinate. -Rhizomata cylindrical, with circular root-areoles. Internal structure of -stem, an axis of scalariform vessels enclosed in a sheath of imperfect -woody tissue and covered with a cellular bark more dense externally. -Fruit, naked sac-like spore-cases, in pairs or clusters, terminal or -lateral. - -The Scottish specimens conform to these characters in so far as they are -known, but not having as yet afforded fruit or internal structure, they -cannot be specifically determined with certainty. More complete specimens -should be carefully searched for, and will no doubt be found. - -In Belgium, M. Crepin has described a new species from the Upper Devonian -of Condroz under the name _P. Condrusianum_ (1875). It wants, however, -some of the more important characters of the genus, and differs in having -a pinnate ramification, giving it the aspect of a fern. In a later paper -(1876) the author considers this species distinct from _Psilophyton_, and -proposes for it a new generic name _Rhacophyton_. - -The characters given by Mr. Carruthers, in his paper of 1873, for the -species _P. Dechenianum_, are very few and general: "Lower branches short -and frequently branching, giving the plant an oblong circumscription." -Yet even these characters do not apply, so far as known, to Miller's -fucoids or Salter's rootlets or Goeppert's _Haliserites_. They merely -express the peculiar mode of branching already referred to in Salter's -_Lepidodendron nothum_. The identification of the former plants with -the _Lepidodendron_ and _Lycopodites_, indeed, rests only on mere -juxtaposition of fragments, and on the slight resemblance of the -decorticated ends of the branches of the latter plants to _Psilophyton_. -It is contradicted by the obtuse ends of the branches of the -_Lepidodendron_ and _Lycopodites_, and by the apparently strobilaceous -termination of some of them. - -Salter's description of his _Lepidodendron nothum_ is quite definite, and -accords with specimens placed in my hands by Mr. Peach: "Stems half an -inch broad, tapering little, branches short; set on at an acute angle, -blunt at their terminations. Leaves in seven to ten rows, very short, -not a line long, and rather spreading than closely imbricate." These -characters, however, in so far as they go, are rather those of the genus -_Lycopodites_ than of _Lepidodendron_, from which this plant differs -in wanting any distinct leaf-bases, and in its short, crowded leaves. -It is to be observed that they apply also to Salter's _Lycopodites -Milleri_, and that the difference of the foliage of that species may be -a result merely of different state of preservation. For these reasons I -am disposed to place these two supposed species together, and to retain -for the species the name _Lycopodites Milleri_. It may be characterised -by the description above given, with merely the modification that the -leaves are sometimes nearly one-third of an inch long and secund (Fig. -17, _supra_, lower figure). - -Decorticated branches of the above species may no doubt be mistaken -for _Psilophyton_, but are nevertheless quite distinct from it, and -the slender branching dichotomous stems, with terminations which, as -Miller graphically states, are "like the tendrils of a pea," are too -characteristic to be easily mistaken, even when neither fruit nor leaves -appear. With reference to fructification, the form of _L. Milleri_ -renders it certain that it must have borne strobiles at the ends of its -branchlets, or some substitute for these, and not naked spore-cases like -those of _Psilophyton_. - -The remarkable fragment communicated by Sir Philip Egerton to Mr. -Carruthers,[BT] belongs to a third group, and has, I think, been quite -misunderstood. I am enabled to make this statement with some confidence, -from the fact that the reverse or counterpart of Sir Philip's specimen -was in the collection of Sir Wyville Thomson, and was placed by him in -my hands in 1870. It was noticed in my paper on "New Devonian Plants," -in the "Journal of the Geological Society of London," and referred to my -genus _Ptilophyton_, as stated above under Section II., page 86 _et seq._ - -[BT] "Journal of Botany," 1873. - -Mr. Salter described, in 1857,[BU] fragments of fossil wood from the -Scottish Devonian, having the structure of Dadoxylon, though very -imperfectly preserved; and Prof. McNab has proposed[BV] the generic name -_Palæopitys_ for another specimen of coniferous wood collected by Hugh -Miller, and referred to by him in the "Testimony of the Rocks." From -Prof. McNab's description, I should infer that this wood may, after all, -be generically identical with the woods usually referred to Dadoxylon -of Unger (_Araucarioxylon_ of Kraus). The description, however, does -not mention the number and disposition of the rows of pores, nor the -structure of the medullary rays, and I have not been able to obtain -access to the specimens themselves. I have described five species of -Dadoxylon from the Middle and Upper Erian of America, all quite distinct -from the Lower Carboniferous species. There is also one species of an -allied genus, Ormoxylon. All these have been carefully figured, and it is -much to be desired that the Scottish specimens should be re-examined and -compared with them. - -[BU] "Journal of the London Geological Society." - -[BV] "Transactions of the Edinburgh Botanical Society," 1870. - -Messrs. Jack and Etheridge have given an excellent summary of our present -knowledge of the Devonian flora of Scotland, in the Journal of the -London Geological Society (1877). From this it would appear that species -referable to the genera _Calamities_, _Lepidodendron_, _Lycopodites_, -_Psilophyton_, _Arthrostigma_, _Archæopteris_, _Caulopteris_, -_Palæopitys_, _Araucarioxylon_, and _Stigmaria_ have been recognised. - -The plants described by these gentlemen from the Old Red Sandstone of -Callender, I should suppose, from their figures and descriptions, to -belong to the genus _Arthrostigma_, rather than to Psilophyton. I do -not attach any importance to the suggestions referred to by them, that -the apparent leaves may be leaf-bases. Long leaf-bases, like those -characteristic of _Lepidofloyos_, do not occur in these humbler plants -of the Devonian. The stems with delicate "horizontal processes" to which -they refer may belong to _Ptilophyton_ or to _Pinnularia_. - -In conclusion, I need scarcely say that I do not share in the doubts -expressed by some British palæontologists as to the distinctness of -the Devonian and Carboniferous floras. In eastern America, where these -formations are mutually unconformable, there is, of course, less room -for doubt than in Ireland and in western America, where they are -stratigraphically continuous. Still, in passing from the one to the -other, the species are for the most part different, and new generic forms -are met with, and, as I have elsewhere shown, the physical conditions of -the two periods were essentially different.[BW] - -[BW] "Reports on Devonian Plants and Lower Carboniferous Plants of -Canada." - -It is, however, to be observed that since--as Stur and others have -shown--_Calamities radiatus_, and other forms distinctively Devonian in -America, occur in Europe in the Lower Carboniferous, it is not unlikely -that the Devonian flora, like that of the Tertiary, appeared earlier in -America. It is also probable, as I have shown in the "Reports" already -referred to, that it appeared earlier in the Arctic than in the temperate -zone. Hence an Arctic or American flora, really Devonian, may readily be -mistaken for Lower Carboniferous by a botanist basing his calculations on -the fossils of temperate Europe. Even in America itself, it would appear, -from recent discoveries in Virginia and Ohio, that certain Devonian forms -lingered longer in those regions than farther to the northeast;[BX] and -it would not be surprising if similar plants occurred in later beds in -Devonshire or in the south of Europe than in Scotland. Still, these -facts, properly understood, do not invalidate the evidence of fossil -plants as to geological age, though errors arising from the neglect of -them are still current. - -[BX] Andrews, "Palæontology of Ohio," vol. ii.; Meek, "Fossil Plants from -Western Virginia," Philosophical Society, Washington, 1875. - - -VI.--Geological Relations of some Plant-bearing Beds of Eastern Canada. -("Report on Erian Plants," 1871.) - -The Gaspé sandstones have been fully described by Sir W. E. Logan, -in his "Report on the Geology of Canada," 1863. He there assigns to -them a thickness of seven thousand and thirty-six feet, and shows that -they rest conformably on the Upper Silurian limestones of the Lower -Helderberg group (Ludlow), and are in their turn overlaid unconformably -by the conglomerates which form the base of the Carboniferous rocks of -New Brunswick. I shall add here merely a few remarks on points in their -physical character connected with the occurrence of plants in them. - -_Prototaxites_ (_Nematophyton_) _Logani_ and other characteristic Lower -Erian plants occur in the base of the sandstones at Little Gaspé. This -fact, along with the occurrence, as stated in my paper of 1863, of -rhizomes of _Psilophyton_ preserving their scalariform structure, in -the upper part of the marine Upper Silurian limestones,[BY] proves the -flora of the Devonian rocks to have had its beginning at least in the -previous geological period, and to characterise the lower as well as the -upper beds of the Devonian series. In this connection I may state that, -from their marine fossils, as well as their stratigraphical arrangement, -Sir W. E. Logan and Mr. Billings regard the lower portions of the Gaspé -sandstones as the equivalents of the Oriskany sandstone of New York. -On the other hand, the great thickness of this formation, the absence -of Lower Devonian fossils from its upper part, and the resemblance of -the upper beds to those of the newer members of the Devonian elsewhere, -render it probable that the Gaspé sandstones, though deficient in the -calcareous members of the system, seen farther to the westward, represent -the whole of the Devonian period. - -[BY] The marine fossils of these beds have been determined by Mr. -Billings. They are Upper Silurian, with an intermixture of Lower Devonian -in the upper part. Fragments of _Nematophyton_ occur in beds of the same -age in the Bay des Chaleurs, at Cape Bon Ami. - -The Gaspé sandstones, as their name imports, are predominantly -arenaceous, and often coarsely so, the sandstones being frequently -composed of large grains and studded with quartz-pebbles. Grey and buff -are prevalent colours, but red beds also occur, more especially in the -upper portion. There are also interstratified shaly beds, sometimes -occurring in groups of considerable thickness, and associated with -fine-grained and laminated argillaceous sandstone, the whole having -in many places the lithological aspect of the coal-measures. At one -place, near the middle of the series, there is a bed of coal from one -inch to three inches in thickness, associated with highly bituminous -shales abounding in remains of plants, and also containing fragments -of crustaceans and fishes (_Pterygotus_, _Ctenacanthus ?_ &c). The -beds connected with this coal are grey sandstones and grey and dark -shales, much resembling those of the ordinary coal formation. The -coal is shining and laminated, and both its roof and floor consist of -laminated bituminous shale with fragments of _Psilophyton_. It has no -true under-clay, and has been, I believe, a peaty mass of rhizomes of -_Psilophyton_. It occurs near Tar Point, on the south side of Gaspé Bay, -a place so named from the occurrence of a thick dyke of trap holding -petroleum in its cavities. The coal is of considerable horizontal extent, -as in its line of strike a similar bed has been discovered on the Douglas -River, about four miles distant. It has not been recognised on the north -side of the bay, though we find there beds, probably on very nearly the -same horizon, holding _Psilophyton_ in situ. - -As an illustration of one of the groups of shaly beds, and of the -occurrence of roots of _Psilophyton_, I may give the following sectional -list of beds seen near "Watering Brook," on the north shore of the bay. -The order is descending: - - FT. IN. - 1. Grey sandstones and reddish pebbly sandstone of great - thickness - 2. Bright-red shale 8 0 - 3. Grey shales with stems of _Psilophyton_, very abundant - but badly preserved 0 5 - 4. Grey incoherent clay, slickensided, and with many - rhizomes and roots of _Psilophyton_ 0 3 - 5. Hard grey clay or shale, with fragments and roots of - _Psilophyton_ 4 0 - 6. Red shale 8 0 - 7. Grey and reddish crumbling sandstone - -Groups of beds similar to the above, but frequently much more rich in -fossils, occur in many parts of the section, and evidently include fossil -soils of the nature of under-clays, on which little else appears to have -grown than a dense herbage of _Psilophyton_, along with plants of the -genus _Arthrostigma_. - -In addition to these shaly groups, there are numerous examples of beds of -shale of small thickness included in coarse sandstones, and these beds -often occur in detached fragments, as if the remnants of more continuous -layers partially removed by currents of water. It is deserving of notice -that nearly all these patches of shale are interlaced with roots or -stems of _Psilophyton_, which sometimes project beyond their limits into -the sandstone, as if the vegetable fibres had preserved the clay from -removal. In short, these lines of patches of shale seem to be remnants -of soils on which _Psilophyton_ has flourished abundantly, and which -have been partially swept away by the currents which deposited the sand. -Some of the smaller patches may even be fragments of tough swamp soils -interwoven with roots, drifted by the agency of the waves or possibly by -ice; such masses are often moved in this way on the borders of modern -swamps on the sea-coast. - -The only remaining point connected with local geology to which I shall -allude is the admirable facilities afforded by the Gaspé coast both for -ascertaining the true geological relations of the beds, and for studying -the Devonian plants, as distinctly exposed on large surfaces of rock. -On the coast of the river St. Lawrence, at Cape Rozier and its vicinity, -the Lower Silurian rocks of the Quebec group are well exposed, and are -overlaid unconformably by the massive Upper Silurian limestones of Cape -Gaspé, which rise into cliffs six hundred feet in height, and can be -seen filled with their characteristic fossils on both sides of the cape. -Resting upon these, and dipping at high angles toward Gaspé Bay, are the -Devonian sandstones, which are exposed in rugged cliffs slightly oblique -to their line of strike, along a coast-line of ten miles in length, to -the head of the bay. On the opposite side of the bay they reappear; and, -thrown into slight undulations by three anticlinal curves, occupy a -line of coast fifteen miles in length. The perfect manner in which the -plant-bearing beds are exposed in these fine natural sections may serve -to account for the completeness with which the forms and habits of growth -of the more abundant species can be described. - -In the Bay des Chaleurs, similar rocks exist with some local variations. -In the vicinity of Campbellton are calcareous and magnesian breccia -or agglomerate, hard shales, conglomerates and sandstones of Lower -Devonian age. The agglomerate and lower shales contain abundant remains -of fishes of the genera _Cephalaspis_, _Coccosteus_, _Ctenacanthus_, -and _Homacanthus_, and also fragments of _Pterygotus_. The shales -and sandstones abound in remains of _Psilophyton_, with which are -_Nematophyton_, _Arthrostigma_, and _Leptophleum_ of the same species -found in the Lower Devonian of Gaspé Bay. These beds near Campbellton dip -to the northward, and the Restigouche River here occupies a synclinal, -for on the opposite side, at Bordeaux Quarry, there are thick beds of -grey sandstone dipping to the southward, and containing large silicified -trunks of Prototaxites, in addition to _Psilophyton_. These beds are -all undoubtedly Lower Erian, but farther to the eastward, on the north -side of the river, there are newer and overlying strata. These are best -seen at Scaumenac Bay, opposite Dalhousie, between Cape Florissant -and Maguacha Point, where they consist of laminated and fine-grained -sandstone, with shales of grey colours, but holding some reddish beds -at top, and overlaid unconformably by a great thickness of Lower -Carboniferous red conglomerate and sandstone. In these beds numerous -fossil fishes have been found, among which Mr. Whiteaves recognises -species of _Pterichthys_, _Glyptolepis_, _Cheirolepis_, &c. With these -are found somewhat plentifully four species of fossil ferns, all of Upper -Erian types, of which one is peculiar to this locality; but the others -are found in the Upper Erian of Perry, in Maine, or in the Cat skill -group of New York. - -In order that distinct notions may be conveyed as to the geological -horizons of the species, I may state that the typical Devonian or Erian -series of Canada and New York may be divided in descending order into--1. -The Chemung group, including the Chemung and Portage sandstones and -shales. 2. The Hamilton group, including the Genesee, Hamilton, and -Marcellus shales. 3. The Corniferous limestone and its associated beds. -4 The Oriskany sandstone. As the Corniferous limestone, which is the -equivalent of the Lower Carboniferous limestone in the Carboniferous -period, is marine, and affords scarcely any plants, we may, as is usually -done for like purposes in the Carboniferous, group it with the Oriskany -under the name Lower Erian. The Hamilton rocks will then be Middle Erian, -and the Chemung group Upper Erian. In the present state of our knowledge, -the series may be co-ordinated with the rocks of Gaspé, New Brunswick, -and Maine, as in the following table: - - | New York | Gaspé | Southern | Coast - Subdivisions. | and | and Bay des | New | of - | Western Canada.| Chaleurs. | Brunswick. | Maine. - --------------+----------------+--------------+--------------+----------- - Upper | Chemung | Upper |Mispec Group. | Perry - Devonian or | Group. | Sandstones. | Shale, |Sandstones. - Erian. | |Long Cove, &c.| Sandstone, | - | | Scauminac | and | - | | Beds. |Conglomerate. | - | | | | - Middle | Hamilton | Middle | Little R. | - Devonian or | Group. | Sandstones. | Group | - Erian. | | Bois Brulé, | (including | - | | Cape Oiseau, | Cordaite | - | | &c. | Shales and | - | | | Dadoxylon | - | | | Sandstone).| - | | | | - Lower | Corniferous | Lower | Lower | - Devonian or | and | Sandstones. |Conglomerates,| - Erian. | Oriskany | Gaspé Basin, | &c. | - | groups. | Little Gaspé,| | - | | &c. | | - | | Campbellton | | - | | Beds. | | - --------------+----------------+--------------+--------------+----------- - -It may be proper, before closing this note, to state the reasons which -have induced me to suggest in the following pages the use of the term -"Erian," as equivalent to "Devonian," for the great system of formations -intervening between the Upper Silurian and the Lower Carboniferous in -America. I have been induced to adopt this course by the following -considerations: 1. The great area of undisturbed and unaltered rocks -of this age, including a thickness in some places of eighteen thousand -feet, and extending from east to west through the Northern States of the -Union and western Canada for nearly seven hundred miles, while it spreads -from north to south from the northern part of Michigan far into the -Middle States, is undoubtedly the most important Devonian area now known -to geologists. 2. This area has been taken by all American geologists -as their typical Devonian region. It is rich in fossils, and these have -been thoroughly studied and admirably illustrated by the New York and -Canadian Surveys. 3. The rocks of this area surround the basin of Lake -Erie, and were named, in the original reports of the New York Survey, -the "_Erie Division_" 4. Great difficulties have been experienced in -the classification of the European Devonian, and the uncertainties thus -arising have tended to throw doubt on the results obtained in America in -circumstances in which such difficulties do not occur. - -These reasons are, I think, sufficient to warrant me in holding the great -_Erie Division_ of the New York geologists as the typical representative -of the rocks deposited between the close of the Upper Silurian and the -beginning of the Carboniferous period, and to use the term Erian as the -designation of this great series of deposits as developed in America, -in so far at least as their flora is concerned. In doing so, I do not -wish to introduce a new name merely for the sake of novelty; but I hope -to keep before the minds of geologists the caution that they should -not measure the Erian formations of America, or the fossils which they -contain, by the comparatively depauperated representatives of this -portion of the geological scale in the Devonian of western Europe. - - -VII.--On the Relations of the so-called "Ursa Stage" of Bear Island with -the Palæozoic Flora of North America. - -The following note is a verbatim copy of that published by me in -1873, and the accuracy of which has now been vindicated by the recent -observations of Nathorst: - -The plants catalogued by Dr. Heer, and characterising what he calls -the "Ursa Stage," are in part representatives of those of the American -flora which I have described as the "Lower Carboniferous Coal-Measures" -(Subcarboniferous of Dana), and whose characteristic species, as -developed in Nova Scotia, I noticed in the "Journal of the Geological -Society" in 1858 (vol. xv.). Dr. Heer's list, however, includes some -Upper Devonian forms; and I would suggest that either the plants of two -distinct beds, one Lower Carboniferous and the other Upper Devonian, have -been near to or in contact with each other and have been intermixed, or -else that in this high northern latitude, in which (for reasons stated -in my "Report on the Devonian Flora"[BZ]) I believe the Devonian plants -to have originated, there was an actual intermixture of the two floras. -In America, at the base of the Carboniferous of Ohio, a transition of -this kind seems to occur; but elsewhere in northeastern America the Lower -Carboniferous plants are usually unmixed with the Devonian. - -[BZ] "Geological Survey of Canada," 1871. - -Dr. Heer, however, proceeds to identify these plants with those of the -American Chemung, and even with those of the Middle Devonian of New -Brunswick, as described by me--a conclusion from which I must altogether -dissent, inasmuch as the latter belong to beds which were disturbed and -partially metamorphosed before the deposition of the lowest Carboniferous -or "Subcarboniferous" beds. - -Dr. Heer's error seems to have arisen from want of acquaintance with the -rich flora of the Middle Devonian, which, while differing in species, has -much resemblance in its general facies, and especially in its richness in -ferns, to that of the coal-formation. - -To geologists acquainted with the stratigraphy and the accompanying -animal fossils, Dr. Heer's conclusions will of course appear untenable; -but they may regard them as invalidating the evidence of fossil plants; -and for this reason it is, I think, desirable to give publicity to the -above statements. - -I consider the British equivalent of the lower coal-measures of eastern -America to be the lower limestone shales, the _Tweedian group_ of Mr. -Tate (1858), but which have sometimes been called the "Calciferous -Sandstone" (a name preoccupied for a Cambrian group in America). This -group does not constitute "beds of passage" to the Devonian, more -especially in eastern America, where the lower coal-formation rests -unconformably on the Devonian, and is broadly distinguished by its -fossils. - -The above notes would not have been extended to so great length, but -for the importance of the Erian flora as the precursor of that of the -Carboniferous, and the small amount of attention hitherto given to it by -geologists and botanists. - - - - -CHAPTER IV. - - THE CARBONIFEROUS FLORA--CULMINATION OF THE - ACROGENS--FORMATION OF COAL. - -Ascending from the Erian to the Carboniferous system, so called because -it contains the greatest deposits of anthracite and bituminous coal, we -are still within the limits of the Palæozoic period. We are still within -the reign of the gigantic club-mosses, cordaites, and taxine pines. At -the close of the Erian there had been over the whole northern hemisphere -great changes of level, accompanied by active volcanic phenomena, and -under these influences the land flora seems to have much diminished. At -length all the old Erian species had become extinct, and their place was -supplied by a meagre group of lycopods, ferns, and pines of different -species from those of the preceding Erian. This is the flora of the Lower -Carboniferous series, the Tweedian of England, the Horton series of Nova -Scotia, the lower coal-measures of Virginia, the culm of Germany. But -the land again subsided, and the period of the marine limestone of the -Lower Carboniferous was introduced. In this the older flora disappeared, -and when the land emerged we find it covered with the rich flora of the -coal-formation proper, in which the great tribes of the lycopods and -cordaites attained their maxima, and the ferns were continued as before, -though under new generic and specific forms. - -[Illustration: Fig. 32.--Foliage from the coal-formation, _a_, -_Alethopteris lonchitica_, fern (Moose River). _b_, _Sphenophyllum -Schlotheimii_ (Pietou). _c_, _Lepidodendron binerve_ (Sydney), _d_, -_Asterophyllites foliosa_ (_?_) (Sydney). _e_, _Cordaites_ (Joggins). -_f_, _Neuropteris rarinervis_, fern (Sydney). _g_, _Odontopteris -subcuneata_, fern (Sydney).] - -There is something very striking in this succession of a new plant -world without any material advance. It is like passing in the modern -world from one district to another, in which we see the same forms of -life, only represented by distinct though allied species. Thus, when -the voyager crosses the Atlantic from Europe to America, he meets with -pines, oaks, birches, poplars, and beeches of the same genera with those -he had left behind; but the species are distinct. It is something like -this that meets us in our ascent into the Carboniferous world of plants. -Yet we know that this is a succession in time, that all our old Erian -friends are dead and buried long ago, and that these are new forms lately -introduced (Fig. 32). - -Conveying ourselves, then, in imagination forward to the time when our -greatest accumulations of coal were formed, and fancying that we are -introduced to the American or European continent of that period, we find -ourselves in a new and strange world. In the Devonian age, and even in -the succeeding Lower Carboniferous, there was in the interior of America -a wide inland sea, with forest belts clinging to its sides or clothing -its islands. But in the coal period this inland sea had given place -to vast swampy flats, and which, instead of the oil-bearing shales -of the Erian, were destined to produce those immense and wide-spread -accumulations of vegetable matter which constitute our present beds of -bituminous and anthracite coal. The atmosphere of these great swamps -is moist and warm. Their vegetation is most exuberant, but of forms -unfamiliar to modern eyes, and they swarm with insects, millipedes, and -scorpions, and with batrachian reptiles large and small, among which we -look in vain for representatives of the birds and beasts of the present -day. - -[Illustration: Fig. 33.--_Sigillariæ_, restored. A, _Sigillaria Brownii_. -B, _Sigillaria elegans_.] - -[Illustration: Fig. 34.--_Sigillaria Lorwayana_, Dawson. _a_, Zones of -fruit-scars. _b_, Leaf-scar enlarged, _c_, Fruit-scar enlarged. See -appended note.] - -[Illustration: Fig. 35.--Stem of _Sigillaria Brownii_. reduced. Natural -size.] - -[Illustration: Fig. 36.--Two ribs of _Sigillaria Brownii_.] - -[Illustration: Fig. 37.--Portion of lower part of stem of _S. Brownii_. -Natural size.] - -Prominent among the more gigantic trees of these swampy forests are -those known to us as _Sigillariæ_ (Fig. 33). They have tall, pillar-like -trunks, often several feet in diameter, ribbed like fluted columns, but -in the reverse way, and spreading at the top into a few thick branches, -which are clothed with long, grass-like leaves. They resemble in some -respects the Lepidodendra of the Erian age, but are more massive, with -ribbed instead of scaly trunks, and longer leaves. If we approach one -of them more closely, we are struck with the regular ribs of its trunk, -dotted with rows of scars of fallen leaves, from which it receives its -name _Sigillaria_, or seal-tree (Figs. 34-37). If we cut into its stem, -we find that, instead of the thin bark and firm wood with which we are -familiar in our modern trees, it has a hard external rind, then a great -thickness of cellular matter with rope-like bands of fibres, constituting -an inner bark, while in the centre is a firm, woody axis of comparatively -small diameter, and somewhat intermediate in its structures between that -of the Lepidodendra and those of the cycads and the taxine conifers. -Thus a great stem, five feet in diameter, may consist principally of -cellular and bast fibres with very little true woody matter. The roots -of this tree are perhaps its most singular feature. They usually start -from the stem in four main branches, then regularly bifurcate several -times, and then run out into great cylindrical cables, running for a -long distance, and evidently intended to anchor the plant firmly in a -soft and oozy soil. They were furnished with long, cylindrical rootlets -placed regularly in a spiral manner, and so articulated that when they -dropped off they left regular rounded scars. They are, in short, the -_Stigmariæ_, which we have already met with in the Erian (Figs. 38, 39). -In Fig. 33 I have endeavoured to restore these strange trees. It is not -wonderful that such plants have caused much botanical controversy. It was -long before botanists could be convinced that their roots are properly -roots at all, and not stems of some aquatic plant. Then the structure of -their stems is most puzzling, and their fruit is an enigma, for while -some have found connected with them cones supposed to resemble those of -lycopods, others attribute to them fruits like those of yew-trees. For -years I have been myself gathering materials from the rich coal-formation -deposits of Nova Scotia in aid of the solution of these questions, and -in the mean time Dr. Williamson, of Manchester, and Renault and other -botanists in France, have been amassing and studying stores of specimens, -and it is still uncertain who may finally be the fortunate discoverer -to set all controversies at rest. My present belief is, that the true -solution consists in the fact that there are many kinds of _Sigillariæ_. -While in the modern forests of America and Europe the species of any of -our ordinary trees, as oaks, birches, or maples, may almost be counted -on one's fingers, Schimper in his vegetable palæontology enumerates -about eighty species of Carboniferous _Sigillariæ_; and while on the one -hand many of these are so imperfectly known that they may be regarded -as uncertain, on the other hand many species must yet remain to be -discovered.[CA] Now, in so vast a number of species there must be a -great range of organisation, and, indeed, it has already been attempted -to subdivide them into several generic groups. The present state of the -question appears to me to be this, that in these _Sigillariæ_ we have -a group divisible into several forms, some of which will eventually be -classed with the Lepidodendra as lycopods, while others will be found -to be naked-seeded phænogams, allied to the pines and cycads, and to a -remarkable group of trees known as _Cordaites_, which we must shortly -notice. - -[CA] In a recent memoir (Berlin, 1887) Stur has raised the number of -species in one subdivision of the _Sigillariæ_ (the _Favulariæ_) to -forty-seven! - -[Illustration: Fig. 38.--_Stigmaria_ root, seen from above, showing its -regular divisions. From "Acadian Geology".] - -[Illustration: Fig. 39.--Portion of bark of _Stigmaria_, showing scars of -attachment of rootlets.] - -Before considering other forms of Carboniferous vegetation, let us -glance at the accumulation of coal, and the agency of the forests of -_Sigillariæ_ therein. Let us imagine, in the first instance, such trees -as those represented in the figures, growing thickly together over vast -swampy flats, with quantities of undergrowth of ferns and other plants -beneath their shade, and accumulating from age to age in a moist soil -and climate a vast thickness of vegetable mould and trunks of trees, and -spores and spore-cases, and we have the conditions necessary for the -growth of coal. Many years ago it was observed by Sir William Logan that -in the coal-field of South Wales it was the rule with rare exceptions -that, under every bed of coal, there is a bed of clay filled with roots -of the _Stigmaria_, already referred to as the root of _Sigillaria_. This -discovery has since been extended to all the coal-fields of Europe and -America, and it is a perfectly conclusive fact as regards the origin of -coal. Each of these "under-clays," as they are called, must, in fact, -have been a soil on which grew, in the first instance, Sigillariæ and -other trees having stigmaria-roots. Thus, the growth of a forest of -_Sigillariæ_ was the first step toward the accumulation of a bed of -coal. More than this, in some of the coarser and more impure coals, -where there has been sufficient earthy matter to separate and preserve -impressions of vegetable forms, we can see that the mass of the coal is -made up of flattened _Sigillariæ_, mixed with vegetable _débris_ of all -kinds, including sometimes vast quantities of lepidodendroid spores, -and the microscopic study of the coal gives similar results (Fig. 40). -Further, on the surfaces of many coals, and penetrating the shales or -sandstones which form their roofs, we find erect stumps of sigillaria -and other trees, showing that the accumulation of the coal terminated as -it had begun, by a forest-growth. I introduce here a section of a few of -the numerous beds of coal exposed in the cliffs of the South Joggins, in -Nova Scotia, in illustration of these facts. We can thus see how in the -slowly subsiding areas of the coal-swamps successive beds of coal were -accumulated, alternating with beds of sandstone and shale (Figs. 41, 42). -For other details of this kind I must refer to papers mentioned in the -sequel. - -[Illustration: Fig. 40.--Vegetable tissues from coal. _a_, _Sigillaria_ -and _Cordaites_. _Calamodendron_.] - -Returning to the more special subject of this work, I may remark that the -lepidodendroid trees and the ferns, both the arborescent and herbaceous -kinds, are even more richly represented in the Carboniferous than in the -preceding Erian, I must, however, content myself with merely introducing -a few representatives of some of the more common kinds, in an appended -note, and here give a figure of a well-known Lower Carboniferous -lepidodendron, with its various forms of leaf-bases, and its foliage and -fruit (Fig. 43), and a similar illustration of an allied generic form, -that known as _Lepidophloios_[CB] (Fig. 44). - -[CB] For full descriptions of these, see "Acadian Geology." - -[Illustration: Fig. 41.--Beds associated with the main coal (S. Joggins, -Nova Scotia). 1, Shale and sandstone--plants with _Spirorbis_ attached; -rain-marks (?). (2, Sandstone and shale, eight feet--erect _Calamites_; -3, Gray sandstone, seven feet; 4, Gray shale, four feet--an erect -coniferous (?) tree, rooted on the shale, passes up through fifteen feet -of the sandstones and shale.) 5, Gray sandstone, four feet. 6, Gray -shale, six inches--prostrate and erect trees, with rootlets, leaves, -_Naiadites_, and _Spirorbis_ on the plants. 7, Main coal-seam, five feet -of coal in two seams. 8, Underclay, with rootlets.] - -Another group which claims our attention is that of the _Calamites_. -These are tall, cylindrical, branchless stems, with whorls of branchlets, -bearing needle-like leaves and spreading in stools from the base, so -as to form dense thickets, like Southern cane-brakes (Fig. 46). They -bear, in habit of growth and fructification, a close relation to our -modern equisetums, or mare's-tails, but, as in other cases we have met -with, are of gigantic size and comparatively complex structure. Their -stems, in cross-section, show radiating bundles of fibres, like those -of exogenous woods, yet the whole plan of structure presents some -curious resemblances to the stems of their humble successors, the modern -mare's-tails. It would seem, from the manner in which dense brakes of -these _Calamites_ have been preserved in the coal-formation of Nova -Scotia, that they spread over low and occasionally inundated flats, and -formed fringes on the seaward sides of the great Sigillaria forests. -In this way they no doubt contributed to prevent the invasion of the -areas of coal accumulation by the muddy waters of inundations, and thus, -though they may not have furnished much of the material of coal, they -no doubt contributed to its purity. Many beautiful plants of the genera -Asterophyllites and _Annularia_ are supposed to have been allied to the -_Calamites_, or to have connected them with the _Rhizocarps_. The stems -and fruit of these plants have strong points of resemblance to those of -_Sphenophyllum_, and the leaves are broad, and not narrow and angular -like those of the true _Calamites_ (Fig. 45). - -[Illustration: Fig. 42.--Erect _Sigillaria_, standing on a coal-seam (S. -Joggins, Nova Scotia).] - -[Illustration: Fig. 43.--_Lepidodendron corrugatum_, Dawson, a tree -characteristic of the Lower Carboniferous, A, Restoration. B, Leaf, -natural size, C, Cone and branch, D, Branch and leaves, E. Various forms -of leaf-areoles. F, _Sporangium_, I, L, M, Bark, with leaf-scars, N, -Bark, with leaf-scars of old stem, O, Decorticated stem (_Knorria_).] - -[Illustration: Fig. 44.--_Lepidophloios Acadianus_, Dawson, a -lepidodendroid tree of the coal-formation, A, Restoration. B, Portion -of bark (two thirds natural size), C, Ligneous surface of the same, F, -Cone (two thirds natural size). G, Leaf (natural, size), K, Portion of -woody cylinder, showing outer and inner series of vessels magnified, L, -Scalariform vessels (highly magnified), M, Various forms of leaf-scars -and leaf-bases (natural size).] - -[Illustration: Fig. 45.--_Asterophyllites_, _Sphenophyllum_, and -_Annularia_. A, _Asterophyllites trinerne_. A^1, Leaf enlarged, B, -_Annularia sphenophylloides_. B^1, Leaf enlarged, C, _Sphenophyllum -erosum_. C^1, Leaflet enlarged. C^2, Scalariform vessel of -_Sphenophyllum_. D, _Pinnularia ramosissima_, probably a root.] - -No one has done more than my friend Dr. Williamson, of Manchester, to -illustrate the structure of Calamites, and he has shown that these -plants, like other cryptogams of the Carboniferous, had mostly stems -with regular fibrous wedges, like those of exogens. The structure of -the stem is, indeed, so complex, and differs so much in different -stages of growth, and different states of preservation, that we are -in danger of falling into the greatest confusion in classifying these -plants. Sometimes what we call a Calamite is a mere cast of its pith -showing longitudinal striæ and constrictions at the nodes. Sometimes -we have the form of the outer surface of the woody cylinder, showing -longitudinal ribs, nodes, and marks of the emission of the branchlets. -Sometimes we have the outer surface of the plant covered with a smooth -bark showing flat ribs, or almost smooth, and having at the nodes regular -articulations with the bases of the verticillate branchlets, or on the -lower part of the stem the marks of the attachment of the roots. The -Calamites grew in dense clumps, budding off from one another, sometimes -at different levels, as the mud or sand accumulated about their stems, -and in some species there were creeping rhizomata or root-stocks (Figs. -46 to 49). - -[Illustration: Fig. 46.--_Calamites_. A, _C. Suckovii_. B, _C. Cistii_. -(From "Acadian Geology.")] - -[Illustration: Fig. 47.--Erect _Calamites_, with roots attached (Nova -Scotia).] - -[Illustration: Fig. 48.--Node of _C. Cistii_, with long leaves (Nova -Scotia).] - -But all Calamites were not alike in structure. In a recent paper[CC] -Dr. Williamson describes three distinct structural types. What he -regards as typical Calamites has in its woody zone wedges of barred -vessels, with thick bands of cellular tissue separating them. A second -type, which he refers to _Calamopitus_, has woody bundles composed of -reticulated or multiporous fibres, with their porous sides parallel to -the medullary rays, which are better developed than in the previous form. -The intervening cellular masses are composed of elongated cells. This is -a decided advance in structure, and is of the type of those forms having -the most woody and largest stems, which Brongniart named _Calamodendron_ -(Fig. 50). A third form, to which Dr. Williamson seems to prefer to -assign this last name, has the tissue of the woody wedges barred, as -in the first, but the medullary rays are better developed than in the -second. In this third form the intermediate tissue, or primary medullary -rays, is truly fibrous, and with secondary medullary rays traversing -it. My own observations lead me to infer that there was a fourth type -of calamitean stem, less endowed with woody matter, and having a -larger fistulous or cellular cavity than any of those described by Dr. -Williamson. - -[CC] "Memoirs of the Philosophical Society," Manchester, 1886-'87. - -[Illustration: Fig. 49.--Erect _Calamites_ (_C. Suckovii_), showing the -mode of growth of new stems (_b_), and different forms of the ribs (_a_, -_c_). (Pictou, Nova Scotia.) Half natural size.] - -There is every reason to believe that all these various and complicated -stems belonged to higher and nobler types of mare's-tails than those of -the modern world, and that their fructification was equisetaceous and of -the form known as _Calamostachys_. - -We have already seen that noble tree-ferns existed in the Erian period, -and these were continued, and their number and variety greatly extended, -in the Carboniferous. In regard to the structure of their stems, and the -method of supporting these by aërial roots, the tree-ferns of all ages -have been nearly alike, and the form and structure of the leaves, except -in some comparatively rare and exceptional types, has also been much the -same. Any ordinary observer examining a collection of coal-formation -ferns recognises at once their kinship to the familiar brackens of our -own time. Their fructification is, unfortunately, rarely preserved, so -that we are not able, in the case of many species, to speak confidently -of their affinities with modern forms; but the knowledge of this subject -has been constantly extending, and a sufficient amount of information -has been obtained to enable us to say something as to their probable -relationships. (Figs. 51 to 55.) - -[Illustration: Fig. 50.--Stems of _Calamodendron_ and tissues magnified -(Nova Scotia), _a_, _b_, Casts of axis in sandstone, with woody envelope -(reduced). _c_, _d_, Woody tissue (highly magnified).] - -The families into which modern ferns are divided are, it must be -confessed, somewhat artificial, and in the case of fossil ferns, in -which the fructification is for the most part wanting, it is still more -so, depending in great part on the form and venation of the divisions -of the fronds. Of about eight families into which modern ferns are -divided, seven are found in a fossil state, and of these, four at least, -the _Cyathaceæ_, the _Ophioglosseæ_, the _Hymenophyllaceæ_, and the -_Marattiaceæ_, go back to the coal-formation.[CD] - -[CD] Mr. R. Kidston has recently described very interesting forms of fern -fructification from the coal-formation of Great Britain, and much has -been done by European palæobotanists, and also by Lesquereux and Fontaine -in America. - -[Illustration: Fig. 51.--Group of coal-formation ferns, A, _Odontopteris -subcuneata_ (Bunbury), B, _Neuropteris cordata_ (Brongniart). C, -_Alethopteris lonchitica_ (Brongniart). D, _Dictyopteris obliqua_ -(Bunbury). E, _Phyllopteris antiqua_ (Dawson), magnified; E^1, Natural -size, F, _Neuropteris cyclopteroides_ (Dawson).] - -[Illustration: Fig. 52.--_Alethopteris grandis_ (Dawson). Middle -coal-formation of Nova Scotia.] - -[Illustration: Fig. 53.--_Cyclopteris_ (_Aneimites_) _Acadica_ (Dawson), -a tree-fern of the Lower Carboniferous. _a_, Pinnules. _b_, Fragment of -petiole. _c_, Remains of fertile pinnules.] - -[Illustration: Fig. 54.--_Sphenopteris latior_, Dawson. Coal-formation, -_a_, Pinnule magnified, with traces of fructification.] - -[Illustration: Fig. 55.--Fructification of Palæozoic ferns, _a_, Thecæ of -_Archæopteris_ (Erian). _b_, Theca of _Senftenbergia_ (Carboniferous). -_c_, Thecæ of _Asterotheca_ (Carboniferous).] - -[Illustration: Fig. 56.--Tree-ferns of the Carboniferous. A, _Megaphyton -magnificum_, Dawson, restored. B, Leaf-scar of the same, two thirds -natural size. B^1, Row of leaf-scars, reduced. C, _Palæopteris Harttii_, -scars half natural size. D, _Acadica_, scars half natural size.] - -Some of these ferns have the more complex kind of spore-case, with a -jointed, elastic ring. It is to be observed, however, that those forms -which have a simple spore-case, either netted or membranous, and without -annulus, are most common in the Devonian and lowest Carboniferous. -Some of the forms in these old rocks are somewhat difficult to place -in the system. Of these, the species of _Archæopteris_, of the Upper -and Middle Erian, are eminent as examples. This type, however, scarcely -extends as high as the coal-formation.[CE] Some of the tree-ferns of the -Carboniferous present very remarkable features. One of these, of the -genus _Megaphyton_, seems to have two rows of great leaves, one at each -side of the stem, which was probably sustained by large bundles of aërial -roots (Fig. 56). - -[CE] The pretty little ferns of the genus _Botrychium_ (moonwort), so -common in American and European woods, seem to be their nearest modern -allies. - -In the Carboniferous, as in the Erian, there are leaves which have been -referred to ferns, but are subject to doubt, as possibly belonging to -broad-leaved taxine trees allied to the gingko-tree of China. One of -these, represented in Fig. 57, has been found in the coal-formation of -Nova Scotia, and referred to the doubtful genus _Noeggerathia_. Fontaine -has proposed for similar leaves found in Virginia the new generic name -_Saportea_. - -[Illustration: Fig. 57.--_Noeggerathia disbar_ (half natural size).] - -Ferns, as might be inferred from their great age, are at the present time -dispersed over the whole world; but their headquarters, and the regions -to which tree-ferns are confined, are the more moist climates of the -tropics and of the southern hemisphere. The coal-swamps of the northern -hemisphere seem to have excelled even these favoured regions of the -present world as a paradise for ferns. - -I have already stated that the Carboniferous constitutes the headquarters -of the _Cordaites_ (Fig. 58), of which a large number of species have -been described, both in Europe and America. We sometimes, though -rarely, find their stems showing structure. In this case we have a -large cellular pith, often divided by horizontal partitions into flat -chambers, and constituting the objects which, when detached, are called -_Sternbergiæ_ (Fig. 62). These Sternbergia piths, however, occur in true -conifers as well, as they do in the modern world in some trees, like our -common butternut, of higher type; and I showed many years ago that the -Sternbergia type may be detected in the young twigs of the balsam-fir -(_Abies balsamifera_). The pith was surrounded by a ring of scalariform -or barred tissue, often of considerable thickness, and in young stems so -important as to have suggested lycopodiaceous affinities. But as the stem -grew in size, a regular ring of woody wedges, with tissue having rounded -or hexagonal pores or discs, like those of pines, was developed. Outside -this was a bark, often apparently of some thickness. This structure in -many important points resembles that of cycads, and also approaches to -the structure of Sigillaria, while in its more highly developed forms it -approximates to that of the conifers. - -[Illustration: Fig. 58.--_Cordaites_ (_Dorycordaites_), Grand d'Eury, -reduced.] - -[Illustration: Fig. 59.--Fruits of _Cordaites_ and Taxine Conifers -(coal-formation. Nova Scotia.) A, _Antholithes squamosus_ (two thirds). -B, _A. rhabdocarpi_. (two thirds). B^1, Carpel restored. C, _A. spinosus_ -(natural size). D, _Trigonocarpum intermedium_. E, _T. Noeggerathii_. -F, _T. avellanum_. G, _Rhabdocarpus insignis_, reduced. H, _Antholithes -pygmæus_. I, _Cardiocarpum fluitans_. K, _Cardiocarpum bisectum_. L, -_Sporangites papillata_, lycopodiaceous macrospores (natural size and -magnified).] - -On the stems so constructed were placed long and often broad many-nerved -leaves, with rows of stomata or breathing-pores, and attached by somewhat -broad bases to the stem and branches. The fruit consisted of racemes, or -clusters of nutlets, which seem to have been provided with broad lateral -wings for flotation in the air, or in some cases with a pulpy envelope, -which flattens into a film. There seem to have been structures of both -these kinds, though in the state of preservation of these curious seeds -it is extremely difficult to distinguish them. In the first case they -must have been intended for dissemination by the wind, like the seeds -of spruces. In the latter case they may have been disseminated like the -fruits of taxine trees by the agency of animals, though what these were -it would be difficult to guess. These trees had very great reproductive -power, since they produced numerous seeds, not singly or a few together, -as in modern yews, but in long spikes or catkins bearing many seeds (Fig. -59). - -It is to be observed that the Cordaites, or the _Cordaitinæ_, as -they have been called, as a family,[CF] constitute another of those -intermediate groups with which we have already become familiar. On -the one hand they approach closely to the broader-leaved yews like -Gingko, Phyllocladus, and Podocarpus, and, on the other hand, they -have affinities with Cycadaceæ, and even with Sigillariæ. They were -beautiful and symmetrical trees, adding something to the variety of the -rather monotonous Palæozoic forests. They contributed also somewhat to -the accumulation of coal. I have found that some thin beds are almost -entirely composed of their leaves, and the tissues of their wood are not -infrequent in the mineral charcoal of the larger coal-seams. There is -no evidence that their roots were of the stigmaroid type, though they -evidently grew in the same swampy flats with the Sigillariæ and Calamites. - -[CF] Engler; Cordaitées of Renault. - -It may, perhaps, be well to say here that I believe there was a -considerably wide range of organisation in the Cordaitinæ as well as in -the Calamites and Sigillariæ, and that it will eventually be found that -there were three lines of connection between the higher cryptogams and -the phænogams, one leading from the lycopods by the Sigillariæ, another -leading by the Cordaites, and the third leading from the Equisetums by -the Calamites. Still further back the characters afterward separated in -the club-mosses, mare's-tails, and ferns, were united in the Rhizocarps, -or, as some now, but I think somewhat unreasonably, prefer to call -them, the "heterosporous Filicinæ." In the more modern world, all the -connecting links have become extinct and the phænogams stand widely -separated from the higher cryptogams. I do not make these remarks in -a Darwinian sense, but merely to state what appear to be the lines of -natural affinity and the links wanting to give unity to the system of -nature. - -Of all the trees of the modern world, none are perhaps so widely -distributed as the pines and their allies. On mountain-tops and -within the Arctic zone, the last trees that can struggle against the -unfavourable conditions of existence are the spruces and firs, and in -the warm and moist islands of the tropics they seem equally at home -with the tree-ferns and the palms. We have already seen that they are -a very ancient family, and in the sandstones of the coal-formation -their great trunks are frequently found, infiltrated with calcareous or -silicious matter, and still retaining their structure in the greatest -perfection (Fig. 60). So far as we know, the foliage of some of them -which constitutes the genera _Walchia_ and _Araucarites_ of some authors -(Figs. 60, 63) was not dissimilar from that of modern yews and spruces, -though there is reason to believe that some others had broad, fern-like -leaves like those of the gingko. None of them, so far as yet certainly -known, were cone-bearing trees, their fruit having probably been similar -to that of the yews (Fig. 61). The minute structures of their stems are -nearer to those of the conifers of the islands of the southern hemisphere -than to that of those in our northern climes--a correlation, no doubt, to -the equable climate of the period. There is not much evidence that they -grew with the Sigillariæ in the true coal-swamps, though some specimens -have been found in this association. It is more likely that they were in -the main inland and upland trees, and that in consequence they are mostly -known to us by drifted trunks borne by river inundations into the seas -and estuaries. - -[Illustration: Fig. 60.--Coniferous wood and foliage (Carboniferous). A, -_Araucarites gracilis_, reduced, b, _Dadoxylon Acadianum_ (radial), 90 -diams.; B^1 (tangential), 90 diams; B^2, cell showing areolation, 250 -diams. C, _Dadoxylon materiarium_ (radial), 90 diams.; C^1 (tangential), -90 diams. C^2, cell showing areolation, 250 diams. D, _Dadoxylon -antiquius_ (radial), 90 diams.; D^1 (tangential), 90 diams.; D^2, cell -showing areolation, 250 diams.] - -[Illustration: Fig. 61.--__Trigonocarpum Hookeri_, Dawson from the -coal-measures of Cape Breton. Probably the fruit of a Taxine tree. A, -Broken specimen magnified twice natural size, B, Section magnified: _a_, -the testa; _b_, the tegmen; _c_, the nucleus; _d_, the embryo, _c_, -Portion of the surface of the inner coat more highly magnified.] - -A remarkable fact in connection with them, and showing also the manner in -which the most durable vegetable structures may perish by decay, is that, -like the Cordaites, they had large piths with transverse partitions, a -structure which, as I have already mentioned, appears on a minute scale -in the twigs of the fir-tree, and that sometimes casts of these piths in -sandstone appear in a separate form, constituting what have been named -_Sternbergiæ_ or _Artisiæ_. As Renault well remarks with reference to -Cordaites, the existence of this chambered form of pith implies rapid -elongation of the stem, so that the Cordaites and conifers of the -coal-formation were probably quickly growing trees (Fig. 62). - -[Illustration: Fig. 62.--_Sternbergia_ pith of _Dadoxylon_. A, Specimen -(natural size), showing remains of wood at _a_, _a_. B, Junction of -wood and pith, magnified. C, Cells of the wood of do., _a_, _a_; _b_, -medullary ray; _c_, areolation.] - -The same general statements may be made as to the coal-vegetation as in -relation to that of the Erian. In the coal period we have found none of -the higher exogens, and there are only obscure and uncertain indications -of the presence of endogens, which we may reserve for a future chapter; -but gymnosperms abound and are highly characteristic. On the other hand, -we have no mosses or lichens, and very few Algæ, but a great number of -ferns and Lycopodiaceæ or club-mosses (Fig. 63). Thus, the coal-formation -period is botanically a meeting-place of the lower phænogams and the -higher cryptogams, and presents many forms which, when imperfectly known, -have puzzled botanists in regard to their position in one or other -series. In the present world, the flora most akin to that of the coal -period is that of warm, temperate regions in the southern hemisphere. It -is not properly a tropical flora, nor is it the flora of a cold region, -but rather indicative of a moist and equable climate. Still, we must bear -in mind that we may often be mistaken in reasoning as to the temperature -required by extinct species of plants, differing from those now in -existence. Further, we must not assume that the climatal conditions of -the northern hemisphere were in the coal period at all similar to those -which now prevail. As Sir Charles Lyell has shown, a less amount of land -in the higher latitudes would greatly modify climates, and there is -every reason to believe that in the coal period there was less land than -now. Further, it has been shown by Tyndall that a very small additional -amount of carbonic acid in the atmosphere would, by obstructing the -radiation of heat from the earth, produce almost the effect of a glass -roof or conservatory, extending over the whole world. Again, there is -much in the structure of the leaves of the coal-plants, as well as in -the vast amount of carbon which they accumulated in the form of coal, -and the characteristics of the animal life of the period, to indicate, -on independent grounds, that the carboniferous atmosphere differed -from that of the present world in this way, or in the presence of more -carbonic acid--a substance now existing in the very minute proportion -of one thousandth of the whole--a quantity adapted to the present -requirements of vegetable and animal life, but probably not to those of -the coal period. - -[Illustration: Fig. 63.--_Walchia imbricatula_, S. N., Permian, Prince -Edward Island.] - -Thus, if we inquire as to any analogous distribution of plants in the -modern world, we find this only in the warmer insular climates of the -southern hemisphere, where ferns, lycopods, and pines appear under forms -somewhat akin to those of the Carboniferous, but mixed with other types, -some of which are modern, others allied to those of the next succeeding -geological ages of the Mesozoic and Tertiary; and under these periods it -will be more convenient to make comparisons. - -The readers of recent English popular works on geology will have observed -the statement reiterated that a large proportion of the material of -the great beds of bituminous coal is composed of the spore-cases of -lycopodiaceous plants--a statement quite contrary to that resulting -from my microscopical examinations of the coal of more than eighty -coal-beds in Nova Scotia and Cape Breton, as stated in "Acadian Geology" -(page 463), and more fully in my memoir of 1858 on the "Structures -in Coal,"[CG] and that of 1866, on the "Conditions of Accumulation -of Coal."[CH] The reason of this mistake is, that an eminent English -naturalist, happening to find in certain specimens of English coal a -great quantity of remains of spores and spore-cases, though even in his -specimens they constitute only a small portion of the mass, and being -apparently unacquainted with what others had done in this field, wrote a -popular article for the "Contemporary Review," in which he extended an -isolated and exceptional fact to all coals, and placed this supposed -origin of coal in a light so brilliant and attractive that he has been -followed by many recent writers. The fact is, as stated in "Acadian -Geology," that trunks of _Sigillariæ_ and similar trees constitute a -great part of the denser portion of the coal, and that the cortical -tissues of these rather than the wood remain as coal. But cortical or -epidermal tissues in general, whether those of spore-cases or other -parts of plants, are those which from their resistance to water-soakage -and to decay, and from their highly carbonaceous character, are best -suited to the production of coal. In point of fact, spore-cases, though -often abundantly present, constitute only an infinitesimal part of the -matter of the great coal-beds. In an article in "The American Journal -of Science," which appeared shortly after that above referred to, I -endeavoured to correct this error, though apparently without effect in -so far as the majority of British geological writers are concerned. From -this article I have taken with little change the following passages, as -it is of importance in theoretical geology that such mistakes, involving -as they do the whole theory of coal accumulation, should not continue to -pass current. The early part of the paper is occupied with facts as to -the occurrence of spores and spore-cases as partial ingredients in coal. -Its conclusions are as follows: It is not improbable that sporangites, -or bodies resembling them, may be found in most coals; but it is most -likely that their occurrence is accidental rather than essential to coal -accumulation, and that they are more likely to have been abundant in -shales and cannel coals, deposited in ponds or in shallow waters in the -vicinity of lycopodiaceous forests, than in the swampy or peaty deposits -which constitute the ordinary coals. It is to be observed, however, -that the conspicuous appearance which these bodies, and also the strips -and fragments of epidermal tissue, which resemble them in texture, -present in slices of coal, may incline an observer, not having large -experience in the examination of coals, to overrate their importance; and -this I think has been done by most microscopists, especially those who -have confined their attention to slices prepared by the lapidary. One -must also bear in mind the danger arising from mistaking concretionary -accumulations of bituminous matter for sporangia. In sections of the -bituminous shales accompanying the Devonian coal above mentioned, there -are many rounded yellow spots, which on examination prove to be the -spaces in the epidermis of _Psilophyton_ through which the vessels -passing to the leaves were emitted. To these considerations I would add -the following, condensed from the paper above referred to (p. 139), in -which the whole question of the origin of coal is fully discussed:[CI] - -[CG] "Journal of the Geological Society," vol. xv. - -[CH] _Ibid._, vol. xxii. - -[CI] See also "Acadian Geology," 2d ed., pp. 138, 461, 493. - -1. The mineral charcoal or 'mother coal' is obviously woody tissue -and fibres of bark, the structure of the varieties of which, and the -plants to which it probably belongs, I have discussed in the paper above -mentioned. - -2. The coarser layers of coal show under the microscope a confused mass -of fragments of vegetable matter belonging to various descriptions of -plants, and including, but not usually in large quantities, sporangites. - -3. The more brilliant layers of the coal are seen, when separated by thin -laminæ of clay, to have on their surfaces the markings of _Sigillariæ_ -and other trees, of which they evidently represent flattened specimens, -or rather the bark of such specimens. Under the microscope, when their -structures are preserved, these layers show cortical tissues more -abundantly than any others. - -4. Some thin layers of coal consist mainly of flattened layers of leaves -of _Cordaites_ or _Pychnophyllum_. - -5. The _Stigmaria_ under-clays and the stumps of _Sigillaria_ in the -coal-roofs equally testify to the accumulation of coal by the growth of -successive forests, more especially of _Sigillariæ_. There is, on the -other hand, no necessary connection of sporangite-beds with Stigmarian -soils. Such beds are more likely to be accumulated in water, and -consequently to constitute bituminous shales and cannels. - -6. _Lepidodendron_ and its allies, to which the spore-cases in question -appear to belong, are evidently much less important to coal accumulation -than _Sigillaria_, which cannot be affirmed to have produced spore-cases -similar to those in question, even though the observation of Goldenberg -as to their fruit can be relied on; the accuracy of which, however, I am -inclined to doubt. - -On the whole, then, while giving due credit to those who have advocated -the spore-theory of coal, for directing attention to this curious and no -doubt important constituent of mineral fuel, and admitting that I may -possibly have given too little attention to it, I must maintain that -sporangite-beds are exceptional among coals, and that cortical and woody -matters are the most abundant ingredients in all the ordinary kinds; and -to this I cannot think that the coals of England constitute an exception. - -It is to be observed, in conclusion, that the spore-cases of plants, -in their indestructibility and richly carbonaceous character, only -partake of qualities common to most suberous and epidermal matters, as I -have explained in the publications already referred to. Such epidermal -and cortical substances are extremely rich in carbon and hydrogen, -in this resembling bituminous coal. They are also very little liable -to decay, and they resist more than other vegetable matters aqueous -infiltration--properties which have caused them to remain unchanged, -and to continue free from mineral additions more than other vegetable -tissues. These qualities are well seen in the bark of our American white -birch. It is no wonder that materials of this kind should constitute -considerable portions of such vegetable accumulations as the beds of -coal, and that when present in large proportion they should afford richly -bituminous beds. All this agrees with the fact, apparent on examination -of the common coal, that the greater number of its purest layers consist -of the flattened bark of _Sigillariæ_ and similar trees, just as any -single flattened trunk embedded in shale becomes a layer of pure coal. -It also agrees with the fact that other layers of coal, and also the -cannels and earthy bitumens, appear under the microscope to consist of -finely comminuted particles, principally of epidermal tissues, not only -from the fruits and spore-cases of plants, but also from their leaves and -stems. These considerations impress us, just as much as the abundance of -spore-cases, with the immense amount of the vegetable matter which has -perished during the accumulation of coal, in comparison with that which -has been preserved. - -I am indebted to Dr. T. Sterry Hunt for the following very valuable -information, which at once places in a clear and precise light the -chemical relations of epidermal tissue and spores with coal. Dr. Hunt -says: "The outer bark of the cork-tree, and the cuticle of many if not -all other plants, consists of a highly carbonaceous matter, to which -the name of _suberin_ has been given. The spores of _Lycopodium_ also -approach to this substance in composition, as will be seen by the -following, one of two analyses by Duconi,[CJ] along with which I give -the theoretical composition of pure cellulose or woody fibre, according -to Payen and Mitscherlich, and an analysis of the suberin of cork, from -_Quercus suber_, from which the ash and 2·5 per cent of cellulose have -been deducted.[CK] - -[CJ] Liebig and Kopp, "Jahresbuch," 1847-'48. - -[CK] Gmelin, "Handbook," xv., 145. - - ---------+-----------+--------+------------ - | Cellulose.| Cork. | Lycopodium. - ---------+-----------+--------+------------ - Carbon | 44·44 | 65·73 | 64·80 - Hydrogen | 6·17 | 8·33 | 8·73 - Nitrogen | .... | 1·50 | 6·18 - Oxygen | 49·39 | 24·44 | 20·29 - +-----------+--------+------------ - Total | 100·00 | 100·00 | 100·00 - ---------+-----------+--------+------------ - - -"This difference is not less striking when we reduce the above centesimal -analyses to correspond with the formula of cellulose, C{24}H{20}O{20}, -and represent cork and _Lycopodium_ as containing twenty-four equivalents -of carbon. For comparison I give the composition of specimens of peat, -brown coal, lignite, and bituminous coal:[CL] - -[CL] "Canadian Naturalist," vi., 253. - -Cellulose C{24}H{20}O{20} - -Cork C{24}H{18-2/10}O{6-7/10} - -Lycopodium C{24}H{19-4/10}NO{5-6/10} - -Peat (Vaux) C{24}H{14-4/10}O{10} - -Brown coal (Schröther) C{24}H{14-3/10}O{10-6/10} - -Lignite (Vaux) C{24}H{11-3/10}O{6-4/10} - -Bituminous coal (Regnault) C{24}H{10}O{3-3/10} - -"It will be seen from this comparison that, in ultimate composition, cork -and _Lycopodium_ are nearer to lignite than to woody fibre, and may be -converted into coal with far less loss of carbon and hydrogen than the -latter. They in fact approach closer in composition to resins and fats -than to wood, and, moreover, like those substances repel water, with -which they are not easily moistened, and thus are able to resist those -atmospheric influences which effect the decay of woody tissue." - -I would add to this only one further consideration. The nitrogen -present in the _Lycopodium_ spores, no doubt, belongs to the protoplasm -contained in them, a substance which would soon perish by decay; and -subtracting this, the cell-walls of the spores and the walls of the -spore-cases would be most suitable material for the production of -bituminous coal. But this suitableness they share with the epidermal -tissue of the scales of strobiles, and of the stems and leaves of ferns -and lycopods, and, above all, with the thick, corky envelope of the -stems of _Sigillariæ_ and similar trees, which, as I have elsewhere -shown,[CM] from its condition in the prostrate and erect trunks contained -in the beds associated with coal, must have been highly carbonaceous -and extremely enduring and impermeable to water. In short, if, instead -of "spore-cases," we read "epidermal tissues in general, including -spore-cases," all that has been affirmed regarding the latter will -be strictly and literally true, and in accordance with the chemical -composition, microscopical characters, and mode of occurrence of coal. It -will also be in accordance with the following statement, from my paper on -the "Structures in Coal," published in 1859: - -[CM] "Vegetable Structures in Coal," "Journal of Geological Society," -xv., 626. "Conditions of Accumulation of Coal," _ibid._, xxii., 95. -"Acadian Geology," 197, 464. - -"A single trunk of _Sigillaria_ in an erect forest presents an epitome of -a coal-seam. Its roots represent the _Stigmaria_ under-clay; its bark the -compact coal; its woody axis the mineral charcoal; its fallen leaves (and -fruits), with remains of herbaceous plants growing in its shade, mixed -with a little earthy matter, the layers of coarse coal. The condition of -the durable outer bark of erect trees concurs with the chemical theory -of coal, in showing the especial suitableness of this kind of tissue for -the production of the purer compact coals. It is also probable that the -comparative impermeability of the bark to mineral infiltration is of -importance in this respect, enabling this material to remain unaffected -by causes which have filled those layers, consisting of herbaceous -materials and decayed wood, with pyrites and other mineral substances." - -We need not go far in search of the uses of the coal vegetation, when .we -consider the fact that the greatest civilised nations are dependent on -it for their fuel. Without the coal of the Carboniferous period and the -iron-ore which is one of the secondary consequences of coal accumulation, -just as bog-ores of iron occur in the subsoils of modern peats, it would -have been impossible either to sustain great nations in comfort in the -colder climates of the northern hemisphere or to carry on our arts and -manufactures. The coal-formation yields to Great Britain alone about one -hundred and sixty million tons of coal annually, and the miners of the -United States extract mainly from the same formation nearly a hundred -million tons, while the British colonies and dependencies produce about -five million tons; and it is a remarkable fact that it is to the English -race that the greatest supply of this buried power and heat and light has -been given. - -The great forests of the coal period, while purifying the atmosphere of -its excess of unwholesome carbonic acid, were storing up the light and -heat of Palæozoic summers in a form in which they could be recovered in -our human age, so that, independently of their uses to the animals which -were their contemporaries, they are indispensable to the existence of -civilised man. - -Nor can we hope soon to be able to dispense with the services of -this accumulated store of fuel. The forests of to-day are altogether -insufficient for the supply of our wants, and though we are beginning -to apply water-power to the production of electricity, and though some -promising plans have been devised for the utilisation of the direct heat -and light of the sun, we are still quite as dependent as any of our -predecessors on what has been done for us in the Palæozoic age. - -In the previous pages I have said little respecting the physical -geography of the Carboniferous age; but, as may be inferred from the -vegetation, this in the northern hemisphere presented a greater expanse -of swampy flats little elevated above the sea than we find in any other -period. As to the southern hemisphere, less is known, but the conditions -of vegetation would seem to have been essentially the same. - -Taking the southern hemisphere as a whole, I have not seen any evidence -of a Lower Devonian or Upper Silurian flora; but in South Africa and -Australia there are remains of Upper Devonian or Lower Carboniferous -plants. These were succeeded by a remarkable Upper Carboniferous or -Permian group, which spread itself all over India, Australia, and South -Africa,[CN] and contains some forms (_Vertebraria_, _Phyllotheca_, -_Glossopteris_, &c. ) not found in rocks of similar age in the northern -hemisphere, so that, if the age of these beds has been correctly -determined, the southern hemisphere was in advance in relation to some -genera of plants. This, however, is to be expected when we consider that -the Triassic and Jurassic flora of the north contains or consists of -intruders from more southern sites. These beds are succeeded in India by -others holding cycads, &c., of Upper Jurassic or Lower Cretaceous types -(Rajmahal and Jabalpur groups). - -[CN] Wyley, "Journal Geol. Society," vol. xxiii., p. 172; Daintree, -_ibid._, vol. xxviii.; also Clarke and McCoy. - -Blanford has shown that there is a very great similarity in this series -all over the Australian and Indian region.[CO] Hartt and Darby have in -like manner distinguished Devonian and Carboniferous forms in Brazil -akin to those of the northern hemisphere. Thus the southern hemisphere -would seem to have kept pace with the northern, and according to Blanford -there is evidence there of cold conditions in the Permian, separating -the Palæozoic flora from that of the Mesozoic, in the same manner that -Ramsay has supposed a similar period of cold to have done north of the -equator. This would imply a very great change of climate, since we have -evidence of the extension of the Lower Carboniferous flora at least as -far north as Spitzbergen. The upper coal-formation we cannot, however, -trace nearly so far north; so that a gradual refrigeration may have been -going on before the Permian. Thus in both hemispheres there was a general -similarity in the later Palæozoic flora, and perhaps similar conditions -leading to its extinction and to its replacement by that to be described -in the next chapter. - -[CO] "Journal Geol. Society," vol. xxxi. - - - * * * * * - - -NOTES TO CHAPTER IV. - -I. Characters and Classification of Palæozoic Plants. - -In the space available in this work it would be impossible to enter fully -into the classification of Palæozoic plants; but it may be well to notice -some important points for the guidance of those who may desire to collect -specimens; more especially as much uncertainty exists as to affinities -and very contradictory statements are made. The statements below may -be regarded as the results of actual observation and of the study of -specimens _in situ_ in the rocks, as well as in the cabinet and under the -microscope. - -Gymnospermeæ. - -_Family_ Coniferæ; _Genus_ Dadoxylon, Endlicher; Araucarites, Goeppert; -Araucarioxylon, Kraus. - -The trunks of this genus occur from the Middle Devonian to the Permian -inclusive, as drift-logs calcified, silicified, or pyritised. The -only foliage associated with them is of the type of _Walchia_ and -_Araucarites_--viz., slender branches with numerous small spiral acicular -leaves. Two of the coal-formation species, _D. materiarum_ and another, -had foliage of this type. That of the others is unknown. They are all -distinct from the wood of _Cordaites_, for which see under that genus. - -The following are North American species: - - _Trunks._ - - _Dadoxylon Ouangondianum_, Dn. M. Erian Report, 1871.[CP] - _D. Halli_, Dn. " " - _D. Newberryi_, Dn. " " - _D. Clarkii_, Dn. (Cordæoxylon ?) " Report, 1882. - _D. Acadianum_, Dn. Coal-formation Acadian Geology. - and millstone - grit. - _D. Materiarum_, Dn. Do. and Permo- " - Carb. - _D._ (_Palæoxylon_) _antiquius_, Dn. L. Carboniferous. " - _D. annulatum_, Dn. Coal-formation. " - _Ormoxylon Erianum_, Dn. Erian Report, 1871. - - - _Foliage._ - - _Araucarites gracilis_, Dn. N. Coal-formation " - and Permian. - { Report on - _Walchia robusta_, Dn. Permian. { Prince Edward - _W. imbricatula_, Dn. " { Island. - -[CP] "Geological Survey of Canada: Fossil Plants of Erian and Upper -Silurian Formations," by J. W. Dawson. - -All of the above can be vouched for as good species based upon -microscopic examination of a very large number of trunks from different -parts of North America. The three Erian species of _Dadoxylon_ and _D. -antiquius_ from the Lower Carboniferous have two or more rows of cells -in the medullary rays. The last named has several rows, and is a true -_Palæoxylon_ allied to _D. Withami_ of Great Britain. _D. materiarium_ -is specially characteristic of the upper coal-formation and Permian, -and to it must belong one or both of the species of foliage indicated -above. _D. Clarkii_ has very short, simple medullary rays of only a few -cells superimposed, and has an inner cylinder of scalariform vessels, -approaching in these points to _Cordaites_. _Ormoxylon_ has a very -peculiar articulated pith and simple medullary rays. - -Witham in 1833 described several Carboniferous species of pine-wood, -under the generic name Pinites, separating under the name _Pitus_ species -which appeared to have the discs on the cell-walls separate and in -transverse lines. Witham's name was changed by Goeppert to _Araucarites_, -to indicate the similarity of these woods to Araucaria, _Pinites_ being -reserved for trees more closely allied to the ordinary pines. Endlicher, -restricting Araucarites to foliage, etc., of Araucaria-like trees, gave -the name _Dadoxylon_ to the wood; and this, through Unger's "Genera and -Species," has gained somewhat general acceptance. Endlicher also gave the -name _Pissadendron_ to the species which Witham had called _Pitus_; but -Brongniart proposed the name _Palæoxylon_ to include all the species with -thick and complex medullary rays, whatever the arrangement of the discs. -In Schimper's new work Kraus substitutes _Araucarioxylon_ for Endlicher's -_Dadoxylon_, and includes under _Pissadendron_ all the species placed by -Brongniart in _Palæoxylon_. - -To understand all this confusion, it may be observed that the characters -available in the determination of Palæozoic coniferous wood are chiefly -the form and arrangement of the wood-cells, the character of the bordered -pores or discs of their walls, and the form and composition of the -medullary rays. - -The character on which Witham separated his genus _Pitus_ from _Pinites_ -is, as I have ascertained by examination of slices of one of his original -specimens kindly presented to me by Mr. Sanderson, of Edinburgh, -dependent on state of preservation, the imperfectly preserved discs -or areolations of the walls of the fibre presenting the appearance of -separate and distinct circles, while in other parts of the same specimens -these discs are seen to be contiguous and to assume hexagonal forms, so -that in this respect they do not really differ from the ordinary species -of _Dadoxylon_. The true character for subdividing those species which -are especially characteristic of the Carboniferous, is the composite -structure of the medullary rays, which are thick and composed of several -radial piles of cells placed side by side. This was the character -employed by Brongniart in separating the genus _Palæoxylon_, though he -might with convenience have retained Witham's name, merely transferring -to the genus the species of Witham's _Pinites_ which have complex -medullary rays. The Erian rocks present the greatest variety of types, -and _Palæoxylon_ is especially characteristic of the Lower Carboniferous, -while species of _Dadoxylon_ with two rows of bordered pores and simple -medullary rays are especially plentiful in the upper coal-formation and -Permo-Carboniferous. - -The following table will clearly show the distinctive characters and -relations of the genera in question, as held by the several authors above -referred to: - -_Wood of Palæozoic Conifers._ - - Woody | Medullary rays | Generic | Geological - fibres. | and pith. | names. | age. - -------------+--------------------+---------------------+--------------- - No discs. | One or two series | _Aporoxylon_, | Devonian - | of cells. | Unger. | (Erian). - -------------+--------------------+---------------------+--------------- - | Complex, or of two | { _Pitus_, | - | or more series of | { Witham. | Middle and - | or more series of | { _Palæoxylon_, | Lower - | cells. | { Brongniart. | Carboniferous - | Pith Sternbergian. | { _Pissadendron_, | and Devonian. - | | { Endlicher. | - +--------------------+---------------------+--------------- - Discs in one | Simple, or of one | { _Araucarites_, | - series | row of cells. | { Goeppert | Upper - contiguous, | Pith Sternbergian. | { _Dadoxylon_, | Carboniferous - or in | | { Endlicher. | and Permian. - several | | { _Araucarioxylon_, | - series | | { Schimper. | - spirally +--------------------+---------------------+--------------- - arranged. | Pith in spherical | _Ormoxylon_,[CQ] Dn. | Devonian. - | chambers. | | - +--------------------+---------------------+--------------- - | Medullary sheath | | Devonian. - | scalariform. | _Dadoxylon_ | - | Medullary rays | (Cordæoxylon),[CR] | - | frequent, simple, | Dn. | - | short. | | - -------------+--------------------+---------------------+--------------- - -[CQ] Type _O. Erianum_, Dn., "Report on Canadian Plants," 1871. - -[CR] Type _D. Clarkii_, Dn., "Report on Canadian Plants," 1882. This may -be wood of Cordaites, to which it approaches very closely. - - -_Family_ Cordaites, _Genus_ Cordaites, Brongniart. - -Trunks marked by transverse scars of attachment of bases of leaves; -leaves broad, with many parallel veins, and attached by a broad -base; pistillate and staminate catkins of the nature of Antholithes. -Fruit winged or pulpy, of the kind known as _Cardiocarpum_. Stem -with a Sternbergia pith, usually large, surrounded by a ring of -pseudo-scalariform vessels, and with a cylinder usually narrow, of woody -wedges, with bordered pores in one or more series, and with simple -medullary rays. - -From specimens kindly presented to me by Prof. Renault, I have been -able to ascertain that the stems of some at least of these plants -(Eucordaites) are distinct in structure from all the species of -_Dadoxylon_, above mentioned, except _D. Clarkii_, of the Erian. They may -be regarded as intermediate between those of conifers and cycads, which -is indeed the probable position of these remarkable plants. - -Grand d'Eury has divided the _Cordaites_ into sub-genera, as follows: - -1. _Eucordaites._--Leaves spatulate, obovate, elliptical, or lanceolate, -sessile, entire, with rounded apices and of leathery consistency. The -leaves are from twenty to ninety centimetres in length. The nerves are -either equally or unequally strong. - -2. _Dorycordaites._--Leaves lanceolate, with sharp points; nerves -numerous, fine, and equal in strength. The leaves attain a length of from -forty to fifty centimetres. - -3. _Poacordaites._--Leaves narrow, linear, entire, blunt at the point, -with nerves nearly equally strong. The leaves are as much as forty -centimetres in length. - -To these Renault and Zeiller have added a fourth group, _Scutocordaites_. - -_Genus_ Sternbergia. - -This is merely a provisional genus intended to receive casts of the pith -cylinders of various fossil trees. Their special peculiarity is that, -as in the modern _Cecropia peltata_, and some species of _Ficus_, the -pith consists of transverse dense partitions which, on the elongation -of the internodes, become separated from each other, so as to produce a -chambered pith cavity, the cast of which shows transverse furrows. The -young twigs of the modern _Abies balsamifera_ present a similar structure -on a minute scale. I have ascertained and described such pith-cylinders -in large stems of _Dadoxylon Ouangondianum_, and _D. materiarium_. They -occur also in the stems of _Cordaites_ and probably of _Sigillariæ_. I -have discussed these curious fossils at length in "Acadian Geology" and -in the "Journal of the Geological Society of London," 1860. The following -summary is from the last-mentioned paper: - -_a._ As Prof. Williamson and the writer have shown, many of the -_Sternbergia_ piths belong to coniferous trees of the genus _Dadoxylon_. - -_b._ A few specimens present multiporous tissue, of the type of -_Dictyoxylon_, a plant of unknown affinities, and which, according to -Williamson, has a _Sternbergia_ pith. - -_c._ Other examples show a true scalariform tissue, comparable with that -of _Lepidodendron_ or _Sigillaria_, but of finer texture. Corda has shown -that plants of the type of the former genus (his _Lomatophloios_) had -_Sternbergia_ piths. Some plants of this group are by external characters -loosely reckoned by botanists as ribless _Sigillariæ_ (_Clathraria_); but -I believe that they are not related even ordinally to that genus. - -_d._ Many Carboniferous _Sternbergiæ_ show structures identical with -those described above as occurring in _Cordaites_, and also in some of -the trees ordinarily reckoned as _Sigillariæ_. - -_Genus_ Cardiocarpum. - -I have found at least eight species of these fruits in the Erian and -Carboniferous of New Brunswick and Nova Scotia, all of which are -evidently fruits of gymnospermous trees. They agree in having a dense -coaly nucleus of appreciable thickness, even in the flattened specimens, -and surrounded by a thin and veinless wing or margin. They have thus -precisely the appearance of samaras of many existing forest-trees, some -of which they also resemble in the outline of the margin, except that the -wings of samaras are usually veiny. The character of the nucleus, and the -occasional appearance in it of marks possibly representing cotyledons or -embryos, forbids the supposition that they are spore-cases. They must -have been fruits of phænogams. Whether they were winged fruits or seeds, -or fruits with a pulpy envelope like those of cycads and some conifers, -may be considered less certain. The not infrequent distortion of the -margin is an argument in favour of the latter view, though this may also -be supposed to have occurred in samaras partially decayed. On the other -hand, their being always apparently flattened in one plane, and the -nucleus being seldom, if ever, found denuded of its margin, are arguments -in favour of their having been winged nutlets or seeds. Until recently I -had regarded the latter view as more probable, and so stated the matter -in the second edition of "Acadian Geology." I have, however, lately -arrived at the conclusion that the _Cardiocarpa_ of the type of _C. -cornutum_ were gymnospermous seeds, having two cotyledons embedded in an -albumen and covered with a strong membranous or woody tegmen surrounded -by a fleshy outer coat, and that the notch at the apex represents the -foramen or micropyle of the ovule. The structure was indeed very similar -to that of the seeds of _Taxus_ and of _Salisburia_. With respect to some -of the other species, however, especially those with very broad margins, -it still appears likely that they were winged. - -The _Cardiocarpa_ were borne in racemes or groups, and it seems certain -that some of them at least are the seeds of _Cordaites_. The association -of some of them and of those of the next genus with _Sigillariæ_ is so -constant that I cannot doubt that some of them belong to plants of that -genus, or possibly to taxine conifers. The great number of distinct -species of these seeds, as compared with that of known trees which could -have produced them, is very remarkable. - -_Genus_ Trigonocarpum. - -These are large angled nuts contained in a thick envelope, and showing -internal structures resembling those of the seeds of modern _Taxineæ_. -There are numerous species, as well as allied seeds referred to the -provisional genera _Rhabdocarpus_ and _Carpolithes_. In _Trigonocarpum -Hookeri_ I have described the internal structure of one of those seeds, -and many fine examples from the coal-field of St. Etienne, in France, -have been described by Brongniart, so that their internal structure is -very well known. - -_Genus_ Antholithes. - -This is also a provisional genus, to include spikes of floral organs, -some of which are known to have belonged to _Cordaites_, others probably -to _Sigillariæ_. - - -Of Uncertain Affinities. - -_Family_ Sigillariaceæ. - -Under this name palæobotanists have included a great number of trees -of the Carboniferous system, all of which are characterised by broad -leaf-sears, with three vascular scars, and usually arranged in -vertical rows, and by elongated three-nerved leaves, and roots of the -stigmaria type--that is, with rounded pits, marking the attachment of -rootlets spirally arranged. These trees, however, collected in the -genus Sigillaria by arbitrary characters, which pass into those of -the Lepidodendroid trees, have been involved in almost inextricable -confusion, to disentangle which it will be necessary to consider: 1. The -external characters of _Sigillariæ_, and trees confounded with them. 2. -Subdivision of _Sigillariæ_ by external markings. 3. The microscopic -character of their stems. 4. What is known of their foliage and fruit. - -1. _Characters of Sigillaroid and Lepidodendroid Trunks_. - -It may be premised that the modes of determination in fossil botany -are necessarily different from those employed in recent botany. The -palæobotanist must have recourse to characters derived from the leaves, -the scars left by their fall, and the internal structures of the stem. -These parts, held in little esteem by botanists in describing modern -plants, and much neglected by them, must hold the first place in the -regard of the fossil botanist, whereas the fructification, seldom -preserved, and generally obscure, is of comparatively little service. It -is to be remarked also that in such generalised plants as those of the -Palæozoic, remarkable rather for the development of the vegetative than -of the reproductive organs, the former rise in importance as compared -with their value in the study of modern plants. - -In _Sigillariæ_, _Lepidodendra_, &c., the following surfaces of the stem -may be presented to our inspection: - -1. The outer surface of the epidermis without its leaves, but with -the leaf-bases and leaf-scars more or less perfectly preserved. On -this surface we may recognise: (1) Cellular swellings or projections -of the bark to which the leaves are attached. These may be called -leaf-bases, and they are sometimes very prominent. (2) The actual mark -of the attachment of the leaf situated in the most prominent part of -the leaf-base. This is the _leaf-scar_. (3) In the leaf-scar when well -preserved we can see one or more minute punctures or prominences which -are the points where the vascular bundles passing to the leaf found exit. -These are the vascular scars. - -When the leaves are attached, the leaf-scars and vascular scars cannot -be seen, but the leaf-bases can be made out. Hence it is important, if -possible, to secure specimens with and without the leaves. In flattened -specimens the leaf-bases are often distorted by pressure and marked with -furrows which must not be mistaken for true structural characters. The -leaf-bases, which are in relief on the outer surface of the stem, of -course appear as depressions on the mould in the containing rock, in -which the markings often appear much more distinctly than on the plant -itself. - -2. The outer surface of the epidermis may have been removed or may be -destroyed by the coarseness of the containing rock. In this case the -leaf-bases are usually preserved on the surface of the outer or corky -bark, but the leaf-scars and vascular scars have disappeared. This gives -that condition of Lepidodendroid trees to which the name _Knorria_ has -been applied. When plants are in this state careful inspection may -sometimes discover traces of the leaf-scars on portions of the stem, and -thus enable the _Knorria_ to be connected with the species to which it -belongs. - -3. The outer or corky bark may be removed, exposing the surface of the -inner or fibrous and cellular bark, which in the plants in question is -usually of great thickness. In this case neither the leaf-bases nor the -scars are seen, but punctures or little furrows or ridges appear where -the vascular bundles entered the inner bark. Specimens in this state are -usually said to be decorticated, though only the outer bark is removed. -It is often difficult to determine plants in this condition, unless some -portion of the stem can be found still retaining the bark; but when care -is taken in collecting, it will not infrequently be found that the true -outer surface can be recovered from the containing rock, especially if -a coaly layer representing the outer bark intervenes between this and -the inner impression. Specimens of this kind, taken alone, have been -referred to the genera _Knorria_, _Bothrodendron_, and _Halonia_. - -4. In some cases, though not frequently, the outer surface of the -ligneous cylinder is preserved. It almost invariably presents a regularly -striated or irregularly wrinkled appearance, depending upon the vertical -woody wedges, or the positions of the medullary rays or vascular bundles. -Specimens of this kind constituted some of the _Endogenites_ of the -older botanists, and the genus _Schizodendron_ of Eichwald appears to -include some of them. Many of them have also been incorrectly referred to -Calamites. - -5. In some cases the cast of the medullary cylinder or pith may alone -be preserved. This may be nearly smooch or slightly marked by vertical -striæ, but more usually presents a transverse striation, and not -infrequently the transverse constrictions and septa characteristic of the -genus Sternbergia. Loose _Sternbergiæ_ afford little means of connecting -them with the species to which they belong, except by the microscopic -examination of the shreds of the ligneous cylinder which often cling to -them.[CS] - -[CS] See my paper, "Journal of Geological Society," vol. xxvii. - -These facts being premised, the following general statements may be made -respecting some of the more common Palæozoic genera, referring, however, -principally to the perfect markings as seen on the epidermis: - -_Sigillaria._--Leaf-bases hexagonal or elongated, or confluent on a -vertical ridge. Leaf-scars hexagonal or shield-shaped. Vascular scars -three, the two lateral larger than the central. This last character -is constant, depending on the fact that the leaves of Sigillaria have -two or more vascular bundles. All so-called _Sigillariæ_ having the -central vascular scar largest, or only one vascular bundle, should be -rejected from this genus. In young branches of branching _Sigillariæ_ the -leaf-scars sometimes appear to be spiral, but in the older stems they -form vertical rows; interrupted, however, by transverse rows or bands -of _fruit-scars_, each with a single large central vascular scar, and -which have borne the organs of fructification. _Arthrocaulis_ of McCoy is -founded on this peculiarity. - -_Syringodendron._--Differs from Sigillaria in the leaf-scars, which are -circular and with a single vascular bundle. It is a matter of doubt -whether these plants were of higher rank than Sigillaria tending toward -the pines, or of lower rank tending toward Cyclostigma. Their leaf-bases -form vertical ridges. - -_Lepidodendron._--Leaf-bases rhombic, oval, or lanceolate, moderately -prominent. Leaf-scars rhombic or sometimes shield-shaped or heart-shaped, -in the middle or upper part of the leaf-base. Vascular scars three--the -middle one always largest and corresponding to the single nerve of the -leaf; the lateral ones sometimes obsolete. - -In older stems three modes of growth are observed. In some species -the expansion of the bark obliterates the leaf-bases and causes the -leaf-scars to appear separated by wide spaces of more or less wrinkled -bark, which at length becomes longitudinally furrowed and simulates the -ribbed character of Sigillaria. In others the leaf-bases grow in size -as the trunk expands, so that even in large trunks they are contiguous -though much larger than those on the branches. In others the outer bark, -hardening at an early age, is incapable of either of the above changes, -and merely becomes cleft into deep furrows in the old trunks. - -_Lepidophloios._--Leaf-bases transverse and prominent--often very much -so. Leaf-scars transversely rhombic or oval with three vascular scars, -the central largest. Leaves very long and one-nerved. Large strobiles -or branchlets borne in two ranks or spirally on the sides of the stem, -and leaving large, round scars (_cone-scars_), often with radiating -impressions of the basal row of scales. - -Species with long or drooping leaf-bases have been included in -_Lepidophloios_ and _Lomatophloios_, Species with short leaf-bases and -cone-scars in two rows have been called _Ulodendron_, and some of them -have been included in Sigillaria (sub-genus _Clathraria_). Decorticated -stems are Bothrodendron and _Halonia_. Some of the species approach near -to the last genus, especially to the Lepidodendra with rhombic leaf-bases -like _L. tetragonum_. - -_Cyclostigma._--Leaf-bases undeveloped. Leaf-scars circular or -horseshoe-shaped, small, with a central vascular scar. In old trunks of -Cyclostigma the leaf-scars become widely separated, and sometimes appear -in vertical rows. Young branches of Lepidodendron sometimes have the -leaf-scars similar to those of Cyclostigma. - -_Leptophleum._--Leaf-bases flat, rhombic; leaf-scars obsolete; vascular -scar single, central. The last two genera are characteristically Devonian. - -In contradistinction from the trees above mentioned, the following -general statements may be made respecting other groups: - -In conifers the leaf-bases are usually elongated vertically, often scaly -in appearance, and with the leaf-scar terminal and round, oval, or -rhombic, and with a single well-marked vascular scar. - -In Calamites, Calamodendron, and Asterophyllites the scars of the -branchlets or leaves are circular or oval, with only a single vascular -scar, and situated in verticils at the top of well-marked nodes of the -stem. - -In tree-ferns the leaf-bases are large and usually without a distinct -articulating surface. The vascular bundles are numerous. Protopteris -has rounded leaf-scars with a large horseshoe-shaped bundle of vessels -above and small bundles below. Caulopteris has large elliptic or oval -leaf-scars with vascular scars disposed concentrically. Palæopteris,[CT] -of Geinitz, has the leaf-scars transversely oval and the vascular bundles -confluent in a transverse band with an appendage or outlying bundle -below. Stemmatopteris has leaf-scars similar to those of Caulopteris, but -the vascular bundles united into a horseshoe-shaped band. - -[CT] This name, preoccupied by Geinitz, has been inadvertently misapplied -to the Devonian ferns of the genus _Archæopteris_. - - -2. _Subdivision of Sigillariæ in Accordance with their Markings_. - -The following groups may be defined in this way; but, being based on one -character only, they are of course in all probability far from natural: - -1. _Sigillaria_, Brongniart. Type, _Sigillaria reniformis_, Brongniart, -or _S. Brounii_, Dawson.--Stem with broad ribs, usually much broader than -the usually oval or elliptical tripunctate areoles, but disappearing at -base, owing to expansion of the stem. Leaves narrow, long, three-nerved. - -2. _Rhytidolepis_, Sternberg. Type, _S. scutellata_, Brongniart.--Ribs -narrow, and often transversely striate. Areoles large, hexagonal or -shield-shaped, tripunctate. Leaves as in last group. Kings of rounded -scars on the stems and branches mark attachment of fruit. It is possible -that some of the smaller stems of this group may be branches of trees of -group first. - -3. _Syringodendron_, Sternberg. Type, _S. organum_, L. and H., _S. -oculata_, Brongniart.--Stems ribbed; areoles small and round, and -apparently with a single scar, or three closely approximated. These are -rare, and liable to be confounded with decorticated examples of other -groups; but I have some specimens which unquestionably represent the -external surface. - -4. _Favularia_, Sternberg. Type, _Sigillaria elegans_ of -Brongniart.--Leaf-bases hexagonal, or in young branches elliptical, in -vertical rows, but without distinct ribs, except in old or decorticated -stems. Fruit borne in verticils on the branches bearing transverse rows -of rounded scars. Leaves somewhat broad and longitudinally striate. - -5. _Leioderma_, Goldenberg. Type, _S. Sydnensis_, Dawson.--Ribs obsolete. -Cortical and ligneous surfaces striate. Vascular scars double, elongate -longitudinally, and alike on cortical and inner surfaces. Areoles in rows -and distinct; stigmaria-roots striate, with small and distinct areoles. - -6. _Clathraria_, Brongniart. Type, _S. Menardi_, Brongniart.--Areoles -hexagonal, not in distinct rows, but having a spiral appearance. Some -of the plants usually referred to this group are probably branches of -_Favularia_. Others are evidently fragments of plants of the genus -_Lepidophloios_. - - -3. _Internal Structures of Sigillaria-Stems_. - -I long ago pointed out, on the evidence of the external markings and -mode of growth, that the stems of _Sigillariæ_ must have been exogenous, -and this conclusion has now been fully confirmed by the microscopic -researches of Williamson, not only in the case of _Sigillariæ_, but -of _Lepidodendra_ and _Calamodendra_ as well. Confining myself to my -own observations, three types of _Sigillariæ_ are known to me by their -internal structures, though I cannot certainly correlate all of these -with the external markings referred to above. - -1. _Diploxylon_, in which the stem consists of a small internal axis -surrounded by a very thick inner bark and a dense outer cortex. A fine -example from the South Joggins is thus described:[CU] - -[CU] "Journal of the Geological Society of London," November, 1877. - -"The axis of the stem is about six centimetres in its greatest diameter, -and consists of a central pith-cylinder and two concentric coats of -scalariform tissue. The pith-cylinder is replaced by sandstone, and is -about one centimetre in diameter. The inner cylinder of scalariform -tissue is perfectly continuous, not radiated, and about one millimetre -in thickness. Its vessels are somewhat crushed, but have been of large -diameter. Its outer surface, which readily separates from that of the -outer cylinder, is striated longitudinally. The outer cylinder, which -constitutes by much the largest part of the whole, is also composed of -scalariform tissue; but this is radially arranged, with the individual -cells quadrangular in cross-section. The cross-bars are similar on all -the sides and usually simple and straight, but sometimes branching or -slightly reticulated. The wall intervening between the bars has extremely -delicate longitudinal waving lines of ligneous lining, in the manner -first described by Williamson as occurring in the scalariform tissue -of certain _Lepidodendra_. A few small radiating spaces, partially -occupied with pyrites, obscurely represent the medullary rays, which must -have been very feebly developed. The radiating bundles passing to the -leaves run nearly horizontally; but their structure is very imperfectly -preserved. The stem being old and probably long deprived of its leaves, -they may have been partially disorganised before it was fossilised. The -outer surface of the axis is striated longitudinally, and in some places -marked with impressions of tortuous fibres, apparently those of the inner -bark. In the cross-section, where weathered, it shows concentric rings; -but under the microscope these appear rather as bands of compressed -tissue than as proper lines of growth. They are about twenty in number. -This tree has an erect, ribbed trunk, twelve feet in height and fifteen -inches in diameter, swelling to about two feet at the base." - -2. _Favularia Type._--This has been well described by Brongniart and -by Renault,[CV] and differs from the above chiefly in the fact that -the outer exogenous woody zone is composed of reticulated instead of -scalariform tissue, and the inner zone is of the peculiar form which I -have characterised as pseudo-scalariform. - -[CV] "Botanique Fossile," Paris, 1881. - -3. _Sigillaria Proper._--This I have illustrated in my paper in the -"Journal of the Geological Society" for May, 1871, and it appears -to represent the highest and most perfect type of the larger ribbed -_Sigillaria_. This structure I have described as follows, basing my -description on a very fine axis found in an erect stem, and on the -fragments of the woody axis found in the bases of other erect stems: - -_a._ A dense cellular outer bark, usually in the state of compact -coal--but when its structure is preserved, showing a tissue of thickened -parenchymatous cells. - -_b._ A very thick inner bark, which has usually in great part perished, -or been converted into coal, but which, in old trunks, contained a large -quantity of prosenchymatous tissue, very tough and of great durability. -This "bast-tissue" is comparable with that of the inner bark of modern -conifers, and constitutes much of the mineral charcoal of the coal-seams. - -_c._ An outer ligneous cylinder, composed of wood-cells, either with -a single row of large bordered pores,[CW] in the manner of pines -and cycads, or with two, three, or four rows of such pores sometimes -inscribed in hexagonal areoles in the manner of Dadoxylon. This woody -cylinder is traversed by medullary rays, which are short, and composed -of few rows of cells superimposed. It is also traversed by oblique -radiating bundles of pseudo-scalariform tissue proceeding to the leaves. -In some _Sigillariæ_ this outer cylinder was itself in part composed of -pseudo-scalariform tissue, as in Brongniart's specimen of _S. elegans_; -and in others its place may have been taken by multiporous tissue, as in -a case above referred to; but I have no reason to believe that either of -these variations occurred in the typical ribbed species now in question. -The woody fibres of the outer cylinder may be distinguished most readily -from those of conifers, as already mentioned, by the thinness of their -walls, and the more irregular distribution of the pores. Additional -characters are furnished by the medullary rays and the radiating bundles -of scalariform tissue when these can be observed. - -[CW] These are the same with the wood-cells elsewhere called discigerous -tissue, and to which I have applied the terms uniporous and multiporous. -The markings on the walls are caused by an unlined portion of the -cell-wall placed in a disk or depression, and this often surrounded by an -hexagonal rim of thickened wall; but in all cases these structures are -less pronounced than in _Dadoxylon_, and less regular in the walls of the -same cell, as well as in different layers of the tissues of the axis. - -_d._ An inner cylinder of pseudo-scalariform tissue. I have adopted the -term pseudo-scalariform for this tissue, from the conviction that it is -not homologous with the scalariform ducts of ferns and other acrogens, -but that it is merely a modification of the discigerous wood-cells, with -pores elongated transversely, and sometimes separated by thickened bars, -corresponding to the hexagonal areolation of the ordinary wood-cells. -A similar tissue exists in cycads, and is a substitute for the spiral -vessels existing in ordinary exogens. - -_e._ A large medulla, or pith, consisting of a hollow cylinder of -cellular tissue, from which proceed numerous thin diaphragms towards the -centre of the stem. - -These structures of the highest type of _Sigillaria_ are on the one -hand scarcely advanced beyond those of Calamopitus, as described by -Williamson, and on the other approach to those of _Cordaites_, as seen in -specimens presented to me by Renault. - -Finally, as to the fruit of _Sigillariæ_, I have no new facts to offer. -The strobiles or spikes associated with these trees have been variously -described as gymnospermous (Renault) or cryptogamous (Groldenberg and -Williamson). 1 have never seen them in place. Two considerations, -however, have always weighed with me in reference to this subject. One -is the constant abundance of Trigonocarpa and Cardiocarpa in the soil -of the Sigiliaria forests, as I have studied this at the South Joggins. -The other is that the rings of fruit-scars on the branches of Sigiliaria -are homologous with leaf-scars, not with branches, and therefore should -have borne single carpels and not cones or spikes of inflorescence. These -are merely suggestions, but I have no doubt they will be vindicated -by future discoveries, which will, I have no doubt, show that in the -family _Sigillariaceæ_ we have really two families, one possibly of -gymnospermous rank, or at least approaching to this, the other allied to -the Lepidodendra. - - -Cryptogamia. - -(_Acrogenes._) - -_Family_ Lepidodendreæ; _Genus_ Lepidodendron, Sternberg. - -These are arboreal Lycopods having linear one-nerved leaves, stems -branching dichotomously, and with ovate or rhombic leaf-bases bearing -rhombic leaf-scars, often very prominent. The fruit is in scaly -strobiles, terminal or lateral, and there are usually, if not always, -macrospores and microspores in each strobile. The young branches and -stems have a central pith, a cylinder of scalariform tubes sending out -ascending bundles to the leaves through a thick cellular and fibrous -inner bark, and externally a dense cortex confluent with or consisting of -the leaf-bases. Older stems have a second or outer layer of scalariform -fibres in wedges with medullary rays, and strengthening the stem by a -true exogenous growth, much as in the Diploxylon type of Sigiliaria. The -development of this exogenous cylinder is different in amount and rate -in different species.[CX] This different development of the exogenous -axis is accompanied with appropriate external appearances in the stems, -and the changes which take place in their markings. These are of three -kinds. In some species the areoles, at first close together, become, in -the process of the expansion of the stem, separated by intervening spaces -of bark in a perfectly regular manner; so that in old stems, while widely -separated, they still retain their arrangement, while in young stems they -are quite close to one another. This is the case in _L. corrugatum_. In -other species the leaf-scars or bases increase in size in the old stems, -still retaining their forms and their contiguity to each other. This -is the case in _L. undulatum_, and generally in those _Lepidodendra_ -which have large leaf-bases. In these species the continued vitality -of the bark is shown by the occasional production of lateral strobiles -on large branches, in the manner of the modern red pine of America. In -other species the areoles neither increase in size nor become regularly -separated by growth of the intervening bark; but in old stems the bark -splits into deep furrows, between which may be seen portions of bark -still retaining the areoles in their original dimensions and arrangement. -This is the case with _L. Pictoense_. This cracking of the bark no doubt -occurs in very old trunks of the first two types, but not at all to the -same extent. - -[CX] See "Memoirs of Dr. Williamson," in "Philosophical Transactions," -for ample details. - -As a type of Lepidodendron, I may describe one of the oldest -Carboniferous species characteristic of the Lower Carboniferous in -America, and corresponding to _L. Veltheimianum_ of Europe. - -Lepidodendron Corrugatum, Dawson.--(See Fig. 43, _supra_.) "Quarterly -Journal of Geological Society," vol. xv.; "Acadian Geology," page 451. - -_Habit of Growth._--Somewhat slender, with long branches and long, -slender leaves having a tendency to become horizontal or drooping. - -_Markings of Stem._--Leaf-bases disposed in quincunx or spirally, -elongate, ovate, acute at both ends, but more acute and slightly -oblique at the lower end; most prominent in the upper third, and with -a slight vertical ridge. Leaf-scars small, rounded, and showing only -a single punctiform vascular scar. The leaf-scar on the outer surface -is in the upper third of the base; but the obliquity of the vascular -bundle causes it to be nearly central on the inside of the epidermis. -In young succulent shoots the leaf-scars are contiguous and round as -in Cyclostigma, without distinct leaf-bases. In this state it closely -resembles _L. Olivieri_, Eichwald.[CY] - -[CY] Lethæa Rossica, Plate Y, Figs. 12, 13. - -In the ordinary young branches the leaf-scars are contiguous, and closely -resemble those of _L. elegans_, Brongt. (Fig. 43 C). As the branches -increase in diameter the leaf-scars slightly enlarge and sometimes assume -a verticillate appearance (Fig. 43 D). As they still further enlarge they -become separated by gradually increasing spaces of bark, marked with many -waving striæ or wrinkles (Fig. 43 I, N). At the base of old stems the -bark assumes a generally wrinkled appearance without distinct scars. - -_Knorria or Decorticated States._--Of these there is a great variety, -depending on the state of preservation, and the particular longitudinal -ridges. Fig. 43 D shows a form in which the vascular bundles appear -as cylindrical truncate projections. Other forms show the leaf-bases -prominent, or have an appearance of longitudinal ribbing produced by the -expansion of the bark. - -_Structure of Stem._--This is not perfectly preserved in any of my -specimens, but one flattened specimen shows a central medulla with a -narrow ring of scalariform vessels surrounding it, and constituting the -woody axis. The structure is thus similar to that of _L. Harcourtii_, -which I regard as probably the same with the closely allied European -species L. Veltheimianum. - -_Leaves._--These are narrow, one-nerved, curving somewhat rapidly outward -(Figs. 43, B, C, D). They vary from one to two inches in length. - -_Roots._--I have not seen these actually attached, but they occur very -abundantly in the under-clays of some erect forests of these plants at -Horton Bluff, and are of the character of Stigmariæ (Figs. 30, 31). In -some of the under-clays the long, flattened rootlets are excessively -abundant, and show the mark of a central vascular bundle. - -_Fructification._--Cones terminal, short, with many small, acute -imbricate scales. Spore-cases globular, smooth (Fig. 43 C). On the -surface of some shales and sandstones at Horton there are innumerable -round spore-cases of this tree about the size of mustard-seed (Fig. 43 -F). Large slabs are sometimes covered with these, and thin layers of -shale are filled with flattened specimens. - -This is the characteristic species of the Lower Carboniferous -coal-measures, occurring in great profusion at Horton Bluff and its -vicinity, also at Sneid's Mills near Windsor, Noel and Five-Mile River, -at Norton Creek and elsewhere in New Brunswick (Matthew's collection), -and at Antigonish (Honeyman's collection). - -I have received from the lowest Carboniferous beds of Ohio specimens -of this species.[CZ] According to Rogers and Lesquereux similar forms -occur in the Vespertine of Pennsylvania and in the Lower Carboniferous -of Illinois. _L. Veltheimianum_ of western Europe and _L. glincanum_ of -Russia are closely allied Lower Carboniferous species.[DA] - -[CZ] "Journal of Geological Society," November, 1862, p. 313. - -[DA] For comparisons of these see "Report on Plants of Lower -Carboniferous of Canada," p. 21. - -A very different type is furnished by a new species from the middle -coal-formation of Clifton, New Brunswick. - -Lepidodendron Cliftonense, Dawson.--Habit of Growth.--Robust, with thick -branches, and leaves several inches in length. Terminal branches becoming -slender, with shorter leaves. - -_Markings of Stem._--Leaf-bases long oval, pointed at ends, enlarging -with growth of stem. Leaf-scars central, rhombic, transverse. - -_Leaves._--One-nerved, acutely pointed, from four inches in length on the -larger branches to one inch or less on the branchlets. - -_Fructification._--Cones large, cylindrical or long oval, with large -scales of trigonal form, and not elongated but lying close to the -surface. Borne on lateral, slender branchlets, with short leaves. - -_Genus_ Lepidophloios, Sternberg; Ulodendron, L. and H.; Lomatophloios, -Corda. - -_Lepidophloios._--Under this generic name, established by Sternberg, -I include those lycopodiaceous trees of the coal-measures which have -thick branches, transversely elongated leaf-scars, each with three -vascular points and placed on elevated or scale-like protuberances, -long one-nerved leaves, and large lateral strobiles in vertical rows or -spirally disposed. Their structure resembles that of _Lepidodendron_, -consisting of a _Sternbergia_ pith, a slender axis of large scalariform -vessels, giving off from its surface bundles of smaller vessels to the -leaves, a very thick cellular bark, and a thin dense outer bark, having -some elongated cells or bast-tissue on its inner side. In these trees the -exogenous outer cylinder is less developed than in the Lepidodendra, and -is sometimes wanting in stems or branches of some thickness. - -Regarding _L. laricinum_ of Sternberg as the type of the genus, and -taking in connection with this the species described by Goldenberg, -and my own observations on numerous specimens found in Nova Scotia, 1 -have no doubt that _Lomatophloios crassicaulis_ of Corda, and other -species of that genus described by Goldenberg, _Ulodendron_ and -_Bothrodendron_ of Lindley, _Lepidodendron ornatissimum_ of Brongniart, -and _Halonia punctata_ of Geinitz, all belong to this genus, and differ -from each other only in conditions of growth and preservation. Several -of the species of _Lepidostrobus_ and _Lepidophyllum_ also belong to -_Lepidophloios_. - -The species of _Lepidophloios_ are readily distinguished from -_Lepidodendron_ by the form of the areoles, and by the round scars on the -stem, which usually mark the insertion of the large strobiles, though -in barren stems they may also have produced branches; still, the fact -of my finding the strobiles _in situ_ in one instance, the accurate -resemblance which the scars bear to those left by the cones of the red -pine when borne on thick branches, and the actual impressions of the -radiating scales in some specimens, leave no doubt in my mind that -they are usually the marks of cones; and the great size of the cones of -_Lepidophloios_ accords with this conclusion. - -The species of _Lepidophloios_ are numerous, and individuals are quite -abundant in the coal formation, especially toward its upper part. Their -flattened bark is frequent in the coal-beds and their roofs, affording -a thin layer of pure coal, which sometimes shows the peculiar laminated -or scaly character of the bark when other characters are almost entirely -obliterated. The leaves also are nearly as abundant as those of -Sigillaria in the coal-shales. They can readily be distinguished by their -strong, angular midrib. - -The markings of _Lepidophloios_ may easily be mistaken for those of the -_Clathraria_ type of _Sigillaria_. When the stem only is seen, they can -be distinguished by the length of the leaf-bases in _Lepidophloios_, and -by the dominant central vascular scar; also by the one-nerved and ribbed -leaves. Where the large, round marks of the cones are present, these are -an infallible guide, never being present in _Sigillaria_. As the cones -grew on the upper sides of the branches, the impression of the lower side -often shows no cone-scars, or only two lateral rows, whereas on the upper -side of the same branch they appear spirally arranged. I may describe as -an example-- - -_Lepidophloios Acadianus_, Dawson. Leaf-bases broadly rhombic, or in old -stems regularly rhombic, prominent, ascending, terminated by very broad -rhombic scars having a central point and two lateral obscure points. -Outer bark laminated or scaly. Surface of inner bark with single points -or depressions. Leaves long, linear, with a strong keel on one side, -five inches or more in length. Cone-scars sparsely scattered on thick -branches, either in two rows or spirally, both modes being sometimes seen -on the same branch. Scalariform axis scarcely an inch in diameter in a -stem five inches thick. Fruit, an ovate strobile with numerous acute -scales covering small globular spore-cases. This species is closely -allied to _Ulodendron majus_ and _Lepidophloios laricinus_, and presents -numerous varieties of marking. Coal-formation, Nova Scotia. - -_Family_ Calamiteæ; _Genus_ Calamites, Suckow. - -The plants of this genus are unquestionably allied to the modern -_Equisetaceæ_, but excel these so much in variety of form and structure, -and are so capricious in their states of preservation, and so liable to -be mistaken for parts of plants generically different, that they have -given rise to much controversy. The following considerations will enable -us to arrive at some certainty. - -The genus _Calamites_ was originally founded in the longitudinally -ribbed and jointed stems so frequent in the coal-formation, and of which -the common _C. Suckovii_ is a typical form. The most perfect of these -stems represent the outer surface immediately within the epidermis, in -which case transverse lines or constrictions mark the nodes, and at the -nodes there are rounded spots, sometimes indicating radial processes of -the pith, first described by Williamson; in other cases, the attachment -of branchlets, or in some specimens both. But some specimens show the -outer surface of the epidermis, in which case the transverse nodal -lines are usually invisible, though the scars of branchlets may appear. -In still other examples the whole of the outer tissues have perished, -and the so-called Calamite is a cast of the interior of the stem, -showing merely longitudinal ribbing and transverse nodal constrictions. -In studying these plants _in situ_ in the erect Calamite brakes of -the coal-formation of Nova Scotia, one soon becomes familiar with -these appearances, but they are evidently unknown to the majority of -palæobotanists, though described in detail more than twenty years ago. - -When the outer surface is preserved it is sometimes seen to bear -verticils of long needle-like leaves (_C. Cistii_), or of branchlets with -secondary whorls of similar leaves (_C. Suckovii_ and _C. undulatus_). -No Calamite known to me bears broad one-nerved leaves like those of -_Asterophyllites_ and _Annularia_, though the larger stems of these -plants have been described as Calamites, and the term _Calamocladus_ has -been used to include both groups. The base of the Calamite stem usually -terminates in a blunt point, and may be attached to a rhizome, or several -stems may bud out from each other in a group or stool. The roots are long -and cylindrical, sometimes branching. The fruit consists of spikes of -spore-cases, borne in whorls and subtended by linear floral leaves. To -these strobiles the name Calamostachys has been given. - -Williamson has shown that the stem of Calamites consists of a central -pith or cavity of large size surrounded by a cylinder consisting of -alternate wedges of woody and cellular matter, with vertical canals at -the inner sides of the wedges, and slender medullary rays. The thick -cellular wedges intervening between the woody wedges he calls primary -medullary rays; the smaller medullary rays in the wedges, secondary -medullary rays. There is thus a highly complex exogenous stem based on -the same principle with the stem of a common _Equisetum_, but with much -greater strength and complexity. - -Williamson has also shown that there are different sub-types of these -stems. More especially he refers to the three following: - -(_a_) _Calamites_ proper, which has the woody wedges of scalariform or -barred tissue with thin medullary rays, and the thick primary medullary -rays are cellular. - -(_b_) _Calamopitus_ has reticulated or multiporous tissue in the woody -wedges with medullary rays, and the primary medullary wedges are composed -of elongated cells. - -(_c_) _Calamodendron_ has the woody wedges of barred tissue as in _a_, -with medullary rays, but has the intervening medullary wedges of an -elongated tissue approaching to woody fibre, and also with medullary rays. - -To these I would add a fourth type, which I have described, from the -coal-formation of Nova Scotia.[DB] - -[DB] "Quarterly Journal of the Geological Society," 1871. - -(_d_) _Eucalamodendron_ differs from _Calamodendron_ in having true -bordered pores or pseudo-scalariform slit-pored tissue, and corresponds -to the highest type of calamitean stem. - -I would also add that under _a_ and _b_ there are some species in which -the woody cylinder is very thin in comparison to the size of the stem. In -_c_ and _d_ the woody cylinder is thick and massive, and the stems are -often large and nodose. - -As an example of an ordinary Calamite in which the external surface and -foliage are preserved, I may quote the following from my report on the -"Flora of the Lower Carboniferous and Millstone Grit," 1873: - -Calamites Undulatus, Brongniart.--This species is stated by Brongniart -to be distinguished from the _C. Suckovii_, the characteristic Calamite -of the middle coal-formation, by its undulated ribs marked with peculiar -cellular reticulation. He suggests that it may be merely a variety of -_C. Suckovii_, an opinion in which Schimper coincides; but since I have -received large additional collections from Mr. Elder, containing not -only the stems and branches, but also the leaves and rhizomes, I am -constrained to regard it as a distinct though closely allied species. - -The rhizomata are slender, being from one to two inches in diameter, -and perfectly flattened. They are beautifully covered with a cellular -reticulation on the thin bark, and show occasional round areoles marking -the points of exit of the rootlets. I have long been familiar with -irregular flattened stems thus reticulate, but have only recently been -able to connect them with this species of Calamite. - -The main stems present a very thin carbonaceous bark reticulated like -the rhizomes. They have flat, broad ribs separated by deep and narrow -furrows, and undulated in a remarkable manner even when the stems are -flattened. This undulation is, however, perhaps an indication of vertical -pressure while the plant was living, as it seems to have had an unusually -thin and feeble cortical layer, and the undulations are apparently best -developed in the lower part of the stem. At the nodes the ribs are often -narrowed and gathered together, especially in the vicinity of the rounded -radiating marks which appear to indicate the points of insertion of -the branches. At the top of each rib we have the usual rounded areole, -probably marking the insertion of a primary branchlet. - -The branches have slender ribs and distant nodes, from which spring -secondary branchlet s in whorls, these bearing in turn small whorls of -acicular leaflets much curved upward, and which are apparently round in -cross section and delicately striate. They are much shorter than the -leaves of _Calamites Suckovii_, and are less dense and less curved than -those of _C. nodosus_, which I believe to be the two most closely allied -species. - -Lesquereux notices this species as characteristic of the lower part of -the Carboniferous in Arkansas. - -It will be observed that I regard the striated and ribbed stems not as -internal axes, but as representing the outer surface of the plants. This -was certainly the case with the present species and with _C. Suckovii_ -and _C. nodosus_. Other species, and especially those which belonged to -Calamodendron, no doubt had a smooth or irregularly wrinkled external -bark; but this gives no good ground for the manner in which some writers -on this subject confound Calamites with Calamodendra, and both with -Asterophyllites and Sphenophyllum. With this no one who has studied these -plants, rooted in their native soils, and with their appendages still -attached, can for a moment sympathise. One of the earliest geological -studies of the writer was a bed of these erect Calamites, which he -showed to Sir C. Lyell in 1844, and described in the "Proceedings of -the Geological Society" in 1851, illustrating the habit of growth as -actually seen well exposed in a sandstone cliff. Abundant opportunities -of verifying the conclusions formed at that time have since occurred, -the results of which have been summed up in the figures in Acadian -Geology, which, though they have been treated by some botanists as merely -restorations, are in reality representations of facts actually observed. - -On these subjects, without entering into details, and referring for these -to the elaborate discussions of Schimper, Williamson, and McNab, and to -my paper on the subject, "Journal of the Geological Society," vol. xxvii, -p. 54, I may remark: - -1. That the aërial stems of ordinary Calamites had a thin cortical layer, -with lacunæ and fibrous bundles and multiporous vessels--the whole not -differing much from the structure of modern Equiseta. - -2. Certain arborescent forms, perhaps allied to the true Calamites, -as well as possibly the old underground stems of ordinary species[DC] -assumed a thick-walled character in which the tissues resembled the -wedges of an exogen, and abundance of pseudo-scalariform fibres were -developed, while the ribbing of the external surface became obsolete or -was replaced by a mere irregular wrinkling. - -[DC] Williamson, "Transactions of the Royal Society." McNab, in -"Proceedings of the Edinburgh Botanical Society." - -3. Sufficient discrimination has not been exercised in separating casts -of the internal cavities of Calamites and Calamodendron from those -representing other surfaces and the proper external surface. - -4. There is no excuse for attributing to Calamites the foliage of -Annularia, Asterophyllites, and Sphenophyllum, since these leaves have -not been found attached to true Calamite stems, and since the structure -of the stems of Asterophyllites as described by Williamson, and that of -Sphenophyllum as described by the writer,[DD] are essentially different -from those of Calamites. - -[DD] "Journal of the Geological Society," 1866. - -5. As the species above described indicates, good external characters can -be found for establishing species of this genus, and these species are of -value as marks of geological age. - -_Genus_ Archæocalamites, Sternberg. - -This genus has been established to include certain Calamites of the -Devonian and Lower Carboniferous, in which the furrows on the stem do not -alternate at the nodes or joints, and the leaves in one species at least -bifurcate. _C. radiatus_, Brongniart, is the typical species. In North -America it occurs in the Erian, probably as low as the Middle Erian. In -Europe it has so far been recognised in the Lower Carboniferous only. I -have, however, seen stems from alleged Devonian beds in Devonshire which -may have belonged to this species. - -_Family_ Asterophylliteæ; _Genus_ Asterophyllites, Brongniart. - -Stems ribbed and jointed like the _Calamites_, but with inflated nodes -and a stout internal woody cylinder, which has been described by -Williamson. From the joints proceeded whorls of leaves or of branchlets, -bearing leaves which differed from those of _Calamites_ in their having -a distinct middle rib or vein. The fructification consisted of long -slender cones or spikes, having whorls of scales bearing the spore-cases. -Some authors speak of _Asterophyllites_ as only branches and leaves of -_Calamites_; but though at first sight the resemblance is great, a close -inspection shows that the leaves of Asterophyllites have a true midrib, -which is wanting in _Calamites_. - -_Genus_ Annularia.--It is perhaps questionable whether these plants -should be separated from _Asterophyllites_, The distinction is that -they produce branches in pairs, and that their whorls of leaves are -one-sided and usually broader than those of _Asterophyllites_, and united -into a ring at their insertion on the stem. One little species, _A. -sphenophylloides_, is very widely distributed. - -Pinnularia--a provisional genus---includes slender roots or stems -branching in a pinnate manner, and somewhat irregularly. They are very -abundant in the coal shales, and were probably not independent plants, -but aquatic roots belonging to some of the plants last mentioned. -The probability of this is farther increased by their resemblance in -miniature to the roots of _Calamites_. They are always flattened, but -seem originally to have been round, with a slender thread-like axis of -scalariform vessels, enclosed in a soft, smooth, cellular bark. - -_Family_ Rhizocarpeæ; _Genus_ Sphenophyllum. - -Leaves in whorls, wedge-shaped, with forking veins. Fructification on -spikes, with verticils of sporocarps. These plants are by some regarded -as allied to the _Calamiteæ_ and _Asterophylliteæ_, by others as a high -grade of Rhizocarps of the type of Marsilia. The stem had a star-shaped -central bundle of scalariform or reticulato-scalariform vessels. - -_Genus_ Sporangites. (_Sporocarpon_, Williamson.) - -Under this name we may provisionally include those rounded spherical -bodies found in the coal and its accompanying beds, and also in -the Erian, which may be regarded as Macrospores or Sporocarps of -Protosalvinia, or other Rhizocarpean plants akin to those described above -in Chapter III, which see for description. - -_Genus_ Protosalvinia.--Under this we include sporocarps allied to those -of _Salvinia_, as described in Chapter III. - - -_Family_ Filices. - -Under this head I shall merely refer to a few groups of special interest, -and to the provisional arrangement adopted for the fronds of ferns when -destitute of fructification. - -The external appearances of trunks of tree-ferns have been already -referred to. - -With respect to tree ferns, the oldest known examples are those from -the Middle Devonian of New York and Ohio, which I have described in the -"Journal of the Geological Society," 1871 and 1881. As these are of some -interest, I have reproduced their descriptions in a note appended to -Chapter III, which see. - -The other forms most frequently occurring in the Carboniferous are -_Caulopteris_, _Palæopteris_, and _Megaphyton_[DE] Stems showing merely -masses of aërial roots are known by the name _Psaronius_. - -[DE] See my "Acadian Geology," also below. - -With reference to the classification of Palæozoic ferns, this has -hitherto been quite arbitrary, being based on mere form and venation of -fronds, but much advance has recently been made in the knowledge of their -fructification, warranting a more definite attempt at classification. The -following are provisional genera usually adopted: - -1. _Cyclopteris_, Brongniart.--Leaflets more or less rounded or -wedge-shaped, without midrib, the nerves spreading from the point of -attachment. This group includes a great variety of fronds evidently of -different genera, were their fructification known; and some of them -probably portions of fronds, the other parts of which may be in the next -genus. - -2. _Neuropteris_, Brongniart.--Fronds pinnate, and with the leaflets -narrowed at the base; midrib often not distinct, and disappearing toward -the apex. Nervures equal, and rising at an acute angle. Ferns of this -type are among the most abundant in the coal-formation. - -3. _Odontopteris_, Brongniart.--In these the frond is pinnate, and -the leaflets are attached by their whole base, with the nerves either -proceeding wholly from the base, or in part from an indistinct midrib, -which soon divides into nervures. - -4. _Dictyopteris_, Gutbier.--This is a beautiful style of fern, with -leaflets resembling those of _Neuropteris_, but the veins arranged -in a network of oval spaces. Only a few species are known in the -coal-formation. - -5. _Lonchopteris_, Brongniart.--Ferns with netted veins like the above, -but with a distinct midrib, and the leaflets attached by the whole base. -Of this, also, we can boast but few species. - -6. _Sphenopteris_, Brongniart.--These are elegant ferns, very numerous -in species, and most difficult to discriminate. Their most distinctive -characters are leaflets narrowed at the base, often lobed, and with -nervures dividing in a pinnate manner from the base. - -7. _Phyllopteris_, Brongniart.--These are pinnate, with long lanceolate -pinnules, having a strong and well-defined midrib, and nerves proceeding -from it very obliquely, and dividing as they proceed toward the margin. -The ferns of this genus are for the most part found in formations more -recent than the Carboniferous; but I have referred to it, with some -doubt, one of our species. - -8. _Alethopteris_, Brongniart.--This genus includes many of the most -common coal-formation ferns, especially the ubiquitous _A. lonchitica_, -which seems to have been the common brake of the coal-formation, -corresponding to _Pteris aquilina_ in modern Europe and America. These -are brake-like ferns, pinnate, with leaflets often long and narrow, -decurrent on the petiole, adherent by their whole base, and united at -base to each other. The midrib is continuous to the point, and the -nervures run off from it nearly at right angles. In some of these ferns -the fructification is known to have been marginal, as in _Pteris_. - -9. _Pecopteris_, Brongniart.--This genus is intermediate between the -last and _Neuropteris_. The leaflets are attached by the whole base, -but not usually attached to each other; the midrib, though slender, -attains to the summit; the nervures are given off less obliquely than -in _Neuropteris_. This genus includes a large number of our most common -fossil ferns. - -10. _Beinertia_, Goeppert.--A genus established by Goeppert for a curious -Pecopteris-like fern, with flexuous branching oblique nervures becoming -parallel to the edge of the frond. - -11. _Hymenophyllites_, Goeppert.--These are ferns similar to -Sphenopteris, but divided at the margin into one-nerved lobes, in the -manner of the modern genus _Hymenophyllum_. - -12. _Palæopteris_, Geinitz.--This is a genus formed to include certain -trunks of tree-ferns with oval transverse scars of leaves. - -13. _Caulopteris_, Lindley and Hutton.--Is another genus of fossil trunks -of tree-ferns, but with elongate scars of leaves. - -14. _Psaronius_, Cotta.--Includes other trunks of tree-ferns with -alternate scars or thick scales, and ordinarily with many aërial roots -grouped round them, as in some modern tree-ferns. - -15. _Megaphyton_, Artis.--Includes trunks of tree-ferns which bore their -fronds, which were of great size, in two rows, one on each side of the -stem. These were very peculiar trees, less like modern ferns than any -of the others. My reasons for regarding them as ferns are stated in the -following extract from a recent paper: - -"Their thick stems, marked with linear scars and having two rows of -large depressed areoles on the sides, suggest no affinities to any known -plants. They are usually ranked with _Lepidodendron_ and _Ulodendron_, -but sometimes, and probably with greater reason, are regarded as allied -to tree-ferns. At the Joggins a very fine species (_M. magnificum_) has -been found, and at Sydney a smaller species (_M. humile_); but both -are rare and not well preserved. If the large scars bore cones and the -smaller bore leaves, then, as Brongniart remarks, the plant would much -resemble _Lepidophloios_, in which the cone-scars are thus sometimes -distichous. But the scars are not round and marked with radiating scales -as in _Lepidophloios_; they are reniform or oval, and resemble those -of tree-ferns, for which reason they may be regarded as more probably -leaf-scars; and in that case the smaller linear scars would indicate -ramenta, or small aërial roots. Further, the plant described by Corda -as _Zippea disticha_ is evidently a _Megaphyton_, and the structure -of that species is plainly that of a tree-fern of somewhat peculiar -type. On these grounds I incline to the opinion of Geinitz that these -curious trees were allied to ferns, and bore two rows of large fronds, -the trunks being covered with coarse hairs or small aërial roots. At -one time I was disposed to suspect that they may have crept along the -ground; but a specimen from Sydney shows the leaf-stalks proceeding from -the stem at an angle so acute that the stem must, I think, have been -erect. From the appearance of the scars it is probable that only a pair -of fronds were borne at one time at the top of the stem; and, if these -were broad and spreading, it would be a very graceful plant. To what -extent plants of this type contributed to the accumulation of coal I have -no means of ascertaining, their tissues in the state of coal not being -distinguishable from those of ferns and _Lycopodiaceæ_." - -16. For descriptions of the genus _Archæopteris_ and other Erian ferns, -see Chapter III. - - - - -CHAPTER V. - - THE FLORA OF THE EARLY MESOZOIC. - - -Great physical changes occurred at the close of the Carboniferous age. -The thick beds of sediment that had been accumulating in long lines -along the primitive continents had weighed down the earth's crust. Slow -subsidence had been proceeding from this cause in the coal-formation -period, and at its close vast wrinklings occurred, only surpassed by -those of the old Laurentian time. Hence in the Appalachian region of -America we have the Carboniferous beds thrown into abrupt folds, their -shales converted into hard slates, their sandstones into quartzite and -their coals into anthracite, and all this before the deposition of the -Triassic Red Sandstones which constitute the earliest deposit of the -great succeeding Mesozoic period. In like manner the coal-fields of Wales -and elsewhere in western Europe have suffered similar treatment, and -apparently at the same time. - -This folding is, however, on both sides of the Atlantic limited to a -band on the margin of the continents, and to certain interior lines of -pressure, while in the middle, as in Ohio and Illinois in America, and -in the great interior plains of Europe, the coal-beds are undisturbed -and unaltered. In connection with this we have an entire change in the -physical character of the deposits, a great elevation of the borders -of the continents, and probably a considerable deepening of the seas, -leading to the establishment of general geographical conditions which -still remain, though they have been temporarily modified by subsequent -subsidences and re-elevations. - -Along with this a great change was in progress in vegetable and animal -life. The flora and fauna of the Palæozoic gradually die out in the -Permian and are replaced in the succeeding Trias by those of the Mesozoic -time. Throughout the Permian, however, the remains of the coal-formation -flora continue to exist, and some forms, as the _Calamites_, even seem -to gain in importance, as do also certain types of coniferous trees. The -Triassic, as well as the Permian, was marked by physical disturbances, -more especially by great volcanic eruptions discharging vast beds and -dykes of lava and layers of volcanic ash and agglomerate. This was the -case more especially along the margins of the Atlantic, and probably -also on those of the Pacific. The volcanic sheets and dykes associated -with the Red Sandstones of Nova Scotia, Connecticut, and New Jersey are -evidences of this. - -At the close of the Permian and beginning of the Trias, in the midst of -this transition time of physical disturbance, appear the great reptilian -forms characteristic of the age of reptiles, and the earliest precursors -of the mammals, and at this time the old Carboniferous forms of plants -finally pass away, to be replaced by a flora scarcely more advanced, -though different, and consisting of pines, cycads, and ferns, with -gigantic equiseta, which are the successors of the genus _Calamites_, -a genus which still survives in the early Trias. Of these groups the -conifers, the ferns, and the equiseta are already familiar to us, and, in -so far as they are concerned, a botanist who had studied the flora of the -Carboniferous would have found himself at home in the succeeding period. -The cycads are a new introduction. The whole, however, come within the -limits of the cryptogams and the gymnosperms, so that here we have no -advance.[DF] - -[DF] Fontaine's "Early Mesozoic Flora of Virginia" gives a very good -summary of this flora in America. - -[Illustration: Fig. 64.--Jurassic vegetation. Cycads and pines. (After -Saporta.)] - -As we ascend, however, in the Mesozoic, we find new and higher types. -Even within the Jurassic epoch, the next in succession to the Trias, -there are clear indications of the presence of the endogens, in species -allied to the screw-pines and grasses; and the palms appear a little -later, while a few exogenous trees have left their remains in the Lower -Cretaceous, and in the Middle and Upper Cretaceous these higher plants -come in abundantly and in generic forms still extant, so that the dawn -of the modern flora belongs to the Middle and Upper Cretaceous. It will -thus be convenient to confine ourselves in this chapter to the flora of -the earlier Mesozoic. - -Passing over for the present the cryptogamous plants already familiar -in older deposits, we may notice the new features of gymnospermous and -phænogamous life, as they present themselves in this earlier part of the -great reptilian age, and as they extended themselves with remarkable -uniformity in this period over all parts of the world. For it is a -remarkable fact that, if we place together in our collections fossil -plants of this period from Australia, India, China, Siberia, Europe, -or even from Greenland, we find wonderfully little difference in their -aspect. This uniformity we have already seen prevailed in the Palæozoic -flora; and it is perhaps equally marked in that of the Mesozoic. Still we -must bear in mind that some of the plants of these periods, as the ferns -and pines, for example, are still world-wide in their distribution; but -this does not apply to others, more especially the cycads (Fig. 65). - -[Illustration: Fig. 65.--_Podozamites lanceolatus_, Sternb. L. -Cretaceous.] - -The cycads constitute a singular and exceptional type in the modern -world, and are limited at present to the warmer climates, though very -generally distributed in these, as they occur in Africa, India, Japan, -Australia, Mexico, Florida, and the West Indies. In the Mesozoic age, -however, they were world-wide in their distribution, and are found as far -north as Greenland, though most of the species found in the Cretaceous -of that country are of small size/ and may have been of low growth, so -that they may have been protected by the snows of winter. The cycads -have usually simple or unbranching stems, pinnate leaves borne in a -crown at top, and fruits which, though somewhat various in structure and -arrangement, are all of the simpler form of gymnospermous type. The stems -are exogenous in structure, but with slender wood and thick bark, and -barred tissue, or properly as tissue intermediate between this and the -disc-bearing fibres of the pines. - -Though the cycads have a considerable range of organisation and of -fructification, and though some points in reference to the latter might -assign them a higher place, on the whole they seem to occupy a lower -position than the conifers or the cordaiteæ of the Carboniferous. -In the Carboniferous some of the fern-like leaves assigned to the -genus _Noeggerathia_ have been shown by Stur and Weiss to have been -gymnosperms, probably allied to cycads, of which they may be regarded at -least as precursors. Thus the cycadean type does not really constitute an -advance in grade of organisation in the Mesozoic, any further than that, -in the period now in question, it becomes much more developed in number -and variety of forms. But the conifers would seem to have had precedence -of it for a long time in the Palæozoic, and it replaces in the Mesozoic -the _Cordaites_, which in many respects excelled it in complexity. - -The greater part of the cycads of the Mesozoic age would seem to have had -short stems and to have constituted the undergrowth of woods in which -conifers attained to greater height. An interesting case of this is the -celebrated dirt-bed of the quarries of the Isle of Portland, long ago -described by Dean Buckland. In this fossil soil trunks of pines, which -must have attained to great height, are interspersed with the short, -thick stems of cycads, of the genus named _Cycadoidea_ by Buckland, -and which from their appearance are called "fossil birds' nests" by the -quarrymen. Some, however, must have attained a considerable height so as -to resemble palms. - -The cycads, with their simple, thick trunks, usually marked with rhombic -scars, and bearing broad spreading crowns of large, elegantly formed -pinnate leaves, must have formed a prominent part of the vegetation -of the northern hemisphere during the whole of the Mesozoic period. A -botanist, had there been such a person at the time, would have found -this to be the case everywhere from the equator to Spitzbergen, and -probably in the southern hemisphere as well, and this throughout all -the long periods from the Early Trias to the Middle Cretaceous. In a -paper published in the "Linnæan Transactions" for 1868, Dr. Carruthers -enumerates twenty species of British Mesozoic cycads, and the number -might now be considerably increased. - -[Illustration: Fig. 66.--_Salisburia_ (Gingko) _Sibirica_, Heer. L. -Cretaceous, Siberia and North America.] - -The pines present some features of interest. We have already seen their -connection with the broad-leaved _Cordaites_, and in the Permian there -are some additional types of broad-leaved coniferæ. In the Mesozoic we -have great numbers of beautiful trees, with those elegant fan-shaped -leaves characteristic of but one living species, the Salisburia, or -gingko-tree of China. It is curious that this tree, though now limited -to eastern Asia, will grow, though it rarely fruits, in most parts of -temperate Europe, and in America as far north as Montreal, and that in -the Mesozoic period it occupied all these regions, and even Siberia and -Greenland, and with many and diversified species (Fig. 66). - -_Salisburia_ belongs to the yews, but an equally curious fact applies to -the cypresses. The genus _Sequoia_, limited at present to two species, -both Californian, and one of them the so-called "big tree," celebrated -for the gigantic size to which it attains, is represented by species -found as far back at least as the Lower Cretaceous, and in every part -of the northern hemisphere.[DG] It seems to have thriven in all these -regions throughout the Mesozoic and early Kainozoic, and then to have -disappeared, leaving only a small remnant to represent it in modern days. -A number of species have been described from the Mesozoic and Tertiary, -all of them closely related to those now existing (Fig. 67). - -[DG] In the Eocene of Australia. - -[Illustration: Fig. 67.--_Sequoia Smithiana_, Heer. L. Cretaceous.] - -The following notice of these trees is for the most part translated, with -some modifications and abridgment, from a paper read by the late Prof. -Heer before the Botanical Section of the Swiss Natural History Society: - -The name itself deserves consideration. It is that of an Indian of the -Cherokee tribe, Sequo Yah, who invented an alphabet without any aid from -the outside world of culture, and taught it to his tribe by writing it -upon leaves. This came into general use among the Cherokees, before the -white man had any knowledge of it; and afterward, in 1828, a periodical -was published in this character by the missionaries. Sequo Yah was -banished from his home in Alabama, with the rest of his tribe, and -settled in New Mexico, where he died in 1843. - -When Endlicher was preparing his synopsis of the conifers, in 1846, and -had established a number of new genera, Dr. Jacbon Tschudi, then living -with Endlicher, brought before his notice this remarkable man, and asked -him to dedicate this red-wooded tree to the memory of a literary genius -so conspicuous among the red men of America. Endlicher consented to do -so, and only endeavored to make the name pronounceable by changing two of -its letters. - -Endlicher founded the genus on the redwood of the Americans, _Taxodium -sempervirens_ of Lamb; and named the species _Sequoia sempervirens_. -These trees form large forests in California, which extend along the -coast as far as Oregon. Trees are there met with of 300 feet in height -and 20 feet in diameter. The seeds have been brought to Europe a number -of years ago, and we already see in upper Italy and around the Lake of -Geneva, and in England, high trees; but, on the other hand, they have not -proved successful around Zurich. - -In 1852, a second species of Sequoia was discovered in California, which, -under the name of big tree, soon attained a considerable celebrity. -Lindley described it, in 1853, as _Wellingtonia gigantea_; and, in the -following year, Decaisne and Torrey proved that it belonged to Sequoia, -and that it accordingly should be called _Sequoia gigantea_. - -While the _Sequoia sempervirens_, in spite of the destructiveness of -the American lumbermen, still forms large forests along the coast, the -_Sequoia gigantea_ is confined to the isolated clumps which are met with -inland at a height of 5,000 to 7,000 feet above sea-level, and are much -sought after by tourists as one of the wonders of the country. Reports -came to Europe concerning the largest of them which were quite fabulous, -but we have received accurate accounts of them from Prof. Whitney. The -tallest tree measured by him has a height of 325 feet, and in the case of -one of the trees the number of the rings of growth indicated an age of -about 1,300 years. It had a girth of 50 to 60 feet. - -We know only two living species of _Sequoia_, both of which are confined -to California. The one (_S. sempervirens_) is clothed with erect leaves, -arranged in two rows, very much like our yew-tree, and bears small, round -cones; the other (_S. gigantea_) has smaller leaves, set closely against -the branches, giving the tree more the appearance of the cypress. The -cones are egg-shaped, and much larger. These two types are therefore -sharply defined. - -Both of these trees have an interesting history. If we go back into the -Tertiary, this same genus meets us with a long array of species. Two of -these species correspond to those living at present: the _S. Langsdorfii_ -to the _S. sempervirens_, and the _S. Couttsiæ_ to the _S. gigantea_.[DH] -But, while the living species are confined to California, in the Tertiary -they are spread over several quarters of the globe. - -[DH] _S. Couttsiæ_ has leaves like _S. gigantea_, and cones like those of -_8. sempervirens_. - -Let us first consider the _Sequoia Langsdorfii_. This was first -discovered in the lignite of Wetterau, and was described as _Taxites -langsdorfii_. Heer found it in the upper Rhone district, and there lay -beside the twigs the remains of a cone, which showed that the _Taxites -Langsdorfii_ of Brongniart belonged to the Californian genus Sequoia -established by Endlicher. He afterward found much better preserved -cones, together with seeds, along with the plants of east Greenland, -which fully confirmed the determination. At Atanekerdluk in Greenland -(about 70° north latitude) this tree is very common. The leaves, and -also the flowers and numerous cones, leave no doubt that it stands very -near to the modern redwood. It differs from it, however, in having -a much larger number of scales in the cone. The tree is also found -in Spitzbergen at nearly 78° north latitude, where Nordenskiöld has -collected, at Cape Lyell, wonderfully preserved branches. From this high -latitude the species can be followed down through the whole of Europe -as far as the middle of Italy (at Senegaglia, Gulf of Spezia). In Asia, -also,, we can follow it to the steppes of Kirghisen, to Possiet, and to -the coast of the Sea of Japan, and across to Alaska and Sitka. It is -recognized by Mr. Starkie Gardner as one of the species found in the -Eocene of Mull in the Hebrides.[DI] It is thus known in Europe, Asia, and -America, from 43° to 78° north latitude, while its most nearly related -living species, perhaps even descended from it, is now confined to -California. - -[DI] It is _Fareites Campbelli_ of Forbes. - -With this _S. Langsdorfii_, three other Tertiary species are -nearly related (_S. brevifolia_, Hr., _S. disticha_, Hr., and _S. -Nordenskiöldi_, Hr.). These have been met with in Greenland and -Spitzbergen, and one of them has lately been found in the United States. -Three other species, in addition to these, have been described by -Lesquereux, which appear to belong to the group of the _S. Langsdorfii_, -viz., _S. longifolia_, Lesq., _S. angustifolia_, and _S. acuminata_, -Lesq. Several species also occur in the Cretaceous and Eocene of Canada. - -These species thus answer to the living _Sequoia sempervirens_; but we -can also point to Tertiary representatives of the _S. gigantea_. Their -leases are stiff and sharp-pointed, are thinly set round the branches, -and lie forward in the same way: the egg-shaped cones are in some cases -similar. - -There are, however, in the early Tertiary six species, which fill up -the gap between _S. sempervirens_ and _S. gigantea_. They are the _S. -Couttsiæ_, _S. affinis_, Lesq., _S. imbricata_, Hr., _S. sibirica_, Hr., -_S. Heerii_, Lesq., and _S. biformis_, Lesq. Of these, _S. Couttsiæ_, -Hr., is the most common and most important species. It has short leaves, -lying along the branch, like _S. gigantea_, and small, round cones, like -_S. Langsdorfii_ and _sempervirens_. Bovey Tracey in Devonshire has -afforded splendid specimens of cones, seeds, and twigs, which have been -described in the "Philosophical Transactions." More lately, Count Saporta -has described specimens of cones and twigs from Armissan. Specimens of -this species have also been found in the older Tertiary of Greenland, so -that it must have had a wide range. It is very like to the American _S. -affinis_, Lesq. - -In the Tertiary there have been already found fourteen well-marked -species, which thus include representatives of the two living types, _S. -sempervirens_ and _S. gigantea_. - -We can follow this genus still further back. If we go back to the -Cretaceous age, we find ten species, of which five occur in the Urgon -of the Lower Cretaceous, two in the Middle, and three in the Upper -Cretaceous. Among these, the Lower Cretaceous exhibits the two types -of the Sequoia sempervirens and _S. gigantea_. To the former the _S. -Smithiana_ answers, and to the latter, the _Reichenbachii_, Gein. The -_S. Smithiana_ stands indeed uncommonly near the _S. Langsdorfii_, both -in the appearance of the leaves on the twigs and in the shape of the -cones. These are, however, smaller, and the leaves do not become narrower -toward the base. The _S. pectina_, Hr., of the Upper Cretaceous, has its -leaves arranged in two rows, and presents a similar appearance. The _S. -Reichenbachii_ is a type more distinct from those now living and those -in the Tertiary. It has indeed stiff, pointed leaves, lying forward, but -they are arcuate, and the cones are smaller. This tree has been known -for a long time, and it serves in the Cretaceous as a guiding star, -which we can follow from the Urgonian of the Lower Cretaceous up to the -Cenomanian. It is known in France, Belgium, Bohemia, Saxony, Greenland, -and Spitzbergen (also in Canada and the United States). It has been -placed in another genus--Geinitzia--but we can recognise, by the help of -the cones, that it belongs to Sequoia. - -Below this, there is found in Greenland a nearly related species, the _S. -ambigua_, Hr., of which the leaves are shorter and broader, and the cones -round and somewhat smaller. - -The connecting link between _S. Smithiana_ and _Reichenbachii_ is formed -by _S. subulata_, Hr., and _S. rigida_, Hr., and three species (_S. -gracilis_, Hr., _S. fastigiata_ and _S. Gardneriana_, Carr.), with leaves -lying closely along the branch, and which come very near to the Tertiary -species _S. Couttsiæ_. We have therefore in the Cretaceous quite an -array of species, which fill up the gap between the _S. sempervirens_ -and _gigantea_, and show us that the genus Sequoia had already attained -a great development in the Cretaceous. This was still greater in -the Tertiary, in which it also reached its maximum of geographical -distribution. Into the present world the two extremes of the genus have -alone continued; the numerous species forming its main body have fallen -out in the Tertiary. - -If we look still further back, we find in the Jura a great number of -conifers, and, among them, we meet in the genus Pinus with a type which -is highly developed, and which still survives; but for Sequoia we have -till now looked in vain, so that for the present we can not place the -rise of the genus lower than the Urgonian of the Cretaceous, however -remarkable we may think it that in that period it should have developed -into so many species; and it is still more surprising that two species -already make their appearance which approach so near to the living -_Sequoia sempervirens_ and _S. gigantea_. - -Altogether, we have become acquainted, up to the present time, with -twenty-six species of Sequoia. Fourteen of these species are found in the -Arctic zone, and have been described and figured in the "Fossil Flora of -the Arctic Regions." Sequoia has been recognised by Ettingshausen even in -Australia, but there in the Eocene. - -This is, perhaps, the most remarkable record in the whole history of -vegetation. The Sequoias are the giants of the conifers, the grandest -representatives of the family, and the fact that, after spreading over -the whole northern hemisphere and attaining to more than twenty specific -forms, their decaying remnant should now be confined to one limited -region in western America and to two species constitutes a sad memento -of departed greatness.[DJ] The small remnant of _S. gigantea_ still, -however, towers above all competitors, as eminently the "big trees "; -but, had they and the allied species failed to escape the Tertiary -continental submergences and the disasters of the glacial period, this -grand genus would have been to us an extinct type. In like manner the -survival of the single gingko of eastern Asia alone enables us to -understand that great series of taxine trees with fern-like leaves of -which it is the sole representative. - -[DJ] The writer has shown that much of the material of the great lignite -beds of the Canadian Northwest consists of wood of Sequoia of both the -modern types. - -Besides these peculiar and now rare forms, we have in the Mesozoic many -others related closely to existing yews, cypresses, pines, and spruces, -so that the conifers were probably in greater abundance and variety than -they are at this day. - -In this period, also, we find the earliest representatives of -the endogenous plants. It is true that some plants found in the -coal-formation have been doubtfully referred to these, but the earliest -certain examples would seem to be some bamboo-like and screw-pine-like -plants occurring in the Jurassic rocks. Some of these are, it is true, -doubtful forms, but of others there seems to be no question. The modern -_Pandanus_ or screw-pine of the tropical regions, which is not a pine, -however, but a humble relation of the palms, is a stiffly branching -tree, of a candelabra-like form, and with tufts of long leaves on its -branches, and nuts or great hard berries for fruit, borne sometimes in -large masses, and so protected as to admit of their drifting uninjured -on the sea. The stems are supported by masses of aërial roots like those -which strengthen the stems of tree-ferns. These structures and habits -of growth fit the Pandanus for its especial habitat on the shores of -tropical islands, to which its masses of nuts are drifted by the winds -and currents, and on whose shores it can establish itself by the aid of -its aërial roots. - -Some plants referred to the cycads have proved veritable botanical -puzzles. One of these, the _Williamsonia gigas_ of the English oölite, -originally discovered by my friend Dr. Williamson, and named by him -_Zamia gigas_, a very tall and beautiful species, found in rocks of this -age in various parts of Europe, has been claimed by Saporta for the -Endogens, as a plant allied to _Pandanus_. Some other botanists have -supposed the flowers and fruits to be parasites on other plants, like the -modern _Rafflesia_ of Sumatra, but it is possible that after all it may -prove to have been an aberrant cycad. - -The tree-palms are not found earlier than the Middle Cretaceous, where -we shall notice them in the next chapter. In like manner, though a -few Angiosperms occur in rocks believed to be Lower or Lower Middle -Cretaceous in Greenland and the northwest territory of Canada, and in -Virginia, these are merely precursors of those of the Upper Cretaceous, -and are not sufficient to redeem the earlier Cretaceous from being a -period of pines and cycads. - -On the whole, this early Mesozoic flora, so far as known to us, has a -monotonous and mean appearance. It no doubt formed vast forests of tall -pines, perhaps resembling the giant Sequoias of California; but they must -for the most part have been dark and dismal woods, probably tenanted by -few forms of life, for the great reptiles of this age must have preferred -the open and sunny coasts, and many of them dwelt in the waters. Still -we must not be too sure of this. The berries and nuts of the numerous -yews and cycads were capable of affording much food. We know that in -this age there were many great herbivorous reptiles, like _Iguanodon_ -and _Hadrosaurus_, some of them fitted by their structure to feed upon -the leaves and fruits of trees. There were also several kinds of small -herbivorous mammals, and much insect life, and it is likely that few of -the inhabitants of the Mesozoic woods have been preserved as fossils. -We may yet have much to learn of the inhabitants of these forests of -ferns, cycads, and pines. We must not forget in this connection that in -the present day there are large islands, like New Zealand, destitute of -mammalia, and having a flora comparable with that of the Mesozoic in the -northern hemisphere, though more varied. We have also the remarkable -example of Australia, with a much richer flora than that of the early -Mesozoic, yet inhabited only by non-placental mammals, like those of the -Mesozoic. - -The principal legacy that the Mesozoic woods have handed down to our -time is in some beds of coal, locally important, but of far less extent -than those of the Carboniferous period. Still, in America, the Richmond -coal-field in Virginia is of this age, and so are the anthracite beds of -the Queen Charlotte Islands, on the west coast of Canada, and the coal -of Brora in Sutherlandshire. Valuable beds of coal, probably of this -age, also exist in China, India, and South Africa; and jet, which is so -extensively used for ornament, is principally derived from the carbonised -remains of the old Mesozoic pines. - -In the next chapter we have to study a revolution in vegetable life most -striking and unique, in the advent of the forest-trees of strictly modern -types. - - - -NOTE TO CHAPTER V. - -I append to this chapter a table showing the plant-bearing series of the -Cretaceous and Laramie of North America, from a paper in "Trans. R. S. -C," 1885, which see for further details: - -(In Descending Order.) - - Periods. Floras and sub-floras. References. - --------------+---------------------------+----------------------------- - Transition Upper Laramie or Porcupine { Platanus beds of Souris - Eocene to Hill. Fort Union { River and Calgary. Report - Cretaceous. group, U. S. territory. { of Geol. Survey of Canada - { for 1879, and Memoir of - { 1885. - --------------+---------------------------+----------------------------- - Middle Laramie or Willow - Creek beds. - { Lemna and Pistia beds of - Lower Laramie or St. { bad lands of 49th parallel, - Mary River. { Red Deer River, &c., with - Upper { lignites. Report 49th - Cretaceous { Parallel and Memoir of - { 1885. - (Danian and - Senonian). Fox Hill series Marine. - - Fort Pierre series Marine. - - { Sequoia and Brasenia beds - Belly River { of S. Saskatchewan, Belly - { River, &c. with lignites. - { Memoir of 1885. - - Coal measures of Nanaimo, { Memoir of 1883. Many - B.C., probably here. { dicotyledons, palms, &c. - --------------+---------------------------+----------------------------- - Middle Dunvegan series of Peace } - Cretaceous River. Dakota group, } Memoir of 1883. Many - (Turonian and U. S. Amboy clays, } dicotyledons, cycads, &c. - Cenomanian). U. S. } - - Mill Creek beds of Rocky { Dicotyledonous leaves, - Mountains. { similar to Dakota group of - { the U. S. Memoir of 1885. - --------------+---------------------------+----------------------------- - Lower Suskwa River beds and } - Cretaceous Queen Charlotte Island } Cycads, pines, a few - (Neocomian. coal series. Intermediate } dicotyledons. Report Geol. - &c). beds of Rocky } Survey. Memoir of 1885. - Mountains. Potomac } - series of Virginia. } - - Kootanie series of Rocky { Cycads, pines, and ferns. - Mountains. { Memoir of 1885. - --------------+---------------------------+------------------------------ - - - - -CHAPTER VI. - - THE REIGN OF ANGIOSPERMS IN THE LATER CRETACEOUS - AND KAINOZOIC. - - -[Illustration: Fig. 68.--_Populus primæva_, Heer. Cretaceous, of -Greenland. One of the oldest known Angiosperms.] - -It is a remarkable fact in geological chronology that the culmination -of the vegetable kingdom antedates that of the animal. The placental -mammals, the highest group of the animal kingdom, are not known till the -beginning of the Eocene Tertiary. The dicotyledonous Angiosperms, which -correspond to them in the vegetable kingdom, occur far earlier--in the -beginning of the Upper Cretaceous or close of the Lower Cretaceous. The -reign of cycads and pines holds throughout the Lower Cretaceous, but at -the close of that age there is a sudden incoming of the higher plants, -and a proportionate decrease, more especially of the cycads. - -I have already referred to the angiospermous wood supposed to be -Devonian, but I fear to rest any conclusion on this isolated fact. -Beyond this, the earliest indications of plants of this class have -been found in the Lower Cretaceous. Many years ago Heer described and -figured the leaves of a poplar (_Populus primæva_) from the supposed -Lower Cretaceous of Komé, in Greenland (Fig. 68). Two species, a -_Sterculia_ and a _Laurus_ or _Salix_, occur among fossils described by -me in the upper part of the Kootanie series of the Rocky Mountains, and -Fontaine has recently found in the Potomac group of Virginia--believed -to be of Neocomian age--several angiospermous species (_Sassafras_, -_Menispermites_, _Sapindus_, _Aralia_, _Populus_, &c.) mixed with a rich -flora of cycads and pines. These are the early forerunners of the modern -angiospermous flora; but so far as known they do not occur below the -Cretaceous, and in its lower portions only very rarely. When, however, we -ascend into the Upper Cretaceous, whether of Europe or America, there is -a remarkable incoming of the higher plants, under generic forms similar -to those now existing. This is, in truth, the advent of the modern flora -of the temperate regions of the earth. A very interesting tabular view -of its early distribution is given by Ward, in the "American Journal of -Science" for 1884, of which the following is a synopsis, with slight -emendations. I may add that the new discoveries made since 1884 would -probably tend to increase the proportionate number of dicotyledons in the -newer groups. - -Dicotyledonous Trees in the Cretaceous. - - _Upper Senonian_ 179 species. - (Fox Hill group of America.) - - _Lower Senonian_ 81 species. - Upper white chalk of Europe; Fort Pierre - group of America; coal-measures of Nanaimo? - - _Turonian_ 20 species. - Lower white chalk; New Jersey marls; - Belly R. group. - - _Cenomanian._ 357 species. - (Chalk-marl, greensand, and Gault, Niobrara - and Dakota groups of America); Dunvegan - group of Canada; Amboy clays of New Jersey. - - _Neocomian_ 20 species.[DK] - (Lower greensand and Speeton clay, Wealden - and Hastings sands, Kootanie and Queen - Charlotte groups of Canada.) - -[DK] Including an estimate of Fontaine's undescribed species. - -Thus we have a great and sudden inswarming of the higher plants of -modern types at the close of the Lower Cretaceous. In relation to this, -Saporta, one of the most enthusiastic of evolutionists, is struck by -this phenomenon of the sudden appearance of so many forms, and some of -them the most highly differentiated of dicotyledonous plants. The early -stages of their evolution may, he thinks, have been obscure and as yet -unobserved, or they may have taken place in some separate region, or -mother country as yet undiscovered, or they may have been produced by -a rapid and unusual multiplication of flower-haunting insects! Or it -is even conceivable that the apparently sudden elevation of plants may -have been due to causes still unknown. This last seems, indeed, the only -certain inference in the case, since, as Saporta proceeds to say in -conclusion: "Whatever hypothesis one may prefer, the fact of the rapid -multiplication of dicotyledons, and of their simultaneous appearance in a -great number of places in the northern hemisphere at the beginning of the -Cenomanian epoch, cannot be disputed."[DL] - -[DL] "Monde des Plantes," p. 197. - -The leaves described by Heer, from the Middle Cretaceous of Greenland, -are those of a poplar (_P. primæva_). Those which I have described from -a corresponding horizon in the Rocky Mountains are a _Sterculites_ (_S. -vetustula_), probably allied to the mallows, and an elongated leaf, -_Laurophyllum_ (_L. crassinerve_) (Fig. 69), which may, however, have -belonged to a willow rather than a laurel. These are certainly older than -the Dakota group of the United States and the corresponding formations -in Canada. On the eastern side of the American continent, in Virginia, -the Potomac series is supposed to be of Lower Cretaceous age, and here -Fontaine, as already stated, has found an abundant flora of cycads, -conifers, and ferns, with a few angiospermous leaves, which have not yet -been described. - -[Illustration: Fig. 69.--_Stercalia_ and _Laurophyllum_ or Salix, the -oldest Angiosperms Known in the Cretaceous of Canada.] - -In the Canadian Rocky Mountains, a few hundreds of feet above the beds -holding the beforementioned species, are the shales of the Mill Creek -series, rich in many species of dicotyledonous leaves, and corresponding -in age with the Dakota group, whose fossils have been so well described, -first by Heer and Capellini, and afterward by Lesquereux. We may take -this Dakota group and the quader-sand stone of Germany as types of the -plant-bearing Cenomanian, and may notice the forms occurring in them. - -In the first place, we recognise here the successors of our old friends, -the ferns and the pines, the latter represented by such genera as -_Taxites_, _Sequoia_, _Glyptostrobus_, _Gingko_, and even _Pinus_ itself. -We also have a few cycads, but not so dominant as in the previous -ages. The fan-palms are well represented, both in America and in the -corresponding series in Europe, especially by the genus _Sabal_, which -is the characteristic American type of fan-palm, and there is one genus -which Saporta regards as intermediate between the fan-palms and the -pinnately leaved species. There are also many fragments of stems and -leaves of carices and grasses, so that these plants, now so important -to the nourishment of man and his companion animals, were already -represented. - -[Illustration: Fig. 70.--Vegetation of Later Cretaceous. Exogens and -palms. (After Saporta.)] - -But the great feature of the time was its dicotyledonous forests, and I -have only to enumerate the genera supposed to be represented in order -to show the richness of the time in plants of this type. It may be -necessary to explain here that the generic names used are mostly based -on leaves, and consequently cannot be held as being absolutely certain, -since we know that at present one genus may have considerable variety -in its leaves, and, on the other hand, that plants of different genera -may be very much alike in their foliage. There is, however, undoubtedly -a likeness in plan or type of structure in leaves of closely allied -plants, and, therefore, if judiciously studied, they can be determined -with at least approximate certainty.[DM] More especially we can attain -to much certainty when the fruits as well as the leaves are found, -and when we can obtain specimens of the wood, showing its structure. -Such corroboration is not wanting, though unfortunately the leaves -of trees are generally found drifted away from the other organs once -connected with them. In my own experience, however, I have often found -determinations of the leaves of trees confirmed by the discovery of their -fruits or of the structure of their stems. Thus, in the rich cretaceous -plant-beds of the Dunvegan series we have beech-nuts associated in -the same beds with leaves referred to _Fagus_. In the Laramie beds I -determined many years ago nuts of the _Trapa_ or water-chestnut, and -subsequently Lesquereux found, in beds in the United States, leaves which -he referred to the same genus. Later, I found in collections made on the -Red Deer River of Canada my fruits and Lesquereux's leaves on the same -slab. The presence of trees of the genera _Carya_ and _Juglans_ in the -same formation was inferred from their leaves, and specimens have since -been obtained of silicified wood, with the microscopic structure of the -modern butternut. Still we are willing to admit that determinations from -leaves alone are liable to doubt. - -[DM] Great allowance has to be made for the variability of leaves of the -same species. The modern hazel (_C. rostrata_) is a case in point. Its -leaves, from different parts of the same plant, are so dissimilar in form -and size that they might readily be regarded as of different species. - -In the matter of names of fossil leaves, I sympathise very strongly -with Dr. Nathorst, of Stockholm, in his objection to the use of modern -generic names for mere leaves, and would be quite content to adopt some -non-committal termination, as that of "_phyllum_" or "_ites_" suggested -by him. I feel, however, that almost as much is taken for granted if a -plant is called Corylophyllum or _Corylites_, as if called _Corylus_. In -either case a judgment is expressed as to its affinities, which if wrong -under the one term is wrong under the other; and after so much has been -done by so many eminent botanists, it seems inexpedient to change the -whole nomenclature for so small and questionable an advantage. I wish -it, however, to be distinctly understood that plants catalogued on the -evidence of leaves alone are for the most part referred to certain genera -on grounds necessarily imperfect, and their names are therefore subject -to correction, as new facts may be obtained. - -The more noteworthy modern genera included in the Dakota flora, as -catalogued by Lesquereux, are the following: _Liquidambar_, the -sweet-gum, is represented both in America and Europe, the leaves -resembling those of the modern species, but with entire edges, which -seems to be a common peculiarity of Cretaceous foliage.[DN] _Populus_ -(poplar), as already stated, appears very early in Greenland, and -continues with increasing number of species throughout the Cretaceous and -Tertiary. _Salix_ (willow) appears only a little later and continues. Of -the family _Cupuliferæ_ we have _Fagus_ (beech), _Quercus_ (oak), and -_Castanea_ (chestnut), which appear together in the Dakota group and -its equivalents. Fruits of some of the species are known, and also wood -showing structure. _Betula_ (birch) is represented by a few species, -and specimens of its peculiar bark are also common. _Alnus_ (alder) -appears in one species at least. The genus Plat anus (Fig. 71), that of -the plane-trees, represented at present by one European and one American -species, has several species in the Cretaceous, though the plane-trees -seem to culminate in the early part of the succeeding Eocene, where -there are several species with immense leaves. The large leaves, -known as _Credneria_, found in the Cenomanian of Europe, and those -called _Protophyllum_ (Fig. 72) in America, appear to be nearer to the -plane-trees than to any others, though representing an extinct type. The -laurels are represented in this age, and the American genus Sassafras, -which has now only one species, has not one merely but several species in -the Cretaceous. _Diospyros_, the persimmon-tree, was also a Cretaceous -genus. - -[DN] With reference to this, something may be learned from the leaves -of modern trees. In these, young shoots have leaves often less toothed -and serrated than those of the adult tree. A remarkable instance is the -_Populus grandidentatus_ of America, the young shoots of which have -entire leaves, quite unlike except in venation those of the parent tree, -and having an aspect very similar to that of the Cretaceous poplars. - -[Illustration: Fig. 71.--_Platanus nobilis_, Newberry, variety -_basilobata_. Laramie. Much reduced.] - -[Illustration: Fig. 72.--_Protophyllum boreale_, Dawson, reduced. Upper -Cretaceous, Canada.] - -The single species of the beautiful _Liriodendron_, or tulip-tree, is -a remnant of a genus which had several Cretaceous species (Figs. 74, -75). The magnolias, still well represented in the American flora, were -equally plentiful in the Cretaceous (Fig. 73). The walnut family were -well represented by species of _Juglans_ (butternut) and _Carya_, or -hickory. In all, no less than forty-eight genera are present belonging -to at least twenty-five families, running through the whole range of the -dicotyledonous exogens. This is a remarkable result, indicating a sudden -profusion of forms of these plants of a very striking character. It is -further to be observed that some of the genera have many species in the -Cretaceous and dwindle toward the modern. In others the reverse is the -case--they have expanded in modern times. In a number there seems to have -been little change. - -[Illustration: Fig. 73.--_Magnolia magnifica_, Dawson, reduced. Upper -Cretaceous, Canada.] - -Dr. Newberry has given, in the "Bulletin of the Torrey Botanical Club" an -interesting _résumé_ of the history of the beautiful _Liriodendron_, or -tulip-tree, which may be taken as an example of a genus which has gone -down in importance in the course of its geological history. - -"The genus _Liriodendron_, as all botanists know, is represented in the -present flora by a single species, 'the tulip-tree' which is confined -to eastern America, but grows over all the area lying between the Lakes -and the Gulf, the Mississippi and the Atlantic. It is a magnificent -tree, on the whole, the finest in our forests. Its cylindrical trunk, -sometimes ten feet in diameter, carries it beyond all its associates in -size, while the beauty of its glossy, lyre-shaped leaves and tulip-like -flowers is only surpassed by the flowers and foliage of its first cousin, -_Magnolia grandiflora_. That a plant so splendid should stand quite alone -in the vegetation of the present day excited the wonder of the earlier -botanists, but the sassafras, the sweet-gum, and the great Sequoias of -the far West afford similar examples of isolation, and the latter are -still more striking illustrations of solitary grandeur." (Figs. 74 and -75.) - -[Illustration: Fig. 74.--_Liriodendron Meekii_, Heer. (After Lesquereux.)] - -[Illustration: Fig. 75.--_Liriodendron primævum_, Newberry. (After -Newberry.)] - -"Three species of _Liriodendron_ are indicated by leaves found in the -Amboy clays--Middle Cretaceous--of New Jersey, and others have been -obtained from the Dakota group in the West, and from the Upper Cretaceous -strata of Greenland. Though differing considerably among themselves in -size and form, all these have the deep sinus of the upper extremity -so characteristic of the genus, and the nervation is also essentially -the same. Hence, we must conclude that the genus _Liriodendron_, now -represented by a single species, was in the Cretaceous age much more -largely developed, having many species, and those scattered throughout -many lands. In the Tertiary age the genus continued to exist, but -the species seem to have been reduced to one, which is hardly to be -distinguished from that now living. In many parts of Europe leaves of -the tulip-tree have been found, and it extended as far south as Italy. -Its presence there was first made known by Unger, in his 'Synopsis,' -page 232, and in his 'Genera et Species,' page 443, where he describes -it under the name of _Liriodendron procaccinii_. The genus has also been -noticed in Europe by Massalongo, Heer, and Ettingshausen, and three -species have been distinguished. All these are, however, so much like the -living species that they should probably be united with it. We here have -a striking illustration of the wide distribution of a species which has -retained its characters both of fruit and leaf quite unchanged through -long migrations and an enormous lapse of time. - -"In Europe the tulip-tree, like many of its American associates, seems -to have been destroyed by the cold of the Ice period, the Mediterranean -cutting off its retreat, but in America it migrated southward over the -southern extension of the continent and returned northward again with the -amelioration of the climate." - -Leaves of _Liriodendron_ have been recognised in the Cretaceous of -Greenland, though it is now a tree of the warm temperate region, and -Lesquereux describes several species from the Dakota group. But the genus -has not yet been recognised in the Laramie or in the Upper Cretaceous of -British Columbia. In the paper above quoted, Newberry describes three new -species from the Amboy clays, one of which he considers identical with a -Greenland form referred by Heer to _L. Meekii_ of the Dakota group. Thus, -if all Lesquereux's species are to be accepted, the genus begins in the -Middle Cretaceous with at least nine American species. - -In New Jersey the Amboy clays are referred to the same age with the -Dakota beds of the West. In these Dr. Newberry has found a rich flora, -including many angiosperms. The following is condensed from a preliminary -notice in the "Bulletin of the Torrey Botanical Club":[DO] - -[DO] March, 1886. - -"The flora of the Amboy clays is closely related to that of the Dakota -group--most of the genera and some of the species being identical--so -that we may conclude they were nearly contemporaneous, though the absence -in New Jersey of the Fort Benton and Niobrara groups of the upper -Missouri and the apparent synchronism of the New Jersey marls and the -Pierre group indicate that the Dakota is a little the older. - -"At least one-third of the species of the Amboy clays seem to be -identical with leaves found in the Upper Cretaceous clays of Greenland -and Aachen (Aix la Chapelle), which not only indicates a chronological -parallelism, but shows a remarkable and unexpected similarity in the -vegetation of these widely separated countries in the middle and last -half of the Cretaceous age. The botanical character of the flora of the -Amboy clays will be seen from the following brief synopsis: - -"_Algæ._--A small and delicate form, allied to Chondrites. - -"_Ferns._--Twelve species, generally similar and in part identical with -those described by Heer from the Cretaceous beds of Greenland, and -referred to the genera _Dicksonia_, _Gleichenia_, and _Aspidium_. - -"_Cycads._--Two species, probably identical with the forms from Greenland -described by Heer under the names of _Podozamites marginatus_ and _P. -tenuinervis_. - -"_Conifers._--Fourteen species, belonging to the genera _Moriconia_, -_Brachyphyllum_, _Cunninghamites_, _Pinus_, _Sequoia_, and others -referred by Heer to _Juniperus_, _Libocedrus_, _Frenelopsis_, _Thuya_, -and _Dammara_. Of these, the most abundant and most interesting -are _Moriconia cyclotoxon_--the most beautiful of conifers--and -_Cunninghamites elegans_, both of which occur in the Cretaceous clays of -Aachen, Prussia, and Patoot, Greenland. The _Brachyphyllum_ was a large -and strong species, with imbricated cones, eight inches in length. - -"The angiosperms form about seventy species, which include three of -_Magnolia_, four of _Liriodendron_, three or four of _Salix_, three of -_Celastrophyllum_ (of which one is identical with a Greenland species), -one _Celastrus_ (also found in Greenland), four or five _Aralias_, -two _Sassafras_, one _Cinnamomum_, one _Hedera_; with leaves that -are apparently identical with those described by Heer as belonging -to _Andromeda_, _Cissites_, _Cornus_, _Dewalquea_, _Diospyros_, -_Eucalyptus_, _Ficus_, _Ilex_, _Juglans_, _Laurus_, _Menispermites_, -_Myrica_, _Myrsine_, _Prunus_, _Rhamnus_, and others not yet determined. - -"Some of the Aralias had palmately-lobed leaves, nearly a foot in -diameter, and two of the tulip-trees (_Liriodendron_) had leaves quite -as large as those of the living species. One of these had deeply lobed -leaves, like those of the white oak. Of the other, the leaves resembled -those of the recent tulip-tree, but were larger. Both had the peculiar -emargination and the nervation of _Liriodendron_. - -"Among the most interesting plants of the collection are fine species of -_Bauhinia_ and _Hymenæa_. Of these, the first is represented by a large -number of leaves, some of which are six or seven inches in diameter. -They are deeply bilobed, and have the peculiar and characteristic form -and nervation of the leaves of this genus. _Bauhinia_ is a leguminous -genus allied to _Cercis_, and now inhabits tropical and warm temperate -climates in both hemispheres. Only one species occurs in the United -States, _Bauhinia lunarioides_, Gray, found by Dr. Bigelow on the Rio -Grande. - -"_Hymenæa_ is another of the leguminosæ, and inhabits tropical America. A -species of this genus has been found in the Upper Cretaceous of France, -but quite different from the one before us, in which the leaves are much -larger, and the leaflets are united in a common petiole, which is winged; -this is a modification not found in the living species, and one which -brings it nearer to _Bauhinia_. - -"But the most surprising discovery yet made is that of a number of quite -large helianthoid flowers, which I have called _Palæanthus_. These -are three to four inches in diameter, and exhibit a scaly involucre, -enclosing what much resembles a fleshy receptacle with achenia. From -the border of this radiate a number of ray florets, one to two inches -in length, which are persistent and must have been scarious, like -those of _Helichrysum_. Though these flowers so much resemble those -of the compositæ, we are not yet warranted in asserting that such is -certainly their character. In the Jurassic rocks of Europe and India -some flowers not very unlike these have been found, which have been -named _Williamsonia_, and referred to cycads by Carruthers. A similar -fossil has been found in the Cretaceous rocks of Greenland, and named -by Heer _Williamsonia cretacea_, but he questions the reference of the -genus to the Cycadeæ, and agrees with Nathorst in considering all the -species of _Williamsonia_ as parasitic flowers, allied to _Brugmansia_ -or _Rafflesia_. The Marquis of Saporta regards them as monocotyledons, -similar to _Pandanus_. More specimens of the flowers now exhibited -will perhaps prove--what we can now only regard as probable--that the -Compositæ, like the _Leguminosæ_, _Magnoliaceæ_, _Celastraceæ_, and -other highly organised plants, formed part of the Cretaceous flora. No -composite flowers have before been found in the fossil state, and, as -these are among the most complex and specialised forms of florescence, it -has been supposed that they belonged only to the recent epoch, where they -were the result of a long series of formative changes." - -The above presents some interesting new types not heretofore found in the -Middle Cretaceous. More especially the occurrence of large flowers of the -composite type presents a startling illustration of the early appearance -of a very elevated and complex form. Great interest also attaches to -these Amboy beds, as serving, with those of Aix and Greenland, to show -that the margins of the Atlantic were occupied with a flora similar to -that occurring at the same time in the interior plateau of North America -and on the Pacific slope. - -The beds at Aix-la-Chapelle are, however, probably somewhat newer than -the Dakota or Amboy beds, and correspond more nearly in age with those -of the Cretaceous coal-field of Vancouver Island, where there is a -very rich Upper Cretaceous flora, which I have noticed in detail in -the "Transactions of the Royal Society of Canada."[DP] In these Upper -Cretaceous beds there are fan-palms as far north at least as the latitude -of 49°, indicating a very mild climate at this period. This inference -is corroborated by the Upper Cretaceous flora of Atané and Patoot in -Greenland, as described by Heer. - -[DP] Vol. ii., 1884. - -The dicotyledonous plants above referred to are trees and shrubs. Of the -herbaceous exogens of the period we know less. Obviously their leaves -are less likely to find their way into aqueous deposits than the leaves -of trees. They are, besides, more perishable, and in densely wooded -countries there are comparatively few herbaceous plants. I have examined -the beds of mud deposited at the mouth of a woodland streamlet, and have -found them stored with the fallen leaves of trees, but it was in vain to -search for the leaves of herbaceous plants. - -[Illustration: Fig. 76.--_Brasenia antiqua_. Upper Cretaceous, South -Saskatchewan River. Natural size, _a_, _b_, Diagrams of venation, -slightly enlarged.] - -The climate of North America and Europe, represented by the Cenomanian -vegetation, is not tropical but warm temperate; but the flora was more -uniform than at present, indicating a very equable climate and the -possibility of temperate genera existing within the Arctic circle, and it -would seem to have become warmer toward the close of the period. - -The flora of the Cenomanian is separated in most countries from that of -the Senonian, or uppermost Cretaceous, by a marine formation holding few -plants. This depends on great movements of elevation and depression, to -which we must refer in the sequel. In a few regions, however, as in the -vicinity of the Peace River in Canada, there are plant-bearing beds which -serve to bridge over the interval between the Early Cenomanian and the -later Cretaceous.[DQ] - -[DQ] See paper by the author in the "Transactions of the Royal Society of -Canada," 1882. - -To this interval also would seem to belong the Belly River series of -western Canada, which contains important beds of Coal, but is Closely -associated with the marine Fort Pierre series. A very curious herbaceous -plant of this group, which I have named _Brasenia antiqua_, occurs in the -beds associated with one of the coals. It is a close ally of the modern -_B. peltata_, an aquatic plant which occurs in British Columbia and in -eastern America, and is also said to be found in Japan, Australia, and -India, a width of distribution appropriate to so old a type (Fig. 76). - -In so far as vegetable life is concerned, the transition from the Upper -Cretaceous to the Tertiary or Kainozoic is easy, though in many parts -of the world, and more especially in western Europe, there is a great -gap in the deposits between the upper Chalk and the lowest Eocene. -With reference to fossil plants, Schimper recognises in the Kainozoic, -beginning with the oldest, five formations--Palæocene, Eocene, Oligocene, -Miocene, and Pliocene. Throughout these a flora, similar to that of the -Cretaceous on the one hand and the modern on the other, though with -important local peculiarities, extends. There is evidence, however, -of a gradual refrigeration, so that in the Pliocene the climates of -the northern hemisphere were not markedly different from their present -character. - -In the first instance an important error was committed by palæobotanists, -in referring to the Miocene many deposits really belonging to the Eocene. -This arose from the early study of the rich plant-bearing Miocene beds of -Switzerland, and from the similarity of the flora all the way from the -Middle Cretaceous to the later Tertiary. The differences are now being -worked out, and we owe to Mr. Starkie Gardner the credit of pointing -these out in England, and to the Geological Survey of Canada that of -collecting the material for exhibiting them in the more northern part of -America. - -In the great interior plain of America there rests on the Cretaceous -a series of clays and sandstones with beds of lignite, some of them -eighteen feet in thickness. This was formerly known as the lignitic or -lignite Tertiary, but more recently as the Laramie series. These beds -were deposited in fresh or brackish water, in an internal sea or group of -lakes and swamps, when the continent was lower than at present. They have -been studied both in the United States[DR] and Canada; and, though their -flora was originally referred by mistake to the Miocene, it is now known -to be Eocene or Palæocene, or even in part a transition group between -the latter and the Cretaceous. The following remarks, taken chiefly from -recent papers by the author,[DS] will serve to illustrate this: - -[DR] See more especially the elaborate and valuable reports by Lesquereux -and Newberry, and a recent memoir by Ward on "Types of the Laramie -Flora," "Bulletins of the United States Geological Survey," 1887. - -[DS] "Transactions of the Royal Society of Canada," 1886-'87. - -On the geological map of Canada the Laramie series, formerly known as -the lignitic or lignite Tertiary, occurs, with the exception of a few -outliers, in two large areas west of the 100th meridian, and separated -from each other by a tract of older Cretaceous rocks, over which the -Laramie beds may have extended, before the later denudation of the region. - -The most eastern of these areas, that of the Souris River and Wood -Mountain, extends for some distance along the United States boundary, -between the 102d and 109th meridians, and reaches northward to about -thirty miles south of the "elbow" of the South Saskatchewan River, which -is on the parallel of 51° north. In this area the lowest beds of the -Laramie are seen to rest on those of the Fox Hill group of the Upper -Cretaceous, and at one point on the west they are overlaid by beds of -Miocene Tertiary age, observed by Mr. McConnell, of the Geological -Survey, in the Cypress Hills, and referred by Cope, on the evidence of -mammalian remains, to the White River division of the United States -geologists, which is regarded by them as Lower Miocene.[DT] The age of -the Laramie beds is thus stratigraphically determined to be between the -Fox Hill Cretaceous and the Lower Miocene. They are also undoubtedly -continuous with the Fort Union group of the United States geologists on -the other side of the international boundary, and they contain similar -fossil plants. They are divisible into two groups--a lower, mostly -argillaceous, and to which the name of "Bad Lands beds" may be given, -from the "bad lands" of Wood Mountain, where they are well exposed, and -an upper, partly arenaceous member, which may be named the Souris River -or Porcupine Creek division. In the lower division are found reptilian -remains of Upper Cretaceous type, with some fish remains more nearly -akin to those of the Eocene.[DU] Neither division has as yet afforded -mammalian remains. - -[DT] "Report of the Geological Survey of Canada," 1885. - -[DU] Cope, in Dr. G. M. Dawson's "Report on the 49th Parallel." - -The western area is of still larger dimensions, and extends along the -eastern base of the Rocky Mountains from the United States boundary -to about the 55th parallel of latitude, and stretches eastward to the -111th meridian. In this area, and more especially in its southern part, -the officers of the Geological Survey of Canada have recognised three -divisions, as follows: (1) The Lower Laramie or St. Mary River series, -corresponding in its character and fossils to the Lower or Bad Lands -division of the other area. (2) A middle division, the Willow Creek beds, -consisting of clays, mostly reddish, and not recognised in the other -area. (3) The Upper Laramie or Porcupine Hills division, corresponding -in fossils, and to some extent in mineral character, to the Souris River -beds of the eastern area. - -The fossil plants collected by Dr. G. M. Dawson in the eastern area were -noticed by the author in an appendix to Dr. Dawson's report on the 49th -parallel, in 1875, and a collection subsequently made by Dr. Selwyn -was described in the "Report of the Geological Survey of Canada" for -1879-'80. Those of the western area, and especially collections made by -myself near Calgary in 1883, and by officers of the Geological Survey in -1884, have been described in the "Transactions of the Royal Society of -Canada" vols. iii. and iv. - -In studying these fossil plants, I have found that there is a close -correspondence between those of the Lower and Upper Laramie in the two -areas above referred to respectively, and that the flora of the Lower -Laramie is somewhat distinct from that of the Upper, the former being -especially rich in certain aquatic plants, and the latter much more -copious on the whole, and much more rich in remains of forest-trees. This -is, however, possibly an effect rather of local conditions than of any -considerable change in the flora, since some Upper Laramie forms recur -as low as the Belly River series of the Cretaceous, which is believed on -stratigraphical grounds to be considerably older than the Lower Laramie. - -With reference to the correlation of these beds with those of the United -States, some difficulty has arisen from the tendency of palæobotanists -to refer the plants of the Upper Laramie to the Miocene age, although -in the reports of Mr. Clarence King, the late director of the United -States Geological Survey, these beds are classed, on the evidence of -stratigraphy and animal fossils, as Upper Cretaceous. More recently, -however, and partly perhaps in consequence of the views maintained by the -writer since 1875, some change of opinion has occurred, and Dr. Newberry -and Mr. Lesquereux seem now inclined to admit that what in Canada we -recognise as Upper Laramie is really Eocene, and the Lower Laramie -either Cretaceous or a transition group between this and the Eocene. In -a recent paper [DV] Dr. Newberry gives a comparative table, in which he -correlates the Lower Laramie with the Upper Cretaceous of Vancouver -Island and the Faxoe and Maestricht beds of Europe, while he regards the -Upper Laramie as equivalent to European Eocene. Except in so far as the -equivalence of the Lower Laramie and Vancouver Island beds is concerned, -this corresponds very nearly with the conclusions of the writer in a -paper published last year[DW]--namely, that we must either regard the -Laramie as a transition Cretaceo-Eocene group, or must institute our -line of separation in the Willow Creek or Middle Laramie division, which -has, however, as yet afforded no fossil plants. I doubt, however, the -equivalence of the Vancouver beds and the Lower Laramie, except perhaps -in so far as the upper member of the former is concerned. I have also to -observe that in the latest report of Mr. Lesquereux he still seems to -retain in the Miocene certain formations in the West, which from their -fossil plants I should be inclined to regard as Eocene.[DX] - -[DV] Newberry, "Transactions of the New Fork Academy," February, 1886. - -[DW] "Transactions of the Royal Society of Canada," vol. ii. - -[DX] While these sheets were going through the press I received a very -valuable report of Mr. Lester F. Ward upon the Laramie of the United -States. I have merely had time to glance at this report, but can see that -the views of the author agree closely with those above expressed. - -Two ferns occurring in these beds are remarkable as evidence of the -persistence of species, and of the peculiarities of their ancient and -modern distribution. _Onoclea sensibilis_, the very common sensitive -fern of eastern America, is extremely abundant in the Laramie beds over -a great area in the West. Mr. Starkie Gardner and Dr. Newberry have also -shown that it is identical with the _Filicites Hebridicus_ of Forbes, -from the early Eocene beds of the Island of Mull, in Scotland. Thus we -have a species once common to Europe and America, but now restricted -to the latter, and which has continued to exist over all the vast ages -between the Cretaceous and the present day. In the Laramie beds I have -found associated with this species another and more delicate fern, -the modern _Davallia_ (_Stenloma_) _tenuifolia_, but this, unlike its -companion, no longer occurs in America, but is found in the mountains of -Asia. This is a curious illustration of the fact that frail and delicate -plants may be more ancient than the mountains or plains on which they -live. - -There are also some very interesting and curious facts in connection with -the conifers of the Laramie. One of the most common of these is a _Thuja_ -or arbor vitæ (the so-called "cedar" of Canada). The Laramie species has -been named _T. interrupta_ by Newberry, but it approaches very closely -in its foliage to _T. occidentalis_, of eastern Canada, while its fruit -resembles that of the western species, _T. gigantea_. - -Still more remarkable are the Sequoias to which we have already referred, -but which in the Laramie age seem to have been spread over nearly -all North America. The fossil species are of two types, representing -respectively the modern _S. gigantea_ and _S. sempervirens_, and their -wood, as well as that of Thuja, is found in great abundance in the -lignites, and also in the form of silicified trunks, and corresponds -with that of the recent species. The Laramie contains also conifers -of the genera _Glyptostrobus_, _Taxodium_, and _Taxus_; and the -genus _Salisburia_ or gingko--so characteristic of the Jurassic and -Cretaceous--is still represented in America as well as in Europe in the -early Eocene. - -We have no palms in the Canadian or Scottish Palæocene, though I -believe they are found further south. The dicotyledonous trees are -richly represented. Perhaps the most conspicuous were three species of -_Platanus_, the leaves of which sometimes fill the sandstones, and one -of which, _P. nobilis_, Newberry, sometimes attains the gigantic size of -a foot or more in diameter of its blade. The hazels are represented by a -large-leaved species, _C. Macquarrii_, and by leaves not distinguishable -from those of the modern American species, _C. Americana_ and _C. -rostrata_. There are also chestnuts and oaks. But the poplars and willows -are specially abundant, being represented by no less than six species, -and it would seem that all the modern types of poplar, as indicated by -the forms and venation of the leaves, existed already in the Laramie, and -most of them even in the Upper Cretaceous. _Sassafras_ is represented by -two species, and the beautiful group of _Viburnum_,, to which the modern -tree-cranberry belongs, has several fine species, of some of which both -leaves and berries have been found. The hickories and butternuts are -also present, the horse-chestnut, the _Catalpa_ and _Sapindus_, and some -curious leaves which seem to indicate the presence of the modern genus -_Symphorocarpus_, the snow-berry tribe. - -The above may suffice to give an idea of the flora of the older Eocene -in North America, and I may refer for details to the works of Newberry, -Lesquereux, and Ward, already cited. I must now add that the so-called -Miocene of Atanekerdluk, Greenland, is really of the same age, as also -the "Miocene" of Mull, in Scotland, of Antrim, in Ireland, and of Bovey -Tracey, in the south of England, and the Gelinden, or "Heersian" beds, -of Belgium, described by Saporta. In comparing the American specimens -with the descriptions given by Gardner of the leaf-beds at Ardtown, in -Mull, we find, as already stated, _Onoclea sensibilis_, common to both. -The species of _Sequoia_, _Gingko_, _Taxus_, and _Glyptostrobus_ are -also identical or closely allied, and so are many of the dicotyledonous -leaves. For example, _Platanoides Hebridicus_ is very near to _P. -nobilis_, and _Corylus Macquarrii_ is common to both formations, as well -as _Populus Arctica_ and _P. Richardsoni_. I may add that ever since -1875-'76, when I first studied the Laramie plants, I have maintained -their identity with those of the Fort Union group of the United States, -and of the so-called Miocene of McKenzie River and Greenland, and that -the whole are Paleocene; and this conclusion has now been confirmed by -the researches of Gardner in England, and by the discovery of true Lower -Miocene beds in the Canadian northwest, overlying the Laramie or lignite -series. - -In a bulletin of the United States Geological Survey (1886), Dr. White -has established in the West the continuous stratigraphical succession of -the Laramie and the Wahsatch Eocene, thus placing the Laramie conformably -below the Lower Eocene of that region. Cope has also described as the -Puerta group a series of beds holding vertebrate fossils, and forming a -transition from the Laramie to the Wahsatch. White also testifies that -a number of fresh-water mollusks are common to the Wahsatch and the -Laramie. This finally settles the position of the Laramie so far as the -United States geologists are concerned, and shows that the flora is to be -regarded as Eocene if not Upper Cretaceous, in harmony with what has been -all along maintained in Canada. An important _résumé_ of the flora has -just been issued by Ward in the bulletins of the United States Geological -Survey (1887). - -Before leaving this part of the subject, I would deprecate the remark, -which I see occasionally made, that fossil plants are of little value in -determining geological horizons in the Cretaceous and Tertiary. I admit -that in these periods some allowance must be made for local differences -of station, and also that there is a generic sameness in the flora of the -northern hemisphere, from the Cenomanian to the modern, yet these local -differences and general similarity are not of a nature to invalidate -inferences as to age. No doubt, so long as palæobotanists seemed obliged, -in deference to authority, and to the results of investigations limited -to a few European localities, to group together, without distinction, all -the floras of the later Cretaceous and earlier Tertiary, irrespective -of stratigraphical considerations, the subject lost its geological -importance. But, when a good series has been obtained in any one region -of some extent, the case becomes different. Though there is still much -imperfection in our knowledge of the Cretaceous and Tertiary floras -of Canada, I think the work already done is sufficient to enable any -competent observer to distinguish by their fossil plants the Lower, -Middle, and Upper Cretaceous, and the latter from the Tertiary; and, with -the aid of the work already done by Lesquereux and Newberry in the United -States, to refer approximately to its true geological position any group -of plants from beds of unknown age in the West. - -An important consequence arising from the above statements is that -the period of warm climate which enabled a temperate flora to exist -in Greenland was that of the later Cretaceous and early Eocene rather -than, as usually stated, the Miocene. It is also a question admitting of -discussion whether the Eocene flora of latitudes so different as those of -Greenland, Mackenzie River, northwest Canada, and the United States, were -strictly contemporaneous, or successive within a long geological period -in which climatal changes were gradually proceeding. The latter statement -must apply at least to the beginning and close of the period; but the -plants themselves have something to say in favour of contemporaneity. The -flora of the Laramie is not a tropical but a temperate flora, showing no -doubt that a much more equable climate prevailed in the more northern -parts of America than at present. But this equability of climate implies -the possibility of a great geographical range on the part of plants. -Thus it is quite possible and indeed highly probable that in the Laramie -age a somewhat uniform flora extended from the Arctic seas through the -great central plateau of America far to the south, and in like manner -along the western coast of Europe. It is also to be observed that, as -Gardner points out, there are some differences indicating a diversity -of climate between Greenland and England, and even between Scotland -and Ireland and the south of England, and we have similar differences, -though not strongly-marked, between the Laramie of northern Canada and -that of the United States. When all our beds of this age from the Arctic -sea to the 49th parallel have been ransacked for plants, and when the -palæobotanists of the United States shall have succeeded in unravelling -the confusion which now exists between their Laramie and the Middle -Tertiary, the geologist of the future will be able to restore with much -certainty the distribution of the vast forests which in the early Eocene -covered the now bare plains of interior America. Further, since the -break which in western Europe separates the flora of the Cretaceous from -that of the Eocene does not exist in America, it will then be possible -to trace the succession from the Mesozoic flora of the Trias and of the -Queen Charlotte Islands and Kootanie series of the Lower Cretaceous up -to the close of the Eocene; and to determine, for America at least, the -manner and conditions under which the angiospermous flora of the later -Cretaceous succeeded to the pines and cycads which characterised the -beginning of the Cretaceous period. In so far as Europe is concerned, -this may be more difficult, since the want of continuity of land from -north to south seems there to have been fatal to the continuance of some -plants during changes of climate, and there were also apparently in the -Kainozoic period invasions at certain times of species from the south and -east, which did not occur to the same extent in America. - -In recent reports on the Tertiary floras of Australia and New -Zealand,[DY] Ettingshausen holds that the flora of the Tertiary, as a -whole, was of a generalised character; forms now confined to the southern -and northern hemispheres respectively being then common to both. It would -thus seem that the present geographical diversities must have largely -arisen from the great changes in climate and distribution of land and -water in the later Tertiary. - -[DY] "Geological Magazine," August, 1887. - -The length of our discussion of the early angiospermous flora does not -permit us to trace it in detail through the Miocene and Pliocene, but -we may notice the connection through these in the next chapter, and may -refer to the magnificent publications of Heer and Lesquereux on the -Tertiary floras of Europe and America respectively. - - - - -CHAPTER VII. - - PLANTS FROM THE TERTIARY TO THE MODERN PERIOD. - - -It may be well to begin this chapter with a sketch of the general -physical and geological conditions of the period which was characterised -by the advent and culmination of the dicotyledonous trees. - -In the Jurassic and earliest Cretaceous periods the prevalence, over the -whole of the northern hemisphere and for a long time, of a monotonous -assemblage of gymnospermous and acrogenous plants, implies a uniform and -mild climate, and facility for intercommunication in the north. Toward -the end of the Jurassic and beginning of the Cretaceous, the land of the -northern hemisphere was assuming greater dimensions, and the climate -probably becoming a little less uniform. Before the close of the Lower -Cretaceous period the dicotyledonous flora seems to have been introduced, -under geographical conditions which permitted a warm temperate climate to -extend as far north as Greenland. - -In the Cenomanian or Middle Cretaceous age we find the northern -hemisphere tenanted with dicotyledonous trees closely allied to those of -modern times, though still indicating a climate much warmer than that -which at present prevails. In this age, extensive but gradual submergence -of land is indicated by the prevalence of chalk and marine limestones -over the surface of both continents; but a circumpolar belt seems to -have been maintained, protecting the Atlantic and Pacific basins from -floating ice, and permitting a temperate flora of great richness to -prevail far to the north, and especially along the southern margins and -extensions of the circumpolar land. These seem to have been the physical -conditions which terminated the existence of the old Mesozoic flora and -introduced that of the Middle Cretaceous. - -As time advanced the quantity of land gradually increased, and the -extension of new plains along the older ridges of land was coincident -with the deposition of the great Laramie series, and with the origination -of its peculiar flora, which indicates a mild climate and considerable -variety of station in mountain, plain, and swamp, as well as in great -sheets of shallow and weedy fresh water. - -In the Eocene and Miocene periods, the continents gradually assumed their -present form, and the vegetation became still more modern in aspect. -In that period of the Eocene, however, in which the great nummulitic -limestones were deposited, a submergence of land occurred on the eastern -continent which must have assimilated its physical conditions to those of -the Middle Cretaceous. This great change, affecting materially the flora -of Europe, was not equally great in America, which also by the north and -south extension of its mountain-chains permitted movements of migration -not possible in the Old World. From the Eocene downward, the remains of -land-animals and plants are found chiefly in lake-basins occupying the -existing depressions of the land, though more extensive than those now -remaining. It must also be borne in mind that the great foldings and -fractures of the crust of the earth which occurred at the close of the -Eocene, and to which the final elevation of such ranges as the Alps and -the Rocky Mountains belongs, permanently modified and moulded the forms -of the continents. - -These statements raise, however, questions as to the precise equivalence -in time of similar floras found in different latitudes. However -equable the climate, there must have been some appreciable difference -in proceeding from north to south. If, therefore, as seems in every -way probable, the new species of plants originated on the Arctic land -and spread themselves southward, this latter process would occur most -naturally in times of gradual refrigeration or of the access of a more -extreme climate--that is, in times of the elevation of land in the -temperate latitudes, or, conversely, of local depression of land in the -Arctic, leading to invasions of northern ice. Hence, the times of the -prevalence of particular types of plants in the far north would precede -those of their extension to the south, and a flora found fossil in -Greenland might be supposed to be somewhat older than a similar flora -when found farther south. It would seem, however, that the time required -for the extension of a new flora to its extreme geographical limit is so -small, in comparison with the duration of an entire geological period, -that, practically, this difference is of little moment, or at least does -not amount to antedating the Arctic flora of a particular type by a whole -period, but only by a fraction of such period. - -It does not appear that, during the whole of the Cretaceous and Eocene -periods, there is any evidence of such refrigeration as seriously to -interfere with the flora, but perhaps the times of most considerable -warmth are those of the Dunvegan group in the Middle Cretaceous, and -those of the later Laramie and oldest Eocene. - -It would appear that no cause for the mild temperature of the Cretaceous -needs to be invoked, other than those mutations of land and water which -the geological deposits themselves indicate. A condition, for example, of -the Atlantic basin in which the high land of Greenland should be reduced -in elevation, and at the same time the northern inlets of the Atlantic -closed against the invasion of Arctic ice, would at once restore climatic -conditions allowing of the growth of a temperate flora in Greenland. -As Dr. Brown has shown,[DZ] and as I have elsewhere argued, the absence -of light in the Arctic winter is no disadvantage, since, during the -winter, the growth of deciduous trees is in any case suspended; while the -constant continuance of light in the summer is, on the contrary, a very -great stimulus and advantage. - -[DZ] "Florula Discoana." - -It is a remarkable phenomenon in the history of genera of plants in -the later Mesozoic and Tertiary, that the older genera appear at once -in a great number of specific types, which become reduced as well as -limited in range down to the modern. This is, no doubt, connected with -the greater differentiation of local conditions in the modern; but it -indicates also a law of rapid multiplication of species in the early life -of genera. The distribution of the species of _Salisburia_, _Sequoia_, -_Platanus_, _Sassafras_, _Liriodendron_, _Magnolia_, and many other -genera, affords remarkable proofs of this. - -Gray, Saporta, Heer, Newberry, Lesquereux, and Starkie Gardner have all -ably discussed these points; but the continual increase of our knowledge -of the several floras, and the removal of error as to the dates of their -appearance, must greatly conduce to clearer and more definite ideas. In -particular, the prevailing opinion that the Miocene was the period of the -greatest extension of warmth and of a temperate flora into the Arctic, -must be abandoned in favour of the later Cretaceous and Eocene; and, if -I mistake not, this will be found to accord better with the evidence of -general geology and of animal fossils. - -In these various revolutions of the later Cretaceous and Kainozoic -periods, America, as Dr. Gray has well pointed out, has had the advantage -of a continuous stretch of high land from north to south, affording a -more sure refuge to plants in times of submergence, and means of escape -to the south in times of refrigeration. Hence, the greater continuity -of American vegetation and the survival of genera like _Sequoia_ and -_Liriodendron_, which have perished in the Old World. Still, there are -some exceptions to this, for the gingko-tree is a case of survival in -Asia of a type once plentiful in America, but now extinct there. Eastern -Asia has had, however, some considerable share of the same advantage -possessed by America, with the addition, referred to by Gray, of a better -and more insular climate. - -But our survey of these physical conditions can not be considered -complete till we shall have considered the great Glacial age of the -Pleistocene. It is certain that throughout the later Miocene and Pliocene -the area of land in the northern hemisphere was increasing, and the large -and varied continents were tenanted by the noblest vegetation and the -grandest forms of mammalian life that the earth has ever witnessed. As -the Pliocene drew to a close, a gradual diminution of warmth came on, -and more especially a less equable climate, and this was accompanied -with a subsidence of the land in the temperate regions and with changes -of the warm ocean-currents. Thus gradually the summers became cooler -and the winters longer and more severe, the hill-tops became covered -with permanent snows, glaciers ploughed their way downward into the -plains, and masses and fields of floating ice cooled the seas. In these -circumstances the richer and more delicate forms of vegetation must have -been chilled to death or obliged to remove farther south, and in many -extensive regions, hemmed in by the advance of the sea on the one hand -and land-ice on the other, they must have altogether perished. - -Yet even in this time vegetation was not altogether extinct. Along the -Gulf of Mexico in America, and in the Mediterranean basin in Europe, -there were still some remains of a moderate climate and certain boreal -and arctic forms moving southward continued to exist here and there in -somewhat high latitudes, just as similar plants now thrive in Grinnell -Land within sight of the snows of the Greenland mountains. A remarkable -summary of some of these facts as they relate to England was given by an -eminent English botanist, Mr. Carruthers, in his address as President of -the Biological Section of the British Association at Birmingham in 1886. -At Cromer, on the coast of Norfolk, the celebrated forest-bed of newer -Pliocene age, and containing the remains of a copious mammalian fauna, -holds also remains of plants in a state admitting of determination. These -have been collected by Mr. Reid, of the Geological Survey, and were -reported on by Carruthers, who states that they represent a somewhat -colder temperature than that of the present day. I quote the following -details from the address. - -With reference to the plants of the forest-bed or newer Pliocene he -remarks as follows: - -"Only one species (_Trapa natans_, Willd.) has disappeared from our -islands. Its fruits, which Mr. Reid found abundantly in one locality, -agree with those of the plants found until recently in the lakes of -Sweden. Four species (_Prunus speciosa_, L., _[OE]nanthe Tichenalii_, -Sm., _Potamogeton pterophyllus_, Sch., and _Pinus abies_, L.) are found -at present only in Europe, and a fifth (_Potamogeton trichoides_, Cham.) -extends also to North America; two species (_Peucedanum palustre_, -Moench, and _Pinus sylvestris_, L.) are found also in Siberia, while six -more (_Sanguisorba officinalis_, L., _Rubus fruticosus_, L., 5 _Cornus -sanguinea_, L., _Euphorbia amygdaloides_, L., _Quercus robur_, L., and -_Potamogeton crispus_, L.) extend into western Asia, and two (_Fagus -sylvatica_, L., and _Alnus glutinosa_, L.) are included in the Japanese -flora. Seven species, while found with the others, enter also into the -Mediterranean flora, extending to North Africa: these are _Thalictrum -minus_, L., _Thalictrum flavum_, L., _Ranunculus repens_, L., _Stellaria -aquatica_, Scop., _Corylus avellana_, L., _Yannichellia palustris_, L., -and _Cladium mariscus_, Br. With a similar distribution in the Old World, -eight species (_Bidens tripartita_, L., _Myosotis cæspitosa_, Schultz, -_Suæda maritima_, Dum., _Ceratophyllum demersum_,, L., _Sparganium -ramosum_, Huds., _Potamogeton pectinatus_, L., _Carex paludosa_, Good., -and _Osmunda regalis_, L.) are found also in North America. Of the -remainder, ten species (_Nuphar luteum_, Sm., _Menyanthes trifoliata_, -L., _Stachys palustris_, L., _Rumex maritimus_, L., _Rumex acetosella_, -L., _Betula alba_, L., _Scirpus pauciflorus_, Lightf., _Taxus baccata_, -L., and _Isoetes lacustris_, L.) extend round the north temperate -zone, while three (_Lycopus europæus_, L., _Alisma plantago_, L., and -_Phragmites communis_, Trim), having the same distribution in the north, -are found also in Australia, and one (_Hippuris vulgaris_, L.) in the -south of South America. The list is completed by _Ranunculus aquatilis_, -L., distributed over all the temperate regions of the globe, and _Scirpus -lacustris_, L., which is found in many tropical regions as well." - -He remarks that these plants, while including species now very widely -scattered, present no appreciable change of characters. - -Above this bed are glacial clays, which hold other species indicating an -extremely cold climate. They are few in number, only _Salix polaris_, a -thoroughly arctic species, and its ally, _S. cinerea_, L., and a moss, -_Hypnum turgescens_, Schimp., no longer found in Britain, but an Alpine -and arctic species. This bed belongs to the beginning of the Glacial -period, the deposits of which have as yet afforded no plants in England. -But plants occur in post-glacial and upper-glacial beds in different -parts of England, to which Carruthers thus refers: - -"The period of great cold, during which arctic ice extended far into -temperate regions, was not favorable to vegetable life. But in some -localities we have stratified clays with plant-remains later than the -Glacial epoch, yet indicating that the great cold had not then entirely -disappeared. In the lacustrine beds at Holderness is found a small -birch (_Betula nana_, L.), now limited in Great Britain to some of the -mountains of Scotland, but found in the arctic regions of the Old and -New World and on Alpine districts in Europe, and with it _Prunus padus_, -L., _Quercus robur_, L., _Corylus avellana_, L., _Alnus glutinosa_, L., -and _Pinus sylvestris_, L. In the white clay-beds at Bovey Tracey of -the same age there occur the leaves of _Arctostaphylos uva-ursi_, L., -three species of willow, viz., _Salix cinerea_, L., _S. myrtilloides_, -L., and _S. polaris_, Wahl., and in addition to our Alpine _Betula -nana_, L., the more familiar _B. alba_, L. Two of these plants have -been lost to our flora from the change of climate that has taken place, -viz., _Salix myrtilloides_, L., and _S. polaris_, Wahl.; and _Betula -nana_, L., has retreated to the mountains of Scotland. Three others -(_Dryas octopetala_, L., _Arctostaphylos uva-ursi_, L., and _Salix -herbacea_, L.) have withdrawn to the mountains of northern England, -Wales, and Scotland, while the remainder are still found scattered over -the country. Notwithstanding the diverse physical conditions to which -these plants have been subjected, the remains preserved in these beds -present no characters by which they can be distinguished from the living -representatives of the species." - -One of the instances referred to is very striking. At Bovey Tracey the -arctic beds rest directly on those holding the rich, warm temperate flora -of the Eocene; so that here we have the evidence of fossil plants to show -the change from the climate of the Eocene to that of arctic lands, and -the modern vegetation to indicate the return of a warm temperature. - -In Canada, in the Pleistocene beds known as the Leda clays, intervening -between the lower boulder clay and the Saxicava sand, which also holds -boulders, there are beds holding fossil plants, in some places intermixed -with sea-shells and bones of marine fishes, showing that they were -drifted into the sea at a time of submergence. These remains are boreal -rather than arctic in character, and with the remains of drift-wood often -found in the boulder deposits serve to indicate that there were at all -times oases of hardy life in the glacial deserts, just as we find these -in polar lands at the present day. I condense from a paper on these -plants[EA] the following facts, with a few additional notes: - -[EA] "Canadian Naturalist," 1866. - -The importance of all information bearing on the temperature of the -Post-pliocene period invests with much interest the study of the -land-plants preserved in deposits of this age. Unfortunately, these -are few in number, and often not well preserved. In Canada, though -fragments of the woody parts of plants occasionally occur in the marine -clays and sands, there is only one locality which has afforded any -considerable quantity of remains of their more perishable parts. This -is the well-known deposit of Leda clay at Green's Creek, on the Ottawa, -celebrated for the perfection in which the skeletons of the capelin -and other fishes are preserved in the calcareous nodules imbedded in -the clay. In similar nodules, contained apparently in a layer somewhat -lower than that holding the ichthyolites, remains of land-plants are -somewhat abundant, and, from their association with shells of _Leda -glacialis_, seem to have been washed down from the land into deep water. -The circumstances would seem to have been not dissimilar from those -at present existing in the northeast arm of Gaspé Basin, where I have -dredged from mud now being deposited in deep water, living specimens of -_Leda limatula_, mixed with remains of land-plants. - -The following are the species of plants recognised in these nodules: - -1. _Drosera rotundifolia_, Linn. In a calcareous nodule from Green's -Creek, the leaf only preserved. This plant is common in bogs in Canada, -Nova Scotia, and Newfoundland, and thence, according to Hooker, to the -Arctic circle. It is also European. - -[Illustration: Fig. 77.--_Gaylussaccia resinosa_. Pleistocene, Canada.] - -2. _Acer spicatum_, Lamx. (_Acer montanum_, Aiton.) Leaf in a nodule from -Green's Creek. Found in Nova Scotia and Canada, also at Lake Winnipeg, -according to Richardson. - -3. _Potentilla Canadensis_, Linn. In nodules from Green's Creek; leaves -only preserved. I have had some difficulty in determining these, but -believe they must be referred to the species above named, or to _P. -simplex_, Michx., supposed by Hooker and Gray to be a variety. It occurs -in Canada and New England, but I have no information as to its range -northward. - -4. _Gaylussaccia resinosa_, Torrey and Gray. Leaf in nodule at Green's -Creek. Abundant in New England and in Canada, also on Lake Huron and the -Saskatchewan, according to Richardson (Fig. 77). - -5. _Populus balsamifera_, Linn. Leaves and branches in nodules at Green's -Creek. This is by much the most common species, and its leaves are of -small size, as if from trees growing in cold and exposed situations. The -species is North American and Asiatic, and abounds in New England and -Canada. It extends to the Arctic circle, and is abundant on the shores -of the Great Slave Lake and on the McKenzie River, and according to -Richardson constitutes much of the drift timber of the Arctic coast (Fig. -78). - -[Illustration: Fig. 78.--_Populus balsamifera_. Pleistocene, Canada.] - -6. _Thuja occidentalism_ Linn. Trunks and branches in the Leda clay -at Montreal. This tree occurs in New England and Canada, and extends -northward into the Hudson Bay territories. It is a northern though -not arctic species in its geographical range. According to Lyell it -occurs associated with the bones of Mastodon in New Jersey. From the -great durability of its wood, it is one of the trees most likely to be -preserved in aqueous deposits. - -7. _Potamogeton perfoliatus_, Linn. Leaves and seeds in nodules at -Green's Creek. Inhabits streams of the Northern States and Canada, and -according to Richardson extends to Great Slave Lake. - -8. _Potamogeton pusillus._ Quantities of fragments which I refer to this -species occur in nodules at Green's Creek. They may possibly belong to a -variety of _P. hybridus_ which, together with _P. natans_, now grows in -the river Ottawa, where it flows over the beds containing these fossils. - -9. _Cariceæ and Gramineæ._ Fragments in nodules from Green's Creek appear -to belong to plants of these groups, but I cannot venture to determine -their species. - -10. _Equisetum scirpoides_, Michx. Fragments in nodules, Green's Creek. -This is a widely distributed species, occurring in the Northern States -and Canada. - -11. _Fontinalis._ In nodules at Green's Creek there occur, somewhat -plentifully, branches of a moss apparently of the genus _Fontinalis_. - -[Illustration: Fig. 79.--Frond of _Fucus_. Pleistocene, Canada.] - -12. _Algæ._ With the plants above mentioned, both at Green's Creek and at -Montreal, there occur remains of sea-weeds (Fig. 79). They seem to belong -to the genera _Fucus_ and _Ulva_, but I cannot determine the species. -A thick stem in one of the nodules would seem to indicate a large -_Laminaria_. With the above there are found at Green's Creek a number of -fragments of leaves, stems, and fruits, which I have not been able to -refer to their species, principally on account of their defective state -of preservation. - -None of the plants above mentioned is properly arctic in its -distribution, and the assemblage may be characterised as a selection from -the present Canadian flora of some of the more hardy species having the -most northern range. Green's Creek is in the central part of Canada, near -to the parallel of 46°, and an accidental selection from its present -flora, though it might contain the same species found in the nodules, -would certainly include with these, or instead of some of them, more -southern forms. More especially the balsam poplar, though that tree -occurs plentifully on the Ottawa, would not be so predominant. But such -an assemblage of drift-plants might be furnished by any American stream -flowing in the latitude of 50° to 55° north. If a stream flowing to the -north, it might deposit these plants in still more northern latitudes, as -the McKenzie River does now. If flowing to the south, it might deposit -them to the south of 50°. In the case of the Ottawa, the plants could -not have been derived from a more southern locality, nor probably from -one very far to the north. We may therefore safely assume that the -refrigeration indicated by these plants would place the region bordering -the Ottawa in nearly the same position with that of the south coast of -Labrador fronting on the Gulf of St. Lawrence at present. The absence of -all the more arctic species occurring in Labrador should perhaps induce -us to infer a somewhat milder climate than this. - -The moderate amount of refrigeration thus required would in my opinion -accord very well with the probable conditions of climate deducible from -the circumstances in which the fossil plants in question occur. At the -time when they were deposited the sea flowed up the Ottawa valley to a -height of 200 to 400 feet above its present level, and the valley of the -St. Lawrence was a wide arm of the sea, open to the arctic current. Under -these conditions the immense quantities of drift-ice from the northward, -and the removal of the great heating surface now presented by the low -lands of Canada and New England, must have given for the Ottawa coast -of that period a summer temperature very similar to that at present -experienced on the Labrador coast, and with this conclusion the marine -remains of the Leda clay, as well as the few land molluscs whose shells -have been found in the beds containing the plants, and which are species -still occurring in Canada, perfectly coincide. - -The climate of that portion of Canada above water at the time when these -plants were imbedded may safely be assumed to have been colder in summer -than at present, to an extent equal to about 5° of latitude, and this -refrigeration may be assumed to correspond with the requirements of -the actual geographical changes implied. In other words, if Canada was -submerged until the Ottawa valley was converted into an estuary inhabited -by species of _Leda_, and frequented by capelin, the diminution of the -summer heat consequent on such depression would be precisely suitable to -the plants occurring in these deposits, without assuming any other cause -of change of climate. - -I have arranged elsewhere the Post-pliocene deposits of the central -part of Canada, as consisting of, in ascending order: (1) The boulder -clay; (2) a deep-water deposit, the Leda clay; and (3) a shallow-water -deposit, the Saxicava sand. But, although I have placed the boulder clay -in the lowest position, it must be observed that I do not regard this as -a continuous layer of equal age in all places. On the contrary, though -locally, as at Montreal, under the Leda clay, it is in other places and -at other levels contemporaneous with or newer than that deposit, which -itself also locally contains boulders. - -At Green's Creek the plant-bearing nodules occur in the lower part of the -Leda clay, which contains a few boulders, and is apparently in places -overlaid by large boulders, while no distinct boulder clay underlies -it. The circumstances which accumulated the thick bed of boulder clay -near Montreal were probably absent in the Ottawa valley. In any case we -must regard the deposits of Green's Creek as coeval with the Leda clay -of Montreal, and with the period of the greatest abundance of _Leda -glacialis_, the most exclusively arctic shell of these deposits. In other -words, I regard the plants above mentioned as probably belonging to the -period of greatest refrigeration of which we have any evidence, of course -not including that mythical period of universal incasement in ice, of -which, as I have elsewhere endeavoured to show, in so far as Canada is -concerned, there is no evidence whatever.[EB] - -[EB] Notes on Post-Pliocene of Canada, "Canadian Naturalist," 1872. - -The facts above stated in reference to Post-pliocene plants concur, with -all the other evidence I have been able to obtain, in the conclusion that -the refrigeration of Canada in the Post-pliocene period consisted of a -diminution of the summer heat, and was of no greater amount than that -fairly attributable to the great depression of the land and the different -distribution of the ice-bearing arctic current. - -In connection with the plants above noticed, it is interesting to -observe that at Green's Creek, at Pakenham Mills, at Montreal, and at -Clarenceville on Lake Champlain, species of Canadian _Pulmonata_ have -been found in deposits of the same age with those containing the plants. -The species which have been noticed belong to the genera _Lymnea_ and -_Planorbis_. - -The Glacial age was, fortunately, not of very long duration, though its -length has been much exaggerated by certain schools of geologists,[EC] -It passed away, and a returning cosmic spring gladdened the earth, and -was ushered in by a time of great rainfall and consequent denudation -and deposit, which has been styled the "Pluvial Period" The remains of -the Pliocene forests then returned--with somewhat diminished numbers of -species--from the south and again occupied the land, though they have -not been able, in their decimated condition, to restore the exuberance -of the flora of the earlier Tertiary. In point of fact, as we shall -see in the next chapter, it is the floras originating within the polar -circle and coming down from the north that are rich and copious. Those -that, after periods of cold or submergence, return from the south, are -comparatively poor. Hence the modern flora is far inferior to that of the -Middle Kainozoic. In America, however, and in eastern Asia, for reasons -already stated, the return was more abundant than in Europe. - -[EC] This I have long maintained on grounds connected with Pleistocene -fossils, amount of denudation and deposit, &c., and I am glad to see that -Prestwich, the best English authority on such subjects, has recently -announced similar conclusions, based on independent reasons. - -Simultaneously with the return of the old temperate flora, the arctic -plants that had overspread the land retreated to mountain-tops, now bared -of ice and snow, and back to the polar lands whence they came; and so it -happens that, on the White Mountains, the Alps, and the Himalayas, we -have insular patches of the same groups of plants that exist around the -pole. - -These changes need not have required a very long time, for the -multiplication and migration of plants are very rapid, especially when -aided by the agency of migratory animals. Many parts of the land must, -indeed, have been stocked with plants from various sources, and by -agencies--as that of the sea--which might at first sight seem adverse to -their distribution. The British Islands, for example, have no indigenous -plants. Their flora consists mainly of Germanic plants, which must have -migrated to Britain in that very late period of the Post-glacial when -the space now occupied by the North Sea was mostly dry land. Other -portions of it are Scandinavian plants, perhaps survivors of the Glacial -age, or carried by migratory birds; and still another element consists -of Spanish plants, brought north by spring migrants, and establishing -themselves in warm and sheltered spots, just as the arctic plants do on -the bleak hill-tops. The Bermudas, altogether recent islands, have one -hundred and fifty species of native plants, all of which are West Indian -and American, and must have been introduced by the sea-currents or by -migratory birds. - -And so the earth became fitted for the residence of modern man. Yet it is -not so good or Edenic a world as it once was, or as it may yet become, -were another revolution to restore a mild climate to the arctic regions, -and to send down a new swarm of migratory species to renew the face of -the earth and restore it to its pristine fertility of vegetable life. - -Thus closes this long history of the succession of plants, reaching -from the far back Laurentian to the present day. It has, no doubt, many -breaks, and much remains to be discovered. Yet it may lead us to some -positive conclusions regarding the laws of the introduction of plants. - -One of these, and perhaps the most remarkable of all, is that certain -principles were settled very far back, and have remained ever since. -We have seen that in the earliest geological periods all that pertains -to the structure, powers, and laws of the vegetable cell was already -fixed and settled. When we consider how much this implies of mechanical -structure and chemical and vital property, the profound significance -of this statement becomes apparent. The relations in these respects -between the living cell and the soil, the atmosphere and the sunshine, -were apparently as perfect in the early Palæozoic as in any subsequent -time. The same may be said of the structures of the leaf and of the -stem. In such old forms as Nematophyton these were, it is true, peculiar -and rudimentary, but in the Devonian and Carboniferous the structure -of leaves and stems embodied all the parts and principles that we find -at present. In regard to fructification there has been more progress, -for, so far as we know, the highest and most complex forms of flowery, -fruits, and seeds belong to the more recent periods, and simpler forms -were at least dominant in the older times. Yet even in this respect the -great leading laws and structures of bisexual reproduction were perfected -in the early Palæozoic, and the improvements introduced in the gymnosperm -and the angiosperm of later periods have consisted mainly in additions of -accessory parts, and in modifications and refinements suited to the wants -of the higher and more complex types. - - - - -CHAPTER VIII. - -GENERAL LAWS OF ORIGIN AND MIGRATIONS OF PLANTS.--RELATIONS OF RECENT -AND FOSSIL FLORAS. - - -The origination of the successive floras which have occupied the northern -hemisphere in geological time, not, as one might at first sight suppose, -in the sunny climes of the south, but under the arctic skies, is a fact -long known or suspected. It is proved by the occurrence of fossil plants -in Greenland, in Spitzbergen, and in Grinnell Land, under circumstances -which show that these were their primal homes. The fact bristles with -physical difficulties, yet is fertile of the most interesting theoretical -deductions, to reach which we may well be content to wade through some -intricate questions. Though not at all a new fact, its full significance -seems only recently to have dawned on the minds of geologists, and within -the last few years it has produced a number of memoirs and addresses to -learned societies, besides many less formal notices.[ED] - -[ED] Saporta, "Ancienne Végétation Polaire"; Hooker, "Presidential -Address to Royal Society," 1878; Thistleton Dyer, "Lecture on Plant -Distribution"; Mr. Starkie Gardner, "Letters in 'Nature,'" 1878, &c. The -basis of most of these brochures is to be found in Heer's "Flora Fossilis -Arctica." - -The earliest suggestion on the subject known to the writer is that of -Prof. Asa Gray, in 1867, with reference to the probable northern source -of the related floras of North America and eastern Asia. With the aid -of the new facts disclosed by Heer and Lesquereux, Gray returned to -the subject in 1872, and more fully developed this conclusion with -reference to the Tertiary floras,[EE] and he has recently still further -discussed these questions in an able lecture on "Forest Geography and -Archæology."[EF] In this he puts the case so well and tersely that we may -quote the following sentences as a text for what follows: - -[EE] Address to American Association. - -[EF] "American Journal of Science," xvi., 1818. - -"I can only say, at large, that the same species (of Tertiary fossil -plants) have been found all round the world; that the richest and -most extensive finds are in Greenland; that they comprise most of -the sorts which I have spoken of, as American trees which once lived -in Europe--magnolias, sassafras, hickories, gum-trees, our identical -southern cypress (for all we can see of difference), and especially -_Sequoias_, not only the two which obviously answer to the two -big-trees now peculiar to California, but several others; that they -equally comprise trees now peculiar to Japan and China, three kinds of -gingko-trees, for instance, one of them not evidently distinguishable -from the Japan species which alone survives; that we have evidence, not -merely of pines and maples, poplars, birches, lindens, and whatever -else characterise the temperate zone forests of our era, but also of -particular species of these, so like those of our own time and country -that we may fairly reckon them as the ancestors of several of ours. Long -genealogies always deal more or less in conjecture; but we appear to -be within the limits of scientific inference when we announce that our -existing temperate trees came from the north, and within the bounds of -nigh probability when we claim not a few of them as the originals of -present species. Remains of the same plants have been found fossil in our -temperate region as well as in Europe." - -Between 1860 and 1870 the writer was engaged in working out all that -could be learned of the Devonian plants of eastern America, the oldest -known flora of any richness, and which consists almost exclusively of -gigantic, and to us grotesque, representatives of the club-mosses, -ferns, and mares'-tails, with some trees allied to the cycads and pines. -In this pursuit nearly all the more important localities were visited, -and access was had to the large collections of Prof. Hall and Prof. -Newberry, in New York and Ohio, and to those made in the remarkable -plant-bearing beds of New Brunswick by Messrs. Matthew and Hartt. In -the progress of these researches, which developed an unexpectedly rich -assemblage of species, the northern origin of this old flora seemed to be -established by its earlier culmination in the northeast, in connection -with the growth of the American land to the southward, which took place -after the great Upper Silurian subsidence, by elevations beginning in -the north while those portions of the continent to the southwest still -remained under the sea. The same result was indicated by the persistence -in the Carboniferous of the south and west of old Erian forms, like -_Megalopteris_. - -When, in 1870, the labours of those ten years were brought before the -Royal Society of London, in the Bakerian lecture of that year, and in a -memoir illustrating no less than one hundred and twenty-five species of -plants older than the great Carboniferous system, these deductions were -stated in connection with the conclusions of Hall, Logan, and Dana, as -to the distribution of sediment along the northeast side of the American -continent, and the anticipation was hazarded that the oldest Palæozoic -floras would be discovered to the north of Newfoundland. Mention was also -made of the apparent earlier and more copious birth of the Devonian flora -in America than in Europe, a fact which is itself connected with the -greater northward extension of this continent. - -The memoir containing these results was not published by the Royal -Society, but its publication was secured in a less complete form in the -reports of the "Geological Survey of Canada." The part of the memoir -relating to Canadian fossil plants, with a portion of the theoretical -deductions, was published in a report issued in 1871.[EG] In this report -the following language was used: - -[EG] "Fossil Plants of the Devonian and Upper Silurian Formations of -Canada," pp. 92, twenty plates, Montreal, 1871. - -"In eastern America, from the Carboniferous period onward, the centre -of plant distribution has been the Appalachian chain. From this the -plants and sediments extended westward in times of elevation, and to this -they receded in times of depression. But this centre was nonexistent -before the Devonian period, and the centre for this must have been to -the northeast, whence the great mass of older Appalachian sediment -was derived. In the Carboniferous period there was also an eastward -distribution from the Appalachians, and links of connection in the -Atlantic bed between the floras of Europe and America. In the Devonian -such connection can have been only far to the northeast. It is therefore -in Newfoundland, Labrador, and Greenland that we are to look for the -oldest American flora, and in like manner on the border of the old -Scandinavian nucleus for that of Europe. - -"Again, it must have been the wide extension of the sea of the -corniferous limestone that gave the last blow to the remaining flora of -the Lower Devonian; and the re-elevation in the middle of that epoch -brought in the Appalachian ridges as a new centre, and established -a connection with Europe which introduced the Upper Devonian and -Carboniferous floras. Lastly, from the comparative richness of the later -Erian[EH] flora in eastern America, especially in the St. John beds, it -might be a fair inference that the northeastern end of the Appalachian -ridge was the original birthplace or centre of creation of what we may -call the later Palæozoic flora, or of a large part of that flora." - -[EH] See pages 107 and 108. - -When my paper was written I had not seen the account published by -the able Swiss palæobotanist Heer, of the remarkable Devonian flora -of Bear Island, near Spitzbergen.[EI] From want of acquaintance with -the older floras of America and western Europe, Heer fell into the -unfortunate error of regarding the whole of Bear Island plants as -Lower Carboniferous, a mistake which his great authority has tended to -perpetuate, and which has even led to the still graver error of some -European geologists, who do not hesitate to regard as Carboniferous the -fossil plants of the American deposits from the Hamilton to the Chemung -groups inclusive, though these belong to formations underlying the oldest -Carboniferous, and characterised by animal remains of unquestioned -Devonian age. In 1872 I addressed a note to the Geological Society of -London on the subject of the so-called "Ursa stage" of Heer, showing -that, though it contained some forms not known at so early a date in -temperate Europe, it was clearly, in part at least, Devonian when tested -by North American standards; but that in this high latitude, in which, -for reasons stated in the report above referred to, I believed the -Devonian plants to have originated, there might be an intermixture of the -two floras. But such a mixed group should in that latitude be referred -to a lower horizon than if found in temperate regions. Dr. Nathorst, -as already stated, has recently obtained new facts which go to show -that plants of two distinct horizons may have been intermixed in the -collections submitted to Heer. - -[EI] "Transactions of the Swedish Academy" 1871; "Journal of the London -Geological Society," vol. xxviii. - -Between 1870 and 1873 my attention was turned to the two sub-floras -intermediate between those of the Devonian and the coal-formation, the -floras of the Lower Carboniferous (Subcarboniferous of some American -geologists) and the Millstone Grit, and in a report upon these[EJ] -similar deductions were expressed. It was stated that in Newfoundland -the coal-beds seem to belong to the Millstone Grit series, and as we -proceed southward they belong to progressively newer portions of the -Carboniferous system. The same fact is observed in the coal-beds of -Scotland, as compared with those of England, and it indicates that the -coal-formation flora, like that of the Devonian, spread itself from the -north, and this accords with the somewhat extensive occurrence of Lower -Carboniferous rocks and fossils in the Parry Islands and elsewhere in the -arctic regions. - -[EJ] "Fossil Plants of Lower Carboniferous and Millstone Grit Formations -of Canada," pp. 47, ten plates, Montreal, 1873. - -Passing over the comparatively poor flora of the earlier Mesozoic, -consisting largely of cycads, pines, and ferns, and as yet little -known in the arctic, and which may have originated in the south, -though represented, according to Heer, by the supposed Jurassic flora -of Siberia, we find, especially at Komé and Atané in Greenland, an -interesting occurrence of those earliest precursors of the truly modern -forms of plants which appear in the Cretaceous, the period of the English -chalk and of the New Jersey greensands. There are two plant-groups of -this age in Greenland; one, that of Komé, consists almost entirely of -ferns, cycads, and pines, and is of decidedly Mesozoic aspect. This is -called Lower Cretaceous. The other, that of Atané, holds remains of many -modern temperate genera, as _Populus_, _Myrica_, _Ficus_, _Sassafras_, -and _Magnolia_. This is regarded as Upper Cretaceous. Resting upon -these Upper Cretaceous beds, without the intervention of any other -formation,[EK] are beds rich in plants of much more modern appearance, -and referred by Heer to the Miocene period, a reference, as we have -seen, not warranted by comparison with the Tertiary plants of Europe or -of America. Still farther north this so-called Miocene assemblage of -plants appears in Spitzbergen and Grinnell Land; but there, owing to the -predominance of trees allied to the spruces, it has a decidedly more -boreal character than in Greenland, as might be anticipated from its -nearer approach to the pole.[EL] - -[EK] Nordenskiöld, "Expedition to Greenland," "Geological Magazine," 1872. - -[EL] Yet even here the bald cypress (_Taxodium distichum_), or a tree -nearly allied to it, is found, though this species is now limited to -the Southern States. Fielden and De Ranee, "Journal of the Geological -Society," 1878. - -If now we turn to the Cretaceous and Tertiary floras of western America, -as described by Lesquereux, Newberry, and others, we find in the lowest -Cretaceous rocks there known--those of the Dakota group--which may be -in the lower part of the Middle Cretaceous, a series of plants[EM] -essentially similar to those of the so-called Upper Cretaceous of -Greenland. They occur in beds indicating land and fresh-water conditions -as prevalent at the time over great areas of the interior of America. -But overlying this plant-bearing formation we have an oceanic limestone -(the Niobrara), corresponding in many respects to the European chalk, -and extending far north into the British territory,[EN] indicating that -the land of the Lower Cretaceous was replaced by a vast Mediterranean -Sea, filled with warm water from the equatorial currents, and not -invaded by cold waters from the north. This is succeeded by thick Upper -Cretaceous deposits of clay and sandstone, with marine remains, though -very sparsely distributed; and these show that further subsidence or -denudation in the north had opened a way for the arctic currents, killing -out the warm-water animals of the Niobrara group, and rilling up the -Mediterranean of that period. Of the flora of these Upper Cretaceous -periods, which must have been very long, we know something in the -interior regions, from the discovery of a somewhat rich flora in the -Dunvegan beds of the Peace River district, on the northern shore of the -great Cretaceous Mediterranean;[EO] and on the coast of British Columbia -we have the remarkable Cretaceous coal-field of Vancouver Island, which -holds the remains of plants of modern genera, and, indeed, of almost -as modern aspect as those of the so-called Miocene of Greenland. They -indicate, however, a warmer climate as then prevalent on the Pacific -coast, and in this respect correspond with a peculiar transition flora, -intermediate between the Cretaceous and Eocene or earliest Tertiary of -the interior regions, and which is described by Lesquereux as the Lower -Lignitic. - -[EM] Lesquereux, "Report on Cretaceous Flora." - -[EN] G. M. Dawson, "Report on Forty-ninth Parallel." - -[EO] "Reports of Dr. G. M. Dawson, Geological Survey of Canada." Also, -"Transactions of the Royal Society of Canada," vol. i. - -Immediately above these Upper Cretaceous beds we have the great -Lignite Tertiary of the West--the Laramie group of recent American -reports--abounding in fossil plants, at one time regarded as Miocene, -but now known to be Lower Eocene, though farther south extending upward -toward the Miocene age.[EP] These beds, with their characteristic plants, -have been traced into the British territory north of the forty-ninth -parallel, and it has been shown that their fossils are identical with -those of the McKenzie River valley, described by Heer as Miocene, and -probably also with those of Alaska, referred to the same age.[EQ] Now -this truly Eocene flora of the temperate and northern parts of America -has so many species in common with that called Miocene in Greenland that -its identity can scarcely be doubted. These facts have led to scepticism -as to the Miocene age of the upper plant-bearing beds of Greenland, and -more especially Mr. J. Starkie Gardner has ably argued, from comparison -with the Eocene flora of England and other considerations, that they are -really of that earlier date.[ER] - -[EP] Lesquereux's "Tertiary Flora"; "White on the Laramie Group"; -Stevenson, "Geological Relations of Lignitic Groups," American -Philosophical Society, June, 1875; Dawson, "Transactions of the Royal -Society of Canada," vol. iv.; Ward, "Bulletin of United States Geological -Survey." - -[EQ] G. M. Dawson, "Report on the Geology of the Forty-ninth Parallel," -where full details on these points may be found. "Transactions of the -Royal Society of Canada," vol. iv. - -[ER] "Nature," December 12, 1878. - -In looking at this question, we may fairly assume that no climate, -however equable, could permit the vegetation of the neighbourhood of -Disco in Greenland to be exactly identical with that of Colorado and -Missouri, at a time when little difference of level existed in the two -regions. Either the southern flora migrated north in consequence of a -greater amelioration of climate, or the northern flora moved southward as -the climate became colder. The same argument, as Gardner has ably shown, -applies to the similarity of the Tertiary plants of temperate Europe to -those of Greenland. If Greenland required a temperature of about 50°, -as Heer calculates, to maintain its Eocene flora, the temperature of -England and that of the Southwestern States must have been higher, though -probably more equable, than at present. - -We cannot certainly affirm anything respecting the migrations of these -floras, but there are some probabilities which deserve attention. The -ferns and cycads of the so-called Lower Cretaceous of Greenland are -nothing but a continuation of the previous Jurassic flora. Now this was -established at an equally early date in the Queen Charlotte Islands,[ES] -and still earlier in Virginia,[ET] The presumption is, therefore, -that it came from the south. It has, indeed, the facies of a southern -hemisphere and insular flora, and probably spread itself northward as -far as Greenland, at a time when our northern continents were groups of -islands, and when the ocean currents were carrying warm water far toward -the arctic regions. The flora which succeeds this in the sections at -Atané has no special affinities with the southern hemisphere, and is of -a more temperate and continental character.[EU] It is not necessarily -Upper Cretaceous, since it is similar to that of the Dakota group farther -south, and this is at least Middle Cretaceous. This flora must have -originated either somewhere in temperate America or within the Arctic -circle, and it must have replaced the older one by virtue of increasing -coolness and continental character of climate. It must, therefore, have -been connected with that elevation of the land which took place at the -beginning of the Cretaceous. During this elevation it spread over all -western America at one time or another, and, as the land again subsided -under the sea of the Niobrara chalk, it assumed an aspect more suited -to a warm climate, but still held its place on such islands as remained -above water along the Pacific coast and in the north, and it continued -to exist on these islands till the colder seas of the Upper Cretaceous -had again given place to the warm plains and land-locked brackish seas -or fresh-water lakes of the Laramie period (Eocene). Thus the true Upper -Cretaceous marks a cool period intervening between the so-called Upper -Cretaceous (really Middle Cretaceous) and the so-called Miocene (really -Lower Eocene) floras of Greenland. - -[ES] "Reports of the Geological Survey of Canada." - -[ET] Fontaine has well described the Mesozoic flora of Virginia, -"American Journal of Science," January, 1879, and "Report on Early -Mesozoic Floras." - -[EU] In the "Proceedings of the Royal Society of Tasmania," 1887, Mr. R. -M. Johnston, F. L. S., states that in the Miocene beds of Tasmania trees -of European genera abound. The Mesozoic flora of that island is of the -usual conifero-cycadean type. Ettingshausen makes a similar statement in -the "Geological Magazine" respecting the Tertiary flora of Australia and -New Zealand, stating that, like the Tertiary floras of Europe, they have -a mixed character, being partly of types now belonging to the northern -hemisphere. - -This latter established itself in Greenland, and probably all around the -Arctic circle, in the warm period of the earliest Eocene, and, as the -climate of the northern hemisphere became gradually reduced from that -time till the end of the Pliocene, it marched on over both continents to -the southward, chased behind by the modern arctic flora, and eventually -by the frost and snow of the Glacial age. This history may admit of -correction in details; but, so far as present knowledge extends, it is in -the main not far from the truth. - -Perhaps the first great question which it raises is that as to the causes -of the alternations of warm and cold climates in the north, apparently -demanded by the vicissitudes of the vegetable kingdom. Here we may set -aside the idea that in former times plants were suited to endure greater -cold than at present. It is true that some of the fossil Greenland -plants are of unknown genera, and many are species new to us; but we are -on the whole safe in affirming that they must have required conditions -similar to those necessary to their modern representatives, except within -such limits as we now find to hold in similar cases among existing -plants. Still we know that at the present time many species found in -the equable climate of England will not live in Canada, though species -to all appearance similar in structure are native here. There is also -some reason to suppose that species when new may have greater hardiness -and adaptability than when in old age and verging toward extinction. In -any case these facts can account for but a small part of the phenomena, -which require to be explained by physical changes affecting the earth as -a whole, or at least the northern hemisphere. Many theoretical views have -been suggested on this subject, and perhaps the most practical way of -disposing of these will be first to set aside a number which are either -precluded by the known facts, incapable of producing the effects, or -altogether uncertain as to their possible occurrence. - -1. In this class we may place the theory that the poles of the earth have -changed their position. Independently of astronomical objections, there -is good geological evidence that the poles of the earth must have been -nearly in their present places from the dawn of life until now. From the -Laurentian upward, those organic limestones which mark the areas where -warm and shallow equatorial water was spreading over submerged continents -are so disposed as to prove the permanence of the poles. In like manner -all the great foldings of the crust of the earth have followed lines -which are parts of great circles tangent to the existing polar circles. -So, also, from the Cambrian age the great drift of sediment from the -north has followed the line of the existing Arctic currents from the -northeast to the southwest, throwing itself, for example, along the line -of the Appalachian uplifts in eastern America, and against the ridge of -the Cordilleras in the west. - -2. Some of the above considerations, along with astronomical evidence, -prevent us from assuming any considerable change in the obliquity of the -axis of the earth during geological time. - -3. That the earth and the sun have diminished in heat during geological -time seems probable; but physical and geological facts alike render it -certain that this influence could have produced no appreciable effect, -even in the times of the earliest floras, and certainly not in the case -of Tertiary vegetation. - -4. It has been supposed that the earth may have at different times -traversed more or less heated zones of space, giving alternations of warm -and cold temperature. No such differences in space are, however, known, -nor does there seem any good ground for imagining their existence. - -5. The heat of the sun is known to be variable, and the eleven years' -period of sun-spots has recently attracted much attention as producing -appreciable effects on the seasons. There may possibly be longer cycles -of solar energy, or the sun may be liable, like some variable stars, to -paroxysms of increased energy. Such changes are possible, and may fairly -be taken into the account, provided that we fail to find known causes -sufficient to account for the phenomena. - -Of well-known causes there seem to be but three. These are: First, that -urged by Lyell--viz., the varying distribution of land and water along -with that of marine currents; secondly, the varying eccentricity of -the earth's orbit, along with the precession of the equinoxes, and the -effects of this on oceanic circulation, as illustrated by Croll; thirdly, -the different conditions of the earth's atmosphere with reference to -radiation, as argued by Tyndall and Hunt. As these causes are all founded -on known facts, and not exclusive of each other, we may consider them -together. I shall take the Lyellian theory first, regarding it as the -most important, and the best supported by geological facts. - -We know that the present distribution of land and water greatly -influences climate, more especially by affecting that of the ocean -currents and of the winds, and by the different action of land as -compared with water in the reception and radiation of heat. The -present distribution of land gives a large predominance to the arctic -and sub-arctic regions, as compared with the equatorial and with the -antarctic; and we might readily imagine other distributions that would -give very different results. But this is not an imaginary case. We -know that, while the forms and positions of the great continents have -been fixed from a very early date, they have experienced many great -submergences and re-elevations, and that these have occurred in somewhat -regular sequence, as evidenced by the cyclical alternations of organic -limestones and earthy sediments in successive geological formations. - -An example bearing on our present subject may serve to illustrate this. -In the latter part of the Upper Silurian period (the Lower Helderberg -age), vast areas of the American continent[EV] were covered with an -ocean in which were deposited organic limestones whose fossils show -that this great interior sea was pervaded by equatorial waters bringing -food and warmth, while the incipient ranges of the Appalachians on the -east, and the Cordilleras on the west, and the Laurentian axis on the -north, fenced off from it the colder arctic waters. How different must -the climate of America and of the region north of it have been in these -circumstances from that which prevails at present, or from that which -prevailed in certain other periods, when it was open to the incursions -of the arctic ice-laden currents, bearing loads of fine sediment![EW] It -was in these circumstances, and in the similar circumstances in which the -great Corniferous limestone of the Devonian was deposited--a limestone -showing in its rich coral fauna even warmer waters than those of the -Lower Helderberg--that the Devonian flora took its origin in the north -and advanced southward over new lands in process of emergence from the -sea. The somewhat similar condition evidenced by the Lower Carboniferous -limestone preceded the advent of the great and rich flora of the -coal-formation. - -[EV] See a memoir and map by Prof. Hall, "Reports of the Regents of New -York," 1874-'75. - -[EW] It seems certain that the faunæ of the old limestones, like the -Trenton, Niagara, Lower Helderberg, and Corniferous, belong to warm and -sheltered sea areas, and that those rich in graptolites and trilobites, -enclosed in muddy sediments, belong to the colder arctic waters. Such -arctic faunæ are those of the Quebec group and of the Utica shale, and to -some extent that of the Hamilton group. - -Lyell's theory on this subject has, I think, in some recent publications, -been somewhat misapprehended. It is true that he stated hypothetically -two contrasted conditions of distribution, in one of which all the land -was equatorial, in another all polar; but he did not suppose that these -conditions had actually occurred; and even in his earlier editions, -before the recent discoveries and discussions as to ocean currents, -he was always careful to attach due value to these in connection with -subsidences and elevations.[EX] In his later editions he introduced more -full references to current action, and also stated Croll's theory, but -still maintained the validity of his original conclusions. - -[EX] See "Principles of Geology," edition of 1840, chapter vii. - -The sufficiency of this Lyellian theory to account for the facts, in so -far as plants are concerned, may, I think, be inferred from the course -of the isothermal lines at present. The south end of Greenland is on -the latitude of Christiania in Norway on the one hand, and of Fort -Liard in the Peace River region on the other; and while Greenland is -clad in ice and snow, wheat and other grains, and the ordinary trees -of temperate climates, grow at the latter places,[EY] It is evident, -therefore, that only exceptionally unfavourable circumstances prevent -the Greenland area from still possessing a temperate flora, and these -unfavourable circumstances possibly tell even on the localities with -which we have compared it. Further, the mouth of the McKenzie River is in -the same latitude with Disco, near which are some of the most celebrated -localities of fossil Cretaceous and Tertiary plants. Yet the mouth of -the McKenzie River enjoys a much more favourable climate and has a much -more abundant flora than Disco. If north Greenland were submerged, and -low land reaching to the south terminated at Disco, and if from any cause -either the cold currents of Baffin's Bay were arrested, or additional -warm water thrown into the North Atlantic by the Gulf Stream, there is -nothing to prevent a mean temperature of 45° Fahr. from prevailing at -Disco; and the estimate ordinarily formed of the requirements of its -extinct floras is 50°,[EZ] which is probably above rather than below the -actual temperature required. - -[EY] See "Macoun's Report," "Geological Survey of Canada," and -Richardson's "Boat Voyage." - -[EZ] Heer. See, also, papers by Prof. Haughton and by Gardner in "Nature" -for 1878. - -Since, then, geological facts assure us of mutations of the continents -much greater than those apparently required to account for the changes of -climate implied in the existence of the ancient arctic floras, it does -not seem absolutely necessary to invoke any others.[FA] If, however, -there are other true causes which might either aid or counteract those -above referred to, it may be well to consider them. - -[FA] Sir William Thomson, "Transactions of the Geological Society of -Glasgow," February 22, 1878. - -Mr. Croll has, in his valuable work "Climate and Time" and in various -memoirs, brought forward an ingenious astronomical theory to account -for changes of climate. This theory, as stated by himself in a recent -paper,[FB] is that when the eccentricity of the earth's orbit is at a -high value, and the northern winter solstice is in perihelion, agencies -are brought into operation which make the southeast trade-winds stronger -than the northeast, and compel them to blow over upon the northern -hemisphere as far as the Tropic of Cancer. The result is that all the -great equatorial currents of the ocean are impelled into the northern -hemisphere, which thus, in consequence of the immense accumulation of -warm water, has its temperature raised, so that ice and snow must to a -great extent disappear from the arctic regions. In the prevalence of -the converse conditions, the arctic zone becomes clad in ice, and the -southern has its temperature raised. - -[FB] "Cataclysmic Theories of Geological Climate," "Geological Magazine," -May, 1878. - -At the same time, according to Croll's calculations, the accumulation -of ice on either pole would tend, by shifting the earth's centre of -gravity, to raise the level of the ocean and submerge the land on the -colder hemisphere. Thus a submergence of land would coincide with a cold -condition, and emergence with increasing warmth. Facts already referred -to, however, show that this has not always been the case, but that in -many cases submergence was accompanied with the influx of warm equatorial -waters and a raised temperature, this apparently depending on the -question of local distribution of land and water; and this in its turn -being regulated not always by mere shifting of the centre of gravity, -but by foldings occasioned by contraction, by equatorial subsidences -resulting from the retardation of the earth's rotation, and by the excess -of material abstracted by ice and frost from the arctic regions, and -drifted southward along the lines of arctic currents. This drifting must -in all geological times have greatly exceeded, as it certainly does at -present, the denudation caused by atmospheric action at the equator, -and must have tended to increase the disposition to equatorial collapse -occasioned by retardation of rotation.[FC] - -[FC] Croll, in "Climate and Time," and in a note read before the British -Association in 1876, takes an opposite view; but this is clearly contrary -to the facts of sedimentation, which show a steady movement of _débris_ -toward the south and southwest. - -While such considerations as those above referred to tend to reduce -the practical importance of Mr. Croll's theory., on the other hand -they tend to remove one of the greatest objections against it--namely, -that founded on the necessity of supposing that glacial periods recur -with astronomical regularity in geological time. They cannot do so if -dependent on other causes inherent in the earth itself, and producing -important movements of its crust. - -The third great cause of warmer climates in the past is the larger -proportion of carbon dioxide, or carbonic-acid gas, in the atmosphere in -early geological times, as proved by the immense amount of carbon now -sealed up in limestone and coal, and which must at one time have been in -the air. It has been shown that a very small additional quantity of this -substance would so obstruct radiation of heat from the earth as to act -almost like a glass roof. If, however, the quantity of carbonic acid, -great at first, was slowly and regularly removed, even if, as suggested -by Hunt, small additional supplies were gradually added from space, this -cause could have affected only the very oldest floras. But it is known -that some comets and meteorites contain carbonaceous matter, and this -allows us to suppose that accessions of carbon may have been communicated -at irregular intervals. If so, there may have been cycles of greater -and less abundance of this substance, and an atmosphere rich in carbon -dioxide might at one and the same time afford warmth and abundance of -food to plants. - -It thus appears that the causes of ancient vicissitudes of climate are -somewhat complex, and when two or more of them happened to coincide very -extreme changes might result, having most important bearings on the -distribution of plants. - -This may help us to deal with the peculiarities of the great Glacial age, -which may have been rendered exceptionally severe by the combination of -several of the causes of refrigeration. We must not suppose, however, -that the views of those extreme glacialists who suppose continental -ice-caps reaching half way to the equator are borne out by facts. In -truth, the ice accumulating round the pole must have been surrounded by -water, and there must have been tree-clad islands in the midst of the icy -seas, even in the time of greatest refrigeration. This is proved by the -fact that, in the Leda clay of eastern Canada, which belongs to the time -of greatest submergence, and whose fossil shells show sea-water almost -at the freezing-point, there are leaves of poplars and other plants -which must have been drifted from neighbouring shores. Similar remains -occur in clays of like origin in the basin of the great lakes and in the -West. These have been called "interglacial," but there is no evidence to -prove that they are not truly glacial. Thus, while we need not suppose -that plants existed within the Arctic circle in the Glacial age, we have -evidence that those of the cold temperate and sub-arctic zones continued -to exist pretty far north. At the same time the warm temperate flora -would be driven to the south, except where sustained in insular spots -warmed by the equatorial currents. It would return northward on the -re-elevation of the land and the renewal of warmth. - -If, however, our modern flora is thus one that has returned from the -south, this would account for its poverty in species as compared with -those of the early Tertiary. Groups of plants descending from the north -have been rich and varied. Returning from the south they are like the -shattered remains of a beaten army. This, at least, has been the case -with such retreating floras as those of the Lower Carboniferous, the -Permian, and the Jurassic, and possibly that of the Lower Eocene of -Europe. - -The question of the supply of light to an arctic flora is much less -difficult than some have imagined. The long summer day is in this respect -a good substitute for a longer season of growth, while a copious covering -of winter snow not only protects evergreen plants from those sudden -alternations of temperature which are more destructive than intense -frost, and prevents the frost from penetrating to their roots, but, by -the ammonia which it absorbs, preserves their greenness. According to -Dr. Brown, the Danish ladies of Disco long ago solved this problem.[FD] -He informs us that they cultivate in their houses most of our garden -flowers--as roses, fuchsias, and geraniums--showing that it is merely -warmth and not light that is required to enable a sub-tropical flora to -thrive in Greenland. Even in Canada, which has a flora richer in some -respects than that of temperate Europe, growth is effectually arrested -by cold for nearly six months, and though there is ample sunlight there -is no vegetation. It is, indeed, not impossible that in the plans of the -Creator the continuous summer sun of the arctic regions may have been -made the means for the introduction, or at least for the rapid growth and -multiplication, of new and more varied types of plants. - -[FD] "Florula Discoana," Botanical Society of Edinburgh, 1868. - -Much, of course, remains to be known of the history of the old floras, -whose fortunes I have endeavoured to sketch, and which seem to have been -driven like shuttle-cocks from north to south, and from south to north, -especially on the American continent, whose meridional extension seems to -have given a field specially suited for such operations. - -This great stretch of the western continent, from north to south, is also -connected with the interesting fact that, when new floras are entering -from the arctic regions, they appear earlier in America than in Europe, -and that in times when old floras are retreating from the south old -genera and species linger longer in America. Thus, in the Devonian and -Cretaceous new forms of those periods appear in America long before they -are recognized in Europe, and in the modern epoch forms that would be -regarded in Europe as Miocene still exist. Much confusion in reasoning -as to the geological ages of the fossil floras has arisen from want of -attention to this circumstance. - -What we have learned respecting this wonderful history has served -strangely to change some of our preconceived ideas. We must now be -prepared to admit that an Eden can be planted even in Spitzbergen, that -there are possibilities in this old earth of ours which its present -condition does not reveal to us; that the present state of the world is -by no means the best possible in relation to climate and vegetation; that -there have been and might be again conditions which could convert the -ice-clad arctic regions into blooming paradises, and which at the same -time would moderate the fervent heat of the tropics. We are accustomed to -say that nothing is impossible with God; but how little have we known of -the gigantic possibilities which lie hidden under some of the most common -of his natural laws! - -These facts have naturally been made the occasion of speculations as -to the spontaneous development of plants by processes of varietal -derivation. It would, from this point of view, be a nice question to -calculate how many revolutions of climate would suffice to evolve the -first land-plant; what are the chances that such plant would be so -dealt with by physical changes as to be preserved and nursed into a -meagre flora like that of the Upper Silurian or the Jurassic; how many -transportations to Greenland would suffice to promote such meagre flora -into the rich and abundant forests of the Upper Cretaceous, and to -people the earth with the exuberant vegetation of the early Tertiary. -Such problems we may never be able to solve. Probably they admit of no -solution, unless we invoke the action of an Almighty mind, operating -through long ages, and correlating with boundless power and wisdom -all the energies inherent in inorganic and organic nature. Even then -we shall perhaps be able to comprehend only the means by which, after -specific types have been created, they may, by the culture of their -Maker, be "sported" into new varieties or subspecies, and thus fitted -to exist under different conditions or to occupy higher places in the -economy of nature. - -Before venturing on such extreme speculations as some now current on -questions of this kind, we would require to know the successive extinct -floras as perfectly as those of the modern world, and to be able to -ascertain to what extent each species can change either spontaneously -or under the influence of struggle for existence or expansion under -favourable conditions, and under arctic semi-annual days and nights, or -the shorter days of the tropics. Such knowledge, if ever acquired, it may -take ages of investigation to accumulate. - -As to the origin and mode of introduction of successive floras, I am, for -the reasons above stated, not disposed to dogmatise, or to adopt as final -any existing theory of the development of the vegetable kingdom. Still, -some laws regulating the progress of vegetable life may be recognised, -and I propose to state these in connection with the Palæozoic floras, to -which my own studies have chiefly related. - -Fossil plants are almost proverbially uncertain with reference to their -accurate determination, and have been regarded as of comparatively little -utility in the decision of general questions of palæontology. This -results principally from the fragmentary condition in which they have -been studied, and from the fact that fragments of animal structures are -more definite and instructive than corresponding portions of plants. - -It is to be observed, however, that our knowledge of fossil plants -becomes accurate in proportion to the extent to which we can carry the -study of specimens in the beds in which they are preserved, so as to -examine more perfect examples than those usually to be found in museums. -When structures are taken into the account, as well as external forms, we -can also depend more confidently on our results. Further, the abundance -of specimens to be obtained in particular beds often goes far to make up -for their individual imperfection. The writer of these pages has been -enabled to avail himself very fully of these advantages; and on this -account, if on no other, feels entitled to speak with some authority on -theoretical questions. - -It is an additional encouragement to pursue the subject, that, when -we can obtain definite information as to the successive floras of any -region, we thereby learn much as to climate and vicissitudes in regard to -the extent of land and water; and that, with reference to such points, -the evidence of fossil plants, when properly studied, is, from the close -relation of plants to those stations and climates, even more valuable -than that of animal fossils. - -It is necessary, however, that in pursuing such inquiries we should have -some definite views as to the nature and permanence of specific forms, -whether with reference to a single geological period or to successive -periods; and I may be excused for stating here some general principles, -which I think important for our guidance. - -1. Botanists proceed on the assumption, vindicated by experience, that, -within the period of human observation, species have not materially -varied or passed into each other. We may make, for practical purposes, -the same assumption with regard to any given geological period, and may -hold that for each such period there are specific types which, for the -time at least, are invariable. - -2. When we inquire what constitutes a good species for any given period, -we have reason to believe that many names in our lists represent merely -varietal forms or erroneous determinations. This is the case even in the -modern flora; and in fossil floras, through the poverty of specimens, -their fragmentary condition, and various states of preservation, it -is still more likely to occur. Every revision of any group of fossils -detects numerous synonyms, and of these many are incapable of detection -without the comparison of large suites of specimens. - -3. We may select from the flora of any geological period certain -forms, which I shall call _specific types_, which may for such period -be regarded as unchanging. Having settled such types, we may compare -them with similar forms in other periods, and such comparisons will -not be vitiated by the uncertainty which arises from the comparison of -so-called species which may, in many cases, be mere varietal forms, as -distinguished from specific types. Our types may be founded on mere -fragments, provided that these are of such a nature as to prove that they -belong to distinct forms which cannot pass into each other, at least -within the limits of one geological period. - -4. When we compare the specific types of one period with those of another -immediately precedent or subsequent, we shall find that some continue -unchanged through long intervals of geological time, that others are -represented by allied forms regarded either as varietal or specific, and -as derived or otherwise, according to the view which we may entertain as -to the permanence of species. On the other hand, we also find new types -not rationally deducible on any theory of derivation from those known -in other periods. Further, in comparing the types of a poor period with -those of one rich in species, we may account for the appearance of new -types in the latter by the deficiency of information as to the former; -where many new types appear in the poorer period this conclusion seems -less probable. For example, new types appearing in poor formations, like -the Lower Erian and Lower Carboniferous, have greater significance than -if they appeared in the Middle Erian or in the Coal Measures. - -5. When specific types disappear without any known successors, under -circumstances in which it seems unlikely that we should have failed to -discover their continuance, we may fairly assume that they have become -extinct, at least locally; and where the field of observation is very -extensive, as in the great coal-fields of Europe and America, we may -esteem such extinction as practically general, at least for the northern -hemisphere. When many specific types become extinct together, or in close -succession, we may suppose that such extinction resulted from physical -changes; but where single types disappear, under circumstances in which -others of similar habit continue, we may not unreasonably conjecture -that, as Pictet has argued in the case of animals, such types may have -been in their own nature limited in duration, and may have died out -without any external cause. - -6. With regard to the _introduction_ of specific types we have not as -yet a sufficient amount of information. Even if we freely admit that -ordinary specific forms, as well as mere varieties, may result from -derivation, this by no means excludes the idea of primitive specific -types originating in some other way. Just as the chemist, after analysing -all compounds and ascertaining all allotropic forms, arrives at length at -certain elements not mutually transmutable or derivable, so the botanist -and zoölogist must expect sooner or later to arrive at elementary -specific types, which, if to be accounted for at all, must be explained -on some principle distinct from that of derivation. The position of -many modern biologists, in presence of this question, may be logically -the same with that of the ancient alchemists with reference to the -chemical elements, though the fallacy in the case of fossils may be of -more difficult detection. Our business at present, in the prosecution of -palæobotany, is to discover, if possible, what are elementary or original -types, and, having found these, to enquire as to the law of their -creation. - -7. In prosecuting such questions geographical relations must be carefully -considered. When the floras of two successive periods have existed in -the same region, and under circumstances that render it probable that -plants have continued to grow on the same or adjoining areas throughout -these periods, the comparison becomes direct, and this is the case with -the Erian and Carboniferous floras in northeastern America. But, when -the areas of the two formations are widely separated in space as well -as in time, any resemblances of facies that we may observe may have no -connection whatever with an unbroken continuity of specific types. - -I desire, however, under this head, to affirm my conviction that, -with reference to the Erian and Carboniferous floras of North America -and of Europe, the doctrine of "homotaxis," as distinct from actual -contemporaneity, has no place. The succession of formations in the -Palæozoic period evidences a similar series of physical phenomena on the -grandest scale throughout the northern hemisphere. The succession of -marine animals implies the continuity of the sea-bottoms on which they -lived. The headquarters of the Erian flora in America and Europe must -have been in connected or adjoining areas in the North Atlantic. The -similarity of the Carboniferous flora on the two sides of the Atlantic, -and the great number of identical species, proves a still closer -connection in that period. These coincidences are too extensive and too -frequently repeated to be the result of any accident of similar sequence -at different times, and this more especially as they extend to the more -minute differences in the features of each period, as, for instance, the -floras of the Lower and Upper Devonian, and of the Lower, Middle, and -Upper Carboniferous. - -8. Another geographical question is that which relates to centres of -dispersion. In times of slow subsidence of extensive areas, the plants -inhabiting such areas must be narrowed in their range and often separated -from one another in detached spots, while, at the same time, important -climatal changes must also occur. On the re-emergence of the land such -of these species as remained would again extend themselves over their -former areas of distribution, in so far as the new climatal and other -conditions would permit. We would naturally suppose that the first of -the above processes would tend to the elimination of varieties, the -second, to their increase; but, on the other I hand, the breaking up of a -continental flora into that of distinct islets, and the crowding together -of many forms, might be a process fertile in the production of some -varieties if fatal to others. - -Further, it is possible that these changes of subsidence may have some -connection with the introduction, as well as with the extinction, even of -specific types. It is certain, at least, in the case of land-plants, that -such types come in most plentifully immediately after elevation, though -they are most abundantly preserved in periods of slow subsidence. I do -not mean, however, that this connection is one of cause and effect; there -are, indeed, indications that it is not so. One of these is, that in some -cases the enlargement of the area of the land seems to be as injurious to -terrestrial species as its diminution. - -9. Another point on which I have already insisted, and which has been -found to apply to the Tertiary as well as to the Palæozoic floras, is the -appearance of new types within the arctic and boreal areas, and their -migration southward. Periods in which the existence of northern land -coincided with a general warm temperature of the northern hemisphere seem -to have been those most favourable to the introduction of new forms of -land-plants. Hence, there has been throughout geological time a general -movement of new floras from the Palæarctic and Nearctic regions to the -southward. - -Applying the above considerations to the Erian and Carboniferous floras -of North America, we obtain some data which may guide us in arriving at -general conclusions. The Erian flora is comparatively poor, and its -types are in the main similar to those of the Carboniferous. Of these -types a few only reappear in the middle coal-formation under identical -forms; a great number appear under allied forms; some altogether -disappear. The Erian flora of New Brunswick and Maine occurs side by -side with the Carboniferous of the same region; so does the Erian of New -York and Pennsylvania with the Carboniferous of those States. Thus we -have data for the comparison of successive floras in the same region. In -the Canadian region we have, indeed, in direct sequence, the floras of -the Upper Silurian, the Lower, Middle, and Upper Erian, and the Lower, -Middle, and Upper Carboniferous, all more or less distinct from each -other, and affording an admirable series for comparison in a region whose -geographical features are very broadly marked. All these floras are -composed in great part of similar types, and probably do not indicate -very dissimilar general physical conditions, but they are separated from -each other by the great subsidences of the Corniferous limestone and the -Lower Carboniferous limestone, and by the local but intense subterranean -action which has altered and disturbed the Erian beds toward the close -of that period. Still, these changes were not universal. The Corniferous -limestone is absent in Gaspé, and probably in New Brunswick, where, -consequently, the Erian flora could continue undisturbed during that long -period. The Carboniferous limestone is absent from the slopes of the -Appalachians in Pennsylvania, where a retreat may have been afforded to -the Upper Erian and Lower Carboniferous floras. The disturbances at the -close of the Erian were limited to those eastern regions where the great -limestone-producing subsidences were unfelt, and, on the other hand, are -absent in Ohio, where the subsidences and marine conditions were almost -at a maximum. - -Bearing in mind these peculiarities of the area in question, we may now -group in a tabular form the distinct specific types recognised in the -Erian system, indicating, at the same time, those which are represented -by identical species in the Carboniferous, those represented by similar -species of the same general type, and those not represented at all. -For example, _Calamites cannæformis_ extends as a species into the -Carboniferous; _Asterophyllites latifolia_ does not so extend, but is -represented by closely allied species of the same type; _Nematophyton_ -disappears altogether before we reach the Carboniferous. - -_Table of Erian and Carboniferous Specific Types._ - - Erian types. Represented in By identical By related - Carboniferous-- types. forms. - - 1. Syringoxylon mirabile ? - 2. Nematoxylon - 3. Nematophyton - 4. Aporoxylon - 5. Ormoxylon - 6. Dadoxylon * - 7. Sigillaria Vanuxemii * - 8. S. palpebra * - 9. Didymophyllum - 10. Calamodendron * - 11. Calamites transitionis * - 12. C. cannæformis * - 13. Asterophyllites scutigera * - 14. A. latifolia - 15. Annularia laxa - 16. Sphenophyllum antiquum * - 17. Cyclostigma - 18. Arthrostigma - 19. Lepidodendron Gaspianum * - 20. L. corrugatum * - 21. Lycopodites Matthewi * - 22. L. Richardsoni - 23. Ptilophyton Vanuxemii - 24. Lepidophloios antiquus * - 25. Psilophyton princeps - 26. P. robustius - 27. Cordaites Robbii * - 28. C. angustifolia - 29. Archæopteris Jacksoni - 30. Aneimites obtusa * - 31. Platyphyllum Brownii - 32. Cyclopteris varia * - 33. C. obtusa - 34. Neuropteris polymorpha * - 35. N. serrulata * - 36. N. retorquata * - 37. N. resecta - 38. Megalopteris Dawsoni. - 39. Sphenopteris Hoeninghausi * - 40. S. Harttii * - 41. Hymenophyllites curtilobus - 42. H. obtusilobus * - 43. Alethopteris discrepans * - 44. Pecopteris serrulata * - 45. P. preciosa - 46. Trichomanites * - 47. Callipteris * - 48. Cardiocarpum * - 49. C. Crampii - 50. Antholithes * - 51. Trigonocarpum * - -Of the above forms, fifty-one in all, found in the Erian of eastern -America, all, except the last four, are certainly distinct specific -types. Of these only four reappear in the Carboniferous under identical -species, but no less than twenty-six reappear under representative or -allied forms, some at least of which a derivationist might claim as -modified descendants. On the other hand, nearly one half of the Devonian -types are unknown in the Carboniferous, while there remain a very large -number of Carboniferous types not accounted for by anything known in -the Devonian. Further, a very poor flora, including only two or three -types, is the predecessor of the Erian flora in the Upper Silurian, -and the flora again becomes poor in the Upper Devonian and Lower -Carboniferous. Every new species discovered must more or less modify the -above statements, and the whole Erian flora of America, as well as the -Carboniferous, requires a thorough comparison with that of Europe before -general conclusions can be safely drawn. In the mean time I may indicate -the direction in which the facts seem to point by the following general -statements: - -1. Some of the forms reckoned as specific in the Devonian and -Carboniferous may be really derivative races. There are indications that -such races may have originated in one or more of the following ways: (1) -By a natural tendency in synthetic types to become specialised in the -direction of one or other of their constituent elements. In this way -such plants as _Arthrostigma_ and _Psilophyton_ may have assumed new -varietal forms. (2) By embryonic retardation or acceleration,[FE] whereby -certain species may have had their maturity advanced or postponed, thus -giving them various grades of perfection in reproduction and complexity -of structure. The fact that so many Erian and Carboniferous plants seem -to be on the confines of the groups of Acrogens and Gymnosperms may be -supposed favourable to such exchanges. (3) The contraction and breaking -up of floras, as occurred in the Middle Erian and Lower Carboniferous, -may have been eminently favourable to the production of such varietal -forms as would result from what has been called the "struggle for -existence." (4) The elevation of a great expanse of new land at the -close of the Middle Erian and the beginning of the coal period would, by -permitting the extension of species over wide areas and fertile soils, -and by removing the pressure previously existing, be eminently favourable -to the production of new, and especially of improved, varieties. - -[FE] In the manner illustrated by Hyatt and Cope. - -2. Whatever importance we may attach to the above supposed causes of -change, we still require to account for the origin of our specific -types. This may forever elude our observation, but we may at least hope -to ascertain the external conditions favourable to their production. In -order to attain even to this it will be necessary to inquire critically, -with reference to every acknowledged species, what its claims to -distinctness are, so that we may be enabled to distinguish specific types -from mere varieties. Having attained to some certainty in this, we may be -prepared to inquire whether the conditions favourable to the appearance -of new varieties were also those favourable to the creation of new types, -or the reverse--whether these conditions were those of compression -or expansion, or to what extent the appearance of new types may be -independent of any external conditions, other than those absolutely -necessary for their existence. I am not without hope that the further -study of fossil plants may enable us thus to approach to a comprehension -of the laws of the creation, as distinguished from those of the continued -existence of species. - -3. In the present state of our knowledge we have no good ground either -to limit the number of specific types beyond what a fair study of -our material may warrant, or to infer that such primitive types must -necessarily have been of low grade, or that progress in varietal -forms has always been upward. The occurrence of such an advanced and -specialised type as that of _Dadoxylon_ in the Middle Devonian should -guard us against these errors. The creative process may have been -applicable to the highest as well as to the lowest forms, and subsequent -deviations must have included degradation as well as elevation. I can -conceive nothing more unreasonable than the statement sometimes made that -it is illogical or even absurd to suppose that highly organised beings -could have been produced except by derivation from previously existing -organisms. This is begging the whole question at issue, depriving science -of a noble department of inquiry on which it has as yet barely entered, -and anticipating by unwarranted assertions conclusions which may perhaps -suddenly dawn upon us through the inspiration of some great intellect, -or may for generations to come baffle the united exertions of all the -earnest promoters of natural science. Our present attitude should not be -that of dogmatists, but that of patient workers content to labour for a -harvest of grand generalisations which may not come till we have passed -away, but which, if we are earnest and true to Nature and its Creator, -may reward even some of us. - -Within the human period great changes of distribution of plants have -occurred, chiefly through the agency of man himself, and we have -had ample evidence that plants are able to establish themselves and -prosper in climates and conditions to which unaided they could not have -transported themselves, as, for instance, in the case of European weeds -naturalised in Australia and New Zealand. There is, however, no reason -to believe that any specific change has occurred to any plant within the -Pleistocene or modern period. - -In a recent address, delivered to the biological section of the British -Association, Mr. Carruthers has discussed this question, and has shown -that the earliest vegetable specimens described by Dr. Schweinfurth from -the Egyptian tombs present no appearance of change. This fact appears -also in the leaves and other organs of plants preserved in the nodules -in the Pleistocene clays of the Ottawa, and in specimens of similar age -found in various places in Britain and the continent of Europe.[FF] - -[FF] "Proceedings British Association," 1886, "Pleistocene Plants of -Canada," Canadian Naturalist, 1866. - -The difficulties attending the ordinary theories of evolution as applied -to plants have been well set forth by the same able botanist in his -"Presidential Address to the Geological Association in 1877," a paper -which deserves careful study. One of his illustrations is that ancient -willow, _Salix polaris_, referred to in a previous chapter, which now -lives in the arctic regions, and is found fossil in the Pleistocene beds -at Cromer and at Bovey Tracey. - -He notes the fact that the genus _Salix_ is a very variable one, -including 19 subgeneric groups and 160 species, with no less than 222 -varieties and 70 hybrids. _Salix polaris_ belongs to a subgeneric group -containing 29 species, which are arranged in four sections, that to which -_S. polaris_ belongs containing six species. Now it is easy to construct -a theoretical phylogeny of the derivation of the willows from a supposed -ancestral source, but when we take our little _S. polaris_ we find -that this one twig of our ancestral tree takes us back without change -to the Glacial period. The six species would take us still farther, -and the sections, sub-genera, and genus at the same rate would require -an incalculable amount of past time. He concludes the inquiry in the -following terms: - -"But when we have reached the branch representing the generic form we -have made but little progress in the phylogenesis of _Salix_. With -_Populus_ this genus forms a small order, Salicineæ, The two genera are -closely allied, yet separated by well-marked characters; it is not, -however, difficult to conceive of both having sprung from a generalised -form. But there is no record of such a form. The two genera appear -together among the earliest known dicotyledons, the willows being -represented by six and the poplars by nine species. The ordinal form, if -it ever existed, must necessarily be much older than the period of the -Upper Cretaceous rocks, that is, than the period to which the earliest -known dicotyledons belong. - -"The Salicineæ are related to five other natural orders, in all of which -the apetalous flowers are arranged in catkins. These different though -allied orders must be led up by small modifications to a generalised -amentiferous type, and thereafter the various groups of apetalous -plants by innumerable eliminations of differentiating characters until -the primitive form of the apetalous plant is reached. Beyond this the -uncurbed imagination will have more active work in bridging over the gap -between Angiosperms and Gymnosperms, in finding the intermediate forms -that led up to the vascular cryptogams, and on through the cellular -plants to the primordial germ. Every step in this phylogenetic tree -must be imagined. The earliest dicotyledon takes us not a step farther -back in the phylogenetic history of _Salix_ than that supplied by -existing vegetation. All beyond the testimony of our living willows is -pure imagination, unsupported by a single fact. So that here, also, the -evidence is against evolution, and there is none in favour of it." - -It is easy to see that similar difficulties beset every attempt to trace -the development of plants on the principle of slow and gradual evolution, -and we are driven back on the theory of periods of rapid origin, as we -have already seen suggested by Saporta in the case of the Cretaceous -dicotyledons. Such abrupt and plentiful introduction of species over -large areas at the same time, by whatever cause effected--and we are -at present quite ignorant of any secondary causes--becomes in effect -something not unlike the old and familiar idea of creation. Science -must indeed always be baffled by questions of ultimate origin, and, -however far it may be able to trace the chain of secondary causation -and development, must at length find itself in the presence of the -great Creative Mind, who is "before all things and in whom all things -consist." - - - - -APPENDIX. - - - I.--COMPARATIVE VIEW OF THE SUCCESSIVE PALÆOZOIC - FLORAS OF NORTHEASTERN AMERICA AND - GREAT BRITAIN. - -In eastern Canada there is a very complete series of fossil plants, -extending from the Silurian to the Permian, and intermediate in its -species between the floras of interior America and of Europe. I may -use this succession, mainly worked out by myself,[FG] to summarise the -various Palæozoic floras and sub-floras, in order to give a condensed -view of this portion of the history of the vegetable kingdom, and to -direct attention to the important fact, too often overlooked, that there -is a definite succession of fossil plants as well as of animals, and -that this is important as a means of determining geological horizons. -A British list for comparison has been kindly prepared for me by Mr. -R. Kidston, F. Gr. S. For lists referring to the western and southern -portions of America, I may refer to the reports of Lesquereux and -Fontaine and White.[FH] - -[FG] "Acadian Geology," "Reports on Fossil Plants of Canada," Geological -Survey of Canada. - -[FH] "Geological Surveys of Pennsylvania, Ohio, and Illinois." - -In this connection I am reminded, by an excellent little paper of M. -Zeiller,[FI] on Carboniferous plants from the region of the Zambesi, -in Africa, that the flora which in the Carboniferous period extended -over the temperate portions of the northern hemisphere and far into the -arctic, also passed across the equator and prevailed in the southern -hemisphere. Of eleven species brought from the Zambesi by M. Lapierre -and examined by M. Zeiller, all were identical with European species -of the upper coal-formation, and the same fact has been observed in the -coal flora of the Cape Colony.[FJ] These facts bear testimony to the -remarkable uniformity of climate and vegetation in the coal period, and -I perfectly agree with Zeiller that they show, when taken in connection -with other parallelisms in fossils, an actual contemporaneousness of the -coal flora over the whole world. - -[FI] Paris, 1883. - -[FJ] Grey, "Journal of the Geological Society," vol. xxvii. - - -1. Carboniferous Flora. - -(1) _Permo-Carboniferous Sub-Flora_: - -This occurs in the upper member of the Carboniferous system of Nova -Scotia and Prince Edward Island, originally named by the writer the -Newer Coal-formation, and more recently the Permo-Carboniferous, and -the upper beds of which may not improbably be contemporaneous with the -Lower Permian or Lower Dyas of Europe. In this formation there is a -predominance of red sandstones and shales, and it contains no productive -beds of coal. Its fossil plants are for the most part of species found -in the Middle or Productive Coal-formation, but are less numerous, and -there are a few new forms akin to those of the European Permian. The most -characteristic species of the upper portion of the formation, which has -the most decidedly Permian aspect, are the following: - - _Dadoxylon materiarium_, Dawson. - * _Walchia_ (_Araucarites_) _robusta_, Dn. - * _W._ (_A._) _gracilis_, Dn. - * _W. imbricatula_, Dn. - _Calamites Suckovii_, Brongt. - _C. Cistii_, Brongt. - * _C. gigas_, Brongt. - _Neuropteris rarinervis_, Bunbury. - _Alethopteris nervosa_, Brongt. - _Pecopteris arborescens_, Brongt. - * _P. rigida_, Dn. - _P. oreopteroides_, Brongt. - * _Cordaites simplex_, Dn. - -Of these species, those marked with an asterisk have not yet been found -in the middle or lower members of the Carboniferous system. They will -be found described, and several of them figured, in my "Report on the -Geology of Prince Edward Island."[FK] The others are common and widely -diffused Carboniferous species, some of which have extended to the -Permian period in Europe as well. From the upper beds, characterised by -these and a few other species, there is a gradual passage downward into -the productive coal-measures, and a gradually increasing number of true -coal-formation species. - -[FK] 1871. - -It is worthy of remark here that the association in the -Permo-Carboniferous of numerous trunks of _Dadoxylon_ with the branches -of _Walchia_ and with fruits of the character of _Trigonocarpa_, seems to -show that these were parts of one and the same plant. - -This formation represents the Upper Barren Measures of West Virginia, -which are well described by Fontaine and White,[FL] and the reasons -which these authors adduce for considering the latter equivalent to the -European Permian will apply to the more northern and eastern deposits -as well, though these have afforded fewer species of plants, and are -apparently less fully developed. - -[FL] "Report on the Permian Flora of Western Virginia and South -Pennsylvania," 1880. - -(2) _Coal-formation Sub-Flora_: - -The Middle or Productive Coal-formation, containing all the beds of coal -which are mined in Nova Scotia and Cape Breton, is the headquarters of -the Carboniferous flora. From this formation I have catalogued[FM] one -hundred and thirty-five species of plants; but, as several of these are -founded on imperfect specimens, the number of actual species may be -estimated at one hundred and twenty. Of these more than one half are -species common to Europe and America. No less than nineteen species -are _Sigillariæ_, and about the same number are _Lepidodendra_. About -fifty are ferns and thirteen are _Calamites_, _Asterophyllites_, and -_Sphenophylla_. The great abundance and number of species of Sigillariæ, -Lepidodendra, and ferns are characteristic of this sub-flora; and among -the ferns certain species of _Neuropteris_, _Pecopteris_, _Alethopteris_, -and _Sphenopteris_ greatly preponderate. - -[FM] "Acadian Geology," and "Report on Flora of Lower Carboniferous," -1873. - -These beds are the equivalents of the Middle Coal-measures, or Productive -Coal-measures of Pennsylvania, Ohio, &c., and of the coal-formation -proper of various European countries. Very many of the species are common -to Nova Scotia and Pennsylvania; but in proceeding westward the number of -identical species seems to diminish. - -(3) _The Millstone Grit Sub-Flora_: - -In this formation the abundance of plants and the number of species -are greatly diminished.[FN] Trunks of coniferous trees of the species -_Dadoxylon Acadianum_, having wide wood-cells with three or more series -of discs and complex medullary rays, become characteristic. _Calamites -undulatum_ is abundant and seems to replace _C. Suckovii_, though _C. -cannæformis_ and _C. cistii_ continue. _Sigillariæ_ become very rare, -and the species of Lepidodendron are few, and mostly those with large -leaf-bases. _Lepidophloios_ still continues, and _Cordaites_ abounds in -some beds. The ferns are greatly reduced, though a few characteristic -coal-formation species occur, and the genus _Cardiopteris_ appears. Beds -of coal are rare in this formation; but where they occur there is in -connection with them a remarkable anticipation of the rich coal-formation -flora, which would thus seem to have existed locally in the Millstone -Grit period, but to have found itself limited by generally unfavorable -conditions. In America, as in Europe, it is in the north that this -earlier development of the coal-flora occurs, while in the south there -is a lingering of old forms in the newer beds. In Newfoundland and Cape -Breton, for instance, as well as in Scotland, productive coal-beds and a -greater variety of species of plants occur in this formation. - -[FN] "Report on Fossil Plants of the Lower Carboniferous and Millstone -Grit of Canada," 1873. - -The following would appear to be the equivalents of this formation, in -flora and geological position: - -1. The Seral Conglomerate of Rogers in Pennsylvania, &c. - -2. The Lower Coal-formation Conglomerate and Chester groups of Illinois -(Worthen). - -3. The Lower Carboniferous Sandstone of Kentucky, Alabama, and Virginia. - -4. The Millstone Grit and Yoredale rocks of northern England, and the -Culmiferous of Devonshire. - -5. The Moor rock and Lower Coal-measures of Scotland. - -6. Flagstones and Lower Shales of the south of Ireland, and Millstone -Grit of the north of Ireland. - -7. The Jüngste Grauwacke of the Hartz, Saxony, and Silesia. - -(4) _The Carboniferous Limestone Series_: - -This affords few fossil plants in eastern America, and in so far as known -they are similar to those of the next group. In Scotland it is richer -in plants, but, according to Mr. Kidston, these are largely similar -to those of the underlying beds, though with some species which extend -upward into the Millstone Grit. In Scotland the alga named _Spirophyton_ -and _Archæocalamites radiatus_--which in America are Erian--appear in -this formation. - -(5) _The Lower Carboniferous Sub-Flora_: - -This group of plants is best seen in the shales of the Horton series, -under the Lower Carboniferous marine limestones. It is small and -peculiar. The most characteristic species are the following: - -_Dadoxylon_ (_Palæoxylon_) _antiquius_, Dn.--A species with large -medullary rays of three or more series of cells. - -_Lepidodendron corrugatum_, Dn.--A species closely allied to _L. -Veltheimianum_ of Europe, and which is its American representative. -This is perhaps the most characteristic plant of the formation. It is -very abundant, and presents very protean appearances, in its old stems, -branches, twigs, and _Knorria_ forms. It had well-characterised stigmaria -roots, and constitutes the oldest erect forest known in Nova Scotia. - -_Lepidodendron tetragonum_, Sternberg. - -_L. obovatum_, Sternb. - -_L. aculeatum_, Sternb. - -_L. dichotomum_, Sternb. - -The four species last mentioned are comparatively rare, and the specimens -are usually too imperfect to render their identification certain, but -Lepidodendra are especially characteristic trees of this horizon. - -_Cyclopteris_ (_Aneimites_) _Acadica_, Dn.--A very characteristic -fern, allied in the form of its fronds to _C. tenuifolia_ of Goeppert, -to _C. nana_ of Eichwald, and to _Adiantites antiquus_ of Stur. Its -fructification, however, is nearer to that of _Aneimia_ than to that of -_Adiantum_. - -Ferns of the genera Cardiopteris and _Hymenophyllites_ also occur, though -rarely. - -_Ptilophyton plumula_, Dn.--This is the latest appearance of this Erian -genus, which also occurs in the Lower Carboniferous of Europe and of the -United States. - -_Cordaites borassifolia_, Brongt. - -On the whole, this small flora is markedly distinct from that of the -Millstone Grit and true coal-formation, from which it is separated by the -great length of time required for the deposition of the marine limestones -and their associated beds, in which no land-plants have been found; nor -is this gap filled up by the conglomerates and coarse arenaceous beds -which, as I have explained in "Acadian Geology," in some localities take -the place of the limestones, as they do also in the Appalachian region -farther south. - -The palæobotanical and stratigraphical equivalents of this series abroad -would seem to be the following: - -1. The Vespertine group of Rogers in Pennsylvania. - -2. The Kinderhook group of Worthen in Illinois. - -3. The Marshall group of Winchell in Michigan. - -4. The Waverley sandstone (in part) of Ohio. - -5. The Lower or False Coal-measures of Virginia. - -6. The Calciferous sandstones of McLaren, or Tweedian group of Tate in -Scotland. - -7. The Lower Carboniferous slate and Coomhala grits of Jukes in Ireland. - -8. The Culm and Culm Grauwacke of Germany. - -9. The Graywacke or Lower Coal-measures of the Vosges, as described by -Schimper. - -10. The Older Coal-formation of the Ural, as described by Eichwald. - -11. The so-called "Ursa Stage" of Heer includes this, but he has united -it with Devonian beds, so that the name cannot be used except for -the local development of these beds at Bear Island, Spitsbergen. The -Carboniferous plants of arctic America, Melville Island, &c., as well as -those of Spitzbergen, appear all to be Lower Carboniferous.[FO] - -[FO] "Notes on Geological Map of the Northern Portion of the Dominion of -Canada," by Dr. G. M. Dawson, 1887. - -All of the above groups of rocks are characterised by the prevalence of -_Lepidodendra_ of the type of _L. corrugatum_, _L. Veltheimianum_, and -_L. Glincanum_; pines of the sub-genus _Pitus_ of Witham, _Palæoxylon_ -of Brongniart, and peculiar ferns of the genera _Cyclopteris_, -_Cardiopteris_, _Triphyllopteris_, and _Sphenopteris_. In all the regions -above referred to they form the natural base of the great Carboniferous -system. - -In Virginia, according to Fontaine and White, types, such as -Archæopteris, which in the north are Upper Erian, occur in this group. -Unless there have been some errors in fixing the lower limit of the -Vespertine, this would indicate a longer continuance of old forms in the -south. - -2. Erian Flora. - -(1) _Upper Erian Sub-Flora_: - -This corresponds to the Catskill and Chemung of the New York series, and -to the Upper Devonian of Europe. - -The flora of this formation, which consists mostly of sandstones, is not -rich. Its most distinctive species on both sides of the Atlantic seem to -be the ferns of the genus _Archæopteris_, along with species referred to -the genus _Cyclopteris_, but which, in so far as their barren fronds are -concerned, for the most part resemble _Archæopteris_. - -The characteristic American species are _Archæopteris Jacksoni_, -_A. Rogersi_, and _A. Gaspiensis_. _Cyclopteris obtusa_ and _C._ -(_Platyphyllum_) _Brownii_ are also very characteristic species. In -Europe, _Archæopteris Hibernica_ is a prevalent species. - -_Leptophleum rhombicum_ and fragments of _Psilophyton_ are also found in -the Upper Erian. There is evidence of the existence of vast numbers of -_Rhizocarps_ in this period, in the deposits of spore-cases (_Sporangites -Huronensis_) in the shales of Kettle Point, Lake Huron; and in deposits -of similar character in Ohio and elsewhere in the West. - -The Upper Erian flora is thus very distinct from that of the Lower -Carboniferous, and the unconformable relation of the beds in the -Northeast may perhaps indicate a considerable lapse of time. Still, -even in localities where there appears to be a transition from the -Carboniferous into the Devonian, as in the Western States and in Ireland, -the characteristic flora of each formation may be distinguished, though, -as already stated, there is apparently some mixture in the South. - -(2) _Middle Erian Sub-Flora_: - -Both in Canada and the United States that part of the great Erian system -which may be regarded as its middle division, the Hamilton and Marcellus -shales of New York, the Cordaites shales of St. John, New Brunswick, and -the middle shales and sandstones of the Gaspé series, presents conditions -more favourable to the abundant growth of land-plants than either the -upper or lower member. In the St. John beds, in particular, there is a -rich fern flora, comparable with that of the coal-formation, and numerous -stipes of ferns and trunks of tree-ferns have been found in the Hamilton -and Corniferous series in the West, as well as trunks of _Dadoxylon_. It -is, however, distinguished by a prevalence of small and delicate species, -and by such forms as _Hymenophyllites_ and the smaller Sphenopterids, and -also by some peculiar ferns, as _Archæopteris_ and _Megalopteris_. In -addition to ferns, it has small _Lepidodendra_, of which _L. Gaspianum_ -is the chief. _Calamiteæ_ occur, _Archæocalamites radiatus_ being the -dominant species. This plant, which in Europe appears to reach up into -the Lower Carboniferous, is so far strictly Erian in northeast America. -_Sigillariæ_ scarcely appear, but _Cordaites_ is abundant, and the -earliest known species of _Dadoxylon_ appear, while the Psilophyton, so -characteristic of the Lower Erian, still continues, and the remarkable -aquatic plants of the genus _Ptilophyton_ are locally abundant. - -(3) _Lower Erian Sub-Flora_: - -This belongs to the Lower Devonian sandstones and shales, and is -best seen in that formation at Gaspé and the Bay des Chaleurs. It is -equivalent to the Oriskany sandstone, so far as its animal fossils and -mineral character are concerned. It is characterised by the absence -of true ferns, _Calamites_ and _Sigillariæ_, and by the presence -of such forms as _Psilophyton_, _Arthrostigma_, _Leptophleum_, and -_Nematophyton_. _Lepidodendron Gaspianum_ and _Leptophleum_ already -occur, though not nearly so abundant as Psilophyton. - -The Lower Erian plants have an antique and generalised aspect which would -lead us to infer that they are near the beginning of the land-flora, or -perhaps in part belong to the close of an earlier flora still in great -part unknown and few indications of land-plants have been found earlier. - -At Campbellton and Scaumenac Bay, on the Bay des Chaleurs, fossil fishes -of genera characteristic of the Lower and Upper Devonian horizons -respectively, occur in association with fossil plants of these horizons, -and have been described by Mr. Whiteaves.[FP] - -[FP] "Transactions of the Royal Society of Canada." - -It is interesting to note that, as Fontaine and White have observed, -certain forms which are Erian in the northeast are found in the Lower -members of the Carboniferous in West Virginia, indicating the southward -march of species in these periods. - -3. The Silurian Flora and still Earlier Indications of Plants. - -In the upper beds of the Silurian, those of the Helderberg series, we -still find _Psilophyton_ and _Nematophyton_; but below these we know no -land-plants in Canada. In the United States, Lesquereux and Claypole have -described remains which may indicate the existence of lycopodiaceous and -annularian types as far back as the beginning of the Upper Silurian, or -even as low as the Hudson River group, and Hicks has found _Nematophyton_ -and _Psilophyton_ in beds about as old in Wales, along with the uncertain -stems named _Berwynia_. In the Lower Silurian the _Protannularia_ of -the Skiddaw series in England may represent a land-plant, but this is -uncertain, and no similar species has been found in Canada. - -The Cambrian rocks are so far barren of land-plants; the so-called -_Eophyton_ being evidently nothing but markings, probably produced by -crustaceans and other aquatic animals. In the still older Laurentian the -abundant beds of graphite probably indicate the existence of plants, but -whether aquatic or terrestrial it is impossible to decide at present. - -It would thus appear that our certain knowledge of land-vegetation begins -with the Upper Silurian or the Silurio-Cambrian, and that its earliest -forms were Acrogens allied to Lycopods, and prototypal trees, forerunners -of the Acrogens or the gymnosperms. In the Lower Devonian little advance -is made. In the Middle Devonian this meagre flora had been replaced by -one rivalling that of the Carboniferous, and including pines, tree-ferns, -and arboreal forms of Lycopods and of equisetaceous plants, as well as -numerous herbaceous plants. At the close of the Erian the flora again -became meagre, and continued so in the Lower Carboniferous. It again -became rich and varied in the Middle Carboniferous, to decay in the -succeeding Permian. - - - - -II.--HEER'S LATEST RESULTS IN THE GREENLAND FLORA. - - -A very valuable report of Prof. Steenstrup, published in Copenhagen in -1883, the year in which Heer died, contains the results of his last -work on the Greenland plants, and is so important that a summary of its -contents will be interesting to all students of fossil botany or of the -vicissitudes of climate which the earth has undergone.[FQ] - -[FQ] Meddelelser om Gronland, Hefte V., Copenhagen, 1883. - -The plant-bearing beds of Greenland are as follows, in ascending order: - -1. Cretaceous. - -1. The _Komé_ series, of black shales resting on the Laurentian gneiss. -These beds are found at various other localities, but the name above -given is that by which they are generally known. Their flora is limited -to ferns, cycads, conifers, and a few endogens, with only _Populus -primæva_ to represent the dicotyledons. These beds are regarded as Lower -Cretaceous (Urgonian), but the animal fossils would seem to give them -a rather higher position. They may be regarded as equivalent to the -Kootanie and Queen Charlotte beds in Canada, and the Potomac series in -Virginia. - -2. The _Atané_ series. These also are black shales with dark-coloured -sandstones. They are best exposed at Upernavik and Waigat. Here -dicotyledonous leaves abound, amounting to ninety species, or more than -half the whole number of species found. The fossil plants resemble those -of the Dakota series of the United States and the Dunvegan series of -Canada, and the animal fossils indicate the horizon of the Fort Pierre or -its lower part. They may be regarded as representing the lower part of -the Upper Cretaceous. The genera _Populus_, _Myrica_, _Quercus_, _Ficus_, -_Platanus_, _Sassafras_, _Laurus_, _Magnolia_, and _Liriodendron_ -are among those represented in these beds, and the peculiar genera -_Macclintockia_ and _Credneria_ are characteristic. The genus _Pinus_ is -represented by five species, _Sequoia_ by five, and _Salisburia_ by two, -with three of the allied genus _Baiera_. There are many ferns and cycads. - -3. The _Patoot_ series. These are yellow and red shales, which seem to -owe their colour to the spontaneous combustion of pyritous lignite, in -the manner observed on the South Saskatchewan and the Mackenzie rivers. -Their age is probably about that of the Fox-Hill group or Senonian, -and the Upper Cretaceous of Vancouver Island, and they afford a large -proportion of dicotyledonous leaves. The genera of dicotyledons are -not dissimilar from those of Atané, but we now recognise _Betula_ and -_Alnus_, _Comptonia_, _Planera_, _Sapotacites_, _Fraxinus_, _Viburnum_, -_Cornus_, _Acer_, _Celastrus_, _Paliurus_, _Ceanothus_, _Zizyphus_, and -_Cratægus_ as new genera of modern aspect. - -On the whole there have been found in all these beds 335 species, -belonging to 60 families, of which 36 are dicotyledonous, and represent -all the leading types of arborescent dicotyledons of the temperate -latitudes. The flora is a warm temperate one, with some remarkable -mixtures of sub-tropical forms, among which perhaps the most remarkable -are _Kaidocarpum_ referred to the _Pandaneæ_, and such exogens as _Ficus_ -and _Cinnamomum_. - -2. Tertiary. - -4. The _Unartok_ series. This is believed to be Eocene. It consists of -sandstone, which appears on the shores of Disco Island, and possibly at -some other places on the coast. The beds rest directly and apparently -conformably on the Upper Cretaceous, and have afforded only eleven -species of plants. _Magnolia_ is represented by two species, _Laurus_ -by two, _Platanus_ by two, and one of these said to be identical with a -species found by Lesquereux in the Laramie,[FR] _Viburnum_, _Juglans_, -_Quercus_, each by one species; the ubiquitous _Sequoias_ by _S. -Langsdorfii_. This is pretty clearly a Lower Laramie flora. - -[FR] _Viburnum marginatum_ of Lesquereux. - -5. The _Atanekerdluk_ series, consisting of shaly beds, with limestone -intercalated between great sheets of basalt, much like the Eocene of -Antrim and the Hebrides. These beds have yielded 187 species, principally -in bands and concretions of siderite, and often in a good state of -preservation. They are referred to the Lower Miocene, but, as explained -in the text, the flora is more nearly akin to that of the Eocene of -Europe and the Laramie of America. The animal fossils are chiefly -fresh-water shells. _Onoclea sensibilis_, several conifers, as _Taxites_ -_Olriki_, _Taxodium distichum_, _Glyptostrobus Europæus_, and _Sequoia -Langsdorfii_, and 42 of the dicotyledons are recognised as found also -in American localities. Of these, a large proportion of the more common -species occur in the Laramie of the Mackenzie River and elsewhere in -northwest Canada, and in the western United States. It is quite likely -also that several species regarded as distinct may prove to be identical. - -It would seem that throughout the whole thickness of these Tertiary beds -the flora is similar, so that it is probable it belongs altogether to the -Eocene rather than to the Miocene. - -No indication has been observed of any period of cold intervening between -the Lower Cretaceous and the top of the Tertiary deposits, so that, in -all the vast period which these formations represent, the climate of -Greenland would seem to have been temperate. There is, however, as is -the case farther south, evidence of a gradual diminution of temperature. -In the Lower Cretaceous the probable mean annual temperature in latitude -71° north is stated as 21° to 22° centigrade, while in the early Tertiary -it is estimated at 12° centigrade. Such temperatures, ranging from 71° -to 53° of Fahrenheit, represent a marvellously warm climate for so high -a latitude. In point of fact, however, the evidence of warm climates in -the arctic regions, in the Palæozoic as well as in the Mesozoic and early -Tertiary, should perhaps lead us to conclude that, relatively to the -whole of geological time, the present arctic climate is unusually severe, -and that a temperate climate in the arctic regions has throughout -geological time been the rule rather than the exception. - - - - -III.--MINERALISATION OF FOSSIL PLANTS. - - -The state of preservation of fossil plants has been referred to -incidentally in several places in the text; but the following more -definite statements may be of service to the reader. - -I. Organic remains imbedded in aqueous deposits may occur in an unchanged -condition, or only more or less altered by decay. This is often the case -with such enduring substances as bark and wood, and even with leaves, -which appear as thin carbonaceous films when the layers containing -them are split open. In the more recent deposits such remains occur -little modified, or perhaps only slightly changed by partial decay of -their more perishable parts. In the older formations, however, they -are usually found in a more or less altered condition, in which their -original substance has been wholly or in part changed into coaly, or -bituminous, or anthracitic or graphitic matter, so that leaves are -sometimes represented by stains of graphite, as if drawn on stone with a -lead-pencil. Yet even in this case some portion of the original substance -remains, and without any introduction of foreign material. - -II. On the other hand, such remains are often mineralised by the filling -of their pores or the replacement of their tissues with mineral matter, -so that they become hard and stony, and sometimes retain little or -nothing of their original substance. The more important of these changes, -in so far as they affect fossil plants, may be arranged under the -following heads: - -(_a_) _Infiltration_ of mineral matter which has penetrated the pores -of the fossil in a state of solution. Thus the pores of fossil wood are -often filled with calcite, quartz, oxide of iron, or sulphide of iron, -while the woody walls of the cells and vessels remain in a carbonised -state, or converted into coaly matter. When wood is preserved in this -way it has a hard and stony aspect; but we can sometimes dissolve away -the mineral matter, and restore the vegetable tissue to a condition -resembling that before mineralisation. This is especially the case when -calcite is the mineralising substance. We sometimes find, on microscopic -examination, that even cavities so small as those of vegetable cells and -vessels have been filled with successive coats of different kinds of -mineral matter. - -(_b_) Organic matters may be entirely _replaced_ by mineral -substances. In this case the cavities and pores have been first -filled, and then--the walls or solid parts being removed by decay or -solution--mineral matter, either similar to that filling the cavities, -or differing in colour or composition, has been introduced. Silicified -wood often occurs in this condition. In the case of silicified wood, it -sometimes happens that the cavities of the fibers have been filled with -silica, and the wood has been afterward removed by decay, leaving the -casts of the tubular fibers as a loose filamentous substance. Some of -the Tertiary coniferous woods of California are in this state, and look -like asbestus, though they show the minute markings of the tissue under -the microscope. In the case of silicified or agatized woods, it would -seem that the production of carbon dioxide from the decaying wood has -caused the deposition of silica in its place, from alkaline solutions -of that substance, and thus the carbon has been replaced, atom by atom, -by silicon, until the whole mass has been silicified, yet retaining -perfectly its structure. - -(_c_) The cavities left by fossils which have decayed may be filled with -clay, sand, or other foreign matter, and this, becoming subsequently -hardened into stone, may constitute a _cast_ of the fossils. Trunks of -trees, roots, &c., are often preserved in this way, appearing as stony -casts, often with the outer bark of the plant forming a carbonaceous -coating on their surfaces. In connection with this state may be -mentioned that in which, the wood having decayed, an entire trunk has -been flattened so as to appear merely as a compressed film of bark, yet -retaining its markings; and that in which the whole of the vegetable -matter having been removed, a mere impression of the form remains. - -Fossils preserved in either of the modes, (_a_) or (_b_), usually show -more or less of their minute structures under the microscope. These may -be observed:--(1) By breaking off small splinters or flakes and examining -them, either as opaque or as transparent objects. (2) By treating the -material with acids, so as to dissolve out the mineral matters, or -portions of them. This method is especially applicable to fossil woods -mineralised with calcite or pyrite. (3) By grinding thin sections. These -are first polished on one face on a coarse stone or emery hone, and then -on a fine hone, then attached by the polished face to glass slips with -a transparent cement or Canada balsam, and ground on the opposite face -until they become so thin as to be translucent. In most cities there are -lapidaries who prepare slices of this kind; but the amateur can readily -acquire the art by a little practice, and the necessary appliances can -be obtained through dealers in minerals or in microscopic materials. -Very convenient cutting and polishing machines, some of them quite small -and portable, are now made for the use of amateurs. In the case of -exogenous woods, three sections are necessary to exhibit the whole of the -structures. One of these should be transverse and two longitudinal, the -latter in radial and tangential planes. - - - - -IV.--GENERAL WORKS ON PALÆOBOTANY. - - -In the text frequent reference has been made to special memoirs and -reports on the fossil plants of particular regions or formations. There -are, however, some general books, useful to students, which may be -mentioned here. Perhaps the most important is Schimper's "Traité de -Paléontologie Végétale." Very useful information is also contained in -Renault's "Cours de Botanique Fossile," and in Balfour's "Introduction to -Palæontological Botany," and Nicholson's "Palæontology." Unger's "Genera -et Species," Brongniart's "Histoire des Végétaux Fossiles," and Lindley -and Button's "Fossil Flora," are older though very valuable works. -Williamson's "Memoirs," in the "Philosophical Transactions," have greatly -advanced our knowledge of the structures of Palæozoic plants. Lastly, -the "Palæophytology" of Schenk, now in course of publication in German -and French, in connection with Zittel's "Palæontology," is an important -addition to manuals of the subject. - - - - -INDEX. - - - Acer, 228. - Acrogens, 6. - Agassiz, Prof., 16. - Alaska, Flora of, 245. - Algæ, real and spurious, 26, 230. - Amboy clays, Flora of, 203. - America, Cretaceous of, 190. - Angiosperms, 6. - Annularia, 122. - Anogens, 6. - Antholithes, 132. - Aporoxylon, 25. - Araucarioxylon, 148. - Araucarites, 134. - Archæocalamites, 170. - Archæopteris, 77, 85. - Arctic origin of plants, 221, 238. - Arthrophycus, 30. - Arthrostigma, 67. - Asterophyllites, 78, 122, 170. - Asteropteris, 77, 85. - Astropolithon, 30. - Atané, Plants of, 242, 281. - Atanekerdluk, Plants of, 283. - Australia, Palæozoic flora of, 147. - Tertiary flora of, 217. - - Bauhinia, 204. - Bear Island, 241. - Betula, 198. - Bilobites, 28. - Bovey Tracey, Plants of, 226. - Brasenia, 207. - Buckland, Dr., 179. - Buthotrephis, 37. - - Calamites, 77, 123, 166. - Calamodendron, 125. - Cambrian flora, 20. - Canada, Erian of, 103. - Carboniferous of, 110. - Laramie of, 209. - Pleistocene of, 227. - Carbon in Laurentian, 9. - Carboniferous flora, 110. - Carboniferous, Climate of, 138. - of Southern Hemisphere, 147. - Cardiocarpum, 82, 153. - Carruthers, Mr., 24, 98, 180. - On modifications of modern plants, 225, 269. - Carya, 196. - Cauda-galli fucoid, 105. - Caulerpites, 29. - Caulopteris, 75, 94. - Clarke, Prof., 51. - Climate, Causes of, 247. - Climate and plants, 216, 220, 232. - of Carboniferous, 138. - of Cretaceous and Eocene, 216. - of Devonian, 47. - of Early Mesozoic, 178. - Climate and plants of Laurentian, 17. - of Pleistocene, 227, 230. - of Pliocene, 223. - Coal, origin of, 117, 139. - Comparison of floras, 272. - Composite, 266. - Cone-in-cone, 36. - Coniferæ, Erian, 78, 96. - Carboniferous, 134, 148. - Mesozoic, etc., 181. - Cope, Mr., 215. - Cordaites, 78, 130, 151. - Corylus, 213. - Crepin, M., 99. - Cretaceous, Flora of, 190. - Climate of, 216. - Croll on climate, 252. - Cromer, Plants of, 224. - Cycads, Mesozoic, 178. - Cyclostigma, 157. - - Dadoxylon, 96, 134, 148. - Dawson, Dr. G. M., 52, 210. - Delgado, Prof., 26. - Dendrophycus, 33. - Derby, Orville, 53. - Devonian flora, 45. - Devonian or Erian, 107, 279. - Climate of, 47. - Dicotyledons, Cretaceous, 192. - Table of, 192. - Dictyolites, 33. - Dictyospongia, 39. - Disco, Exotic plants at, 256. - Flora of, 245, 282. - Drepanophycus, 39. - Drosera, 228. - Dunvegan beds, 244. - - Eocene, Flora of, 208, 214. - Climate of, 216. - Eophyton, 31. - Eopteris, 72. - Eozoon of Laurentian, 9. - Equisetum, 176, 230. - Erian flora, 45, 279. - Climate of, 47. - Erian or Devonian, 107. - Ettingshausen, Dr., 187, 215. - Exogens, Cretaceous, 192. - Tertiary, 213, 224. - - Fagus, 196, 197. - Ferns, Erian, 72. - Carboniferous, 126, 171. - Fructification of, 128. - Stems of, 90, 129. - Tertiary, 212. - Filices, 72, 126, 171. - Flora of Cambrian, 26. - of Carboniferous, 110, 274. - of Cretaceous, 190. - of Early Mesozoic, 175. - of Erian, 45, 279. - of Jurassic, 177, 186. - of Laramie, 209. - of Laurentian, 8. - of Miocene, 220, 223. - of Modern, 219. - of Permian, 274. - of Pleistocene, 223, 227. - of Tertiary, 191, 208, 214, 219. - Fontaine, Prof., 130, 176. - Fontinalis, 230. - Fort Union beds, 210. - Fucoids, 27. - - Gardner, Mr. Starkie, 212. - Geinitz, Dr., 174. - Geological formations, Table of, 4. - Glossopteris, 147. - Glyptodendron, 25. - Glyptostrobus, 194. - Goeppert, Dr., 99. - Grant, Col., 36. - Graphite from plants, 8. - Gray, Dr., Origin of floras, 223, 237. - Greenland, Climate of, 216. - Fossil flora of, 247. - Gulielmites, 35. - Gymnosperms, 6. - - Haliserites, 39. - Hartt, Prof., 53. - Heer, Dr., 108, 181. - Helderberg period, Sea of, 250. - Heterangium, 77. - Hicks, Dr., 21. - Hunt, Dr. Sterry, 13, 143. - Huxley, Prof., 53. - Hymenæa, 204. - - Insects, Erian, 83. - - Juglans, 196. - Jurassic flora, 177. - - Kainozoic flora, 191, 208, 214, 219. - Kidston, Mr. R., 128, 273. - King, Mr. Clarence, 211. - Komé, Plants of, 242, 281. - - Laramie flora, 209, 215. - Laurentian plants, 8. - Laurentian, Climate of, 17. - Laurophyllum, 193. - Laws of introduction of plants, 237, 266. - Leda clay, Flora of, 232. - Lepidodendron, 120, 156, 162. - Lepidophloios, 121, 157, 165. - Leptophleum, 157. - Lesquereux, Mr. L., 169, 214. - Licrophycus, 30. - Lignitic series of America, 208. - Liquidambar, 197. - Liriodendron, 199. - Lower Carboniferous flora, 277. - Logan, Sir W., 48. - Lyell on climate, 249. - - Magnolia, 200. - McConnell, Mr., 209. - McNab, Prof., 169. - Megalopteris, 76. - Megaphyton, 129. - Mesozoic flora, 175. - Climate of, 178. - Migrations of plants, 240, 245. - Miller, Hugh, 98. - Miocene flora, 220. - Miocene, Supposed, 242. - Modern flora, 219. - Modern plants, how modified, 269. - Modifications of plants, 266. - - Nathorst, Dr., 26, 196. - Nematodendreæ, 25. - Nematophycus, 23. - Nematophyton, 21, 22, 42. - Newberry, Dr., 200, 203, 214. - Newfoundland, Fossil plants of, 242. - Newton, Mr., 52. - Nicholson, Dr. A., 20. - Niobrara series, 243, 246. - Noeggerathia, 130. - Northern origin of plants, 238. - - Origin of plants, 237. - Orton, Prof., 51. - - Pachytheca, 21. - Palæanthus, 205. - Palæochorda, 30. - Palæophycus, 30, 38. - Palæozoic floras compared, 273. - Palms, 188, 194. - Pandanus, 188. - Patoot beds, 282. - Peach, Mr., 98. - Petroleum, Origin of, 56. - Phymatoderma, 29. - Plants, Classification of, 6. - Platanus, 198. - Platyphyllum, 74. - Pleistocene climate, 227, 230. - Pleistocene flora, 223, 227. - Pliocene climate, 223. - Podozamites, 178. - Poles, Supposed change of, 248. - Populus, 191, 228. - Potamogeton, 229. - Potentilla, 228. - Protannularia, 21. - Protichnites, 27. - Protophyllum, 199. - Protosalvinia, 52. - Protostigma, 20. - Prototaxites, 21. - Psaronius, 93. - Psilophyton, 64. - Ptilophyton, 62, 86. - - Quercus, 197. - - Rhizocarps, 48. - Rill-marks, 33. - Rusichnites, 28. - - Saccamina, 57. - Salisburia, 180. - Salter, Mr., 98. - Salvinia, 54. - - Saporta, Count de, 26, 193. - Saportea, 57. - Sassafras, 199. - Scalariform tissue, 70. - Schimper, Dr., 116, 169, 208. - Scolithus, 30. - Scottish Devonian, 98. - Sequoia, 181. - Shrinkage cracks, 33. - Sigillaria, 71, 112, 154. - Southern Hemisphere, 217, 273. - Carboniferous in, 147. - Tertiary in, 217. - Sphenophyllum, 61, 122, 171. - Spirophyton, 38. - Spitzbergen, 241. - Sterculites, 193. - Sternbergia, 137, 152. - Stigmaria, 115. - Stur, Dr., on Sigillaria, 116. - Symphorocarpus, 214. - Syringodendron, 156. - Syringoxylon, 82. - - Table of formations, 4. - Tasmania, Fossil plants of, 217, 246. - Tasmanite, 57. - Tertiary period, Flora of, 191, 208, 214, 219. - Tertiary of Australia, 217. - Thallogens, 6. - Thomas, Mr., 51. - Thuja, 213, 229. - Time, Geological, 5. - Trapa, 196. - Tree-ferns, 90, 129. - Triassic flora, 176. - Trigonocarpum, 136, 153. - Tyndall, Prof., 138. - - Ulrich, Prof., 57. - Unartok beds, 281. - Ursa stage of Heer, 108, 241. - - Walchia, 134, 138. - Ward, Mr. L. 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William Dawson - -This eBook is for the use of anyone anywhere in the United States and most -other parts of the world at no cost and with almost no restrictions -whatsoever. You may copy it, give it away or re-use it under the terms of -the Project Gutenberg License included with this eBook or online at -www.gutenberg.org. If you are not located in the United States, you'll have -to check the laws of the country where you are located before using this ebook. - -Title: The Geological History of Plants - -Author: Sir J. William Dawson - -Release Date: January 23, 2016 [EBook #51021] - -Language: English - -Character set encoding: ISO-8859-1 - -*** START OF THIS PROJECT GUTENBERG EBOOK THE GEOLOGICAL HISTORY OF PLANTS *** - - - - -Produced by Tom Cosmas compiled from files made available -at The Internet Archive. - - - - - - -</pre> - - -<div class="fig_center" style="width: 262px;"> -<img src="images/cover.jpg" width="262" height="455" alt="cover" /> -</div> - - -<p class="pmt4 pmb4 caption2">THE INTERNATIONAL SCIENTIFIC SERIES<br /> -VOLUME LXI</p> - -<p><span class="pagenum"><a name="Page_1l" id="Page_1l">« 1 »</a></span></p> - - -<p class="caption2"><span class="smaller">THE</span><br /> -INTERNATIONAL SCIENTIFIC SERIES.</p> - -<hr class="r20" /> - -<p class="center"><b>Each book complete in One Volume, 12mo, and bound in Cloth.</b></p> - -<hr class="r20" /> - - -<table summary="booklist"> -<tr> - <td class="tdr vtop">1.</td> - <td><p class="hanging">FORMS OF WATER: A Familiar Exposition of the Origin and - Phenomena of Glaciers. 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Ralph Abercromby. $1.75.</p></td> -</tr> -<tr> - <td class="tdr vtop">59.</td> - <td><p class="hanging">ANIMAL MAGNETISM. By Alfred Binet and Charles Féré, Assistant - Physician at the Salpêtrière.</p></td> -</tr> -</table> - -<p><span class="pagenum"><a name="Page_i" id="Page_i">« i »</a><br /> -<a name="Page_ii" id="Page_ii">« ii »</a></span></p> - -<hr class="tb" /> - -<div class="fig_center" style="width: 765px;"> -<a id="Frontispiece" name="Frontispiece"></a> -<div class="caption2">DIAGRAM OF THE HISTORY OF PLANTS IN GEOLOGICAL TIME.<br />(Adapted from Ward.)</div> -<img src="images/diagram.png" width="765" height="495" alt="Frontispiece" /> -</div> - - -<p><span class="pagenum"><a name="Page_iii" id="Page_iii">« iii »</a></span></p> - - -<p class="pmt4 caption3">THE INTERNATIONAL SCIENTIFIC SERIES</p> - -<hr class="r20" /> - - -<p class="caption1"><span class="smaller">THE</span><br /> -GEOLOGICAL HISTORY<br /> -OF PLANTS</p> - - -<p class="pmt4 center">BY</p> - -<p class="caption2">SIR J. WILLIAM DAWSON<br /> -<span class="smaller">C. M. G., LL. D., F. R. S., &c.</span></p> - - -<p class="caption4 pmt4 pmb4"><i>WITH ILLUSTRATIONS</i></p> - - -<p class="pmb4 caption3">NEW YORK<br /> -APPLETON AND COMPANY<br /> -1888</p> - -<hr class="chap" /> - - -<p><span class="pagenum"><a name="Page_iv" id="Page_iv">« iv »</a></span></p> - - -<p><span class="pagenum"><a name="Page_v" id="Page_v">« v »</a></span></p> - -<p class="center">Copyright, 1888,<br /> -By D. APPLETON AND COMPANY.</p> - - - -<hr class="chap" /> - - -<p class="caption2">PREFACE.</p> - -<hr class="r10" /> - - -<p>The object of this work is to give, in a connected -form, a summary of the development of the vegetable -kingdom in geological time.</p> - -<p>To the geologist and botanist the subject is one of -importance with reference to their special pursuits, and -one on which it has not been easy to find any convenient -manual of information. It is hoped that its treatment -in the present volume will also be found sufficiently -simple and popular to be attractive to the -general reader.</p> - -<p>In a work of so limited dimensions, detailed descriptions -cannot be given, except occasionally by way of -illustration; but references to authorities will be made -in foot-notes, and certain details, which may be useful to -collectors and students, will be placed in notes appended -to the chapters, so as not to encumber the text.</p> - -<p>The illustrations of this work are for the most part -original; but some of them have previously appeared -in special papers of the author.</p> - -<p class="tdr2">J. W. D.</p> - -<p class="pmb4"><i>February, 1888.</i></p> - - -<p><span class="pagenum"><a name="Page_vi" id="Page_vi">« vi »</a><br /> -<a name="Page_vii" id="Page_vii">« vii »</a></span></p> - - -<p class="caption2">CONTENTS.</p> - - -<table summary="ToC"> -<tr> - <td></td> - <td class="tdr smaller">PAGE</td> -</tr> -<tr> - <td class="caption2" colspan="3">CHAPTER I.</td> -</tr> -<tr> - <td class="smcap" colspan="2">Preliminary Ideas of Geological Chronology and of the - Classification of Plants</td> - <td class="tdr"><a href="#CHAPTER_I">1</a></td> -</tr> -<tr> - <td class="caption2" colspan="3">CHAPTER II.</td> -</tr> -<tr> - <td class="smcap" colspan="2">Vegetation of the Laurentian and Early Paleozoic—Questions - as to Algæ</td> - <td class="tdr"><a href="#CHAPTER_II">8</a></td> -</tr> -<tr> - <td class="caption2" colspan="3">CHAPTER III.</td> -</tr> -<tr> - <td class="smcap" colspan="2">The Erian or Devonian Forests—Origin of Petroleum—The - Age of Acrogens and Gymnosperms</td> - <td class="tdr"><a href="#CHAPTER_III">45</a></td> -</tr> -<tr> - <td class="caption2" colspan="2">CHAPTER IV.</td> -</tr> -<tr> - <td class="smcap" colspan="2">The Carboniferous Flora—Culmination of the - Acrogens—Formation of Coal</td> - <td class="tdr"><a href="#CHAPTER_IV">110</a></td> -</tr> -<tr> - <td class="caption2" colspan="3">CHAPTER V.</td> -</tr> -<tr> - <td class="smcap" colspan="2">The Flora of the Early Mesozoic—Reign of Pines and Cycads</td> - <td class="tdr"><a href="#CHAPTER_V">175</a></td> -</tr> -<tr> - <td class="caption2" colspan="3">CHAPTER VI.</td> -</tr> -<tr> - <td class="smcap" colspan="2">The Reign of Angiosperms in the Later Cretaceous and Early - Tertiary or Kainozoic</td> - <td class="tdr"><a href="#CHAPTER_VI">191</a></td> -</tr> -<tr> - <td class="caption2" colspan="3">CHAPTER VII. - <span class="pagenum"><a name="Page_viii" id="Page_viii">« viii »</a></span> -</td> -</tr> -<tr> - <td class="smcap" colspan="2">Plants from the Tertiary to the Modern Period</td> - <td class="tdr"><a href="#CHAPTER_VII">219</a></td> -</tr> -<tr> - <td class="caption2" colspan="3">CHAPTER VIII.</td> -</tr> -<tr> - <td class="smcap" colspan="2">General Laws of Origin and Migrations of Plants—Relations - of Recent and Fossil Floras</td> - <td class="tdr"><a href="#CHAPTER_VIII">237</a></td> -</tr> -<tr> - <td class="caption2" colspan="3">APPENDIX.</td> -</tr> -<tr> - <td class="tdr">I.</td> - <td class="smcap">Comparative View of Paleozoic Floras</td> - <td class="tdr"><a href="#APPENDIX_I">273</a></td> -</tr> -<tr> - <td class="tdr">II.</td> - <td class="smcap">Heer’s Latest Statements on the Greenland Flora</td> - <td class="tdr"><a href="#APPENDIX_II">281</a></td> -</tr> -<tr> - <td class="tdr">III.</td> - <td class="smcap">Mineralisation of Fossil Plants</td> - <td class="tdr"><a href="#APPENDIX_III">284</a></td> -</tr> -<tr> - <td class="tdr">IV.</td> - <td class="smcap">General Works on Palæobotany</td> - <td class="tdr"><a href="#APPENDIX_IV">286</a></td> -</tr> -</table> - - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_ix" id="Page_ix">« ix »</a></span></p> - - -<p class="caption2">LIST OF ILLUSTRATIONS.</p> - -<table summary="ToC"> -<tr> - <td></td> - <td class="tdr smaller">PAGE</td> -</tr> -<tr> - <td class="tdl">Table of Chronology of Plants</td> - <td class="tdr">(<a href="#Frontispiece">Frontispiece.</a>)</td> -</tr> -<tr> - <td class="tdl">Protannularia Harknessii</td> - <td class="tdr"><a href="#Page_21">21</a></td> -</tr> -<tr> - <td class="tdl">Nematophyton Logani (three Figures)</td> - <td class="tdr"><a href="#Page_22">22</a>, <a href="#Page_23">23</a></td> -</tr> -<tr> - <td class="tdl">Trail of King-Crab</td> - <td class="tdr"><a href="#Page_28">28</a></td> -</tr> -<tr> - <td class="tdl">Trail of Carboniferous Crustacean</td> - <td class="tdr"><a href="#Page_28">28</a></td> -</tr> -<tr> - <td class="tdl">Rusichnites</td> - <td class="tdr"><a href="#Page_29">29</a></td> -</tr> -<tr> - <td class="tdl">Palæophycus</td> - <td class="tdr"><a href="#Page_30">30</a></td> -</tr> -<tr> - <td class="tdl">Astropolithon</td> - <td class="tdr"><a href="#Page_31">31</a></td> -</tr> -<tr> - <td class="tdl">Carboniferous Rill-mark</td> - <td class="tdr"><a href="#Page_33">33</a></td> -</tr> -<tr> - <td class="tdl">Cast of Shrinkage Cracks</td> - <td class="tdr"><a href="#Page_34">34</a></td> -</tr> -<tr> - <td class="tdl">Cone-in-cone</td> - <td class="tdr"><a href="#Page_36">36</a></td> -</tr> -<tr> - <td class="tdl">Buthotrephis</td> - <td class="tdr"><a href="#Page_37">37</a></td> -</tr> -<tr> - <td class="tdl">Silurian Vegetation</td> - <td class="tdr"><a href="#Page_40">40</a></td> -</tr> -<tr> - <td class="tdl">Erian Plants</td> - <td class="tdr"><a href="#Page_49">49</a></td> -</tr> -<tr> - <td class="tdl">Protosalvinia</td> - <td class="tdr"><a href="#Page_54">54</a></td> -</tr> -<tr> - <td class="tdl">Ptilophyton (two Figures)</td> - <td class="tdr"><a href="#Page_62">62</a>, <a href="#Page_63">63</a></td> -</tr> -<tr> - <td class="tdl">Psilophyton (two Figures)</td> - <td class="tdr"><a href="#Page_64">64</a>, <a href="#Page_66">66</a></td> -</tr> -<tr> - <td class="tdl">Sphenophyllum</td> - <td class="tdr"><a href="#Page_65">65</a></td> -</tr> -<tr> - <td class="tdl">Lepidodendron</td> - <td class="tdr"><a href="#Page_66">66</a></td> -</tr> -<tr> - <td class="tdl">Various Ferns</td> - <td class="tdr"><a href="#Page_72">72</a>, <a href="#Page_73">73</a></td> -</tr> -<tr> - <td class="tdl">Archæopteris</td> - <td class="tdr"><a href="#Page_74">74</a></td> -</tr> -<tr> - <td class="tdl">Caulopteris</td> - <td class="tdr"><a href="#Page_75">75</a></td> -</tr> -<tr> - <td class="tdl">Megalopteris</td> - <td class="tdr"><a href="#Page_76">76</a></td> -</tr> -<tr> - <td class="tdl">Calamites</td> - <td class="tdr"><a href="#Page_77">77</a></td> -</tr> -<tr> - <td class="tdl">Asterophyllites</td> - <td class="tdr"><a href="#Page_78">78</a></td> -</tr> -<tr> - <td class="tdl">Dadoxylon</td> - <td class="tdr"><a href="#Page_79">79</a> - <span class="pagenum"><a name="Page_x" id="Page_x">« x »</a></span></td> -</tr> -<tr> - <td class="tdl">Cordaites</td> - <td class="tdr"><a href="#Page_81">81</a></td> -</tr> -<tr> - <td class="tdl">Erian Fruits</td> - <td class="tdr"><a href="#Page_82">82</a></td> -</tr> -<tr> - <td class="tdl">Foliage from the Coal-formation</td> - <td class="tdr"><a href="#Page_111">111</a></td> -</tr> -<tr> - <td class="tdl">Sigillariæ (five Figures)</td> - <td class="tdr"><a href="#Page_112">112</a>-<a href="#Page_114">114</a></td> -</tr> -<tr> - <td class="tdl">Stigmariæ (two Figures)</td> - <td class="tdr"><a href="#Page_115">115</a></td> -</tr> -<tr> - <td class="tdl">Vegetable Tissues</td> - <td class="tdr"><a href="#Page_117">117</a></td> -</tr> -<tr> - <td class="tdl">Coals and Erect Trees (two Figures)</td> - <td class="tdr"><a href="#Page_118">118</a>, <a href="#Page_119">119</a></td> -</tr> -<tr> - <td class="tdl">Lepidodendron</td> - <td class="tdr"><a href="#Page_120">120</a></td> -</tr> -<tr> - <td class="tdl">Lepidophloios</td> - <td class="tdr"><a href="#Page_121">121</a></td> -</tr> -<tr> - <td class="tdl">Asterophyllites, &c.</td> - <td class="tdr"><a href="#Page_122">122</a></td> -</tr> -<tr> - <td class="tdl">Calamites (five Figures)</td> - <td class="tdr"><a href="#Page_123">123</a>-<a href="#Page_125">125</a></td> -</tr> -<tr> - <td class="tdl">Ferns of the Coal-formation (six Figures)</td> - <td class="tdr"><a href="#Page_126">126</a>-<a href="#Page_129">129</a></td> -</tr> -<tr> - <td class="tdl">Noeggerathia dispar</td> - <td class="tdr"><a href="#Page_130">130</a></td> -</tr> -<tr> - <td class="tdl">Cordaites</td> - <td class="tdr"><a href="#Page_131">131</a></td> -</tr> -<tr> - <td class="tdl">Fruits of Cordaites, &c.</td> - <td class="tdr"><a href="#Page_132">132</a></td> -</tr> -<tr> - <td class="tdl">Conifers of the Coal-formation (four Species)</td> - <td class="tdr"><a href="#Page_135">135</a></td> -</tr> -<tr> - <td class="tdl">Trigonocarpum</td> - <td class="tdr"><a href="#Page_136">136</a></td> -</tr> -<tr> - <td class="tdl">Sternbergia</td> - <td class="tdr"><a href="#Page_137">137</a></td> -</tr> -<tr> - <td class="tdl">Walchia imbricatula</td> - <td class="tdr"><a href="#Page_138">138</a></td> -</tr> -<tr> - <td class="tdl">Foliage of the Jurassic Period</td> - <td class="tdr"><a href="#Page_177">177</a></td> -</tr> -<tr> - <td class="tdl">Podozamites</td> - <td class="tdr"><a href="#Page_178">178</a></td> -</tr> -<tr> - <td class="tdl">Salisburia</td> - <td class="tdr"><a href="#Page_180">180</a></td> -</tr> -<tr> - <td class="tdl">Sequoia</td> - <td class="tdr"><a href="#Page_181">181</a></td> -</tr> -<tr> - <td class="tdl">Populus primæva</td> - <td class="tdr"><a href="#Page_191">191</a></td> -</tr> -<tr> - <td class="tdl">Stercalia and Laurophyllum</td> - <td class="tdr"><a href="#Page_194">194</a></td> -</tr> -<tr> - <td class="tdl">Vegetation of the Cretaceous Period</td> - <td class="tdr"><a href="#Page_195">195</a></td> -</tr> -<tr> - <td class="tdl">Platanus</td> - <td class="tdr"><a href="#Page_198">198</a></td> -</tr> -<tr> - <td class="tdl">Protophyllum</td> - <td class="tdr"><a href="#Page_199">199</a></td> -</tr> -<tr> - <td class="tdl">Magnolia</td> - <td class="tdr"><a href="#Page_200">200</a></td> -</tr> -<tr> - <td class="tdl">Liriodendron (two Figures)</td> - <td class="tdr"><a href="#Page_201">201</a></td> -</tr> -<tr> - <td class="tdl">Brasenia</td> - <td class="tdr"><a href="#Page_207">207</a></td> -</tr> -<tr> - <td class="tdl">Gaylussaccia resinosa</td> - <td class="tdr"><a href="#Page_228">228</a></td> -</tr> -<tr> - <td class="tdl">Populus balsamifera</td> - <td class="tdr"><a href="#Page_229">229</a></td> -</tr> -<tr> - <td class="tdl">Fucus</td> - <td class="tdr"><a href="#Page_230">230</a></td> -</tr> -</table> - -<p><span class="pagenum"><a name="Page_1" id="Page_1">« 1 »</a></span></p> - - - - -<p class="caption2"><span class="smaller">THE</span><br /> -GEOLOGICAL HISTORY OF PLANTS.</p> - - -<hr class="r10" /> - - -<p class="caption2"><a name="CHAPTER_I" id="CHAPTER_I">CHAPTER I.</a></p> - -<p class="caption3">PRELIMINARY IDEAS OF GEOLOGICAL CHRONOLOGY AND -OF THE CLASSIFICATION OF PLANTS.</p> - - -<p><span class="smcap">The</span> knowledge of fossil plants and of the history of -the vegetable kingdom has, until recently, been so fragmentary -that it seemed hopeless to attempt a detailed -treatment of the subject of this little book. Our stores -of knowledge have, however, been rapidly accumulating -in recent years, and we have now arrived at a stage when -every new discovery serves to render useful and intelligible -a vast number of facts previously fragmentary and of -uncertain import.</p> - -<p>The writer of this work, born in a district rich in -fossil plants, began to collect and work at these as a -boy, in connection with botanical and geological pursuits. -He has thus been engaged in the study of fossil plants -for nearly half a century, and, while he has published -much on the subject, has endeavoured carefully to keep -within the sphere of ascertained facts, and has made it -a specialty to collect, as far as possible, what has been -published by others. He has also enjoyed opportunities -of correspondence or personal intercourse with most of -<span class="pagenum"><a name="Page_2" id="Page_2">« 2 »</a></span> -the more eminent workers in the subject. Now, in the -evening of his days, he thinks it right to endeavour to -place before the world a summary of facts and of his own -matured conclusions—feeling, however, that nothing can -be final in this matter; and that he can only hope to -sketch the present aspect of the subject, and to point the -way to new developments, which must go on long after -he shall have passed away.</p> - -<p>The subject is one which has the disadvantage of presupposing -some knowledge of the geological history of -the earth, and of the classification and structures of modern -plants; and in order that all who may please to read -the following pages may be placed, as nearly as possible, -on the same level, this introductory chapter will be devoted -to a short statement of the general facts of geological -chronology, and of the natural divisions of the vegetable -kingdom in their relations to that chronology.</p> - -<p>The crust of the earth, as we somewhat modestly term -that portion of its outer shell which is open to our observation, -consists of many beds of rock superimposed on -each other, and which must have been deposited successively, -beginning with the lowest. This is proved by the -structure of the beds themselves, by the markings on -their surfaces, and by the remains of animals and plants -which they contain; all these appearances indicating that -each successive bed must have been the surface before it -was covered by the next.</p> - -<p>As these beds of rock were mostly formed under water, -and of material derived from the waste of land, they are -not universal, but occur in those places where there were -extensive areas of water receiving detritus from the land. -Further, as the distinction of land and water arises primarily -from the shrinkage of the mass of the earth, and -from the consequent collapse of the crust in some places -and ridging of it up in others, it follows that there have, -from the earliest geological periods, been deep ocean-basins, -<span class="pagenum"><a name="Page_3" id="Page_3">« 3 »</a></span> -ridges of elevated land, and broad plateaus intervening -between the ridges, and which were at some times -under water, and at other times land, with many intermediate -phases. The settlement and crumpling of the -crust were not continuous, but took place at intervals; -and each such settlement produced not only a ridging up -along certain lines, but also an emergence of the plains -or plateaus. Thus at all times there have been ridges of -folded rock constituting mountain-ranges, flat expansions -of continental plateau, sometimes dry and sometimes submerged, -and deep ocean-basins, never except in some of -their shallower portions elevated into land.</p> - -<p>By the study of the successive beds, more especially -of those deposited in the times of continental submergence, -we obtain a table of geological chronology which -expresses the several stages of the formation of the earth’s -crust, from that early time when a solid shell first formed -on our nascent planet to the present day. By collecting -the fossil remains embedded in the several layers and -placing these in chronological order, we obtain in like -manner histories of animal and plant life parallel to the -physical changes indicated by the beds themselves. The -facts as to the sequence we obtain from the study of exposures -in cliffs, cuttings, quarries, and mines; and by -correlating these local sections in a great number of places, -we obtain our general table of succession; though it is to -be observed that in some single exposures or series of -exposures, like those in the great canons of Colorado, or -on the coasts of Great Britain, we can often in one locality -see nearly the whole sequence of beds. Let us observe -here also that, though we can trace these series of deposits -over the whole of the surfaces of the continents, yet if -the series could be seen in one spot, say in one shaft sunk -through the whole thickness of the earth’s crust, this -would be sufficient for our purpose, so far as the history -of life is concerned.</p> - -<p><span class="pagenum"><a name="Page_4" id="Page_4">« 4 »</a></span></p> - -<p>The evidence is similar to that obtained by Schliemann -on the site of Troy, where, in digging through successive -layers of <i>débris</i>, he found the objects deposited by -successive occupants of the site, from the time of the -Roman Empire back to the earliest tribes, whose flint -weapons and the ashes of their fires rest on the original -surface of the ground.</p> - -<p>Let us now tabulate the whole geological succession -with the history of animals and plants associated with it:</p> - - -<table summary="plants and animals"> -<tr> - <td class="center bdt bdb">ANIMALS.</td> - <td class="center bdt bdb bdl" colspan="3">SYSTEMS OF FORMATIONS.</td> - <td class="center bdt bdb bdl">PLANTS.</td> -</tr> -<tr> - <td class="tdl">Age of Man and Mammalia.</td> - <td class="tdl bdl">Kainozoic.</td> - <td><img src="images/bracel_86.png" width="11" height="86" alt="{" /></td> - <td class="tdl">Modern,<br />Pleistocene,<br />Pliocene,<br />Miocene,<br />Eocene.</td> - <td class="tdl bdl">Angiosperms and<br /> Palms dominant.</td> -</tr> -<tr> - <td class="tdl">Age of Reptiles.</td> - <td class="tdl bdl">Mesozoic.</td> - <td><img src="images/bracel_86.png" width="11" height="60" alt="{" /></td> - <td class="tdl">Cretaceous,<br />Jurassic,<br />Triassic.</td> - <td class="tdl bdl">Cycads and Pines<br /> dominant.</td> -</tr> -<tr> - <td class="tdl">Age of Amphibians and Fishes.<br /> - Age of Invertebrates.</td> - <td class="tdl bdl">Palæozoic.</td> - <td><img src="images/bracel_86.png" width="11" height="116" alt="{" /></td> - <td class="tdl">Permian,<br />Carboniferous,<br />Erian,<br />Silurian,<br />Ordovician,<br />Cambrian,<br />Huronian (Upper).</td> - <td class="tdl bdl">Acrogens and<br /> Gymnosperms<br /> dominant.</td> -</tr> -<tr> - <td class="tdl bdb">Age of Protozoa.</td> - <td class="tdl bdb bdl">Eozoic.</td> - <td class="bdb"><img src="images/bracel_86.png" width="11" height="60" alt="{" /></td> - <td class="tdl bdb">Huronian (Lower),<br />Upper Laurentian,<br />Middle Laurentian,<br />Lower Laurentian.</td> - <td class="tdl bdb bdl">Protogens and Algæ.</td> -</tr> -</table> - -<p>It will be observed, since only the latest of the systems -of formations in this table belongs to the period of -human history, that the whole lapse of time embraced in -the table must be enormous. If we suppose the modern -period to have continued for say ten thousand years, and -each of the others to have been equal to it, we shall require -two hundred thousand years for the whole. There -is, however, reason to believe, from the great thickness of -the formations and the slowness of the deposition of many -<span class="pagenum"><a name="Page_5" id="Page_5">« 5 »</a></span> -of them in the older systems, that they must have required -vastly greater time. Taking these criteria into -account, it has been estimated that the time-ratios for -the first three great ages may be as one for the Kainozoic -to three for the Mesozoic and twelve for the Palæozoic, -with as much for the Eozoic as for the Palæozoic. This is -Dana’s estimate. Another, by Hull and Houghton, gives -the following ratios: Azoic, 34·3 per cent.; Palæozoic, -42·5 per cent.; Mesozoic and Kainozoic, 23·2 per cent. -It is further held that the modern period is much shorter -than the other periods of the Kainozoic, so that our -geological table may have to be measured by millions of -years instead of thousands.</p> - -<p>We cannot, however, attach any certain and definite -value in years to geological time, but must content ourselves -with the general statement that it has been vastly -long in comparison to that covered by human history.</p> - -<p>Bearing in mind this great duration of geological time, -and the fact that it probably extends from a period when -the earth was intensely heated, its crust thin, and its continents -as yet unformed, it will be evident that the conditions -of life in the earlier geologic periods may have -been very different from those which obtained later. -When we further take into account the vicissitudes of -land and water which have occurred, we shall see that -such changes must have produced very great differences -of climate. The warm equatorial waters have in all -periods, as superficial oceanic currents, been main agents -in the diffusion of heat over the surface of the earth, and -their distribution to north and south must have been -determined mainly by the extent and direction of land, -though it may also have been modified by the changes in -the astronomical relations and period of the earth, and -the form of its orbit.<a name="FNanchor_A_1" id="FNanchor_A_1"></a><a href="#Footnote_A_1" class="fnanchor">[A]</a> We know by the evidence of -<span class="pagenum"><a name="Page_6" id="Page_6">« 6 »</a></span> -fossil plants that changes of this kind have occurred so -great as, on the one hand, to permit the plants of warm -temperate regions to exist within the Arctic Circle; and, -on the other, to drive these plants into the tropics and -to replace them by Arctic forms. It is evident also that -in those periods when the continental areas were largely -submerged, there might be an excessive amount of moisture -in the atmosphere, greatly modifying the climate, in -so far as plants are concerned.</p> - -<div class="footnote"> - -<p><a name="Footnote_A_1" id="Footnote_A_1"></a><a href="#FNanchor_A_1"><span class="label">[A]</span></a> Croll, “Climate and Time.”</p></div> - -<p>Let us now consider the history of the vegetable kingdom -as indicated in the few notes in the right-hand -column of the table.</p> - -<p>The most general subdivision of plants is into the two -great series of Cryptogams, or those which have no manifest -flowers, and produce minute spores instead of seeds; -and Phænogams, or those which possess flowers and produce -seeds containing an embryo of the future plant.</p> - -<p>The Cryptogams may be subdivided into the following -three groups:</p> - -<p>1. <i>Thallogens</i>, cellular plants not distinctly distinguishable -into stem and leaf. These are the Fungi, the -Lichens, and the Algæ, or sea-weeds.</p> - -<p>2. <i>Anogens</i>, having stem and foliage, but wholly cellular. -These are the Mosses and Liverworts.</p> - -<p>3. Acrogens, which have long tubular fibres as well as -cells in their composition, and thus have the capacity of -attaining a more considerable magnitude. These are the -Ferns (<i>Filices</i>), the Mare’s-tails (<i>Equisetaceæ</i>), and the -Club-mosses (<i>Lycopodiaceæ</i>), and a curious little group -of aquatic plants called Rhizocarps (<i>Rhizocarpeæ</i>).</p> - -<p>The Phænogams are all vascular, but they differ much -in the simplicity or complexity of their flowers or seeds. -On this ground they admit of a twofold division:</p> - -<p>1. <i>Gymnosperms</i>, or those which bear naked seeds -not enclosed in fruits. They are the Pines and their -allies, and the Cycads.</p> - -<p><span class="pagenum"><a name="Page_7" id="Page_7">« 7 »</a></span></p> - -<p>2. <i>Angiosperms</i>, which produce true fruits enclosing -the seeds. In this group there are two well-marked subdivisions -differing in the structure of the seed and stem. -They are the <i>Endogens</i>, or inside growers, with seeds having -one seed-leaf only, as the grasses and the palms; and -the <i>Exogens</i>, having outside-growing woody stems, and -seeds with two seed-leaves. Most of the ordinary forest-trees -of temperate climates belong to this group.</p> - -<p>On referring to the geological table, it will be seen -that there is a certain rough correspondence between the -order of rank of plants and the order of their appearance -in time. The oldest plants that we certainly know are -Algæ, and with these there are plants apparently with -the structures of Thallophytes but the habit of trees, and -which, for want of a better name, I may call <i>Protogens</i>. -Plants akin to the Rhizocarps also appear very early. -Next in order we find forests in which gigantic Ferns and -Lycopods and Mare’s-tails predominate, and are associated -with pines. Succeeding these we have a reign of Gymnosperms, -and in the later formations we find the higher -Phænogams dominant. Thus there is an advance in -elevation and complexity along with the advance in -geological time, but connected with the remarkable fact -that in earlier times low groups attain to an elevation -unexampled in later times, when their places are occupied -with plants of higher type.</p> - -<p>It is this historical development that we have to trace -in the following pages, and it will be the most simple -and at the same time the most instructive method to -consider it in the order of time.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_8" id="Page_8">« 8 »</a></span></p> - - - - -<p class="caption2"><a name="CHAPTER_II" id="CHAPTER_II">CHAPTER II.</a></p> - -<p class="caption3">VEGETATION OF THE LAURENTIAN AND EARLY PALÆOZOIC—QUESTIONS AS TO ALGÆ.</p> - - -<p><span class="smcap">Oldest</span> of all the formations known to geologists, and -representing perhaps the earliest rocks produced after our -earth had ceased to be a molten mass, are the hard, crystalline, -and much-contorted rocks named by the late Sir -W. E. Logan Laurentian, and which are largely developed -in the northern parts of North America and Europe, and -in many other regions. So numerous and extensive, indeed, -are the exposures of these rocks, that we have good -reason to believe that they underlie all the other formations -of our continents, and are even world-wide in their -distribution. In the lower part of this great system of -rocks which, in some places at least, is thirty thousand -feet in thickness, we find no traces of the existence of -any living thing on the earth. But, in the middle portion -of the Laurentian, rocks are found which indicate -that there were already land and water, and that the waters -and possibly the land were already tenanted by living -beings. The great beds of limestone which exist in this -part of the system furnish one indication of this. In the -later geological formations the limestones are mostly organic—that -is, they consist of accumulated remains of -shells, corals, and other hard parts of marine animals, -which are composed of calcium carbonate, which the animals -obtain directly from their food, and indirectly from -the calcareous matter dissolved in the sea-water. In like -<span class="pagenum"><a name="Page_9" id="Page_9">« 9 »</a></span> -manner great beds of iron-ore exist in the Laurentian; -but in later formations the determining cause of the -accumulation of such beds is the partial deoxidation and -solution of the peroxide of iron by the agency of organic -matter. Besides this, certain forms known as <i>Eozoon -Canadense</i> have been recognised in the Laurentian limestones, -which indicate the presence at least of one of the -lower types of marine animals. Where animal life is, we -may fairly infer the existence of vegetable life as well, -since the plant is the only producer of food for the animal. -But we are not left merely to this inference. Great -quantities of carbon or charcoal in the form of the substance -known as graphite or plumbago exist in the -Laurentian. Now, in more recent formations we have -deposits of coal and bituminous matter, and we know -that these have arisen from the accumulation and slow -putrefaction of masses of vegetable matter. Further, in -places where igneous action has affected the beds, we -find that ordinary coal has been changed into anthracite -and graphite, that bituminous shales have been converted -into graphitic shales, and that cracks filled with soft -bituminous matter have ultimately become changed into -veins of graphite. When, therefore, we find in the Laurentian -thick beds of graphite and beds of limestone -charged with detached grains and crystals of this substance, -and graphitic gneisses and schists and veins of -graphite traversing the beds, we recognise the same -phenomena that are apparent in later formations containing -vegetable <i>débris</i>.</p> - -<p>The carbon thus occurring in the Laurentian is not -to be regarded as exceptional or rare, but is widely distributed -and of large amount. In Canada more especially -the deposits are very considerable.</p> - -<p>The graphite of the Laurentian of Canada occurs both -in beds and in veins, and in such a manner as to show -that its origin and deposition are contemporaneous with -<span class="pagenum"><a name="Page_10" id="Page_10">« 10 »</a></span> -those of the containing rock. Sir William Logan states<a name="FNanchor_B_2" id="FNanchor_B_2"></a><a href="#Footnote_B_2" class="fnanchor">[B]</a> -that “the deposits of plumbago generally occur in the -limestones or in their immediate vicinity, and granular -varieties of the rock often contain large crystalline plates -of plumbago. At other times this mineral is so finely -disseminated as to give a bluish-grey colour to the limestone, -and the distribution of bands thus coloured seems -to mark the stratification of the rock.” He further -states: “The plumbago is not confined to the limestones; -large crystalline scales of it are occasionally disseminated -in pyroxene rock, and sometimes in quartzite -and in feldspathic rocks, or even in magnetic oxide of -iron.” In addition to these bedded forms, there are also -true veins in which graphite occurs associated with calcite, -quartz, orthoclase, or pyroxene, and either in disseminated -scales, in detached masses, or in bands or layers -“separated from each other and from the wall-rock by -feldspar, pyroxene, and quartz.” Dr. Hunt also mentions -the occurrence of finely granular varieties, and of -that peculiarly waved and corrugated variety simulating -fossil wood, though really a mere form of laminated -structure, which also occurs at Warrensburg, New York, -and at the Marinski mine in Siberia. Many of the veins -are not true fissures, but rather constitute a network of -shrinkage cracks or segregation veins traversing in countless -numbers the containing rock, and most irregular in -their dimensions, so that they often resemble strings of -nodular masses. It is most probable that the graphite of -the veins was originally introduced as a liquid or plastic -hydrocarbon; but in whatever way introduced, the character -of the veins indicates that in the case of the greater -number of them the carbonaceous material must have -been derived from the bedded rocks traversed by these -veins, to which it bears the same relation with the veins -<span class="pagenum"><a name="Page_11" id="Page_11">« 11 »</a></span> -of bitumen found in the bituminous shales of the Carboniferous -and Silurian rocks. Nor can there be any -doubt that the graphite found in the beds has been deposited -along with the calcareous matter or muddy and -sandy sediment of which these beds were originally composed.<a name="FNanchor_C_3" id="FNanchor_C_3"></a><a href="#Footnote_C_3" class="fnanchor">[C]</a></p> - -<div class="footnote"> - -<p><a name="Footnote_B_2" id="Footnote_B_2"></a><a href="#FNanchor_B_2"><span class="label">[B]</span></a> “Geology of Canada,” 1863.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_C_3" id="Footnote_C_3"></a><a href="#FNanchor_C_3"><span class="label">[C]</span></a> Paper by the author on Laurentian Graphite, “Journal of London -Geological Society,” 1876.</p></div> - -<p>The quantity of graphite in the Lower Laurentian -series is enormous. Some years ago, in the township of -Buckingham, on the Ottawa River, I examined a band of -limestone believed to be a continuation of that described -by Sir W. E. Logan as the Green Lake limestone. It -was estimated to amount, with some thin interstratified -bands of gneiss, to a thickness of six hundred feet or -more, and was found to be filled with disseminated crystals -of graphite and veins of the mineral to such an extent -as to constitute in some places one-fourth of the whole; -and, making every allowance for the poorer portions, this -band cannot contain in all a less vertical thickness of -pure graphite than from twenty to thirty feet. In the -adjoining township of Lochaber Sir W. E. Logan notices -a band from twenty-five to thirty feet thick, reticulated -with graphite veins to such an extent as to be mined with -profit for the mineral. At another place in the same district -a bed of graphite from ten to twelve feet thick, and -yielding 20 per cent, of the pure material, is worked. -As it appears in the excavation made by the quarrymen, -it resembled a bed of coal; and a block from this bed, -about four feet thick, was a prominent object in the -Canadian department of the Colonial Exhibition of 1886. -When it is considered that graphite occurs in similar -abundance at several other horizons, in beds of limestone -which have been ascertained by Sir W. E. Logan to have -an aggregate thickness of thirty-five hundred feet, it is -<span class="pagenum"><a name="Page_12" id="Page_12">« 12 »</a></span> -scarcely an exaggeration to maintain that the quantity of -carbon in the Laurentian is equal to that in similar areas -of the Carboniferous system. It is also to be observed -that an immense area in Canada appears to be occupied -by these graphitic and <i>Eozoon</i> limestones, and that rich -graphitic deposits exist in the continuation of this system -in the State of New York, while in rocks believed to -be of this age near St. John, New Brunswick, there is a -very thick bed of graphitic limestone, and associated with -it three regular beds of graphite, having an aggregate -thickness of about five feet.<a name="FNanchor_D_4" id="FNanchor_D_4"></a><a href="#Footnote_D_4" class="fnanchor">[D]</a></p> - -<div class="footnote"> - -<p><a name="Footnote_D_4" id="Footnote_D_4"></a><a href="#FNanchor_D_4"><span class="label">[D]</span></a> Matthew in “Quarterly Journal of the Geological Society,” vol. -xxi., p. 423. “Acadian Geology,” p. 662.</p></div> - -<p>It may fairly be assumed that in the present world, -and in those geological periods with whose organic remains -we are more familiar than with those of the Laurentian, -there is no other source of unoxidized carbon in -rocks than that furnished by organic matter, and that -this has obtained its carbon in all cases, in the first instance, -from the deoxidation of carbonic acid by living -plants. No other source of carbon can, I believe, be -imagined in the Laurentian period. We may, however, -suppose either that the graphitic matter of the Laurentian -has been accumulated in beds like those of coal, or that -it has consisted of diffused bituminous matter similar to -that in more modern bituminous shales and bituminous -and oil-bearing limestones. The beds of graphite near -St. John, some of those in the gneiss at Ticonderoga in -New York, and at Lochaber and Buckingham, and elsewhere -in Canada, are so pure and regular that one might -fairly compare them with the graphitic coal of Rhode -Island. These instances, however, are exceptional, and -the greater part of the disseminated and vein graphite -might rather be likened in its mode of occurrence to the -bituminous matter in bituminous shales and limestones.</p> - -<p><span class="pagenum"><a name="Page_13" id="Page_13">« 13 »</a></span></p> - -<p>We may compare the disseminated graphite to that -which we find in those districts of Canada in which Silurian -and Devonian bituminous shales and limestones have -been metamorphosed and converted into graphitic rocks -not very dissimilar to those in the less altered portions of -the Laurentian.<a name="FNanchor_E_5" id="FNanchor_E_5"></a><a href="#Footnote_E_5" class="fnanchor">[E]</a> In like manner it seems probable that -the numerous reticulating veins of graphite may have -been formed by the segregation of bituminous matter into -fissures and planes of least resistance, in the manner in -which such veins occur in modern bituminous limestones -and shales. Such bituminous veins occur in the Lower -Carboniferous limestone and shale of Dorchester and -Hillsborough, New Brunswick, with an arrangement very -similar to that of the veins of graphite; and in the Quebec -rocks of Point Levi, veins attaining to a thickness of -more than a foot, are filled with a coaly matter having a -transverse columnar structure, and regarded by Logan -and Hunt as an altered bitumen. These palæozoic analogies -would lead us to infer that the larger part of the -Laurentian graphite falls under the second class of deposits -above mentioned, and that, if of vegetable origin, -the organic matter must have been thoroughly disintegrated -and bituminised before it was changed into -graphite. This would also give a probability that the -vegetation implied was aquatic, or at least that it was -accumulated under water.</p> - -<div class="footnote"> - -<p><a name="Footnote_E_5" id="Footnote_E_5"></a><a href="#FNanchor_E_5"><span class="label">[E]</span></a> Granby, Melbourne, Owl’s Head, &c., “Geology of Canada,” 1863, -p. 599.</p></div> - -<p>Dr. Hunt has, however, observed an indication of terrestrial -vegetation, or at least of subaërial decay, in the -great beds of Laurentian iron-ore. These, if formed in -the same manner as more modern deposits of this kind, -would imply the reducing and solvent action of substances -produced in the decay of plants. In this case -such great ore-beds as that of Hull, on the Ottawa, seventy -<span class="pagenum"><a name="Page_14" id="Page_14">« 14 »</a></span> -feet thick, or that near Newborough, two hundred feet -thick,<a name="FNanchor_F_6" id="FNanchor_F_6"></a><a href="#Footnote_F_6" class="fnanchor">[F]</a> must represent a corresponding quantity of vegetable -matter which has totally disappeared. It may be -added that similar demands on vegetable matter as a -deoxidising agent are made by the beds and veins of -metallic sulphides of the Laurentian, though some of -the latter are no doubt of later date than the Laurentian -rocks themselves.</p> - -<div class="footnote"> - -<p><a name="Footnote_F_6" id="Footnote_F_6"></a><a href="#FNanchor_F_6"><span class="label">[F]</span></a> “Geology of Canada,” 1863.</p></div> - -<p>It would be very desirable to confirm such conclusions -as those above deduced by the evidence of actual microscopic -structure. It is to be observed, however, that -when, in more modern sediments, Algæ have been converted -into bituminous matter, we cannot ordinarily obtain -any structural evidence of the origin of such bitumen, -and in the graphitic slates and limestones derived from -the metamorphosis of such rocks no organic structure -remains. It is true that, in certain bituminous shales -and limestones of the Silurian system, shreds of organic -tissue can sometimes be detected, and in some cases, as -in the Lower Silurian limestone of the La Cloche Mountains -in Canada, the pores of brachiopodous shells and -the cells of corals have been penetrated by black bituminous -matter, forming what may be regarded as natural -injections, sometimes of much beauty. In correspondence -with this, while in some Laurentian graphitic rocks, as, -for instance, in the compact graphite of Clarendon, the -carbon presents a curdled appearance due to segregation, -and precisely similar to that of the bitumen in more -modern bituminous rocks, I can detect in the graphitic -limestones occasional fibrous structures which may be -remains of plants, and in some specimens vermicular -lines, which I believe to be tubes of Eozoon penetrated -by matter once bituminous, but now in the state of -graphite.</p> - -<p><span class="pagenum"><a name="Page_15" id="Page_15">« 15 »</a></span></p> - -<p>When palæozoic land-plants have been converted into -graphite, they sometimes perfectly retain their structure. -Mineral charcoal, with structure, exists in the graphitic -coal of Rhode Island. The fronds of ferns, with their -minutest veins perfect, are preserved in the Devonian -shales of St. John, in the state of graphite; and in the -same formation there are trunks of Conifers (<i>Dadoxylon -Ouangondianum</i>) in which the material of the cell-walls -has been converted into graphite, while their cavities -have been filled with calcareous spar and quartz, the -finest structures being preserved quite as well as in comparatively -unaltered specimens from the coal-formation.<a name="FNanchor_G_7" id="FNanchor_G_7"></a><a href="#Footnote_G_7" class="fnanchor">[G]</a> -No structures so perfect have as yet been detected in the -Laurentian, though in the largest of the three graphitic -beds at St. John there appear to be fibrous structures, -which I believe may indicate the existence of land-plants. -This graphite is composed of contorted and slickensided -laminæ, much like those of some bituminous shales and -coarse coals; and in these are occasional small pyritous -masses which show hollow carbonaceous fibres, in some -cases presenting obscure indications of lateral pores. I -regard these indications, however, as uncertain; and it is -not as yet fully ascertained that these beds at St. John -are on the same geological horizon with the Lower Laurentian -of Canada, though they certainly underlie the -Primordial series of the Acadian group, and are separated -from it by beds having the character of the Huronian.</p> - -<div class="footnote"> - -<p><a name="Footnote_G_7" id="Footnote_G_7"></a><a href="#FNanchor_G_7"><span class="label">[G]</span></a> “Acadian Geology,” p. 535. In calcined specimens the structures -remain in the graphite after decalcification by an acid.</p></div> - -<p>There is thus no absolute impossibility that distinct -organic tissues may be found in the Laurentian graphite, -if formed from land-plants, more especially if any plants -existed at that time having true woody or vascular tissues; -but it cannot with certainty be affirmed that such tissues -<span class="pagenum"><a name="Page_16" id="Page_16">« 16 »</a></span> -have been found. It is possible, however, that in the -Laurentian period the vegetation of the land may have -consisted wholly of cellular plants, as, for example, -mosses and lichens; and if so, there would be comparatively -little hope of the distinct preservation of their -forms or tissues, or of our being able to distinguish the -remains of land-plants from those of Algæ.</p> - -<p>We may sum up these facts and considerations in the -following statements: First, that somewhat obscure -traces of organic structure can be detected in the Laurentian -graphite; secondly, that the general arrangement -and microscopic structure of the substance corresponds -with that of the carbonaceous and bituminous matters in -marine formations of more modern date; thirdly, that if -the Laurentian graphite has been derived from vegetable -matter, it has only undergone a metamorphosis similar in -kind to that which organic matter in metamorphosed -sediments of later age has experienced; fourthly, that the -association of the graphitic matter with organic limestone, -beds of iron-ore, and metallic sulphides greatly -strengthens the probability of its vegetable origin; fifthly, -that when we consider the immense thickness and extent -of the Eozoonal and graphitic limestones and iron-ore -deposits of the Laurentian, if we admit the organic origin -of the limestone and graphite, we must be prepared to -believe that the life of that early period, though it may -have existed under low forms, was most copiously developed, -and that it equalled, perhaps surpassed, in its results, -in the way of geological accumulation, that of any -subsequent period.</p> - -<p>Many years ago, at the meeting of the American Association -in Albany, the writer was carrying into the -room of the Geological Section a mass of fossil wood from -the Devonian of Gaspé, when he met the late Professor -Agassiz, and remarked that the specimen was the remains -of a Devonian tree contemporaneous with his -<span class="pagenum"><a name="Page_17" id="Page_17">« 17 »</a></span> -fishes of that age. “How I wish I could sit under its -shade!” was the smiling reply of the great zoölogist; and -when we think of the great accumulations of Laurentian -carbon, and that we are entirely ignorant of the forms -and structures of the vegetation which produced it, we -can scarcely suppress a feeling of disappointment. Some -things, however, we can safely infer from the facts that -are known, and these it may be well to mention.</p> - -<p>The climate and atmosphere of the Laurentian may -have been well adapted for the sustenance of vegetable -life. We can scarcely doubt that the internal heat of the -earth still warmed the waters of the sea, and these warm -waters must have diffused great quantities of mists and -vapours over the land, giving a moist and equable if not a -very clear atmosphere. The vast quantities of carbon dioxide -afterwards sealed up in limestones and carbonaceous -beds must also have still floated in the atmosphere and -must have supplied abundance of the carbon, which constitutes -the largest ingredient in vegetable tissues. Under -these circumstances the whole world must have resembled -a damp, warm greenhouse, and plants loving such an atmosphere -could have grown luxuriantly. In these circumstances -the lower forms of aquatic vegetation and -those that love damp, warm air and wet soil would have -been at home.</p> - -<p>If we ask more particularly what kinds of plants -might be expected to be introduced in such circumstances, -we may obtain some information from the vegetation of -the succeeding Palæozoic age, when such conditions still -continued to a modified extent. In this period the club-mosses, -ferns, and mare’s-tails engrossed the world and -grew to sizes and attained degrees of complexity of structure -not known in modern times. In the previous Laurentian -age something similar may have happened to -Algæ, to Fungi, to Lichens, to Liverworts, and Mosses. -The Algæ may have attained to gigantic dimensions, and -<span class="pagenum"><a name="Page_18" id="Page_18">« 18 »</a></span> -may have even ascended out of the water in some of their -forms. These comparatively simple cellular and tubular -structures, now degraded to the humble position of flat -lichens or soft or corky fungi, or slender cellular mosses, -may have been so strengthened and modified as to constitute -forest-trees. This would be quite in harmony with -what is observed in the development of other plants in -primitive geological times; and a little later in this history -we shall see that there is evidence in the flora of the -Silurian of a survival of such forms.</p> - -<p>It may be that no geologist or botanist will ever be -able to realise these dreams of the past. But, on the -other hand, it is quite possible that some fortunate chance -may have somewhere preserved specimens of Laurentian -plants showing their structure.</p> - -<p>In any case we have here presented to us the strange -and startling fact that the remarkable arrangement of -protoplasmic matter and chlorophyll, which enables the -vegetable cell to perform, with the aid of solar light, the -miracle of decomposing carbon dioxide and water, and -forming with them woody and corky tissues, had already -been introduced upon the earth. It has been well said -that no amount of study of inorganic nature would ever -have enabled any one to anticipate the possibility of the -construction of an apparatus having the chemical powers -of the living vegetable cell. Yet this most marvellous -structure seems to have been introduced in the full plenitude -of its powers in the Laurentian age.</p> - -<p>Whether this early Laurentian vegetation was the -means of sustaining any animal life other than marine -Protozoa, we do not know. It may have existed for its -own sake alone, or merely as a purifier of the atmosphere, -in preparation for the future introduction of land-animals. -The fact that there have existed, even in modern -times, oceanic islands rich in vegetation, yet untenanted -by the higher forms of animal life, prepares us to believe -<span class="pagenum"><a name="Page_19" id="Page_19">« 19 »</a></span> -that such conditions may have been general or universal -in the primeval times we are here considering.</p> - -<p>If we ask to what extent the carbon extracted from -the atmosphere and stored up in the earth has been, -or is likely to be, useful to man, the answer must be -that it is not in a state to enable it to be used as mineral -fuel. It has, however, important uses in the arts, -though at present the supply seems rather in excess of -the demand, and it may well be that there are uses of -graphite still undiscovered, and to which it will yet be -applied.</p> - -<p>Finally, it is deserving of notice that, if Laurentian -graphite indicates vegetable life, it indicates this in vast -profusion. That incalculable quantities of vegetable -matter have been oxidised and have disappeared we may -believe on the evidence of the vast beds of iron-ore; and, -in regard to that preserved as graphite, it is certain that -every inch of that mineral must indicate many feet of -crude vegetable matter.</p> - -<p>It is remarkable that, in ascending from the Laurentian, -we do not at first appear to advance in evidences -of plant-life. The Huronian age, which succeeded the -Laurentian, seems to have been a disturbed and unquiet -time, and, except in certain bands of iron-ore and some -dark slates coloured with carbonaceous matter, we find in -it no evidence of vegetation. In the Cambrian a great -subsidence of our continents began, which went on, -though with local intermissions and reversals, all through -the Siluro-Cambrian or Ordovician time. These times -were, for this reason, remarkable for the great abundance -and increase of marine animals rather than of land-plants. -Still, there are some traces of land vegetation, and we may -sketch first the facts of this kind which are known, and -then advert to some points relating to the earlier Algæ, -or sea-weeds.</p> - -<p>An eminent Swedish geologist, Linnarsson, has described, -<span class="pagenum"><a name="Page_20" id="Page_20">« 20 »</a></span> -under the name of <i>Eophyton</i>, certain impressions -on old Cambrian rocks in Sweden, and which certainly -present very plant-like forms. They want, however, any -trace of carbonaceous matter, and seem rather to be -grooves or marks cut in clay by the limbs or tails of some -aquatic animal, and afterwards filled up and preserved by -succeeding deposits. After examining large series of -these specimens from Sweden, and from rocks of similar -age in Canada, I confess that I have no faith in their -vegetable nature.</p> - -<p>The oldest plants known to me, and likely to have -been of higher grade than Algæ, are specimens kindly -presented to me by Dr. Alleyne Nicholson, of Aberdeen, -and which he had named <i>Buthotrephis Harknessii</i><a name="FNanchor_H_8" id="FNanchor_H_8"></a><a href="#Footnote_H_8" class="fnanchor">[H]</a> and -<i>B. radiata</i>. They are from the Skiddaw rocks of Cumberland. -On examining these specimens, and others -subsequently collected in the same locality by Dr. Gr. M. -Dawson, while convinced by their form and carbonaceous -character that they are really plants, I am inclined to refer -them not to Algæ, but probably to Rhizocarps. They -consist of slender branching stems, with whorls of elongate -and pointed leaves, resembling the genus <i>Annularia</i> of -the coal formation. I am inclined to believe that both -of Nicholson’s species are parts of one plant, and for -this I have proposed the generic name <i>Protannularia</i> -(<a href="#fig1">Fig. 1</a>). Somewhat higher in the Siluro-Cambrian, in -the Cincinnati group of America, Lesquereux has found -some minute radiated leaves, referred by him to the genus -<i>Sphenophyllum</i>,<a name="FNanchor_I_9" id="FNanchor_I_9"></a><a href="#Footnote_I_9" class="fnanchor">[I]</a> which is also allied to Rhizocarps. Still -more remarkable is the discovery in the same beds of a -stem with rhombic areoles or leaf-bases, to which the -name <i>Protostigma</i> has been given.<a name="FNanchor_J_10" id="FNanchor_J_10"></a><a href="#Footnote_J_10" class="fnanchor">[J]</a> If a plant, this may -<span class="pagenum"><a name="Page_21" id="Page_21">« 21 »</a></span> -have been allied to the club-mosses. This seems to be -all that we at present know of land-vegetation in the -Siluro-Cambrian. So far as the remains go, they indicate -the presence of the -families of Rhizocarps -and of Lycopods.</p> - -<div class="footnote"> - -<p><a name="Footnote_H_8" id="Footnote_H_8"></a><a href="#FNanchor_H_8"><span class="label">[H]</span></a> “Geological Magazine,” 1869.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_I_9" id="Footnote_I_9"></a><a href="#FNanchor_I_9"><span class="label">[I]</span></a> <a href="#fig20">See figure</a> in next chapter.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_J_10" id="Footnote_J_10"></a><a href="#FNanchor_J_10"><span class="label">[J]</span></a> <i>Protostigma sigillarioides</i>, Lesquereux.</p></div> - -<div class="fig_right" style="width: 288px;"> -<a id="fig1" name="fig1"></a> -<img src="images/fig1.png" width="288" height="404" alt="" /> -<div class="fig_caption">Fig. 1.—<i>Protannularia Harknessii</i> (Nicholson), -a probable Rhizocarp of the Ordovician -period.</div> -</div> - -<p>If we ascend -into the Upper Silurian, -or Silurian -proper, the evidences -of land vegetation -somewhat -increase. In 1859 I -described, in “The -Journal of the Geological -Society” of -London, a remarkable -tree from the -Lower Erian of -Gaspé, under the -name <i>Prototaxites</i>, -but for which I -now prefer the -name <i>Nematophyton</i>. -When in London, -in 1870, I obtained permission to examine certain -specimens of spore-cases or seeds from the Upper -Ludlow (Silurian) formation of England, and which -had been described by Sir Joseph Hooker under the -name <i>Pachytheca</i>. In the same slabs with these I -found fragments of fossil wood identical with those -of the Gaspé plant. Still later I recognised similar -fragments associated also with <i>Pachytheca</i> in the Silurian -of Cape Bon Ami, New Brunswick. Lastly, Dr. -Hicks has discovered similar wood, and also similar -<span class="pagenum"><a name="Page_22" id="Page_22">« 22 »</a></span> -fruits, in the Denbighshire grits, at the base of the Silurian.<a name="FNanchor_K_11" id="FNanchor_K_11"></a><a href="#Footnote_K_11" class="fnanchor">[K]</a></p> - -<div class="footnote"> - -<p><a name="Footnote_K_11" id="Footnote_K_11"></a><a href="#FNanchor_K_11"><span class="label">[K]</span></a> “Journal of the Geological Society,” August, 1881.</p></div> - -<p><span class="pagenum"><a name="Page_23" id="Page_23">« 23 »</a></span></p> - -<div class="fig_right" style="width: 354px; clear: both;"> -<a id="fig2" name="fig2"></a> -<img src="images/fig2.png" width="354" height="315" alt="" /> -<div class="fig_caption">Fig. 2.—<i>Nematophyton Logani</i> (magnified). Vertical section.</div> -</div> - -<div class="fig_right" style="width: 370px;"> -<a id="fig3" name="fig3"></a> -<img src="images/fig3.png" width="370" height="202" alt="" /> -<div class="fig_caption">Fig. 3.—<i>Nematophyton Logani</i> (magnified). Horizontal section, showing -part of one of the radial spaces, with tubes passing into it.</div> -</div> - -<div class="fig_right" style="width: 373px;"> -<a id="fig4" name="fig4"></a> -<img src="images/fig4.png" width="373" height="453" alt="" /> -<div class="fig_caption">Fig. 4.—<i>Nematophyton Logani</i> (magnified). Restoration.<a name="FNanchor_L_12" id="FNanchor_L_12"></a><a href="#Footnote_L_12" class="fnanchor">[L]</a></div> -</div> - -<div class="footnote"> - -<p><a name="Footnote_L_12" id="Footnote_L_12"></a><a href="#FNanchor_L_12"><span class="label">[L]</span></a> Figs. <a href="#fig2">2</a>, <a href="#fig3">3</a>, and <a href="#fig4">4</a> are drawn from nature by Prof. Penhallow, of -McGill College.</p></div> - -<p>From comparison of this singular wood, the structure -of which is represented in Figs. <a href="#fig2">2</a>, <a href="#fig3">3</a>, and <a href="#fig4">4</a>, with the <i>débris</i> -of fossil taxine woods, mineralised after long maceration -in water, I was inclined to regard <i>Prototaxites</i>, or, as I -have more recently named it, <i>Nematophyton</i>, as a primeval -gymnosperm allied to those trees which Unger had -described from the Erian of Thuringia, under the name -<i>Aporoxylon</i>.<a name="FNanchor_M_13" id="FNanchor_M_13"></a><a href="#Footnote_M_13" class="fnanchor">[M]</a> Later examples of more lax tissues from -branches or young stems, and the elaborate examinations -kindly undertaken for me by Professor Penhallow and -referred to in a note to this chapter, have induced me to -modify this view, and to hold that the tissues of these -singular trees, which seem to have existed from the beginning -<span class="pagenum"><a name="Page_24" id="Page_24">« 24 »</a></span> -of the Silurian age and to have finally disappeared -in the early Erian, are altogether distinct from -any form of vegetation hitherto known, and are possibly -survivors of that prototypal flora to which I have already -referred. They are trees of large size, with a coaly bark -and large spreading roots, having the surface of the stem -smooth or irregularly ribbed, but with a nodose or jointed -appearance. Internally, they show a tissue of long, cylindrical -tubes, traversed by a complex network of horizontal -tubes thinner walled and of smaller size. The tubes are -arranged in concentric zones, which, if annual rings, would -in some specimens indicate an age of one hundred and -fifty years. There are also radiating spaces, which I was -at first disposed to regard as true medullary rays, or which -at least indicate a radiating arrangement of the tissue. -They now seem to be spaces extending from the centre -towards the circumference of the stem, and to have contained -bundles of tubes gathered from the general tissue -and extending outward perhaps to organs or appendages -on the surface. Carruthers has suggested a resemblance -to Algæ, and has even proposed to change the name to -<i>Nematophycus</i>, or “thread-sea-weed”; but the resemblance -is by no means clear, and it would be quite as reasonable -to compare the tissue to that of some Fungi or Lichens, -or even to suppose that a plant composed of cylindrical -tubes has been penetrated by the mycelium or spawn -of a dry-rot fungus. But the tissues are too constant and -too manifestly connected with each other to justify this -last supposition. That the plant grew on land I cannot -doubt, from its mode of occurrence; that it was of durable -and resisting character is shown by its state of preservation; -and the structure of the seeds called <i>Pachytheca</i>, -with their constant association with these trees, give countenance -to the belief that they are the fruit of Nematophyton. -Of the foliage or fronds of these strange -plants we unfortunately know nothing. They seem, however, -<span class="pagenum"><a name="Page_25" id="Page_25">« 25 »</a></span> -to realise the idea of arboreal plants having structures -akin to those of thallophytes, but with seeds so -large and complex that they can scarcely be regarded as -mere spores. They should perhaps constitute a separate -class or order to which the name <i>Nematodendreæ</i> may -be given, and of which <i>Nematophyton</i> will constitute one -genus and <i>Aporoxylon</i> of Unger another.<a name="FNanchor_N_14" id="FNanchor_N_14"></a><a href="#Footnote_N_14" class="fnanchor">[N]</a></p> - -<div class="footnote"> - -<p><a name="Footnote_M_13" id="Footnote_M_13"></a><a href="#FNanchor_M_13"><span class="label">[M]</span></a> “Palæontologie des Thuringer Waldes,” 1856.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_N_14" id="Footnote_N_14"></a><a href="#FNanchor_N_14"><span class="label">[N]</span></a> See report by the author on “Erian Flora of Canada,” 1871 and -1882, for full description of these fossils.</p></div> - -<p>Another question arises as to the possible relation of -these plants to other trees known by their external forms. -The <i>Protostigma</i> of Lesquereux has already been referred -to, and Claypole has described a tree from the Clinton -group of the United States, with large ovate leaf-bases, to -which he has given the name <i>Glyptodendron</i>.<a name="FNanchor_O_15" id="FNanchor_O_15"></a><a href="#Footnote_O_15" class="fnanchor">[O]</a> If the -markings on these plants are really leaf-bases, they can -scarcely have been connected with <i>Nematophyton</i>, because -that tree shows no such surface-markings, though, as we -have seen, it had bundles of tubes passing diagonally to -the surface. These plants were more probably trees with -an axis of barred vessels and thick, cellular bark, like the -<i>Lepidodendron</i> of later periods, to be noticed in the sequel. -Dr. Hicks has also described from the same series of beds -which afforded the fragments of Nematophyton certain -carbonised dichotomous stems, which he has named <i>Berwynia</i>. -It is just possible that these plants may have -belonged to the Nematodendreæ. The thick and dense -coaly matter which they show resembles the bark of these -trees, the longitudinal striation in some of them may -represent the fibrous structure, and the lateral projections -which have been compared to leaves or leaf-bases may -correspond with the superficial eminences of <i>Nematophyton</i>, -and the spirally arranged punctures which it shows -on its surface. In this case I should be disposed to regard -<span class="pagenum"><a name="Page_26" id="Page_26">« 26 »</a></span> -the supposed stigmaria-like roots as really stems, -and the supposed rootlets as short, spine-like rudimentary -leaves. All such comparisons must, however, in the -mean time be regarded as conjectural. We seem, however, -to have here a type of tree very dissimilar to any -even of the later Palæozoic age, which existed throughout -the Silurian, and probably further back, which ceased -to exist early in the Erian age, and before the appearance -of the ordinary coniferous and lepidodendroid trees. -May it not have been a survivor of an old arboreal flora -extending back even to the Laurentian itself?</p> - -<div class="footnote"> - -<p><a name="Footnote_O_15" id="Footnote_O_15"></a><a href="#FNanchor_O_15"><span class="label">[O]</span></a> “American Journal of Science,” 1878.</p></div> - -<p>Multitudes of markings occurring on the surfaces of -the older rocks have been referred to the Algæ or sea-weeds, -and indeed this group has been a sort of refuge for -the destitute to which palæontologists have been accustomed -to refer any anomalous or inexplicable form which, -while probably organic, could not be definitely referred to -the animal kingdom. There can be no question that some -of these are truly marine plants; and that plants of this -kind occur in formations older than those in which we first -find land-plants, and that they have continued to inhabit -the sea down to the present time. It is also true that the -oldest of these Algæ closely resemble in form plants of -this kind still existing; and, since their simple cellular -structures and soft tissues are scarcely ever preserved, -their general forms are all that we can know, so that their -exact resemblance to or difference from modern types can -rarely be determined. For the same reasons it has proved -difficult clearly to distinguish them from mere inorganic -markings or the traces of animals, and the greatest divergence -of opinion has occurred in recent times on these -subjects, as any one can readily understand who consults -the voluminous and well-illustrated memoirs of Nathorst, -Williamson, Saporta, and Delgado.</p> - -<p>The author of this work has given much attention to -these remains, and has not been disposed to claim for the -<span class="pagenum"><a name="Page_27" id="Page_27">« 27 »</a></span> -vegetable kingdom so many of them as some of his contemporaries.<a name="FNanchor_P_16" id="FNanchor_P_16"></a><a href="#Footnote_P_16" class="fnanchor">[P]</a> -The considerations which seem most important -in making such distinctions are the following: -1. The presence or absence of carbonaceous matter. -True Algæ not infrequently present at least a thin film of -carbon representing their organic matter, and this is the -more likely to occur in their case, as organic matters -buried in marine deposits and not exposed to atmospheric -oxidation are very likely to be preserved. 2. In the -absence of organic matter, the staining of the containing -rock, the disappearance or deoxidation of its ferruginous -colouring matter, or the presence of iron pyrite may indicate -the removal of organic matter by decay. 3. When -organic matter and indications of it are altogether absent, -and form alone remains, we have to distinguish from Algæ, -trails and burrows similar to those of aquatic animals, -casts of shrinkage-cracks, water-marks, and rill-marks -widely diffused over the surfaces of beds. 4. Markings -depressed on the upper surfaces of beds, and filled with -the material of the succeeding layer, are usually mere impressions. -The cases of possible exceptions to this are -very rare. On the contrary, there are not infrequently -forms in relief on the surfaces of rocks which are not -Algæ, but may be shallow burrows arched upward on top, -or castings of worms thrown up upon the surface. Sometimes, -however, they may have been left by denudation -of the surrounding material, just as footprints on dry -snow remain in relief after the surrounding loose material -has been drifted away by the wind; the portion consolidated -by pressure being better able to resist the denuding -agency.</p> - -<div class="footnote"> - -<p><a name="Footnote_P_16" id="Footnote_P_16"></a><a href="#FNanchor_P_16"><span class="label">[P]</span></a> “Impressions and Footprints of Aquatic Animals,” “American -Journal of Science,” 1873.</p> - -<p><span class="pagenum"><a name="Page_28" id="Page_28">« 28 »</a></span></p></div> - -<div class="fig_left" style="width: 220px;"> -<a id="fig5" name="fig5"></a> -<img src="images/fig5.png" width="220" height="192" alt="" /> -<div class="fig_caption">Fig. 5.—Trail of a modern king-crab, -to illustrate imitations of -plants sometimes named <i>Bilobites</i>.</div> -</div> - -<div class="fig_right" style="width: 428px;"> -<a id="fig6" name="fig6"></a> -<img src="images/fig6.png" width="428" height="306" alt="" /> -<div class="fig_caption">Fig. 6.—Trail of Carboniferous crustacean (<i>Rusichnites Acadicus</i>), Nova -Scotia, to illustrate supposed Algæ.</div> -</div> - -<p style="clear: both;">The footprints from the Potsdam sandstone in Canada, -for which the name <i>Protichnites</i> was proposed by -Owen, and which were by him referred to crustaceans -probably resembling <i>Limulus</i>, were shown by the writer, -in 1862,<a name="FNanchor_Q_17" id="FNanchor_Q_17"></a><a href="#Footnote_Q_17" class="fnanchor">[Q]</a> to correspond -precisely with those of the -American Limulus (<i>Polyphemus -Occidentalis</i>) (<a href="#fig5">Fig. 5</a>). -I proved by experiment -with the modern animal -that the recurring series -of groups of markings -were produced by the toes -of the large posterior thoracic -feet, the irregular -scratches seen in <i>Protichnites -lineatus</i> by the ordinary -feet, and the central furrow by the tail. It was also -shown that when the Limulus uses its swimming-feet it -produces impressions of the character of those named -<span class="pagenum"><a name="Page_29" id="Page_29">« 29 »</a></span> -<i>Climactichnites</i>, from the same beds which afford <i>Protichnites</i>. -The principal difference between <i>Protichnites</i> -and their modern representatives is that the latter have -two lateral furrows -produced by the -sides of the carapace, -which are -wanting in the former.</p> - -<div class="footnote"> - -<p><a name="Footnote_Q_17" id="Footnote_Q_17"></a><a href="#FNanchor_Q_17"><span class="label">[Q]</span></a> “Canadian Naturalist,” vol. vii.</p></div> - -<p>I subsequently -applied the same -explanation to several -other ancient -forms now known -under the general -name <i>Bilobites</i> -(Figs. <a href="#fig6">6</a> and <a href="#fig7">7</a>).<a name="FNanchor_R_18" id="FNanchor_R_18"></a><a href="#Footnote_R_18" class="fnanchor">[R]</a></p> - -<div class="footnote"> - -<p><a name="Footnote_R_18" id="Footnote_R_18"></a><a href="#FNanchor_R_18"><span class="label">[R]</span></a> The name Bilobites was originally proposed by De Kay for a bivalve -shell (Conocardium). Its application to supposed Algæ was an error, -but this is of the less consequence, as these are not true plants but only -animal trails.</p></div> - -<div class="fig_right" style="width: 295px;"> -<a id="fig7" name="fig7"></a> -<img src="images/fig7.png" width="295" height="377" alt="" /> -<div class="fig_caption">Fig. 7.—<i>Rusophycus</i> (<i>Rusichnites</i>) <i>Grenvillensis</i>, -an animal burrow of the Siluro-Cambrian, -probably of a crustacean, <i>a</i>, Track -connected with it.</div> -</div> - -<p>The tuberculated -impressions -known as <i>Phymatoderma</i> -and <i>Caulerpites</i> -may, as Zeiller -has shown, be -made by the burrowing -of the mole-cricket, -and fine examples occurring in the Clinton formation -of Canada are probably the work of Crustacea. It is -probable, however, that some of the later forms referred -to these genera are really Algæ related to <i>Caulerpa</i>, or -even branches of Conifers of the genus <i>Brachyphyllum</i>.</p> - -<p><span class="pagenum"><a name="Page_30" id="Page_30">« 30 »</a></span></p> - -<p><i>Nereites</i> and <i>Planulites</i> are tracks and burrows of -worms, with or without marks of setæ, and some of the -markings referred to <i>Palæochorda</i>, <i>Palæophycus</i>, and -<i>Scolithus</i> have their places here. Many examples highly -illustrative of the manner of formation of the impressions -are afforded by Canadian rocks (<a href="#fig8">Fig. 8</a>).</p> - -<p>Branching forms referred to <i>Licrophycus</i> of Billings, -and some of those referred to <i>Buthotrephis</i>, Hall, as well -as radiating markings -referable to <i>Scotolithus</i>, -<i>Gyrophyllites</i>, and <i>Asterophycus</i>, -are explained -by the branching -burrows of worms -illustrated by Nathorst -and the author. <i>Astropolithon</i>, -a singular -radiating marking of -the Canadian Cambrian,<a name="FNanchor_S_19" id="FNanchor_S_19"></a><a href="#Footnote_S_19" class="fnanchor">[S]</a> -seems to be something -organic, but of -what nature is uncertain -(<a href="#fig9">Fig. 9</a>).</p> - -<div class="footnote"> - -<p><a name="Footnote_S_19" id="Footnote_S_19"></a><a href="#FNanchor_S_19"><span class="label">[S]</span></a> Supplement to “Acadian Geology.”</p></div> - -<div class="fig_left" style="width: 259px;"> -<a id="fig8" name="fig8"></a> -<img src="images/fig8.png" width="259" height="326" alt="" /> -<div class="fig_caption">Fig. 8.—<i>Palæophycus Beverlyensis</i> (Billings), -a supposed Cambrian Fucoid, -but probably an animal trail.</div> -</div> - -<p><i>Rhabdichnites</i> and -<i>Eophyton</i> belong to impressions -explicable by -the trails of drifting -sea-weeds, the tail-markings of Crustacea, and the ruts -ploughed by bivalve mollusks, and occurring in the Silurian, -Erian, and Carboniferous rocks.<a name="FNanchor_T_20" id="FNanchor_T_20"></a><a href="#Footnote_T_20" class="fnanchor">[T]</a> Among these are -the singular bilobate forms described as <i>Rusophycus</i> by -Hall, and which are probably burrows or resting-places -of crustaceans. The tracks of such animals, when walking, -are the jointed impressions known as <i>Arthrophycus</i> -and <i>Crusiana</i>. I have shown by the mode of occurrence -<span class="pagenum"><a name="Page_31" id="Page_31">« 31 »</a></span> -of these, and Nathorst has confirmed this conclusion by -elaborate experiments on living animals, that these forms -are really trails impressed on soft -sediments by animals and mostly -by crustaceans.</p> - -<div class="footnote"> - -<p><a name="Footnote_T_20" id="Footnote_T_20"></a><a href="#FNanchor_T_20"><span class="label">[T]</span></a> “Canadian Naturalist,” 1864.</p></div> - -<p>I agree with Dr. Williamson<a name="FNanchor_U_21" id="FNanchor_U_21"></a><a href="#Footnote_U_21" class="fnanchor">[U]</a> -in believing that all or nearly all -the forms referred to Crossochorda -of Schimper are really animal impressions -allied to Nereites, and due -either to worms or, as Nathorst has -shown to be possible, to small crustaceans. -Many impressions of this -kind occur in the Silurian beds of -the Clinton series in Canada and -New York, and are undoubtedly -mere markings.</p> - -<div class="footnote"> - -<p><a name="Footnote_U_21" id="Footnote_U_21"></a><a href="#FNanchor_U_21"><span class="label">[U]</span></a> “Tracks from Yoredale Rocks,” “Manchester Literary and Philosophical -Society,” 1885.</p></div> - -<div class="fig_right" style="width: 150px;"> -<a id="fig9" name="fig9"></a> -<img src="images/fig9.png" width="150" height="432" alt="" /> -<div class="fig_caption">Fig. 9.—<i>Astropolithon -Hindii</i>, an organism -of the Lower Cambrian -of Nova Scotia, -possibly vegetable.</div> -</div> - -<p>It is worthy of note that these -markings strikingly resemble the so-called -<i>Eophyton</i>, described by Torell -from the Primordial of Sweden, and -by Billings from that of Newfoundland; -and which also occur abundantly -in the Primordial of New -Brunswick. After examining a series -of these markings from Sweden -shown to me by Mr. Carruthers in -London, and also specimens from Newfoundland and -a large number <i>in situ</i> at St. John, I am convinced -that they cannot be plants, but must be markings of -the nature of <i>Rhabdichnites</i>. This conclusion is based -on the absence of carbonaceous matter, the intimate -union of the markings with the surface of the stone, -<span class="pagenum"><a name="Page_32" id="Page_32">« 32 »</a></span> -their indefinite forms, their want of nodes or appendages, -and their markings being always of such a nature -as could be produced by scratches of a sharp -instrument. Since, however, fishes are yet unknown in -beds of this age, they may possibly be referred to the -feet or spinous tails of swimming crustaceans. Salter -has already suggested this origin for some scratches of -somewhat different form found in the Primordial of -Great Britain. He supposed them to have been the -work of species of <i>Hymenocaris</i>. These marks may, -however, indicate the existence of some free-swimming -animals of the Primordial seas as yet unknown -to us.</p> - -<p>Three other suggestions merit consideration in this -connection. One is that Algæ and also land-plants, drifting -with tides or currents, often make the most remarkable -and fantastic trails. A marking of this kind has -been observed by Dr. G. M. Dawson to be produced by -a drifted Laminaria, and in complexity it resembled the -extraordinary <i>Ænigmichnus multiformis</i> of Hitchcock -from the Connecticut sandstones. Much more simple -markings of this kind would suffice to give species of -<i>Eophyton</i>. Another is furnished by a fact stated to the -author by Prof. Morse, namely, that Lingulæ, when dislodged -from their burrows, trail themselves over the -bottom like worms, by means of their cirri. Colonies of -these creatures, so abundant in the Primordial, may, -when obliged to remove, have covered the surfaces of -beds of mud with vermicular markings. The third is -that the Rhabdichnite-markings resemble some of the -grooves in Silurian rocks which have been referred to -trails of Gasteropods, as, for instance, those from the -Clinton group, described by Hall.</p> - -<p>Another kind of markings not even organic, but altogether -depending on physical causes, are the beautiful -branching rill-marks produced by the oozing of water -<span class="pagenum"><a name="Page_33" id="Page_33">« 33 »</a></span> -out of mud and sand-banks left by the tide, and which -sometimes cover great surfaces with the most elaborate -tracery, on the modern tidal shores as well as in some of -the most ancient rocks. <i>Dendrophycus</i><a name="FNanchor_V_22" id="FNanchor_V_22"></a><a href="#Footnote_V_22" class="fnanchor">[V]</a> of Lesquereux -seems to be an example of rill-mark, as well as <i>Aristophycus</i>, -<i>Clœphycus</i>, and <i>Zygopliycus</i>, of Miller and Dyer, -from the Lower Silurian.</p> - -<div class="footnote"> - -<p><a name="Footnote_V_22" id="Footnote_V_22"></a><a href="#FNanchor_V_22"><span class="label">[V]</span></a> “Coal Flora of Pennsylvania,” vol. iii., Plate 88.</p></div> - -<p>Rill-marks occur in very old rocks,<a name="FNanchor_W_23" id="FNanchor_W_23"></a><a href="#Footnote_W_23" class="fnanchor">[W]</a> but are perhaps -most beautifully preserved in the Carboniferous shales -and argillaceous sandstones, and -even more elaborately on the modern -mud-banks of the Bay of -Fundy.<a name="FNanchor_X_24" id="FNanchor_X_24"></a><a href="#Footnote_X_24" class="fnanchor">[X]</a> Some of these simulate -ferns and fronds of Laminariæ, -and others resemble roots, fucoids -allied to <i>Buthotrephis</i>, or the radiating -worm-burrows already referred -to (<a href="#fig10">Fig. 10</a>).</p> - -<div class="footnote"> - -<p><a name="Footnote_W_23" id="Footnote_W_23"></a><a href="#FNanchor_W_23"><span class="label">[W]</span></a> “Journal of the Geological Society,” vol. xii., p. 251.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_X_24" id="Footnote_X_24"></a><a href="#FNanchor_X_24"><span class="label">[X]</span></a> “Acadian Geology,” 2d ed., p. 26.</p></div> - -<div class="fig_right" style="width: 163px;"> -<a id="fig10" name="fig10"></a> -<img src="images/fig10.png" width="163" height="360" alt="" /> -<div class="fig_caption">Fig. 10.—Carboniferous rill-mark -(Nova Scotia), reduced, -to illustrate pretended -Algæ.</div> -</div> - -<p><i>Shrinkage-cracks</i> are also abundant -in some of the Carboniferous -beds, and are sometimes accompanied -with impressions of rain-drops. -When finely reticulated -they might be mistaken for the -venation of leaves, and, when -complicated with little rill-marks -tributary to their sides, they precisely -resemble the <i>Dictyolites</i> of -Hall from the Medina sandstone -(<a href="#fig11">Fig. 11</a>).</p> - -<p><span class="pagenum"><a name="Page_34" id="Page_34">« 34 »</a></span></p> - -<div class="fig_left" style="width: 295px;"> -<a id="fig11" name="fig11"></a> -<img src="images/fig11.png" width="295" height="318" alt="" /> -<div class="fig_caption">Fig. 11.—Cast of shrinkage cracks (Carboniferous, -Nova Scotia), illustrating pretended Algæ.</div> -</div> - -<p>An entirely different kind of shrinkage-crack is that -which occurs in certain carbonised and flattened plants, -and which sometimes communicates to them a marvellous -resemblance to the netted under surface of an exogenous -leaf. Flattened stems of plants and layers of cortical -matter, when carbonised, shrink in such a manner as to -produce minute reticulated cracks. These become filled -with mineral matter before the coaly substance has been -completely consolidated. A further compression occurs, -causing the coaly substance to collapse, leaving the little -veins of harder mineral matter projecting. These impress -their form upon the clay or shale above and below, -and thus when the mass is broken open we have a carbonaceous -film or thin layer covered with a network of -raised lines, and -corresponding minute -depressed -lines on the shale -in contact with it. -The reticulations -are generally irregular, -but sometimes -they very -closely resemble -the veins of a reticulately -veined -leaf. One of the -most curious specimens -in my possession -was collected -by Mr. Elder -in the Lower Carboniferous -of Horton Bluff. The little veins which form -the projecting network are in this case white calcite; but -at the surface their projecting edges are blackened with -a carbonaceous film.</p> - -<p><i>Slickensided bodies</i>, resembling the fossil fruits described -by Geinitz as <i>Gulielmites</i>, and the objects believed -<span class="pagenum"><a name="Page_35" id="Page_35">« 35 »</a></span> -by Fleming and Carruthers<a name="FNanchor_Y_25" id="FNanchor_Y_25"></a><a href="#Footnote_Y_25" class="fnanchor">[Y]</a> to be casts of cavities filled -with fluid, abound in the shales of the Carboniferous and -Devonian. They are, no doubt, in most cases the results -of the pressure and consolidation of the clay around small -solid bodies, whether organic, fragmentary, or concretionary. -They are, in short, local slickensides precisely -similar to those found so plentifully in the coal under-clays, -and which, as I have elsewhere<a name="FNanchor_Z_26" id="FNanchor_Z_26"></a><a href="#Footnote_Z_26" class="fnanchor">[Z]</a> shown, resulted -from the internal giving way and slipping of the mass as -the roots of Stigmaria decayed within it. Most collectors -of fossil plants in the older formations must, I presume, -be familiar with appearances of this kind in connection -with small stems, petioles, fragments of wood, and carpolites. -I have in my collection petioles of ferns and -fruits of the genus Trigonocarpum partially slickensided -in this way, and which if wholly covered by this kind of -marking could scarcely have been recognised. I have -figured bodies of this kind in my report on the Devonian -and Upper Silurian plants of Canada, believing them, -owing to their carbonaceous covering, to be probably -slickensided fruits, though of uncertain nature. In every -case I think these bodies must have had a solid nucleus of -some sort, as the severe pressure implied in slickensiding -is quite incompatible with a mere “fluid-cavity,” even -supposing this to have existed.</p> - -<div class="footnote"> - -<p><a name="Footnote_Y_25" id="Footnote_Y_25"></a><a href="#FNanchor_Y_25"><span class="label">[Y]</span></a> “Journal of the Geological Society,” June, 1871.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_Z_26" id="Footnote_Z_26"></a><a href="#FNanchor_Z_26"><span class="label">[Z]</span></a> <i>Ibid.</i>, vol. x., p. 14.</p></div> - -<p>Prof. Marsh has well explained another phase of the -influence of hard bodies in producing partial slickensides, -in his paper on <i>Stylolites</i>, read before the American Association -in 1867, and the application of the combined -forces of concretionary action and slickensiding to the -production of the cone-in-cone concretions, which occur -in the coal-formation and as low as the Primordial. I -have figured a very perfect and beautiful form of this -<span class="pagenum"><a name="Page_36" id="Page_36">« 36 »</a></span> -kind from the coal-formation of Nova Scotia, which is -described in “Acadian Geology”<a name="FNanchor_AA_27" id="FNanchor_AA_27"></a><a href="#Footnote_AA_27" class="fnanchor">[AA]</a> (<a href="#fig12">Fig. 12</a>).</p> - -<p>I have referred to these facts here because they are -relatively more important in that older period, which may -be named the age of Algæ, and because their settlement -now will enable us to dispense with discussions of this -kind further on. The able memoirs of Nathorst and -Williamson should be studied by those who desire further -information.</p> - -<div class="footnote"> - -<p><a name="Footnote_AA_27" id="Footnote_AA_27"></a><a href="#FNanchor_AA_27"><span class="label">[AA]</span></a> Appendix, p. 676, edition of 1878.</p></div> - -<div class="fig_left" style="width: 274px;"> -<a id="fig12" name="fig12"></a> -<img src="images/fig12.png" width="274" height="215" alt="" /> -<div class="fig_caption">Fig. 12.—Cone-in-cone concretion (Carboniferous, -Nova Scotia), illustrating pretended Algæ.</div> -</div> - -<p>But it may be asked, “Are there no real examples of -fossil Algæ?” I believe there are many such, but the difficulty -is to distinguish -them. Confining ourselves -to the older -rocks, the following -may be noted:</p> - -<p>The genus <i>Buthotrephis</i> -of Hall, -which is characterised -as having stems, sub-cylindric -or compressed, -with numerous -branches, which -are divaricating and -sometimes leaf-like, -contains some true Algæ. Hall’s <i>B. gracilis</i>, from the -Siluro-Cambrian, is one of these. Similar plants, referred -to the same species, occur in the Clinton and Niagara -formations, and a beautiful species, collected by Col. -Grant, of Hamilton, and now in the McGill College collection, -represents a broader and more frondose type of -distinctly carbonaceous character. It may be described -as follows:</p> - -<p><i>Buthotrephis Grantii</i>, S. N. (<a href="#fig13">Fig. 13</a>).—Stems and -<span class="pagenum"><a name="Page_37" id="Page_37">« 37 »</a></span> -fronds smooth and slightly striate longitudinally, with -curved and interrupted striæ. Stem thick, bifurcating, -the divisions terminating in irregularly pinnate fronds, -apparently truncate at the extremities. The quantity -of carbonaceous -matter present -would indicate -thick, though perhaps -flattened, -stems and dense -fleshy fronds.</p> - -<div class="fig_right" style="width: 305px;"> -<a id="fig13" name="fig13"></a> -<img src="images/fig13.png" width="305" height="558" alt="" /> -<div class="fig_caption">Fig. 13.—<i>Buthotrephis Grantii</i>, a genuine Alga -from the Silurian, Canada.</div> -</div> - -<p>The species -<i>Buthotrephis subnodosa</i> -and <i>B. -flexuosa</i>, from -the Utica shale, -are also certainly -plants, though -it is possible, if -their structures -and fruit were -known, some of -these might be -referred to different -genera. All -of these plants -have either carbonaceous -matter -or produce organic -stains on the -matrix.</p> - -<p>The organism -with diverging -wedge-shaped fronds, described by Hall as <i>Sphenothallus -angustifolius</i>, is also a plant. Fine specimens, in the -collection of the Geological Survey of Canada, show distinct -<span class="pagenum"><a name="Page_38" id="Page_38">« 38 »</a></span> -evidence of the organic character of the wedge-shaped -fronds. It is from the Utica shale, and elsewhere -in the Siluro-Cambrian. It is just possible, as suggested -by Hall, that this plant may be of higher rank than the -Algæ.</p> - -<p>The genus <i>Palæophycus</i> of Hall includes a great variety -of uncertain objects, of which only a few are probably -true Algæ. I have specimens of fragments similar -to his <i>P. virgatus</i>, which show distinct carbonaceous -films, and others from the Quebec group, which seem to -be cylindrical tubes now flattened, and which have contained -spindle-shaped sporangia of large size. Tortuous -and curved flattened stems, or fronds, from the Upper -Silurian limestone of Gaspé, also show organic matter.</p> - -<p>Respecting the forms referred to <i>Licrophycus</i> by -Billings, containing stems or semi-cylindrical markings -springing from a common base, I have been in great -doubt. I have not seen any specimens containing unequivocal -organic matter, and am inclined to think that -most of them, if not the whole, are casts of worm-burrows, -with trails radiating from them.</p> - -<p>Though I have confined myself in this notice to plants, -or supposed plants, of the Lower Palæozoic, it may be -well to mention the remarkable Cauda-Galli fucoids, referred -by Hall to the genus <i>Spirophyton</i>, and which are -characteristic of the oldest Erian beds. The specimens -which I have seen from New York, from Gaspé, and -from Brazil, leave no doubt in my mind that these were -really marine plants, and that the form of a spiral frond, -assigned to them by Hall, is perfectly correct. They -must have been very abundant and very graceful plants -of the early Erian, immediately after the close of the -Silurian period.</p> - -<p>We come now to notice certain organisms referred to -Algæ, and which are either of animal origin, or are of -higher grade than the sea-weeds. We have already discussed -<span class="pagenum"><a name="Page_39" id="Page_39">« 39 »</a></span> -the questions relating to <i>Prototaxites</i>. <i>Drepanophycus</i>, -of Goeppert,<a name="FNanchor_AB_28" id="FNanchor_AB_28"></a><a href="#Footnote_AB_28" class="fnanchor">[AB]</a> I suspect, is only a badly preserved -branch or stem of the Erian land-plant known as Arthrostigma. -In like manner, <i>Haliserites Dechenianus</i>,<a name="FNanchor_AC_29" id="FNanchor_AC_29"></a><a href="#Footnote_AC_29" class="fnanchor">[AC]</a> of -Goeppert, is evidently the land-plant known as <i>Psilophyton</i>. -<i>Sphærococcites dentatus</i> and <i>S. serra</i>—the <i>Fucoides -dentatus</i> and <i>serra</i> of Brongniart, from Quebec—are -graptolites of two species quite common there.<a name="FNanchor_AD_30" id="FNanchor_AD_30"></a><a href="#Footnote_AD_30" class="fnanchor">[AD]</a> <i>Dictyophyton</i> -and <i>Uphantenia</i>, as described by Hall and the -author, are now known to be sponges. They have become -<i>Dictyospongiæ</i>. The curious and very ancient; fossils -referred by Forbes to the genus <i>Oldhamia</i> are perhaps -still subject to doubt, but are usually regarded as Zoöphytes, -though it is quite possible they may be plants. -Though I have not seen the specimens, I have no doubt -whatever that the plants, or the greater part of them, -from the Silurian of Bohemia, described by Stur as Algæ -and Characeæ,<a name="FNanchor_AE_31" id="FNanchor_AE_31"></a><a href="#Footnote_AE_31" class="fnanchor">[AE]</a> are really land-plants, some of them of -the genus <i>Psilophyton</i>. I may say in this connection -that specimens of flattened <i>Psilophyton</i> and <i>Arthrostigma</i>, -in the Upper Silurian and Erian of Gaspé, would -probably have been referred to Algæ, but for the fact that -in some of them the axis of barred vessels is preserved.</p> - -<div class="footnote"> - -<p><a name="Footnote_AB_28" id="Footnote_AB_28"></a><a href="#FNanchor_AB_28"><span class="label">[AB]</span></a> “Fossile Flora,” 1852, p. 92, Table xli.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_AC_29" id="Footnote_AC_29"></a><a href="#FNanchor_AC_29"><span class="label">[AC]</span></a> <i>Ibid.</i>, p. 88, Table ii.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_AD_30" id="Footnote_AD_30"></a><a href="#FNanchor_AD_30"><span class="label">[AD]</span></a> Brongniart, “Vegeteaux Fossiles,” Plate vi., Figs. 7 to 12.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_AE_31" id="Footnote_AE_31"></a><a href="#FNanchor_AE_31"><span class="label">[AE]</span></a> “Proceedings of the Vienna Academy,” 1881. <i>Hostinella</i>, of this -author, is almost certainly <i>Psilophyton</i>, and his <i>Barrandiana</i> seems to include -<i>Arthrostigma</i>, and perhaps leafy branches of <i>Berwynia</i>. These -curious plants should be re-examined.</p></div> - -<p>It is not surprising that great difficulties have occurred -in the determination of fossil Algæ. Enough, however, -remains certain to prove that the old Cambrian and Silurian -seas were tenanted with sea-weeds not very dissimilar -from those of the present time. It is further probable -that some of the graphitic, carbonaceous, and bituminous -<span class="pagenum"><a name="Page_40" id="Page_40">« 40 »</a></span> -shales and limestones of the Silurian owe their carbonaceous -matters to the decomposition of Algæ, though possibly -some of it may have been derived from Graptolites -and other corneous Zoöphytes. In any case, such microscopic -examinations of these shales as I have made, have -not produced any evidence of the existence of plants of -higher grade, while those of the Erian and Carboniferous -periods, similar to the naked eye, abound in such evidence. -It is also to be observed that, on the surfaces of -beds of sandstone in the Upper Cambrian, carbonaceous -<i>débris</i>, which seems to be the remains of either aquatic -or land plants, is locally not infrequent.</p> - -<div class="fig_center" style="width: 391px;"> -<a id="fig14" name="fig14"></a> -<img src="images/fig14.png" width="391" height="503" alt="" /> -<div class="fig_caption">Fig. 14.—Silurian vegetation restored. <i>Protannularia</i>, <i>Berwynia</i>, <i>Nematophyton</i>, -<i>Sphenophyllum</i>, <i>Arthrostigma</i>, <i>Psilophyton</i>.</div> -</div> - -<p><span class="pagenum"><a name="Page_41" id="Page_41">« 41 »</a></span></p> - -<p>Referring to the land vegetation of the older rocks, it -is difficult to picture its nature and appearance. We -may imagine the shallow waters filled with aquatic or amphibious -Rhizocarpean plants, vast meadows or brakes of -the delicate <i>Psilophyton</i> and the starry <i>Protannularia</i> -and some tall trees, perhaps looking like gigantic club-mosses, -or possibly with broad, flabby leaves, mostly cellular -in texture, and resembling Algæ transferred to the air. -Imagination can, however, scarcely realise this strange -and grotesque vegetation, which, though possibly copious -and luxuriant, must have been simple and monotonous in -aspect, and, though it must have produced spores and -seeds and even fruits, these were probably all of the types -seen in the modern acrogens and gymnosperms.</p> - -<p class="p0"> -“In garments green, indistinct in the twilight,<br /> -They stand like Druids of old, with voices sad and prophetic.”<br /> -</p> - -<p>Prophetic they truly were, as we shall find, of the -more varied forests of succeeding times, and they may -also help us to realise the aspect of that still older vegetation, -which is fossilised in the Laurentian graphite; -though it is not impossible that this last may have been of -higher and more varied types, and that the Cambrian and -Silurian may have been times of depression in the vegetable -world, as they certainly were in the submergence of -much of the land.</p> - -<p>These primeval woods served at least to clothe the -nakedness of the new-born land, and they may have sheltered -and nourished forms of land-life still unknown to -us, as we find as yet only a few insects and scorpions in -the Silurian. They possibly also served to abstract from -the atmosphere some portion of its superabundant carbonic -acid harmful to animal life, and they stored up -<span class="pagenum"><a name="Page_42" id="Page_42">« 42 »</a></span> -supplies of graphite, of petroleum, and of illuminating -gas, useful to man at the present day. We may write -of them and draw their forms with, the carbon which -they themselves supplied.</p> - -<hr class="tb" /> - - -<p class="caption3">NOTE TO CHAPTER II.</p> - -<p class="caption3"><span class="smcap">Examination of Prototaxites</span> (<i>Nematophyton</i>), <span class="smcap">by Prof. Penhallow, -of McGill University.</span></p> - -<p>Prof. Penhallow, having kindly consented to re-examine my -specimens, has furnished me with elaborate notes of his facts and -conclusions, of which the following is a summary, but which it is -hoped will be published in full:</p> - -<p>"1. <i>Concentric Layers.</i>—The inner face of each of these is composed -of relatively large tubes, having diameters from 13·6 to 34·6 -micro-millimetres. The outer face has tubes ranging from 13·8 to -27·6 mm. The average diameter in the lower surface approaches to 34, -that in the outer to 13·8. There is, however, no abrupt termination -to the surface of the layers, though in some specimens they separate -easily, with shining surfaces.</p> - -<p>"2. <i>Minute Structure.</i>—In longitudinal sections the principal -part of the structure consists of longitudinal tubes of indeterminate -length, and round in cross-section. They are approximately parallel, -but in some cases may be seen to bend sinuously, and are not in -direct contact. Finer myceloid tubes, 5·33 mm. in diameter, traverse -the structure in all directions, and are believed to branch off -from the larger tubes. In a small specimen supposed to be a branch -or small stem, and in which the vertical tubes are somewhat distant -from one another, this horizontal system is very largely developed; -but is less manifest in the older stems. The tubes themselves show -no structure. The ray-like openings in the substance of the tissue -are evidently original parts of the structure, but not of the nature of -medullary rays. They are radiating spaces running outward in an -interrupted manner or so tortuously that they appear to be interrupted -in their course from the centre towards the surface. They -show tubes turning into them, branching into them, and approximately -horizontal, but tortuous. On the external surface of some -specimens these radial spaces are represented by minute pits irregularly -<span class="pagenum"><a name="Page_43" id="Page_43">« 43 »</a></span> -or spirally arranged. The transverse swellings of the stem -show no difference of structure, except that the tubes or cells may be -a little more tortuous, and a transverse film of coaly matter extends -from the outer coaly envelope inwardly. This may perhaps be -caused by some accident of preservation. The outer coaly layer -shows tubes similar to those of the stem.<a name="FNanchor_AF_32" id="FNanchor_AF_32"></a><a href="#Footnote_AF_32" class="fnanchor">[AF]</a> The horizontal or oblique -flexures of the large tubes seem to be mainly in the vicinity of the -radial openings, and it is in entering these that they have been seen -to branch."</p> - -<div class="footnote"> - -<p><a name="Footnote_AF_32" id="Footnote_AF_32"></a><a href="#FNanchor_AF_32"><span class="label">[AF]</span></a> It is possible that these tubes may be merely part of the stem attached -to the bark, which seems to me to indicate the same dense cellular -structure seen in the bark of <i>Lepidodendra</i>, etc.</p></div> - -<p>The conclusions arrived at by Prof. Penhallow are as follows:</p> - -<p>"1. The plant was not truly exogenous, and the appearance of -rings is independent of the causes which determine the layers of -growth in exogenous plants.</p> - -<p>"2. The plant was possessed of no true bark. Whatever cortical -layer was present was in all probability a modification of the general -structure,<a name="FNanchor_AG_33" id="FNanchor_AG_33"></a><a href="#Footnote_AG_33" class="fnanchor">[AG]</a></p> - -<div class="footnote"> - -<p><a name="Footnote_AG_33" id="Footnote_AG_33"></a><a href="#FNanchor_AG_33"><span class="label">[AG]</span></a> On these points I would reserve the considerations: 1. That there -must have been some relation between the mode of growth of these great -stems and their concentric rings; and, 2. That the evidence of a bark is -as strong as in the case of any Palæozoic tree in which the bark is, as -usual, carbonised.</p></div> - -<p>"3. An intimate relation exists between the large tubular cells -and the myceloid filaments, the latter being a system of small -branches from the former; the branching being determined chiefly in -certain special openings which simulate medullary rays.</p> - -<p>"4. The specimens examined exhibit no evidence of special decay, -and the structure throughout is of a normal character.</p> - -<p>"5. The primary structure consists of large tubular cells without -apparent terminations, and devoid of structural markings, with -which is associated a secondary structure of myceloid filaments arising -from the former.</p> - -<p>"6. The structure of <i>Nematophyton</i> as a whole is unique; at least -there is no plant of modern type with which it is comparable. -Nevertheless, the loose character of the entire structure; the interminable -cells; their interlacing; and, finally, their branching into a -secondary series of smaller filaments, point with considerable force to -the true relationship of the stem as being with Algæ or other Thallophytes -rather than with Grymnosperms. A more recent examination -<span class="pagenum"><a name="Page_44" id="Page_44">« 44 »</a></span> -of a laminated resinous substance found associated with the plant -shows that it is wholly amorphous, and, as indicated by distinct lines -of flow, that it must have been in a plastic state at a former period. -The only evidence of structure was found in certain well-defined -mycelia, which may have been derived from associated vegetable -matter upon which they were growing, and over which the plastic -matrix flowed."</p> - -<p>I have only to add to this description that when we consider that -<i>Nematophyton Logani</i> was a large tree, sometimes attaining a diameter -of more than two feet, and a stature of at least twenty before -branching; that it had great roots, and gave off large branches; that -it was an aërial plant, probably flourishing in the same swampy flats -with <i>Psilophyton</i>, <i>Arthrostigma</i>, and <i>Leptophleum</i>; that the peculiar -bodies known as Pachytheca were not unlikely its fruit—we have -evidence that there were, in the early Palæozoic period, plants -scarcely dreamt of by modern botany. Only when the appendages -of these plants are more fully known can we hope to understand -them. In the mean time, I may state that there were probably different -species of these trees, indicated more particularly by the stems I -have described as <i>Nematoxylon</i> and <i>Celluloxylon</i><a name="FNanchor_AH_34" id="FNanchor_AH_34"></a><a href="#Footnote_AH_34" class="fnanchor">[AH]</a> There were, I -think, some indications that the plants described by Carruthers as -<i>Berwynia</i>, may also be found to have been generically the same. -The resinous matter mentioned by Prof. Penhallow is found in great -abundance in the beds containing <i>Nematophyton</i>, and must, I think, -have been an exudation from its bark.</p> - -<div class="footnote"> - -<p><a name="Footnote_AH_34" id="Footnote_AH_34"></a><a href="#FNanchor_AH_34"><span class="label">[AH]</span></a> “Journal Geol. Society of London,” 1863, 1881.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_45" id="Page_45">« 45 »</a></span></p></div> - - - - -<p class="caption2"><a name="CHAPTER_III" id="CHAPTER_III">CHAPTER III.</a></p> - -<p class="caption3">THE ERIAN OF DEVONIAN FORESTS—ORIGIN OF PETROLEUM—THE AGE OF ACROGENS AND GYMNOSPERMS.</p> - - -<p><span class="smcap">In</span> the last chapter we were occupied with the comparatively -few and obscure remains of plants entombed -in the oldest geological formations. We now ascend to a -higher plane, that of the Erian or Devonian period, in -which, for the first time, we find varied and widely distributed -forests.</p> - -<p>The growth of knowledge with respect to this flora -has been somewhat rapid, and it may be interesting to -note its principal stages, as an encouragement to the hope -that we may yet learn something more satisfactory respecting -the older floras we have just discussed.</p> - -<p>In Goeppert’s memoir on the flora of the Silurian, -Devonian, and Lower Carboniferous rocks, published in -1860,<a name="FNanchor_AI_35" id="FNanchor_AI_35"></a><a href="#Footnote_AI_35" class="fnanchor">[AI]</a> he enumerates twenty species as Silurian, but these -are all admitted to be Algæ, and several of them are remains -which may be fairly claimed by the zoologists as -zoophytes, or trails of worms and mollusks. In the Lower -Devonian he knows but six species, five of which are -Algæ, and the remaining one a <i>Sigillaria</i>, but this is of -very doubtful nature. In the Middle Devonian he gives -but one species, a land-plant of the genus <i>Lepidodendron</i>. -In the Upper Devonian the number rises to fifty-seven, -of which all but seven are terrestrial plants, representing -a large number of the genera occurring in the succeeding -Carboniferous system.</p> - -<div class="footnote"> - -<p><a name="Footnote_AI_35" id="Footnote_AI_35"></a><a href="#FNanchor_AI_35"><span class="label">[AI]</span></a> Jena, 1860.</p> - -<p><span class="pagenum"><a name="Page_46" id="Page_46">« 46 »</a></span></p></div> - -<p>Goeppert does not include in his enumeration the -plants from the Devonian of Gaspé, described by the -author in 1859,<a name="FNanchor_AJ_36" id="FNanchor_AJ_36"></a><a href="#Footnote_AJ_36" class="fnanchor">[AJ]</a> having seen only an abstract of the -paper at the time of writing his memoir, nor does he -appear to have any knowledge of the plants of this age -described by Lesquereux in Roger’s “Pennsylvania.” -These might have added ten or twelve species to his list, -some of them probably from the Lower Devonian. It is -further to be observed that a few additional species had -also been recognised by Peach in the Old Red Sandstone -of Scotland.</p> - -<div class="footnote"> - -<p><a name="Footnote_AJ_36" id="Footnote_AJ_36"></a><a href="#FNanchor_AJ_36"><span class="label">[AJ]</span></a> “Journal of the Geological Society of London,” also “Canadian -Naturalist.”</p></div> - -<p>But from 1860 to the present time a rich harvest of -specimens has been gathered from the Gaspé sandstones, -from the shales of southern New Brunswick, from the -sandstones of Perry in Maine, and from the wide-spread -Erian areas of New York, Pennsylvania, and Ohio. -Nearly all these specimens have passed through my -hands, and I am now able to catalogue about a hundred -species, representing more than thirty genera, and -including all the great types of vascular Cryptogams, the -Gymnosperms, and even one (still doubtful) Angiosperm. -Many new forms have also been described from the Devonian -of Scotland and of the Continent of Europe.</p> - -<p>Before describing these plants in detail, we may refer -to North America for illustration of the physical conditions -of the time. In a physical point of view the northern -hemisphere presented a great change in the Erian -period. There were vast foldings of the crust of the -earth, and great emissions of volcanic rock on both sides -of the Atlantic. In North America, while at one time -the whole interior area of the continent, as far north as -<span class="pagenum"><a name="Page_47" id="Page_47">« 47 »</a></span> -the Great Lakes, was occupied by a vast inland sea, studded -with coral islands, the long Appalachian ridge had begun -to assume, along with the old Laurentian land, something -of the form of our present continent, and on the margins -of this Appalachian belt there were wide, swampy flats and -shallow-water areas, which, under the mild climate that -seems to have characterised this period, were admirably -suited to nourish a luxuriant vegetation. Under this -mild climate, also, it would seem that new forms of plants -were first introduced in the far north, where the long -continuance of summer sunlight, along with great warm th, -seems to have aided in their introduction and early extension, -and thence made their way to the southward, a -process which, as Gray and others have shown, has also -occurred in later geological times.</p> - -<p>The America of this Erian age consisted during the -greater part of the period of a more or less extensive belt -of land in the north with two long tongues descending -from it, one along the Appalachian line in the east, the -other in the region west of the Rocky Mountains. On -the seaward sides of these there were low lands covered -with vegetation, while on the inland side the great interior -sea, with its verdant and wooded islands, realised, -though probably with shallower water, the conditions of -the modern archipelagoes of the Pacific.</p> - -<p>Europe presented conditions somewhat similar, having -in the earlier and middle portions of the period great sea -areas with insular patches of land, and later wide tracts -of shallow and in part enclosed water areas, swarming -with fishes, and having an abundant vegetation on their -shores. These were the conditions of the Eifel and -Devonshire limestones, and of the Old Red Sandstone of -Scotland, and the Kiltorcan beds of Ireland. In Europe -also, as in America, there were in the Erian age great -ejections of igneous rock. On both sides of the Atlantic -there were somewhat varied and changing conditions of -<span class="pagenum"><a name="Page_48" id="Page_48">« 48 »</a></span> -land and water, and a mild and equable climate, permitting -the existence of a rich vegetation in high northern -latitudes. Of this latter fact a remarkable example is -afforded by the beds holding plants of this age in Spitzbergen -and Bear Island, in its vicinity. Here there seem -to be two series of plant-bearing strata, one with the -vegetation of the Upper Erian, the other with that of -the Lower Carboniferous, though both have been united -by Heer under his so-called “Ursa Stage” in which he -has grouped the characteristic plants of two distinct -periods. This has recently been fully established by the -researches of Nathorst, though the author had already -suggested it as the probable explanation of the strange -union of species in the Ursa group of Heer.</p> - -<p>In studying the vegetation of this remarkable period, -we must take merely some of the more important forms -as examples, since it would be impossible to notice all -the species, and some of them may be better treated in -the Carboniferous, where they have their headquarters. -(<a href="#fig15">Fig. 15.</a>)</p> - -<p>I may first refer to a family which seems to have culminated -in the Erian age, and ever since to have occupied -a less important place. It is that of the curious aquatic -plants known as Rhizocarps,<a name="FNanchor_AK_37" id="FNanchor_AK_37"></a><a href="#Footnote_AK_37" class="fnanchor">[AK]</a> and referred to in the last -chapter.</p> - -<div class="footnote"> - -<p><a name="Footnote_AK_37" id="Footnote_AK_37"></a><a href="#FNanchor_AK_37"><span class="label">[AK]</span></a> Or, as they have recently been named by some botanists, “Heterosporous -Filices,” though they are certainly not ferns in any ordinary -sense of that term.</p></div> - -<p>My attention was first directed to these organisms by -the late Sir W. E. Logan in 1869. He had obtained from -the Upper Erian shale of Kettle Point, Lake Huron, -specimens filled with minute circular discs, to which he -referred, in his report of 1863, as “microscopic orbicular -bodies.” Recognising them to be macrospores, or spore-cases, -I introduced them into the report on the Erian -<span class="pagenum"><a name="Page_49" id="Page_49">« 49 »</a></span> -flora, which I was then preparing, and which was published -in 1871, under the name <i>Sporangites Huronensis</i>.</p> - -<div class="fig_center" style="width: 404px;"> -<a id="fig15" name="fig15"></a> -<img src="images/fig15.png" width="404" height="576" alt="" /> -<div class="fig_caption">Fig. 15.—Vegetation of the Devonian period, restored. <i>Calamites</i>, <i>Psilophyton</i>, -<i>Leptophleum</i>, <i>Lepidodendron</i>, <i>Cordaites</i>, <i>Sigillaria</i>, <i>Dadoxylon</i>, -<i>Asterophyllites</i>, <i>Platyphyllum</i>.</div> -</div> - -<p>In 1871, having occasion to write a communication to -the “American Journal of Science” on the question then -raised as to the share of spores and spore-cases in the accumulation -of coal, a question to be discussed in a subsequent -<span class="pagenum"><a name="Page_50" id="Page_50">« 50 »</a></span> -chapter, these curious little bodies were again -reviewed, and were described in substance as follows:</p> - -<p>“The oldest bed of spore-cases known to me is that -at Kettle Point, Lake Huron. It is a bed of brown -bituminous shale, burning with much flame, and under -a lens is seen to be studded with flattened disc-like bodies, -scarcely more than a hundredth of an inch in diameter, -which under the microscope are found to be spore-cases -(or macrospores) slightly papillate externally (or more -properly marked with dark pores), and sometimes showing -a point of attachment on one side and a slit more or -less elongated and gaping on the other. When slices of -the rock are made, its substance is seen to be filled with -these bodies, which, viewed as transparent objects, appear -yellow like amber, and show little structure, except that -the walls can be distinguished from the internal cavity, -which may sometimes be seen to enclose patches of granular -matter. In the shale containing them are also vast -numbers of rounded, translucent granules, which may be -escaped spores (microspores).” The bed containing these -spores at Kettle Point was stated, in the reports of the -“Geological Survey of Canada,” to be twelve or fourteen -feet in thickness, and besides these specimens it contained -fossil plants referable to the species <i>Calamites inornatus</i> -and <i>Lepidodendron primævum</i>, and I not unnaturally -supposed that the Sporangites might be the fruit of the -latter plant. I also noticed their resemblance to the -spore-cases of <i>L. corrugatum</i> of the Lower Carboniferous -(a Lepidodendron allied to <i>L. primævum</i>), and to those -from Brazil described by Carruthers under the name -<i>Flemingites</i>, as well as to those described by Huxley -from certain English coals, and to those of the Tasmanite -or white coal of Australia. The bed at Kettle Point is -shown to be marine by its holding the sea-weed known -as <i>Spirophyton</i>, and shells of <i>Lingula</i>.</p> - -<p>The subject did not again come under my notice till -<span class="pagenum"><a name="Page_51" id="Page_51">« 51 »</a></span> -1882, when Prof. Orton, of Columbus, Ohio, sent me -some specimens from the Erian shales of that State, -which on comparison seemed undistinguishable from -<i>Sporangites Huronensis</i>.<a name="FNanchor_AL_38" id="FNanchor_AL_38"></a><a href="#Footnote_AL_38" class="fnanchor">[AL]</a> Prof. Orton read an interesting -paper on these bodies, at the meeting of the American -Association in Montreal, in which were some new and -striking facts. One of these was the occurrence of such -bodies throughout the black shales of Ohio, extending -“from the Huron River, on the shore of Lake Brie, to -the mouth of the Scioto, in the Ohio Valley, with an -extent varying from ten to twenty miles in breadth,” and -estimated to be three hundred and fifty feet in thickness. -I have since been informed by my friend Mr. Thomas, of -Chicago, that its thickness, in some places at least, must -be three times that amount. About the same time. Prof. -Williams, of Cornell, and Prof. Clarke, of Northampton, -announced similar discoveries in the State of New York, -so that it would appear that beds of vast area and of great -thickness are replete with these little vegetable discs, usually -converted into a highly bituminous, amber-like substance, -giving a more or less inflammable character to the -containing rock.</p> - -<div class="footnote"> - -<p><a name="Footnote_AL_38" id="Footnote_AL_38"></a><a href="#FNanchor_AL_38"><span class="label">[AL]</span></a> These shales have been described, as to their chemical and geological -relations, by Dr. T. Sterry Hunt, “American Journal of Science,” 1863, -and by Dr. Newberry, in the “Reports of the Geological Survey of Ohio,” -vol. i., 1863, and vol. iii., 1878.</p></div> - -<p>Another fact insisted on by Prof. Orton was the absence -of Lepidodendroid cones, and the occurrence of -filamentous vegetable matter, to which the Sporangites -seemed to be in some cases attached in groups. Prof. -Orton also noticed the absence of the trigonal form, which -belongs to the spores of many Lepidodendra, though this -is not a constant character. In the discussion on Prof. -Orton’s paper, I admitted that the facts detailed by him -shook my previous belief of the lycopodiaceous character -<span class="pagenum"><a name="Page_52" id="Page_52">« 52 »</a></span> -of these bodies, and induced me to suspect, with Prof. -Orton, that they might have belonged to some group of -aquatic plants lower than the Lycopods.</p> - -<p>Since the publication of my paper on Rhizocarps in -the Palæozoic period above referred to, I have received -two papers from Mr. Edward Wethered, F. G. S., in one -of which he describes spores of plants found in the lower -limestone shales of the Forest of Dean, and in the other -discusses more generally the structure and origin of Carboniferous -coal-beds.<a name="FNanchor_AM_39" id="FNanchor_AM_39"></a><a href="#Footnote_AM_39" class="fnanchor">[AM]</a> In both papers he refers to the -occurrence in these coals and shales of organisms essentially -similar to the Erian spores.</p> - -<div class="footnote"> - -<p><a name="Footnote_AM_39" id="Footnote_AM_39"></a><a href="#FNanchor_AM_39"><span class="label">[AM]</span></a> “Cotteswold Naturalists' Field Club,” 1884; “Journal of the -Royal Microscopical Society,” 1885.</p></div> - -<p>In the “Bulletin of the Chicago Academy of Science,” -January, 1884, Dr. Johnson and Mr. Thomas, in their -paper on the “Microscopic Organisms of the Boulder Clay -of Chicago and Vicinity,” notice <i>Sporangites Huronensis</i> -as among these organisms, and have discovered them also -in large numbers in the precipitate from Chicago city -water-supply. They refer them to the decomposition of -the Erian shales, of which boulders filled with these organisms -are of frequent occurrence in the Chicago clays. -The Sporangites and their accompaniments in the boulder -clay are noticed in a paper by Dr. G. M. Dawson, in the -“Bulletin of the Chicago Academy,” June, 1885.</p> - -<p>Prof. Clarke has also described, in the “American -Journal of Science” for April, 1885, the forms already -alluded to, and which he finds to consist of macrospores -enclosed in sporocarps. He compares these with my -<i>Sporangites Huronensis</i> and <i>Protosalvinia bilobata</i>, but -I think it is likely that one of them at least is a distinct -species.</p> - -<p>I may add that in the “Geological Magazine” for -1875, Mr. Newton, F. G. S., of the Geological Survey of -<span class="pagenum"><a name="Page_53" id="Page_53">« 53 »</a></span> -England, published a description of the Tasmanite and -Australian white coal, in which he shows that the organisms -in these deposits are similar to my <i>Sporangites -Huronensis</i>, and to the macrospores previously described -by Prof. Huxley, from the Better-bed coal. Mr. Newton -does not seem to have been aware of my previous description -of <i>Sporangites</i>, and proposes the name <i>Tasmanites -punctatus</i> for the Australian form.</p> - -<p>Here we have the remarkable fact that the waste -macrospores, or larger spores of a species of Cryptogamous -plant, occur dispersed in countless millions of tons -through the shales of the Erian in Canada and the United -States.</p> - -<p>No certain clue seemed to be afforded by all these -observations as to the precise affinities of these widely -distributed bodies; but this was furnished shortly after -from an unexpected quarter. In March, 1883, Mr. Orville -Derby, of the Geological Survey of Brazil, sent me -specimens found in the Erian of that country, which -seemed to throw a new light on the whole subject. These -I described and pointed out their connection with <i>Sporangites</i> -at the meeting of the American Association at Minneapolis, -in 1883, and subsequently published my notes -respecting them in its proceedings, and in the “Canadian -Record of Science.”</p> - -<p>Mr. Derby’s specimens contained the curious spiral -sea-weed known as <i>Spirophyton</i>, and also minute rounded -Sporangites like those obtained in the Erian of Ohio, and -of which specimens had been sent to me some years before -by the late Prof. Hartt. But they differed in showing -the remarkable fact that these rounded bodies are -enclosed in considerable numbers in spherical and oval -sacs, the walls of which are composed of a tissue of -hexagonal cells, and which resemble in every respect the -involucres or spore-sacs of the little group of modern -acrogens known as Rhizocarps, and living in shallow -<span class="pagenum"><a name="Page_54" id="Page_54">« 54 »</a></span> -water. More especially they resemble the sporocarps of -the genus <i>Salvinia</i>. This fact opened up an entirely -new field of investigation, and I at once proceeded to -compare the specimens with the fructification of modern -Rhizocarps, and found that substantially these multitudinous -spores embedded in the Erie shales may be regarded -as perfectly analogous to the larger spores of the -modern <i>Salvinia natans</i> of Europe, as may be seen by -the representation of them in <a href="#fig16">Fig. 16</a>.</p> - -<div class="fig_center" style="width: 394px;"> -<a id="fig16" name="fig16"></a> -<img src="images/fig16.png" width="394" height="309" alt="" /> -<div class="fig_caption">Fig. 16.—<i>Sporangites</i> (<i>Protosalvinia</i>). A, <i>Sporangites Braziliensis</i>, natural -size, AX, Same, magnified, B, <i>Sp. biloba</i>, natural size, C, Detached -macrospores. D, Spore-cases of Salvinia natans. DX, Same, magnified. -E, Shale with sporangites, vertical section, highly magnified.</div> -</div> - -<p>The typical macrospores from the Erian shales are -perfectly circular in outline, and in the flattened state appear -as discs with rounded edges, their ordinary diameter -being from one seventy-fifth to one one-hundredth of an -inch, though they vary considerably in size. This, however, -I do not regard as an essential character. The -edges, as seen in profile, are smooth, but the flat surface -often presents minute dark spots, which at first I mistook -<span class="pagenum"><a name="Page_55" id="Page_55">« 55 »</a></span> -for papillæ, but now agree with Mr. Thomas in recognising -them as minute pores traversing the wall of the -disc, and similar to those which Mr. Newton has described -in Tasmanite, and which Mr. Wethered has also recognised -in the similar spores of the Forest of Dean shales. -The walls also sometimes show faint indications of concentric -lamination, as if they had been thickened by successive -deposits.</p> - -<p>As seen by transmitted light, and either in front or in -profile, the discs are of a rich amber colour, translucent -and structureless, except the pores above referred to. -The walls are somewhat thick, or from one-tenth to one-twentieth -the diameter of the disc in thickness. They -never exhibit the triradiate marking seen in spores of Lycopods, -nor any definite point of attachment, though -they sometimes show a minute elongated spot which may -be of this nature, and they are occasionally seen to have -opened by slits on the edge or front, where there would -seem to have been a natural line of dehiscence. The interior -is usually quite vacant or structureless, but in some -cases there are curved internal markings which may indicate -a shrunken lining membrane, or the remains of a -prothallus or embryo. Occasionally a fine granular substance -appears in the interior, possibly remains of microspores.</p> - -<p>The discs are usually detached and destitute of any -envelope, but fragments of flocculent cellular matter are -associated with them, and in one specimen from the corniferous -limestone of Ohio, in Mr. Thomas’s collection, I -have found a group of eight or more discs partly enclosed -in a cellular sac-like membrane of similar character to -that enclosing the Brazilian specimens already referred to.</p> - -<p>The characters of all the specimens are essentially -similar, and there is a remarkable absence of other organisms -in the shale. In one instance only, I have observed -a somewhat smaller round body with a dark centre or -<span class="pagenum"><a name="Page_56" id="Page_56">« 56 »</a></span> -nucleus, and a wide translucent margin, marked by a -slight granulation. Even this, however, may indicate -nothing more than a different state of preservation.</p> - -<p>It is proper to observe here that the wall or enclosing -sac of these macrospores must have been of very dense -consistency, and now appears as a highly bituminous substance, -in this agreeing with that of the spores of Lycopods, -and, like them, having been when recent of a highly -carbonaceous and hydrogenous quality, very combustible -and readily admitting of change into bituminous matter. -In the paper already referred to, on spore-cases in coals, -I have noticed that the relative composition of lycopodium -and cellulose is as follows:</p> - -<table summary="formulae"> -<tr> - <td class="vtop larger">Cellulose,</td> - <td class="tdl larger">C<sub>24</sub>H<sub>20</sub>O<sub>20</sub>.</td> -</tr> -<tr> - <td class="vtop larger">Lycopodium,</td> - <td class="tdl larger">C<sub>42</sub>H<sub>19<sup>4</sup>/<sub>12</sub></sub>NO<sub>5<sup>6</sup>/<sub>10</sub></sub>.</td> -</tr> -</table> - -<p>Thus, such spores are admirably suited for the production -of highly carbonaceous or bituminous coals, etc.</p> - -<p>Nothing is more remarkable in connection with these -bodies than their uniformity of structure and form over -so great areas and throughout so great thickness of rock, -and the absence of any other kind of spore-case. This -is more especially noteworthy in contrast with the coarse -coals and bituminous shales of the Carboniferous, which -usually contain a great variety of spores and sporangia, -indicating the presence of many species of acrogenous -plants, while the Erian shales, on the contrary, indicate the -almost exclusive predominance of one form. This contrast -is well seen in the Bedford shales overlying these -beds, and I believe Lower Carboniferous.<a name="FNanchor_AN_40" id="FNanchor_AN_40"></a><a href="#Footnote_AN_40" class="fnanchor">[AN]</a> Specimens of -these have been kindly communicated to me by Prof. -Orton, and have been prepared by Mr. Thomas. In these -we see the familiar Carboniferous spores with triradiate -markings called <i>Triletes</i> by Reinsch, and which are similar -to those of Lycopodiaceous plants. Still more abundant -<span class="pagenum"><a name="Page_57" id="Page_57">« 57 »</a></span> -are those spinous and hooked spores or sporangia, -to which the names <i>Sporocarpon</i>, <i>Zygosporites</i>, and <i>Traquaria</i> -have been given, and some of which Williamson -has shown to be spores of Lycopodiaceous plants.<a name="FNanchor_AO_41" id="FNanchor_AO_41"></a><a href="#Footnote_AO_41" class="fnanchor">[AO]</a></p> - -<div class="footnote"> - -<p><a name="Footnote_AN_40" id="Footnote_AN_40"></a><a href="#FNanchor_AN_40"><span class="label">[AN]</span></a> According to Newberry, lower part of Waverly group.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_AO_41" id="Footnote_AO_41"></a><a href="#FNanchor_AO_41"><span class="label">[AO]</span></a> <i>Traquaria</i> is to be distinguished from the calcareous bodies found -in the corniferous limestone of Kelly’s Island, which I have described in -the “Canadian Naturalist” as <i>Saccamina Eriana</i>, and believe to be Foraminiferal -tests. They have since been described by Ulrich under a -different name (<i>Moellerina</i>: contribution to “American Palæontology,” -1886). See Dr. Williamson’s papers in “Transactions of Royal Society -of London.”</p></div> - -<p>The true “Sporangites,” on the contrary, are round -and smooth, with thick bituminous walls, which are -punctured with minute transverse pores. In these respects, -as already stated, they closely resemble the bodies -found in the Australian white coal and Tasmanite. The -precise geological age of this last material is not known -with certainty, but it is believed to be Palæozoic.</p> - -<p>With reference to the mode of occurrence of these -bodies, we may note first their great abundance and wide -distribution. The horizontal range of the bed at Kettle -Point is not certainly known, but it is merely a northern -outlier of the great belt of Erian shales referred to by -Prof. Orton, and which extends, with a breadth of ten to -twenty miles, and of great thickness, across the State of -Ohio, for nearly two hundred miles. This Ohio black -shale, which lies at the top of the Erian or the base of -the Carboniferous, though probably mainly of Erian age, -appears to abound throughout in these organisms, and in -some beds to be replete with them. In like manner, in -Brazil, according to Mr. Derby, these organisms are distributed -over a wide area and throughout a great thickness -of shale holding <i>Spirophyton</i>, and apparently belonging -to the Upper Erian. The recurrence of similar forms -in the Tasmanite and white coal of Tasmania and Australia -is another important fact of distribution. To this -<span class="pagenum"><a name="Page_58" id="Page_58">« 58 »</a></span> -we may add the appearance of these macrospores in coals -and shales of the Carboniferous period, though there in -association with other forms.</p> - -<p>It is also to be observed that the Erian shales, and the -Forest of Dean beds described by Wethered, are marine, -as shown by their contained fossils; and, though I have -no certain information as to the Tasmanite and Australian -white coal, they would seem, from the description of -Milligan, to occur in distinctly aqueous, possibly estuarine, -deposits. Wethered has shown that the discs described -by Huxley and Newton in the Better-bed coal -occur in the earthy or fragmentary layers, as distinguished -from the pure coal. Those occurring in cannel -coal are in the same case, so that the general mode of -occurrence implies water-driftage, since, in the case of -bodies so large and dense, wind-driftage to great distances -would be impossible.</p> - -<p>These facts, taken in connection with the differences -between these macrospores and those of any known land-plant -of the Palæozoic, would lead to the inference that -they belonged to aquatic plants, and these vastly abundant -in the waters of the Erian and Carboniferous periods.</p> - -<p>It is still further to be observed that they are not, in -the Erian beds, accompanied with any remains of woody -or scalariform tissues, such as might be expected in connection -with the <i>débris</i> of terrestrial acrogens, and that, -on the other hand, we find them enclosed in cellular -sporocarps, though in the majority of cases these have -been removed by dehiscence or decay.</p> - -<p>These considerations, I think, all point to the probability -which I have suggested in my papers on this subject -referred to above, that we have in these objects the -organs of fructification of plants belonging to the order -<i>Rhizocarpeæ</i>, or akin to it. The comparisons which I -have instituted with the sporocarps and macrospores of -these plants confirm this suggestion. Of the modern -<span class="pagenum"><a name="Page_59" id="Page_59">« 59 »</a></span> -species which I have had an opportunity to examine, -<i>Salvinia natans</i> of Europe perhaps presents the closest -resemblance. In this plant groups of round cellular -sporocarps appear at the bases of the floating fronds. -They are about a line in diameter when mature, and are -of two kinds, one containing macrospores, the other microspores -or antheridia. The first, when mature, hold a -number of closely packed globular or oval sporangia of -loose cellular tissue, attached to a central placenta. Each -of these sporangia contains a single macrospore, perfectly -globular and smooth, with a dense outer membrane (exhibiting -traces of lamination, and showing within an -irregularly vacuolated or cellular structure, probably a -prothallus). I cannot detect in it the peculiar pores -which appear in the fossil specimens. Each macrospore -is about one-seventieth of an inch in diameter when mature. -The sporocarps of the microspores contain a vastly -greater number of minute sporangia, about one two-hundredths -of an inch in diameter. These contain disc-like -antheridia, or microspores of very minute size.</p> - -<p>The discs from Kettle Point and from the Ohio black -shale, and from the shale boulders of the Chicago clays, -are similar to the macrospores of <i>Salvinia</i>, except that -they have a thicker wall and are a little less in diameter, -being about one-eightieth of an inch. The Brazilian -sporocarps are considerably larger than those of the modern -<i>Salvinia</i>, and the macrospores approach in size to -those of the modern species, being one seventy-fifth of an -inch in diameter. They also seem, like the modern species, -to have thinner walls than those from Canada, Ohio, -and Chicago. No distinct indication has been observed -in the fossil species of the inner Sporangium of <i>Salvinia</i>. -Possibly it was altogether absent, but more probably it is -not preserved as a distinct structure.</p> - -<p>With reference to the microspores of <i>Salvinia</i>, it is to -be observed that the sporocarps, and the contained spores -<span class="pagenum"><a name="Page_60" id="Page_60">« 60 »</a></span> -or antheridia, are very delicate and destitute of the dense -outer wall of the macrospores. Hence such parts are -little likely to have been preserved in a fossil state; and -in the Erian shales, if present, they probably appear -merely as flocculent carbonaceous matter not distinctly -marked, or as minute granules not well defined, of which -there are great quantities in some of the shales.</p> - -<p>The vegetation appertaining to the Sporangites has -not been distinctly recognised. I have, however, found -in one of the Brazilian specimens two sporocarps attached -to what seems a fragment of a cellular frond, and numerous -specimens of the supposed Algæ, named <i>Spirophyton</i>, -are found in the shales, but there is no evidence of any -connection of this plant with the <i>Protosalvinia</i>.</p> - -<p>Modern Rhizocarps present considerable differences as -to their vegetative parts. Some, like <i>Pilularia</i>, have -simple linear leaves; others, like <i>Marsilea</i>, have leaves in -whorls, and cuneate in form; while others, like <i>Azolla</i> -and <i>Salvinia</i>, have frondose leaves, more or less pinnate -in their arrangement. If we inquire as to fossils representing -these forms of vegetation, we shall find that some -of the plants to be noticed in the immediate sequel may -have been nearly allied to the Rhizocarps. In the mean -time I may state that I have proposed the generic name -<i>Protosalvinia</i> for these curious macrospores and their -coverings, and have described in the paper in the “Bulletin -of the Chicago Academy of Sciences,” already -quoted, five species which may be referred to this genus.</p> - -<p>These facts lead to inquiries as to the origin of the -bituminous matter which naturally escapes from the -rocks of the earth as petroleum and inflammable gas, or -which may be obtained from certain shales in these forms -by distillation. These products are compounds of carbon -and hydrogen, and may be procured from recent vegetable -substances by destructive distillation. Some vegetable -matters, also, are much richer in carbon and hydrogen -<span class="pagenum"><a name="Page_61" id="Page_61">« 61 »</a></span> -than others, and it is a remarkable fact that the spores of -certain cryptogamous plants are of this kind, as we see in -the inflammable character of the dry spores of Lycopodium; -and we know that the slow putrefaction of such -material underground effects chemical changes by which -bituminous matter can be produced. There is, therefore, -nothing unreasonable in the supposition advanced -by Prof. Orton, that the spores so abundantly contained -in the Ohio black shales are important or principal sources -of the bituminous matter which they contain. Microscopic -sections of this shale show that much of its material -consists of the rich bituminous matter of these spores -(<a href="#fig16">Fig. 16</a>). At the same time, while we may trace the -bitumen of these shales, and of some beds of coal, to this -cause, we must bear in mind that there are other kinds of -bituminous rocks which show no such structures, and may -have derived their combustible material from other kinds -of vegetable matter, whether of marine or of land plants. -We shall better understand this when we have considered -the origin of coal.</p> - -<p>The macrospores above referred to may have belonged -to humble aquatic plants mantling the surfaces of water -or growing up from the bottom, and presenting little -aërial vegetation. But there are other Erian plants, as -already mentioned, which, while of higher structure, may -be of Rhizocarpean affinities.</p> - -<p>One of these is the beautiful plant with whorls of -wedge-shaped leaves, to which the name <i>Sphenophyllum</i> -(see <a href="#fig20">Fig. 20</a>) has been given. Plants referred to this -genus have been described by Lesquereux from the upper -part of the Siluro-Cambrian,<a name="FNanchor_AP_42" id="FNanchor_AP_42"></a><a href="#Footnote_AP_42" class="fnanchor">[AP]</a> and a beautiful little species -occurs in the Erian shales of St. John, New Brunswick.<a name="FNanchor_AQ_43" id="FNanchor_AQ_43"></a><a href="#Footnote_AQ_43" class="fnanchor">[AQ]</a> -The genus is also continued, and is still more -<span class="pagenum"><a name="Page_62" id="Page_62">« 62 »</a></span> -abundant, in the Carboniferous. Many years ago I observed, -in a beautiful specimen collected by Sir W. E. -Logan, in New Brunswick, that the stem of this plant -had an axis of reticulated and scalariform vessels, and an -outer bark.<a name="FNanchor_AR_44" id="FNanchor_AR_44"></a><a href="#Footnote_AR_44" class="fnanchor">[AR]</a> Renault and Williamson have more recently -obtained more perfect specimens, and the former has -figured a remarkably complex triangular axis, containing -punctate and barred vessels, and larger punctate vessels -filling in its angles. Outside of this there is a cellular -inner bark, and this is surrounded by a thick fibrous envelope. -That a structure so complex should belong to -a plant so humble in its affinities is one of the strange -anomalies presented by the old world, and of which we -shall find many similar instances. The fruit of <i>Sphenophyllum</i> -was borne in spikes, with little whorls of bracts -or rudimentary leaves bearing round sporocarps.</p> - -<div class="footnote"> - -<p><a name="Footnote_AP_42" id="Footnote_AP_42"></a><a href="#FNanchor_AP_42"><span class="label">[AP]</span></a> “American Journal of Science.”</p></div> - -<div class="footnote"> - -<p><a name="Footnote_AQ_43" id="Footnote_AQ_43"></a><a href="#FNanchor_AQ_43"><span class="label">[AQ]</span></a> Dawson, “Report on Devonian Plants,” 1870.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_AR_44" id="Footnote_AR_44"></a><a href="#FNanchor_AR_44"><span class="label">[AR]</span></a> “Journal of the Geological Society,” 1865.</p></div> - -<div class="fig_center" style="width: 405px;"> -<a id="fig17" name="fig17"></a> -<img src="images/fig17.png" width="405" height="242" alt="" /> -<div class="fig_caption">Fig. 17.—<i>Ptilophyton plumosum</i> (Lower Carboniferous, Nova Scotia). -Natural size and magnified.</div> -</div> - -<p>A second type of plant, which may have been Rhizocarpean -in its affinities, is that to which I have given the -name <i>Ptilophyton</i>.<a name="FNanchor_AS_45" id="FNanchor_AS_45"></a><a href="#Footnote_AS_45" class="fnanchor">[AS]</a> It consists of beautiful feathery -<span class="pagenum"><a name="Page_63" id="Page_63">« 63 »</a></span> -fronds, apparently bearing on parts of the main stem or -petiole small rounded sporocarps. They are found abundantly -in the Middle Erian of the State of New York, -and also occur in Scotland, while one species appears to -occur in Nova Scotia, as high as the Lower Carboniferous -(Figs. <a href="#fig17">17</a>, <a href="#fig18">18</a>).</p> - -<div class="footnote"> - -<p><a name="Footnote_AS_45" id="Footnote_AS_45"></a><a href="#FNanchor_AS_45"><span class="label">[AS]</span></a> <i>Plumalina</i> of Hall.</p></div> - -<div class="fig_center" style="width: 416px;"> -<a id="fig18" name="fig18"></a> -<img src="images/fig18.png" width="416" height="412" alt="" /> -<div class="fig_caption">Fig. 18.—<i>Ptilophyton Thomsoni</i> (Scotland), <i>a</i>, Impression of plant in -vernation, <i>b</i>, Branches conjecturally restored, <i>c</i>, Branches of <i>Lycopodites -Milleri</i>, on same slab.</div> -</div> - -<p>These organisms have been variously referred to Lycopods, -to Algæ, or to Zoöphytes, but an extended comparison -of American and Scottish specimens has led me to -the belief that they were aquatic plants, more likely to -have been allied to Rhizocarps than to any other group. -Some evidence of this will be given in a note appended -to this chapter.</p> - -<p><span class="pagenum"><a name="Page_64" id="Page_64">« 64 »</a></span></p> - -<div class="fig_left" style="width: 275px;"> -<a id="fig19" name="fig19"></a> -<img src="images/fig19.png" width="275" height="610" alt="" /> -<div class="fig_caption">Fig. 19.—<i>Psilophyton princeps</i>, restored -(Lower Erian, Gaspé). <i>a</i>, Fruit, natural -size. <i>b</i>, stem, natural size, <i>c</i>, Scalariform -tissue of the axis, highly magnified. -In the restoration, one side is represented -in vernation and the other in fruit.</div> -</div> - -<p>Another genus, -which I have named -<i>Psilophyton</i><a name="FNanchor_AT_46" id="FNanchor_AT_46"></a><a href="#Footnote_AT_46" class="fnanchor">[AT]</a> (Figs. <a href="#fig19">19</a>, <a href="#fig21">21</a>), -may be regarded -as a connecting -link between the -Rhizocarps and the -Lycopods. It is so -named from its resemblance, -in some respects, -to the curious -parasitic Lycopods -placed in the modern -genus <i>Psilotum</i>. Several -species have been -described, and they are -eminently characteristic -of the Lower Erian, -in which they -were first discovered -in Gaspé. The typical -species, <i>Psilophyton -princeps</i>, which -fills many beds of shale -and sandstone in Gaspé -Bay and the head -of the neighbouring -Bay des Chaleurs with -its slender stems and -creeping, cord-like rhizomes, -may be thus described:</p> - -<div class="footnote"> - -<p><a name="Footnote_AT_46" id="Footnote_AT_46"></a><a href="#FNanchor_AT_46"><span class="label">[AT]</span></a> “Journal of the Geological Society,” vols, xv., xviii., and xix., “Report -on Devonian Plants of Canada,” 1871.</p></div> - -<p>Stems branching -<span class="pagenum"><a name="Page_65" id="Page_65">« 65 »</a></span> -dichotomously, and covered with interrupted ridges. -Leaves rudimentary, or short, rigid, and pointed; in -barren stems, numerous and spirally arranged; in fertile -stems and branchlets, sparsely scattered or absent; in -decorticated specimens, represented by a -minute punctate scars. Young branches -circinate; rhizomata cylindrical, covered -with hairs or ramenta, and having -circular areoles irregularly disposed, giving -origin to slender cylindrical rootlets. -Internal structure—an axis of scalariform -vessels, surrounded by a cylinder of -parenchymatous cells, and by an outer -cylinder of elongated woody cells. Fructification -consisting of naked oval spore-cases, -borne usually in pairs on slender, -curved pedicels, either lateral or terminal.</p> - -<div class="fig_right" style="width: 125px;"> -<a id="fig20" name="fig20"></a> -<img src="images/fig20.png" width="125" height="184" alt="" /> -<div class="fig_caption">Fig. 20.—<i>Sphenophyllum -antiquum</i> -(Erian, -New Brunswick). -See pp. <a href="#Page_61">61</a>, <a href="#Page_67">67</a>.</div> -</div> - -<p>This species was fully described by me in the papers -referred to above, from specimens obtained from the rich -exposures at Gaspé Bay, and which enabled me to illustrate -its parts more fully, perhaps, than those of any -other species of so great antiquity. In the specimens I -had obtained I was able to recognise the forms of the -rhizomata, stems, branches, and rudimentary leaves, and -also the internal structure of the stems and rhizomata, -and to illustrate the remarkable resemblance of the forms -and structures to those of the modern <i>Psilotum</i>. The -fructification was, however, altogether peculiar, consisting -of narrowly ovate sporangia, borne usually in pairs, -on curved and apparently rigid petioles. Under the -microscope these sporangia show indications of cellular -structure, and appear to have been membranous in character. -In some specimens dehiscence appears to have -taken place by a slit in one side, and, clay having entered -into the interior, both walls of the spore-case can be seen. -In other instances, being flattened, they might be mistaken -<span class="pagenum"><a name="Page_66" id="Page_66">« 66 »</a></span> -for scales. No spores could be observed in any of -the specimens, though in some the surface was marked -by slight, rounded prominences, possibly the impressions -of the spores within. This peculiar and very simple style -of spore-case is also characteristic of other species, and -gives to <i>Psilophyton</i> a very distinct generic character. -These naked spore-cases may be compared to those of -such lycopodiaceous plants as <i>Psilotum</i>, in which the -<span class="pagenum"><a name="Page_67" id="Page_67">« 67 »</a></span> -scales are rudimentary. They also bear some resemblance, -though on a much larger scale, to the spore-cases of some -Erian ferns (<i>Archæopteris</i>), to be mentioned in the -sequel. On the whole, however, they seem most nearly -related to the sporocarps of the Rhizocarpeæ.</p> - -<div class="fig_center" style="width: 335px;"> -<a id="fig21" name="fig21"></a> -<img src="images/fig21.png" width="335" height="532" alt="" /> -<div class="fig_caption">Fig. 21.—<i>Lepidodendron</i> and <i>Psilophyton</i> (Erian, New Brunswick). -A, <i>Lepidodendron Gaspianum</i>. B, C, <i>Psilophyton elegans</i>.</div> -</div> - -<p><i>Arthrostigma</i>, which is found in the same beds with -Psilophyton, was a plant of more robust growth, with -better-developed, narrow, and pointed leaves, borne in a -verticillate or spiral manner, and bearing at the ends of -its branches spikes of naked sporocarps, apparently similar -to those of <i>Psilophyton</i> but more rounded in form. -The two genera must have been nearly related, and the -slender branchlets of <i>Arthrostigma</i> are, unless well preserved, -scarcely distinguishable from the stems of <i>Psilophyton</i>.<a name="FNanchor_AU_47" id="FNanchor_AU_47"></a><a href="#Footnote_AU_47" class="fnanchor">[AU]</a></p> - -<div class="footnote"> - -<p><a name="Footnote_AU_47" id="Footnote_AU_47"></a><a href="#FNanchor_AU_47"><span class="label">[AU]</span></a> Reports of the author on “Devonian Plants,” “Geological Survey of -Canada,” which see for details as to Erian Flora of northeastern America.</p></div> - -<p>If, now, we compare the vegetation of these and similar -ancient plants with that of modern Rhizocarps, we -shall find that the latter still present, though in a depauperated -and diminished form, some of the characteristics -of their predecessors. Some, like <i>Pilularia</i>, have -simple linear leaves; others, like <i>Marsilea</i>, have leaves in -verticils and cuneate in form; while others, like Azolla -and Salvinia, have frondose leaves, more or less pinnate -in their arrangement. The first type presents little that -is characteristic, but there are in the Erian sandstones -and shales great quantities of filamentous and linear objects -which it has been impossible to refer to any genus, -and which might have belonged to plants of the type of -<i>Pilularia</i>. It is quite possible, also, that such plants as -<i>Psilophyton glabrum</i> and <i>Cordaites angustifolia</i>, of which -the fructification is quite unknown, may have been allied -to Rhizocarps. With regard to the verticillate type, we -are at once reminded of <i>Sphenophyllum</i> (<a href="#fig20">Fig. 20</a>), which -<span class="pagenum"><a name="Page_68" id="Page_68">« 68 »</a></span> -many palæobotanists have referred to the <i>Marsiliacæ</i>, -though, like other Palæozoic Acrogens, it presents complexities -not seen in its modern representatives. <i>S. primævum</i> -of Lesquereux is found in the Hudson River -group, and my <i>S. antiquum</i> in the Middle Erian. Besides -these, there are in the Silurian and Erian beds -plants with verticillate leaves which have been placed -with the Annulariæ, but which may have differed from -them in fructification. <i>Annularia laxa</i>, of the Erian, -and <i>Protannularia Harknessii</i>, of the Siluro-Cambrian, -may be given as examples, and must have been aquatic -plants, probably allied to Rhizocarps. It is deserving of -notice, also, that the two best-known species of <i>Psilophyton</i> -(<i>P. princeps</i> and <i>P. robustius</i>), while allied to Lycopods -by the structure of the stem and such rudimentary -foliage as they possess, are also allied, by the form of -their fructification, to the Rhizocarps, and not to ferns, -as some palæobotanists have incorrectly supposed. A -similar remark applies to <i>Arthrostigma</i>; and the beautiful -pinnately leaved <i>Ptilophyton</i> may be taken to represent -that type of foliage as seen in modern Rhizocarps, while -the allied forms of the Carboniferous which Lesquereux -has named <i>Trochophyllum</i>, seem to have had sporocarps -attached to the stem in the manner of <i>Azolla</i>.</p> - -<p>The whole of this evidence, I think, goes to show that -in the Erian period there were vast quantities of aquatic -plants, allied to the modern Rhizocarps, and that the so-called -<i>Sporangites</i> referred to in this paper were probably -the drifted sporocarps and macrospores of some of these -plants, or of plants allied to them in structure and habit, -of which the vegetative organs have perished. I have -shown that in the Erian period there were vast swampy -flats covered with <i>Psilophyton</i>, and in similar submerged -tracts near to the sea the <i>Protosalvinia</i> may have filled -the waters and have given off the vast multitudes of -macrospores which, drifted by currents, have settled in the -<span class="pagenum"><a name="Page_69" id="Page_69">« 69 »</a></span> -mud of the black shales. We have thus a remarkable -example of a group of plants reduced in modern times to -a few insignificant forms, but which played a great role in -the ancient Palæozoic world.</p> - -<p>Leaving the Rhizocarps, we may now turn to certain -other families of Erian plants. The first to attract our -attention in this age would naturally be the Lycopods, -the club-mosses or ground-pines, which in Canada and -the Eastern States carpet the ground in many parts of -our woods, and are so available for the winter decoration -of our houses and public buildings. If we fancy one of -these humble but graceful plants enlarged to the dimensions -of a tree, we shall have an idea of a <i>Lepidodendron</i>, -or of any of its allies (Figs. <a href="#fig15">15</a>, <a href="#fig21">21</a>). These large lycopodiaceous -trees, which in different specific and generic -forms were probably dominant in the Erian woods, resembled -in general those of modern times in their fruit -and foliage, except that their cones were large, and probably -in most cases with two kinds of spores, and their -leaves were also often very long, thus bearing a due proportion -to the trees which they clothed. Their thick -stems required, however, more strength than is necessary -in their diminutive successors, and to meet this want -some remarkable structures were introduced similar to -those now found only in the stems of plants of higher -rank. The cells and vessels of all plants consist of thin -walls of woody matter, enclosing the sap and other contents -of these sacs and tubes, and when strength is required -it is obtained by lining their interior with successive -coats of the hardest form of woody matter, usually -known as lignin. But while the walls remain thin, they -afford free passage to the sap to nourish every part. If -thickened all over, they would become impervious to sap, -and therefore unsuited to one of their most important -functions. These two ends of strength and permeability -are secured by partial linings of lignin, leaving portions of -<span class="pagenum"><a name="Page_70" id="Page_70">« 70 »</a></span> -the original wall uncovered. But this may be done in a -great variety of ways.</p> - -<p>The most ancient of these contrivances, and one still -continued in the world of plants, is that of the barred -or scalariform vessel. This may be either square or hexagonal, -so as to admit of being packed without leaving -vacancies. It is strengthened by a thick bar of ligneous -matter up each angle, and these are connected by cross-bars -so as to form a framework resembling several ladders -fastened together. Hence the name <i>scalariform</i>, or ladder-like. -Now, in a modern Lycopod there is a central -axis of such barred vessels associated with simpler fibres -or elongated cells. Even in <i>Sphenophyllum</i> and <i>Psilophyton</i>, -already referred to as allied to Rhizocarps,<a name="FNanchor_AV_48" id="FNanchor_AV_48"></a><a href="#Footnote_AV_48" class="fnanchor">[AV]</a> there -is such a central axis, and in the former rigidity is given -to this by the vascular and woody elements being arranged -in the form of a three-sided prism or three-rayed -star. But such arrangements would not suffice for a tree, -and hence in the arboreal Lycopods of the Erian age a -more complex structure is introduced. The barred vessels -were expanded in the first instance into a hollow -cylinder filled in with pith or cellular tissue, and the -outer rind was strengthened with greatly thickened cells. -But even this was not sufficient, and in the older stems -wedge-shaped bundles of barred tissue were run out from -the interior, forming an external woody cylinder, and inside -of the rind were placed bundles of tough bast fibres. -Thus, a stem was constructed having pith, wood, and -bark, and capable of additions to the exterior of the -woody wedges by a true exogenous growth. The plan is, -in short, the same with that of the stems of the exogenous -trees of modern times, except that the tissues employed -are less complicated. The structures of these remarkable -<span class="pagenum"><a name="Page_71" id="Page_71">« 71 »</a></span> -trees, and the manner in which they anticipate those of -the true exogens of modern times, have been admirably -illustrated by Dr. Williamson, of Manchester. His -papers, it is true, refer to these plants as existing in the -Carboniferous age, but there is every reason to believe -that they were of the same character in the Erian. The -plan is the same with that now seen in the stems of exogenous -phænogams, and which has long ceased to be used -in those of the Lycopods. In this way, however, large -and graceful lycopodiaceous trees were constructed in the -Erian period, and constituted the staple of its forests.</p> - -<div class="footnote"> - -<p><a name="Footnote_AV_48" id="Footnote_AV_48"></a><a href="#FNanchor_AV_48"><span class="label">[AV]</span></a> First noticed by the author, “Journal of Geological Society,” 1865; -but more completely by Renault, “Comptes Rendus,” 1870.</p></div> - -<p>The roots of these trees were equally remarkable with -their stems, and so dissimilar to any now existing that -botanists were long disposed to regard them as independent -plants rather than roots. They were similar in -general structure to the stems to which they belonged, -but are remarkable for branching in a very regular manner -by bifurcation like the stems above, and for the fact -that their long, cylindrical rootlets were arranged in a -spiral manner and distinctly articulated to the root after -the manner of leaves rather than of rootlets, and fitting -them for growing in homogeneous mud or vegetable -muck. They are the so-called <i>Stigmaria</i> roots, which, -though found in the Erian and belonging to its lycopodiaceous -plants, attained to far greater importance in the -Carboniferous period, where we shall meet with them again.</p> - -<div class="fig_right" style="width: 185px;"> -<a id="fig22" name="fig22"></a> -<img src="images/fig22.png" width="185" height="658" alt="" /> -<div class="fig_caption">Fig. 22.—Erian ferns (New -Brunswick), A, <i>Aneimites -obtusa</i>. C, <i>Neuropteris polymorpha</i>. -F, <i>Sphenopteris -pilosa</i>. N, <i>Hymenophyllites -subfurcatus</i>.</div> -</div> - -<p>There were different types of lycopodiaceous plants -in the Erian. In addition to humble Lycopods like those -of our modern woods and great Lepidodendra, which were -exaggerated Lycopods, there were thick-stemmed and less -graceful species with broad rhombic scars (<i>Leptophleum</i>), -and others with the leaf-scars in vertical rows (<i>Sigillaria</i>), -and others, again, with rounded leaf-scars, looking like -the marks on Stigmaria, and belonging to the genus -<i>Cyclostigma</i>. Thus some variety was given to the arboreal -club-mosses of these early forests. (See <a href="#fig15">Fig. 15</a>.)</p> - -<p><span class="pagenum"><a name="Page_72" id="Page_72">« 72 »</a></span></p> - -<p>Another group of plants which -attained to great development in -the Erian age is that of the Ferns -or Brackens. The oldest of these -yet known are found in the Middle -Erian. The <i>Eopteris</i> of Saporta, -from the Silurian, at one -time supposed to carry this type -much further back, has unfortunately -been found to be a mere -imitative form, consisting of -films of pyrites of leaf-like shapes, -and produced by crystallisation. -In the Middle Erian, however, -more especially in North America, -many species have been found -(Figs. <a href="#fig22">22</a> to <a href="#fig24">24</a>).<a name="FNanchor_AW_49" id="FNanchor_AW_49"></a><a href="#Footnote_AW_49" class="fnanchor">[AW]</a> I have myself -recorded more than thirty species -from the Middle Erian of -Canada, and these belong to several -of the genera found in the -Carboniferous, though some are -peculiar to the Erian. Of the -latter, the best known are perhaps -those of the genus <i>Archæopteris</i> -(<a href="#fig24">Fig. 24</a>), so abundant -in the plant-beds of Kiltorcan -in Ireland, as well as in North -America. In this genus the -fronds are large and luxuriant, -with broad obovate pinnules decurrent, -on the leaf-stalk, and -with simple sac-like spore-cases -borne on modified pinnæ. Another -very beautiful fern found -with <i>Archæopteris</i> is that which I have named <i>Platyphyllum</i>, -and which grew on a creeping stem or parasitically -on stems of other plants, and had marginal fructification.<a name="FNanchor_AX_50" id="FNanchor_AX_50"></a><a href="#Footnote_AX_50" class="fnanchor">[AX]</a> -Another very remarkable fern, which some botanists have -supposed may belong to a higher group than the ferns, is -Megalopteris (<a href="#fig26">Fig. 26</a>).</p> - -<div class="footnote"> - -<p><a name="Footnote_AW_49" id="Footnote_AW_49"></a><a href="#FNanchor_AW_49"><span class="label">[AW]</span></a> For descriptions of these ferns, see reports cited above.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_AX_50" id="Footnote_AX_50"></a><a href="#FNanchor_AX_50"><span class="label">[AX]</span></a> “Reports on Fossil Plants of the Devonian and Upper Silurian of -Canada,” 1871, &c.</p> - -<p><span class="pagenum"><a name="Page_73" id="Page_73">« 73 »</a></span></p></div> - -<div class="fig_center" style="width: 387px;"> -<a id="fig23" name="fig23"></a> -<img src="images/fig23.png" width="387" height="673" alt="" /> -<div class="fig_caption">Fig. 23.—Erian ferns (New Brunswick), B, <i>Cyclopteris valida</i>, and -pinnule enlarged, D, <i>Sphenopteris marginata</i>, and portion enlarged. -E, <i>Sphenopteris Harttii</i>. G, <i>Hymenophyllites curtilobus</i>. H, <i>Hymenophyllites -Gersdorffii</i>, and portion enlarged. I, <i>Alethopteris discrepans</i>, -K, <i>Pecopteris serrulata</i>, L, <i>Pecopteris preciosa</i>. M, <i>Alethopteris Perleyi</i>.</div> -</div> - -<p><span class="pagenum"><a name="Page_74" id="Page_74">« 74 »</a></span></p> - -<div class="fig_center" style="width: 385px;"> -<a id="fig24" name="fig24"></a> -<img src="images/fig24.png" width="385" height="590" alt="" /> -<div class="fig_caption">Fig. 24.—<i>Archæopteris Jacksoni</i>, Dawson (Maine). An Upper Erian -fern, <i>a</i>, <i>b</i>, Pinnules showing venation.</div> -</div> - -<p><span class="pagenum"><a name="Page_75" id="Page_75">« 75 »</a></span></p> - -<div class="fig_center" style="width: 414px;"> -<a id="fig25" name="fig25"></a> -<img src="images/fig25.png" width="414" height="340" alt="" /> -<div class="fig_caption">Fig. 25.—An Erian tree-fern. <i>Caulopteris Lockwoodi</i>, Dawson, -reduced. (From a specimen from Gilboa, New York.)</div> -</div> - -<p>Some of the Erian ferns attained to the dimensions of -tree-ferns. Large stems of these, which must have floated -out far from land, have been found by Newberry in the -marine limestone of Ohio (<i>Caulopteris antiqua</i> and <i>C. -peregrina</i>, Newberry),<a name="FNanchor_AY_51" id="FNanchor_AY_51"></a><a href="#Footnote_AY_51" class="fnanchor">[AY]</a> and Prof. Hall has found in the -Upper Devonian of Gilboa, New York, the remains of a -forest of tree-ferns standing <i>in situ</i> with their great -masses of aërial roots attached to the soil in which they -grew (<i>Caulopteris Lockwoodi</i>, Dn.).<a name="FNanchor_AZ_52" id="FNanchor_AZ_52"></a><a href="#Footnote_AZ_52" class="fnanchor">[AZ]</a></p> - -<div class="footnote"> - -<p><a name="Footnote_AY_51" id="Footnote_AY_51"></a><a href="#FNanchor_AY_51"><span class="label">[AY]</span></a> “Journal of the Geological Society,” 1871.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_AZ_52" id="Footnote_AZ_52"></a><a href="#FNanchor_AZ_52"><span class="label">[AZ]</span></a> <i>Ibid.</i></p></div> - -<div class="fig_center" style="width: 385px;"> -<a id="fig26" name="fig26"></a> -<img src="images/fig26.png" width="385" height="598" alt="" /> -<div class="fig_caption">Fig. 26.—<i>Megalopteris Dawsoni</i>, Hartt (Erian, New Brunswick), <i>a</i>, Fragment -of pinna. <i>b</i>, Point of pinnule, <i>c</i>, Venation, (The midrib is not -accurately given in this figure.)</div> -</div> - -<p>These aërial roots introduce us to a new contrivance -for strengthening the stems of plants by sending out into -the soil multitudes of cord-like cylindrical roots from -<span class="pagenum"><a name="Page_76" id="Page_76">« 76 »</a></span> -various heights on the stem, and which form a series of -stays like the cordage of a ship. This method of support -still continues in the modern tree-ferns of the tropics -and the southern hemisphere. In one kind of tree-fern -<span class="pagenum"><a name="Page_77" id="Page_77">« 77 »</a></span> -stem from the Erian of New York, there is also a special -arrangement for support, consisting of a series of peculiarly -arranged radiating plates of scalariform vessels, not -exactly like those of an exogenous stem, but doing duty -for it (<i>Asteropteris</i>)<a name="FNanchor_BA_53" id="FNanchor_BA_53"></a><a href="#Footnote_BA_53" class="fnanchor">[BA]</a> -Similar plants have -been described from -the Erian of Falkenberg, -in Germany, -and of Saalfeld, in -Thuringia, by Goeppert -and Unger, and -are referred to ferns -by the former, but -treated as doubtful -by the latter,<a name="FNanchor_BB_54" id="FNanchor_BB_54"></a><a href="#Footnote_BB_54" class="fnanchor">[BB]</a> This -peculiar type of tree-fern -is apparently a -precursor of the more -exogenous type of -<i>Heterangium</i>, recently -described and referred -to ferns by -Williamson. Here, -again, we have a mechanical -contrivance -now restricted to -higher plants appropriated -by these old -cryptogams.</p> - -<div class="footnote"> - -<p><a name="Footnote_BA_53" id="Footnote_BA_53"></a><a href="#FNanchor_BA_53"><span class="label">[BA]</span></a> “Journal of the Geological Society,” London, 1881.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_BB_54" id="Footnote_BB_54"></a><a href="#FNanchor_BB_54"><span class="label">[BB]</span></a> “Sphenopteris Refracta,” Goeppert; “Flora des Uebergangsgebirges.” -“Cladoxylon Mirabile,” Unger; “Palæontologie des Thuringer Waldes.”</p></div> - -<table style="width:100%;" summary="fossils"> -<tr> - <td class="center" style="width:50%;"><a id="fig27" name="fig27"></a> - <img src="images/fig27.png" width="279" height="497" alt="" /> - <div class="fig_caption">Fig. 27.—<i>Calamites radiatus</i> (Erian, New - Brunswick).</div> - </td> - <td class="center" style="width:50%;"><a id="fig28" name="fig28"></a> - <img src="images/fig28.png" width="287" height="436" alt="" /> - <div class="fig_caption">Fig. 28.—Asterophyllites (Erian, New Brunswick),<br /> - A, Asterophyllites latifolia. B, Do.,<br /> - apex of stem (?) fruit, <span class="smcap">C</span>, C<sup>1</sup>, <i>A. scutigera</i>.<br /> - D, <i>A. latifolia</i>, larger whorl of leaves. - D<sup>1</sup>, Leaf.</div> - </td> -</tr> -</table> - -<p><span class="pagenum"><a name="Page_78" id="Page_78">« 78 »</a></span></p> - -<p>The history of the ferns in geological time is remarkably -different from that of the Lycopods; for while the -latter have long ago descended from their pristine eminence -to a very humble place in nature, the former still, -in the southern hemisphere at least, retain their arboreal -dimensions and ancient -dominance.</p> - -<p>The family of -the <i>Equisetaceæ</i>, or -mare’s-tails, was also -represented by large -species of <i>Calamites</i> -and by <i>Asterophyllites</i> -in the Erian; -but, as its headquarters -are in the Carboniferous, -we may -defer its consideration -till the next -chapter. (Figs. <a href="#fig27">27</a>, -<a href="#fig28">28</a>.)</p> - -<p>Passing over these -for the present, we -find that the flowering -plants are represented -in the Erian -forests by at least -two types of Gymnosperms, -that of -<i>Taxineæ</i> or yews, -and an extinct family, that of the <i>Cordaites</i> (Figs. <a href="#fig30">30</a>, <a href="#fig31">31</a>). -The yew-trees are closely allied to the pines and spruces, -and are often included with them in the family of <i>Coniferæ</i>. -They differ, however, in the habit of producing berries or -drupe-like fruits instead of cones, and there is some -reason to believe that this was the habit of the Erian -trees of this group, though their wood in some instances -resembles rather that of the Araucaria, or Norfolk -<span class="pagenum"><a name="Page_79" id="Page_79">« 79 »</a></span> -Island pine, than that of the modern yews. These -trees are chiefly known to us by their mineralised trunks, -which are often found like drift-wood on modern sand-banks -embedded in the Erian sandstones or limestones. -It often shows its structure in the most perfect manner -in specimens penetrated by calcite or silica, or by -pyrite, and in which the original woody matter has -been resolved into anthracite or even into graphite. -These trees have true woody tissues presenting that beautiful -arrangement of pores or thin parts enclosed in cup-like -discs, which is characteristic of the coniferous trees, -and which is a great improvement on the barred tissue -already referred to, affording a far more strong, tough, -and durable wood, such as we have in our modern pines -and yews (<a href="#fig29">Fig. 29</a>).</p> - -<div class="fig_center" style="width: 454px;"> -<a id="fig29" name="fig29"></a> -<img src="images/fig29.png" width="454" height="370" alt="" /> -<div class="fig_caption">Fig. 29.—<i>Dadoxylon Ouangondianum</i>, an Erian conifer, A, Fragment -showing Sternberg pith and wood; <i>a</i>, medullary sheath; <i>b</i>, pith; -<i>c</i>, wood; <i>d</i>, section of pith, B, Wood-cell; <i>a</i>, hexagonal areole; -<i>b</i>, pore, <i>c</i>, Longitudinal section of wood, showing, <i>a</i>, areolation, and -<i>b</i>, medullary rays, D, Transverse section, showing, <i>a</i>, wood-cells, and -<i>b</i>, limit of layer of growth, (B, C, D, highly magnified.)</div> -</div> - -<p><span class="pagenum"><a name="Page_80" id="Page_80">« 80 »</a></span></p> - -<p>These primitive pines make their appearance in the -Middle Erian, in various parts of America, as well as in -Scotland and Germany, and they are represented by wood -indicating the presence of several species. I have myself -indicated and described five species from the Erian of -Canada and the United States. From the fact that these -trees are represented by drifted trunks embedded in sandstones -and marine limestones, we may, perhaps, infer that -they grew on the rising grounds of the Erian land, and -that their trunks were carried by river-floods into the sea. -No instance has yet certainly occurred of the discovery of -their foliage or fruit, though there are some fan-shaped -leaves usually regarded as ferns which may have belonged -to such trees. These in that case would have resembled -the modern <i>Gingko</i> of China, and some of the fruits referred -to the genus <i>Cardiocarpum</i> may have been produced -by them. Various names have been given to these -trees. I have preferred that given by Unger, <i>Dadoxylon</i>, -as being more non-committal as to affinities than the -others.<a name="FNanchor_BC_55" id="FNanchor_BC_55"></a><a href="#Footnote_BC_55" class="fnanchor">[BC]</a> Many of these trees had very long internal -pith-cylinders, with curious transverse tubulæ, and which, -when preserved separately, have been named <i>Sternbergia</i>.</p> - -<div class="footnote"> - -<p><a name="Footnote_BC_55" id="Footnote_BC_55"></a><a href="#FNanchor_BC_55"><span class="label">[BC]</span></a> <i>Araucarites</i>, Goeppert; <i>Araucarioxylon</i>, Kraus.</p></div> - -<p>Allied to these trees, and perhaps intermediate between -them and the <i>Cycads</i>, were those known as <i>Cordaites</i> -(<a href="#fig30">Fig. 30</a>), which had trunks resembling those of <i>Dadoxylon</i>, -but with still larger <i>Sternbergia</i> piths and an internal -axis of scalariform vessels, surrounded by a comparatively -thin woody cylinder. Some of them have leaves over a -foot in length, reminding one of the leaves of broad-leaved -grasses or iridaceous plants. Yet their flowers and fruit -seem to have been more nearly allied to the yews than to -any other plants (<a href="#fig31">Fig. 31</a>). Their stems were less woody -<span class="pagenum"><a name="Page_81" id="Page_81">« 81 »</a></span> -and their piths larger than in the true pines, and some -of the larger-leaved species must have had thick, stiff -branches. They are regarded as constituting a separate -family, intermediate between pines and cycads, and, beginning -in the Middle Devonian, they terminate in the -Permian, where, however, some of the most gigantic species -occur. In so far as the form and structure of the -leaves, stems, and fruit are concerned, there is marvellously -little difference between the species found in the -Erian and the Permian. They culminated, however, in -the Carboniferous period, and the coal-fields of southern -France have proved so far the richest in their remains.</p> - -<div class="fig_center" style="width: 402px;"> -<a name="fig30" id="fig30"></a> -<img src="images/fig30.png" width="402" height="510" alt="" /> -<div class="fig_caption">Fig. 30.—<i>Cordaites Robbii</i> (Erian, New Brunswick), <i>a</i>, Group of young -leaves. <i>b</i>, Point of leaf, <i>c</i>, Base of leaf, <i>d</i>. Venation, magnified.</div> -</div> - -<p><span class="pagenum"><a name="Page_82" id="Page_82">« 82 »</a></span></p> - -<div class="fig_center" style="width: 428px;"> -<a name="fig31" id="fig31"></a> -<img src="images/fig31.png" width="428" height="380" alt="" /> -<div class="fig_caption">Fig. 31.—Erian fruits, &c., some gymnospermous, and probably of <i>Cordaites</i> -and Taxine trees (St. John, New Brunswick), A, <i>Cardiocarpum cornutum</i>. -B, <i>Cardiocarpum acutum</i>. C, <i>Cardiocarpum Crampii</i>. D, <i>Cardiocarpum -Baileyi</i>. E, <i>Trigonocarpum racemosum</i>. E<sup>1</sup>, E<sup>2</sup>, Fruits enlarged, -F, <i>Antholithes Devonicus</i>. G, Annularia acuminata, H, <i>Asterophyllites -acicularis</i>. H<sup>2</sup>, Fruit of the same, K, <i>Cardiocarpum</i> -(? young of <i>A.</i>), L, <i>Pinnularia dispalans</i> (probably a root).</div> -</div> - -<p>Lastly, a single specimen, collected by Prof. James -Hall, of Albany, at Eighteen-mile Creek, Lake Erie, has -the structure of an ordinary angiospermous exogen, and -has been described by me as <i>Syringoxylon mirabile</i>.<a name="FNanchor_BD_56" id="FNanchor_BD_56"></a><a href="#Footnote_BD_56" class="fnanchor">[BD]</a> -This unique example is sufficient to establish the fact of -the existence of such plants at this early date, unless some -accident may have carried a specimen from a later formation -<span class="pagenum"><a name="Page_83" id="Page_83">« 83 »</a></span> -to be mixed with Erian fossils. It is to be observed, -however, that the non-occurrence of any similar wood in -all the formations between the Upper Erian and the Middle -Cretaceous suggests very grave doubt as to the authenticity -of the specimen. I record the fact, waiting further -discoveries to confirm it. Of the character of the specimen -which I have described I entertain no doubt.</p> - -<div class="footnote"> - -<p><a name="Footnote_BD_56" id="Footnote_BD_56"></a><a href="#FNanchor_BD_56"><span class="label">[BD]</span></a> “Journal of the Geological Society,” vol. xviii.</p></div> - -<p>We shall be better able to realise the significance and -relations of this ancient flora when we have studied that -of the succeeding Carboniferous. We may merely remark -here on the fact that, in these forests of the Devonian -and in the marshes on their margins, we find a wonderful -expansion of the now modest groups of Rhizocarps -and Lycopods, and that the flora as a whole belongs to -the highest group of Cryptogams and the lowest of Phænogams, -so that it has about it a remarkable aspect of -mediocrity. Further, while there is evidence of some -variety of station, there is also evidence of much equality -of climate, and of a condition of things more resembling -that of the insular climates of the temperate portions of -the southern hemisphere than that of North America or -Europe at present.</p> - -<p>The only animal inhabitants of these Devonian woods, -so far as known, were a few species of insects, discovered -by Hartt in New Brunswick, and described by Dr. Scudder. -Since, however, we now know that scorpions as -well as insects existed in the Silurian, it is probable that -these also occurred in the Erian, though their remains -have not yet been discovered. All the known insects of -the Erian woods are allies of the shad-flies and grasshoppers -(<i>Neuroptera</i> and <i>Orthoptera</i>), or intermediate between -the two. It is probable that the larvæ of most of -them lived in water and fed upon the abundant vegetable -matter there, or on the numerous minute crustaceans and -worms. There were no land vertebrates, so far as known, -but there were fishes (<i>Dipterus</i>, etc.), allied to the modern -<span class="pagenum"><a name="Page_84" id="Page_84">« 84 »</a></span> -Barramunda or <i>Ceratodus</i> of Australia, and with -teeth suited for grinding vegetable food. It is also possible -that some of the smaller plate-covered fishes (Placoganoids, -like <i>Pterichthys</i>) might have fed on vegetable -matter, and, in any case, if they fed on lower animals, the -latter must have subsisted on plants. I mention these -facts to show that the superabundant vegetation of this -age, whether aquatic or terrestrial, was not wholly useless -to animals. It is quite likely, also, that we have yet -much to learn of the animal life of the Erian swamps and -woods.</p> - -<hr class="tb" /> - -<p class="caption3"><a id="NOTES_TO_CHAPTER_III" name="NOTES_TO_CHAPTER_III"></a>NOTES TO CHAPTER III.</p> - -<p class="caption4">I.—<span class="smcap">Classification of Sporangites</span>.</p> - -<p><span class="smcap">It</span> is, of course, very unsatisfactory to give names to mere fragments -of plants, yet it seems very desirable to have some means of -arranging them. With respect to the organisms described above, -which were originally called by me <i>Sporangites</i>, under the supposition -that they were Sporangia rather than spores, this name -has so far been vindicated by the discovery of the spore-cases belonging -to them, so that I think it may still be retained as a provisional -name; but I would designate the whole as <i>Protosalviniæ</i>, meaning -thereby plants with rhizocarpean affinities, though possibly when -better understood belonging to different genera. We may under -these names speak of their detached discs as macrospores and of -their cellular envelopes as sporocarps. The following may be recognized -as distinct forms:</p> - -<p>1. <i>Protosalvinia Huronensis</i>, Dawson, <i>Syn.</i>, <i>Sporangites Huronensis</i>, -“Report on Erian Flora of Canada,” 1871.—Macrospores, in -the form of discs or globes, smooth and thick-walled, the walls penetrated -by minute radiating pores. Diameter about one one-hundredth -of an inch, or a little more, When in situ several macrospores -are contained in a thin cellular sporocarp, probably globular -in form. From the Upper Erian, and perhaps Lower Carboniferous -shales of Kettle Point, Lake Huron, of various places in the State of -Ohio, and in the shale boulders of the boulder clay of Chicago and -vicinity. First collected at Kettle Point by Sir W. E. Logan, and -<span class="pagenum"><a name="Page_85" id="Page_85">« 85 »</a></span> -in Ohio by Prof. Edward Orton, and at Chicago by Dr. H. A. Johnson -and Mr. B. W. Thomas, also in New York by Prof. J. M. Clarke.</p> - -<p>The macrospores collected by Mr. Thomas from the Chicago -clays and shales conform closely to those of Kettle Point, and probably -belong to the same species. Some of them are thicker in the -outer wall, and show the pores much more distinctly. These have -been called by Mr. Thomas <i>S. Chicagoensis</i>, and may be regarded as -a varietal form. Specimens isolated from the shale and mounted -dry, show what seems to have been the hilum or scar of attachment -better than those in balsam.</p> - -<p>Sections of the Kettle Point shale show, in addition to the macrospores, -wider and thinner shreds of vegetable matter, which I am -inclined to suppose to be remains of the sporocarps.</p> - -<p>2. <i>Protosalvinia</i> (<i>Sporangites</i>) <i>Braziliensis</i>, Dawson, “Canadian -Record of Science,” 1883.—Macrospores, round, smooth, a little -longer than those of the last species, or about one seventy-fifth of -an inch in diameter, enclosed in round, oval, or slightly reniform -sporocarps, each containing from four to twenty-four macrospores. -Longest diameter of sporocarps three to six millimetres. Structure -of wall of sporocarps hexagonal cellular. Some sporocarps show no -macrospores, and may possibly contain microspores. The specimens -are from the Erian of Brazil. Discovered by Mr. Orville Derby. -The formation, according to Mr. Derby, consists of black shales below, -about three hundred feet thick, and containing the fucoid known -as Spirophyton, and probably decomposed vegetable matter. Above -this is chocolate and reddish shale, in which the well-preserved specimens -of Protosalvinia occur. These beds are very widely distributed, -and abound in <i>Protosalvinia</i> and <i>Spirophyton</i>.</p> - -<p>3. <i>Protosalvinia</i> (<i>Sporangites</i>) <i>bilobata</i>, Dawson, “Canadian -Record of Science,” 1883.—Sporocarps, oval or reniform, three -to six millimetres in diameter, each showing two rounded -prominences at the ends, with a depression in the middle, and -sometimes a raised neck or isthmus at one side connecting the -prominences. Structure of sporocarp cellular. Some of the specimens -indicate that each prominence or tubercle contained several -macrospores. At first sight it would be easy to mistake these bodies -for valves of <i>Beyrichia</i>.</p> - -<p>Found in the same formations with the last species, though, in so -far as the specimens indicate, not precisely in the same beds. Collected -by Mr. Derby.</p> - -<p>4. <i>Protosalvinia Clarkei</i>, Dawson, <i>P. bilobata</i>, Clarke, “American -Journal of Science.”—Macrospores two-thirds to one millimetre in -<span class="pagenum"><a name="Page_86" id="Page_86">« 86 »</a></span> -diameter. One, two, or three contained in each sporocarp, which is -cellular. The macrospores have very thick walls with radiating tortuous -tubes. Unless this structure is a result of mineral crystallisation, -these macrospores must have had very thick walls and must have -resembled in structure the thickened cells of stone fruits and of the -core of the pear, or the tests of the Silurian and Erian seeds known -as <i>Pachytheca</i>, though on a smaller scale.</p> - -<p>It is to be observed that bodies similar to these occur in the Boghead -earthy bitumen, and have been described by Credner.</p> - -<p>I have found similar bodies in the so-called “Stellar coal” of the -coal district of Pictou, Nova Scotia, some layers of which are filled -with them. They occur in groups or patches, which seem to be enclosed -in a smooth and thin membrane or sporocarp. It is quite -likely that these bodies are generically distinct from <i>Protosalvinia</i>.</p> - -<p>5. <i>Protosalvinia punctata</i>, Newton, “Geological Magazine,” New -Series, December 2d, vol. ii.—Mr. Newton has named the discs -found in the white coal and Tasmanite, <i>Tasmanites</i>, the species being -<i>Tasmanites punctatus</i>, but as my name <i>Sporangites</i> had priority, -I do not think it necessary to adopt this term, though there can be -little doubt that these organisms are of similar character. The same -remark may be made with reference to the bodies described by Huxley -and Newton as occurring in the Better-bed coal.</p> - -<p>In Witham’s “Internal Structure of Fossil Vegetables,” 1833, -Plate XI, are figures of Lancashire cannel which shows <i>Sporangites</i> of -the type of those in the Erian shales. Quekett, in his “Report on the -Torbane Hill Mineral,” 1854, has very well figured similar structures -from the Methel coal and the Lesmahagow cannel coal. These are -the earliest publications on the subject known to me; and Quekett, -though not understanding the nature of the bodies he observed, -holds that they are a usual ingredient in cannel coals.</p> - - -<p class="caption4">II.—<span class="smcap">The Nature and Affinities of Ptilophyton.</span></p> - -<p>(<i>Lycopodites Vanuxemii</i> of “Report on Devonian and Upper -Silurian Plants,” Part I., page 35, <i>L. plumula</i> of “Report on Lower -Carboniferous Plants,” page 24, Plate I., Figs. 7, 8, 9.) In the reports -above referred to, these remarkable pinnate, frond-like objects -were referred to the genus <i>Lycopodites</i>, as had been done by Goeppert -in his description of the European species <i>Lycopodites pennæformis</i>, -which is very near to the American Erian form. Since 1871, -however, there have been many new specimens obtained, and very -various opinions expressed as to their affinities. While Hall has -named some of them <i>Plumalina</i>, and has regarded them as animal -<span class="pagenum"><a name="Page_87" id="Page_87">« 87 »</a></span> -structures, allied to hydroids, Lesquereux has described some of the -Carboniferous forms under the generic name <i>Trochophyllum</i>, which -is, however, more appropriate to plants with verticillate leaves which -are included in this genus. Before I had seen the publications of -Hall and Lesquereux on the subject, I had in a paper on “Scottish -Devonian Plants”<a name="FNanchor_BE_57" id="FNanchor_BE_57"></a><a href="#Footnote_BE_57" class="fnanchor">[BE]</a> separated this group from the genus <i>Lycopodites</i>, -and formed for it the genus <i>Ptilophyton</i>, in allusion to the feather-like -aspect of the species. My reasons for this, and my present information -as to the nature of these plants, may be stated as follows: -Schimper, in his “Palæontologie Vegetale” (possibly from inattention -to the descriptions or want of access to specimens), doubts the -lycopodiaceous character of species of <i>Lycopodites</i> described in my -published papers on plants of the Devonian of America and in my -Report of 1871. Of these, <i>L. Richardsoni</i> and <i>L. Matthewi</i> are undoubtedly -very near to the modern genus <i>Lycopodium</i>. <i>L. Vanuxemii</i> -is, I admit, more problematical; but Schimper could scarcely -have supposed it to be a fern or a fucoid allied to <i>Caulerpa</i> had he -observed that both in my species and the allied <i>L. pennæformis</i> of -Goeppert, which he does not appear to notice, the pinnules are articulated -upon the stem, and leave scars where they have fallen off. -When in Belfast in 1870, my attention was again directed to the -affinities of these plants by finding in Prof. Thomson’s collection a -specimen from Caithness, which shows a plant apparently of this -kind, with the same long narrow pinna? or leaflets, attached, however, -to thicker stems, and rolled up in a circinate manner. It seems -to be a plant in vernation, and the parts are too much crowded and -pressed together to admit of being accurately figured or described; -but I think I can scarcely be deceived as to its true nature. The -circinate arrangement in this case would favour a relationship to -ferns; but some lycopodiaceous plants also roll themselves in this -way, and so do the branches of the plants of the genus <i>Psilophyton</i>. -(<a href="#fig17">Fig. 17</a>, <i>supra</i>.)</p> - -<div class="footnote"> - -<p><a name="Footnote_BE_57" id="Footnote_BE_57"></a><a href="#FNanchor_BE_57"><span class="label">[BE]</span></a> “Canadian Naturalist,” 1878.</p></div> - -<p>The specimen consists of a short, erect stem, on which are placed -somewhat stout alternate branches, extending obliquely outward and -then curving inward in a circinate manner. The lower ones appear -to produce on their inner sides short lateral branchlets, and upon -these, and also upon the curved extremities of the branches, are long, -narrow, linear leaves placed in a crowded manner. The specimen is -thus not a spike of fructification, but a young stem or branch in vernation, -and which when unrolled would be of the form of those -<span class="pagenum"><a name="Page_88" id="Page_88">« 88 »</a></span> -peculiar pinnate <i>Lycopodites</i> of which <i>L. Vanuxemii</i> of the American -Devonian and <i>L. pennæformis</i> of the European Lower Carboniferous -are the types, and it shows, what might have been anticipated -from other specimens, that they were low, tufted plants, circinate in -vernation. The short stem of this plant is simply furrowed, and -bears no resemblance to a detached branch of Lycopodites Milleri -which lies at right angles to it on the same slab. As to the affinities -of the singular type of plants to which this specimen belongs, I may -quote from my “Report on the Lower Carboniferous Plants of -Canada,” in which I have described an allied species, <i>L. plumula</i>:</p> - -<p>“The botanical relations of these plants must remain subject to -doubt, until either their internal structure or their fructification can -be discovered. In the mean time I follow Goeppert in placing them -in what we must regard as the provisional genus <i>Lycopodites</i>. On -the one hand, they are not unlike the slender twigs of <i>Taxodium</i> -and similar Conifers, and the highly carbonaceous character of the -stems gives some colour to the supposition that they may have been -woody plants. On the other hand, they might, so far as form is concerned, -be placed with Algæ of the type of Brongniart’s <i>Chondrites -obtusus</i>, or the modern <i>Caulerpa plumaria</i>. Again, in a plant of -this type from the Devonian of Caithness to which I have referred in -a former memoir, the vernation seems to have been circinate, and -Schimper has conjectured that these plants may be ferns, which -seems also to have been the view of Shumard.”</p> - -<p>On the whole, these plants are allied to Lycopods rather than to -ferns; and as they constitute a small but distinct group, known only, -so far as I am aware, in the Lower Carboniferous and Erian or Devonian, -they deserve a generic name, and I proposed for them in my -“Paper on Scottish Devonian Plants,” 1878, that of <i>Ptilophyton</i>, a -name sufficiently distinct in sound from Psilophyton, and expressing -very well their peculiar feather-like habit of growth. The genus was -defined as follows:</p> - -<p>“Branching plants, the branches bearing long, slender leaves in -two or more ranks, giving them a feathered appearance; vernation -circinate. Fruit unknown, but analogy would indicate that it was -borne on the bases of the leaves or on modified branches with shorter -leaves.”</p> - -<p>The Scottish specimen above referred to was named <i>Pt. Thomsoni</i>, -and was characterised by its densely tufted form and thick -branches. The other species known are: <i>Pt. pennæformis</i>, Goeppert, -L. Carboniferous; <i>Pt. Vanuxemii</i>, Dawson, Devonian; <i>Pt. -plumula</i>, Dawson, L. Carboniferous.</p> - -<p><span class="pagenum"><a name="Page_89" id="Page_89">« 89 »</a></span></p> - -<p>Shumard’s <i>Filicites gracilis</i>, from the Devonian of Ohio, and -Stur’s <i>Pinites antecedens</i>, from the Lower Carboniferous of Silesia, -may possibly belong to the same genus. The Scottish specimen referred -to is apparently the first appearance of this form in the -Devonian of Europe.</p> - -<p>I have at a still later date had opportunities of studying considerable -series of these plants collected by Prof. Williams, of Cornell -University, and prepared a note in reference to them for the American -Association, of which, however, only an abstract has been published. -I have also been favoured by Prof. Lesquereux and Mr. -Lacoe, of Pittston, with the opportunity of studying the specimens -referred to <i>Trochophyllum</i>.</p> - -<p>Prof. Williams’s specimens occur in a dark shale associated with -remains of land-plants of the genera <i>Psilophyton</i>. <i>Rhodea</i>, &c., and -also marine shells, of which a small species of <i>Rhynchonella</i> is often -attached to the stems of the <i>Ptilophyton</i>. Thus these organisms -have evidently been deposited in marine beds, but in association -with land-plants.</p> - -<p>The study of the specimens collected by Prof. Williams develops -the following facts: (1) The plants are not continuous fronds, but -slender stems or petioles, with narrow, linear leaflets attached in a -pinnate manner. (2) The pinnules are so articulated that they break -off, leaving delicate transverse scars, and the lower parts of the stems -are often thus denuded of pinnæ for the length of one or more -inches. (3) The stems curve in such a manner as to indicate a circinate -vernation. (4) In a few instances the fronds were observed -to divide dichotomously toward the top; but this is rare. (5) There -are no indications of cells in the pinnules; but, on the other hand, -there is no appearance of fructification unless the minute granules -which roughen some of the sterns are of this nature. (6) The stems -seem to have been lax and flexuous, and in some instances they -seem to have grown on the petioles of ferns preserved with them in -the same beds. (7) The frequency of the attachment of small brachiopods -to the specimens of <i>Ptilophyton</i> would seem to indicate that -the plant stood erect in the water. (8) Some of the specimens show -so much carbonaceous matter as to indicate that the pinnules were -of considerable consistency. All these characters are those rather -of an aquatic plant than of an animal organism or of a land-plant.</p> - -<p>The specimens communicated by Prof. Lesquereux and Mr. -Lacoe are from the Lower Carboniferous, and evidently represent a -different species with similar slender pitted stems, often partially -denuded of pinnules below; but the pinnules are much broader and -<span class="pagenum"><a name="Page_90" id="Page_90">« 90 »</a></span> -more distant. They are attached by very narrow bases, and apparently -tend to lie on a plane, though they may possibly have been -spirally arranged. On the same slabs are rounded sporangia or -macrospores like those of <i>Lepidodendron</i>, but there is no evidence -that these belonged to <i>Trochophyllum</i>. On the stems of this plant, -however, there are small, rounded bodies apparently taking the places -of some of the pinnules. These may possibly be spore-cases; but -they may be merely imperfectly developed pinnules. Still the fact -that similar small granules appear on the stems of the Devonian -species, favours the idea that they may be organs of fructification.</p> - -<p>The most interesting discovery, however, which results from the -study of Mr. Lacoe’s specimens, is that the pinnules were cylindrical -and hollow, and probably served to float the plant. This would -account for many of the peculiarities in the appearance and mode -of occurrence of the Devonian <i>Ptilophyton</i>, which are readily explained -if it is supposed to be an aquatic plant, attaching itself to -the stems of submerged vegetable remains and standing erect in the -water by virtue of its hollow leaves. It may well, however, have -been a plant of higher organisation than the Algæ, though no doubt -cryptogamous.</p> - -<p>The species of <i>Ptilophyton</i> will thus constitute a peculiar group -of aquatic plants, belonging to the Devonian and Lower Carboniferous -periods, and perhaps allied to Lycopods and Pillworts in their -organisation and fruit, but specially distinguished by their linear -leaves serving as floats and arranged pinnately on slender stems. -The only species yet found within the limits of Canada is <i>Pt. plumula</i>, -found by Dr. Honeyman in the Lower Carboniferous of Nova -Scotia; but as <i>Pt. Vanuxemii</i> abounds in the Erian of New York, -it will no doubt be found in Canada also.</p> - - -<p class="caption4">III.—<span class="smcap">Tree-Ferns of the Erian Period.</span></p> - -<p>As the fact of the occurrence of true tree-ferns in rocks so old -as the Middle Erian or Devonian has been doubted in some quarters, -the following summary is given from descriptions published in -the “Journal of the Geological Society of London” (1871 and 1881), -where figures of the species will be found:</p> - -<p>Of the numerous ferns now known in the Middle and Upper -Devonian of North America, a great number are small and delicate -species, which were probably herbaceous; but there are other species -which may have been tree-ferns. Little definite information, however, -has, until recently, been obtained with regard to their habit of -growth.</p> - -<p><span class="pagenum"><a name="Page_91" id="Page_91">« 91 »</a></span></p> - -<p>The only species known to me in the Devonian of Europe is the -<i>Caulopteris Peachii</i> of Salter, figured in the “Quarterly Journal of -the Geological Society” for 1858. The original specimen of this I -had an opportunity of seeing in London, through the kindness of -Mr. Etheridge, and have no doubt that it is the stem of a small -arborescent fern, allied to the genus <i>Caulopteris</i>, of the coal formation.</p> - -<p>In my paper on the Devonian of Eastern America (“Quarterly -Journal of the Geological Society,” 1862), I mentioned a plant found -by Mr. Richardson at Perry, as possibly a species of <i>Megaphyton</i>, -using that term to denote those stems of tree-ferns which have the -leaf-scars in two vertical series; but the specimen was obscure, and -I have not yet obtained any other.</p> - -<p>More recently, in 1869, Prof. Hall placed in my hands an interesting -collection from Gilboa, New York, and Madison County, New -York, including two trunks surrounded by aërial roots, which I have -described as <i>Psaronius textilis</i> and <i>P. Erianus</i>, in my “Revision of -the Devonian Flora,” read before the Royal Society.<a name="FNanchor_BF_58" id="FNanchor_BF_58"></a><a href="#Footnote_BF_58" class="fnanchor">[BF]</a> In the same -collection were two very large petioles, <i>Rhachiopteris gigantea</i> and -<i>R. palmata</i>, which I have suggested may have belonged to tree-ferns.</p> - -<div class="footnote"> - -<p><a name="Footnote_BF_58" id="Footnote_BF_58"></a><a href="#FNanchor_BF_58"><span class="label">[BF]</span></a> Abstract in “Proceedings of the Royal Society,” May, 1870; also -“Report on Erian Plants of Canada,” 1871.</p></div> - -<p>My determination of the species of <i>Psaronius</i>, above mentioned, -has recently been completely confirmed by the discovery on the part -of Mr. Lockwood, of Gilboa, of the upper part of one of these stems, -with its leaf-scars preserved and petioles attached, and also by some -remarkable specimens obtained by Prof. Newberry, of New York, -from the Corniferous limestone of Ohio, which indicate the existence -there of three species of tree-ferns, one of them with aërial -roots similar to those of the Gilboa specimens. The whole of these -specimens Dr. Newberry has kindly allowed me to examine, and has -permitted me to describe the Gilboa specimen, as connected with -those which I formerly studied in Prof. Hall’s collections. The -specimens from Ohio he has himself named, but allows me to notice -them here by way of comparison with the others. I shall add some -notes on specimens found with the Gilboa ferns.</p> - -<p>It may be further observed that the Gilboa specimens are from -a bed containing erect stumps of tree-ferns, in the Chemung group -of the Upper Devonian, while those from Ohio are from a marine -limestone, belonging to the lower part of the Middle Devonian.</p> - -<p>1. <i>Caulopteris Lockwoodi</i>, Dawson.—Trunk from two to three -<span class="pagenum"><a name="Page_92" id="Page_92">« 92 »</a></span> -inches in diameter, rugose longitudinally. Leaf-scars broad, rounded -above, and radiatingly rugose, with an irregular scar below, arranged -spirally in about five ranks; vascular bundles not distinctly preserved. -Petioles slender, much expanded at the base, dividing at -first in a pinnate manner, and afterwards dichotomously. Ultimate -pinnæ with remains of numerous, apparently narrow pinnules.</p> - -<p>This stem is probably the upper part of one or other of the -species of <i>Psaronius</i> found in the same bed (<i>P. Erianus</i>, Dawson, -and <i>P. textilis</i>, Dawson).<a name="FNanchor_BG_59" id="FNanchor_BG_59"></a><a href="#Footnote_BG_59" class="fnanchor">[BG]</a> It appears to have been an erect stem -embedded in situ in sandstone, and preserved as a cast. The stem -is small, being only two inches, or a little more, in diameter. It -is coarsely wrinkled longitudinally, and covered with large leaf-scars, -each an inch in diameter, of a horseshoe-shape. The petioles, -five of which remain, separate from these scars with a distinct -articulation, except at one point near the base, where probably a -bundle or bundles of vessels passed into the petiole. They retain -their form at the attachment to the stem, but a little distance -from it they are flattened. They are inflated at the base, and somewhat -rapidly diminish in size. The leaf-scars vary in form, and are -not very distinct, but they appear to present a semicircular row of -pits above, largest in the middle. From these there proceed downward -a series of irregular furrows, converging to a second and more -obscure semicircle of pits, within or below which is the irregular scar -or break above referred to. The attitude and form of the petioles -will be seen from <a href="#fig24">Fig. 24</a>, <i>supra</i>.</p> - -<div class="footnote"> - -<p><a name="Footnote_BG_59" id="Footnote_BG_59"></a><a href="#FNanchor_BG_59"><span class="label">[BG]</span></a> Memoir on Devonian Flora, “Proceedings of the Royal Society,” -May, 1870.</p></div> - -<p>The petioles are broken off within a few inches of the stem; -but other fragments found in the same beds appear to show their -continuation, and some remains of their foliage. One specimen -shows a series of processes at the sides, which seem to be the remains -of small pinnæ, or possibly of spines on the margin of the -petiole. Other fragments show the division of the frond, at first in -a pinnate manner, and subsequently by bifurcation; and some fragments -show remains of pinnules, possibly of fertile pinnules. These -are very indistinct, but would seem to show that the plant approached, -in the form of its fronds and the arrangement of its -fructification, to the Cyclopterids of the sub-genus <i>Aneimites</i>, one of -which (<i>Aneimites Acadica</i>), from the Lower Carboniferous of Nova -Scotia, I have elsewhere described as probably a tree-fern,<a name="FNanchor_BH_60" id="FNanchor_BH_60"></a><a href="#Footnote_BH_60" class="fnanchor">[BH]</a> The -<span class="pagenum"><a name="Page_93" id="Page_93">« 93 »</a></span> -fronds were evidently different from those of <i>Archæopteris</i><a name="FNanchor_BI_61" id="FNanchor_BI_61"></a><a href="#Footnote_BI_61" class="fnanchor">[BI]</a> a genus -characteristic of the same beds, but of very different habit of growth. -This accords with the fact that there is in Prof. Hall’s collection a -mass of fronds of <i>Cyclopteris</i> (<i>Archæopteris</i>) Jacksoni, so arranged -as to make it probable that the plant was an herbaceous fern, producing -tufts of fronds on short stems in the ordinary way. The -obscurity of the leaf-scars may render it doubtful whether the plant -above described should be placed in the genus <i>Caulopteris</i> or in <i>Stemmatopteris</i>; -but it appears most nearly allied to the former. The -genus is at present, of course, a provisional one; but I have thought -it only justice to the diligent labours of Mr. Lockwood to name -this curious and interesting fossil <i>Caulopteris Lockwoodi</i>.</p> - -<div class="footnote"> - -<p><a name="Footnote_BH_60" id="Footnote_BH_60"></a><a href="#FNanchor_BH_60"><span class="label">[BH]</span></a> “Quarterly Journal of the Geological Society,” 1860.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_BI_61" id="Footnote_BI_61"></a><a href="#FNanchor_BI_61"><span class="label">[BI]</span></a> The genus to which the well-known <i>Cyclopteris</i> (<i>Adiantites</i>) <i>Hibernicus</i> -of the Devonian of Ireland belongs.</p></div> - -<p>I have elsewhere remarked on the fact that trunks, and petioles, -and pinnules of ferns are curiously dissociated in the Devonian beds—an -effect of water-sorting, characteristic of a period in which the -conditions of deposition were so varied. Another example of this -is, that in the sandstones of Gaspé Bay, which have not as yet afforded -any example of fronds of ferns, there are compressed trunks, -which Mr. Lockwood’s specimens allow me at least to conjecture -may have belonged to tree-ferns, although none of them are sufficiently -perfect for description.</p> - -<p>Mr. Lockwood’s collection includes specimens of <i>Psaronius textilis</i>; -and in addition to these there are remains of erect stems somewhat -different in character, yet possibly belonging to the higher parts -of the same species of tree-fern. One of these is a stem crushed in -such a manner that it does not exhibit its form with any distinctness, -but surrounded by smooth, cylindrical roots, radiating from it in -bundles, proceeding at first horizontally, and then curving downward, -and sometimes terminating in rounded ends. They resemble -in form and size the aërial roots of <i>Psaronius Erianus</i>; and I believe -them to be similar roots from a higher part of the stem, and some -of them young and not prolonged sufficiently far to reach the ground. -This specimen would thus represent the stem of <i>P. Erianus</i> at a -higher level than those previously found. We can thus in imagination -restore the trunk and crown of this once graceful tree-fern, -though we have not the detail of its fronds. Mr. Lockwood’s -collections also contain a specimen of the large fern-petiole which -I have named <i>Rhachiopteris punctata</i>. My original specimen -was obtained by Prof. Hall from the same horizon in New York. -<span class="pagenum"><a name="Page_94" id="Page_94">« 94 »</a></span> -That of Mr. Lockwood is of larger size, but retains no remains of the -frond. It must have belonged to a species quite distinct from <i>Caulopteris -Lockwoodi</i>, but which may, like it, have been a tree-fern.</p> - -<p>2. <i>Caulopteris antiqua</i>, Newberry.—This is a flattened stem, on -a slab of limestone, containing Brachiopods, Trilobites, &c., of the -Corniferous limestone. It is about eighteen inches in length, and -three and a half inches in average breadth. The exposed side shows -about twenty-two large leaf-scars arranged spirally. Each leaf, -where broken off, has left a rough fracture; and above this is a -semicircular impression of the petiole against the stem, which, as -well as the surface of the bases of the petioles, is longitudinally -striated or tuberculated. The structures are not preserved, but -merely the outer epidermis, as a coaly film. The stem altogether -much resembles <i>Caulopteris Peachii</i>, but is of larger size. It differs -from <i>C. Lockwoodi</i> in the more elongated leaf-bases, and in the -leaves being more remotely placed; but it is evidently of the same -general character with that species.</p> - -<p>3. <i>Caulopteris</i> (<i>Protopteris</i>) <i>peregrina</i>, Newberry.—This is a -much more interesting species than the last, as belonging to a generic -or subgeneric form not hitherto recognised below the Carboniferous, -and having its minute structure in part preserved.</p> - -<p>The specimens are, like the last, on slabs of marine limestone of -the Corniferous formation, and flattened. One represents an upper -portion of the stem with leaf-scars and remains of petioles; another -a lower portion, with aërial roots. The upper part is three inches -in diameter, and about a foot in length, and shows thirty leaf-scars -which are about three-fourths of an inch wide, and rather less in -depth. The upper part presents a distinct rounded and sometimes -double marginal line, sometimes with a slight depression in the middle. -The lower part is irregular, and when most perfect shows seven -slender vascular bundles, passing obliquely downward into the stem. -The more perfect leaf-bases have the structure preserved, and show -a delicate, thin-walled, oval parenchyma, while the vascular bundles -show scalariform vessels with short bars in several rows, in the manner -of many modern ferns. Some of the scars show traces of the -hippocrepian mark characteristic of <i>Protopteris</i>; and the arrangement -of the vascular bundles at the base of the scars is the same as -in that genus, as are also the general form and arrangement of the -scars. On careful examination, the species is indeed very near to the -typical <i>P. Sternbergii</i>, as figured by Corda and Schimper.<a name="FNanchor_BJ_62" id="FNanchor_BJ_62"></a><a href="#Footnote_BJ_62" class="fnanchor">[BJ]</a></p> - -<div class="footnote"> - -<p><a name="Footnote_BJ_62" id="Footnote_BJ_62"></a><a href="#FNanchor_BJ_62"><span class="label">[BJ]</span></a> Corda, “Beiträge,” Pl. 48, copied by Schimper, Pl. 52.</p> - -<p><span class="pagenum"><a name="Page_95" id="Page_95">« 95 »</a></span></p></div> - -<p>The genus <i>Protopteris</i> of Sternberg, though the original species -(<i>P. punctata</i>) appears as a <i>Lepidodendron</i> in his earlier plate (Plate -4), and as a <i>Sigillaria</i> (<i>S. punctata</i>) in Brongniart’s great work, is a -true tree-fern; and the structure of one species (<i>P. Cottai</i>) has been -beautifully figured by Corda. The species hitherto described are -from the Carboniferous and Permian.</p> - -<p>The second specimen of this species represents a lower part of -the stem. It is thirteen inches long and about four inches in diameter, -and is covered with a mass of flattened aërial roots lying parallel -to each other, in the manner of the <i>Psaronites</i> of the coal-formation -and of <i>P. Erianus</i> of the Upper Erian or Devonian.</p> - -<p>4. <i>Asteropteris noveboracensis</i>, gen. and sp. n.—The genus <i>Asteropteris</i> -is established for stems of ferns having the axial portion -composed of vertical radiating plates of scalariform tissue embedded -in parenchyma, and having the outer cylinder composed of elongated -cells traversed by leaf-bundles of the type of those of <i>Zygopteris</i>.</p> - -<p>The only species known to me is represented by a stem 2·5 centimetres -in diameter, slightly wrinkled and pitted externally, perhaps -by traces of aërial roots which have perished. The transverse -section shows in the centre four vertical plates of scalariform or imperfectly -reticulated tissue, placed at right angles to each other, and -united in the middle of the stem. At a short distance from the -centre, each of these plates divides into two or three, so as to form -an axis of from ten to twelve radiating plates, with remains of cellular -tissue filling the angular interspaces. The greatest diameter of -this axis is about 1·5 centimetre. Exterior to the axis the stem consists -of elongated cells, with somewhat thick walls, and more dense -toward the circumference. The walls of these cells present a curious -reticulated appearance, apparently caused by the cracking of the -ligneous lining in consequence of contraction in the process of carbonization. -Embedded in this outer cylinder are about twelve vascular -bundles, each with a dumb-bell-shaped group of scalariform -vessels enclosed in a sheath of thick-walled fibres. Each bundle is -opposite to one of the rays of the central axis. The specimen shows -about two inches of the length of the stem, and is somewhat bent, -apparently by pressure, at one end.</p> - -<p>This stem is evidently that of a small tree-fern of a type, so -far as known to me, not before described,<a name="FNanchor_BK_63" id="FNanchor_BK_63"></a><a href="#Footnote_BK_63" class="fnanchor">[BK]</a> and constituting a very -complex and symmetrical form of the group of Palæozoic ferns allied -<span class="pagenum"><a name="Page_96" id="Page_96">« 96 »</a></span> -to the genus <i>Zygopteris</i> of Schimper. The central axis alone has a -curious resemblance to the peculiar stem described by Unger (“Devonian -Flora of Thuringia”) under the name of <i>Cladoxylon mirabile</i>; -and it is just possible that this latter stem may be the axis -of some allied plant. The large aërial roots of some modern tree-ferns -of the genus <i>Angiopteris</i> have, however, an analogous radiating -structure.</p> - -<div class="footnote"> - -<p><a name="Footnote_BK_63" id="Footnote_BK_63"></a><a href="#FNanchor_BK_63"><span class="label">[BK]</span></a> Prof. Williamson, to whom I have sent a tracing of the structure, -agrees with me that it is new.</p></div> - -<p>The specimen is from the collection of Berlin H. Wright, Esq., -of Penn Yan, New York, and was found in the Portage group (Upper -Erian) of Milo, New York, where it was associated with large petioles -of ferns and trunks of <i>Lepidodendra</i>, probably <i>L. Chemungense</i> and -<i>L. primævum</i>.</p> - -<p>The occurrence of this and other stems of tree-ferns in marine -beds has recently been illustrated by the observation of Prof. A. -Agassiz that considerable quantities of vegetable matter can be -dredged from great depths in the sea on the leeward side of the -Caribbean Islands. The occurrence of these trunks further connects -itself with the great abundance of large petioles (<i>Rhachiopteris</i>) in -the same beds, while the rarity of well-preserved fronds is explained -by the coarseness of the beds, and also by the probably long maceration -of the plant-remains in the sea-water.</p> - -<p>In connection with this I may refer to the remarkable facts recently -stated by Williamson<a name="FNanchor_BL_64" id="FNanchor_BL_64"></a><a href="#Footnote_BL_64" class="fnanchor">[BL]</a> respecting the stems known as Heterangium -and <i>Lyginodendron</i>. It would seem that these, while having -strong exogenous peculiarities, are really stems of tree-ferns, thus -placing this family in the same position of advancement with the -Lycopods and Equisetaceæ of the Coal period.</p> - -<div class="footnote"> - -<p><a name="Footnote_BL_64" id="Footnote_BL_64"></a><a href="#FNanchor_BL_64"><span class="label">[BL]</span></a> “Proceedings of the Royal Society,” January 6, 1887.</p></div> - - -<p class="caption4">IV.—<span class="smcap">On Erian Trees of the Genus Dadoxylon, Unger.</span><br /> -(<i>Araucarites</i> <span class="smcap">of Goeppert</span>, <i>Araucarioxylon</i> <span class="smcap">of Kraus.</span>)</p> - -<p>Large woody trunks, carbonised or silicified, and showing wood-cells -with hexagonal areoles having oval pores inscribed in them, -occur abundantly in some beds of the Middle Erian of America, and -constitute the most common kind of fossil wood all the way to the -Trias. They have in the older formations, generally, several rows -of pores on each fibre, and medullary rays composed of two or more -series of cells, but become more simple in these respects in the Permian -and Triassic series. The names <i>Araucarites</i> and <i>Araucarioxylon</i> -are perhaps objectionable, inasmuch as they suppose affinities to -<i>Araucaria</i> which may not exist. Unger’s name, which is non-committal, -<span class="pagenum"><a name="Page_97" id="Page_97">« 97 »</a></span> -is therefore, I think, to be preferred. In my “Acadian -Geology,” and in my “Report on the Geology of Prince Edward -Island,” I have given reasons for believing that the foliage of some -at least of these trees was that known as <i>Walchia</i>, and that they may -have borne nutlets in the manner of Taxine trees (<i>Trigonocarpum</i>, -&c). Grand d’Eury has recently suggested that some of them may -have belonged to <i>Cordaites</i>, or to plants included in that somewhat -varied and probably artificial group.</p> - -<p>The earliest discovery of trees of this kind in the Erian of -America was that of Matthew and Hartt, who found large trunks, -which I afterwards described as <i>Dadoxylon Ouangondianum</i>, in the -Erian sandstone of St. John, New Brunswick, hence named by those -geologists the “Dadoxylon sandstone.” A little later, similar wood -was found by Prof. Hall and Prof. Newberry in the Hamilton group -of New York and Ohio, and the allied wood of the genus <i>Ormoxylon</i> -was obtained by Prof. Hall in the Portage group of the former -State. These woods proved to be specifically distinct from that of -St. John, and were named by me <i>D. Halli</i>, <i>D. Newberryi</i>, and <i>Ormoxylon -Erianum</i>. The three species of <i>Dadoxylon</i> agreed in having -composite medullary rays, and would thus belong to the group -<i>Palæoxylon</i> of Brongniart. In the case of <i>Ormoxylon</i> this character -could not be very distinctly ascertained, but the medullary rays -appeared to be simple.</p> - -<p>I am indebted to Prof. J. M. Clarke, of Amherst College, Massachusetts, -for some well-preserved specimens of another species from -the Genesee shale of Canandaigua, New York. They show small -steins or branches, with a cellular pith surrounded with wood of -coniferous type, showing two to three rows of slit-formed, bordered -pores in hexagonal borders. The medullary sheath consists of -pseudo-scalariform and reticulated fibres; but the most remarkable -feature of this wood is the structure of the medullary rays, which -are very frequent, but short and simple, sometimes having as few -as four cells superimposed. This is a character not before observed -in coniferous trees of so great age, and allies this Middle Erian -form with some Carboniferous woods which have been supposed to -belong to <i>Cordaites</i> or <i>Sigillaria</i>. In any case this structure is new, -and I have named the species <i>Dadoxylon Clarkii</i>, after its discoverer. -The specimens occur, according to Prof. Clarke, in a calcareous layer -which is filled with the minute shells of <i>Styliola fissurella</i> of Hall, -believed to be a Pteropod; and containing also shells of <i>Goniatites</i> -and <i>Gyroceras</i>. The stems found are only a few inches in diameter, -but may be branches of larger trees.</p> - -<p><span class="pagenum"><a name="Page_98" id="Page_98">« 98 »</a></span></p> - -<p>It thus appears that we already know five species of Coniferous -trees of the genus <i>Dadoxylon</i> in the Middle Erian of America, an -interesting confirmation of the facts otherwise known as to the -great richness and variety of this ancient flora. The late Prof. -Goeppert informed me that he had recognised similar wood in the -Devonian of Germany, and there can be no doubt that the fossil -wood discovered by Hugh Miller in the Old Red Sandstone of Scotland, -and described by Salter and McNab, is of similar character, and -probably belongs to the genus <i>Dadoxylon</i>. Thus this type of Coniferous -tree seems to have been as well established and differentiated -into species in the Middle Devonian as in the succeeding Carboniferous.</p> - -<p>I may here refer to the fact that the lower limit of the trees of -this group coincides, in America, with the upper limit of those problematical -trees which in the previous chapter I have named Protogens -(<i>Nematophyton</i>, <i>Celluloxlyon</i>,<a name="FNanchor_BM_65" id="FNanchor_BM_65"></a><a href="#Footnote_BM_65" class="fnanchor">[BM]</a> <i>Nematoxylon</i><a name="FNanchor_BN_66" id="FNanchor_BN_66"></a><a href="#Footnote_BN_66" class="fnanchor">[BN]</a>), though <i>Aporoxylon</i> -of Unger extends, in Thuringia, up to the Upper Devonian -(Cypridina schists).</p> - -<div class="footnote"> - -<p><a name="Footnote_BM_65" id="Footnote_BM_65"></a><a href="#FNanchor_BM_65"><span class="label">[BM]</span></a> “Journal of the Geological Society,” May, 1881.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_BN_66" id="Footnote_BN_66"></a><a href="#FNanchor_BN_66"><span class="label">[BN]</span></a> <i>Ibid.</i>, vol. xix, 1863.</p></div> - - -<p class="caption4">V.—<span class="smcap">Scottish Devonian Plants of Hugh Miller and others.</span><br /> -(Edinburgh Geological Society, 1877.)</p> - -<p>Previously to the appearance of my descriptions of Devonian -plants from North America, Hugh Miller had described forms from -the Devonian of Scotland, similar to those for which I proposed the -generic name <i>Psilophyton</i>; and I referred to these in this connection -in my earliest description of that genus.<a name="FNanchor_BO_67" id="FNanchor_BO_67"></a><a href="#Footnote_BO_67" class="fnanchor">[BO]</a> He had also recognised -what seemed to be plants allied to Lycopods and Conifers. Mr. -Peach and Mr. Duncan had made additional discoveries of this kind, -and Sir J. Hooker and Mr. Salter had described some of these remains. -More recently Messrs. Peach, Carruthers, and McNab have -worked in this field, and still later<a name="FNanchor_BP_68" id="FNanchor_BP_68"></a><a href="#Footnote_BP_68" class="fnanchor">[BP]</a> Messrs. Jack and Etheridge -have summed up the facts and have added some that are new.</p> - -<div class="footnote"> - -<p><a name="Footnote_BO_67" id="Footnote_BO_67"></a><a href="#FNanchor_BO_67"><span class="label">[BO]</span></a> “Journal of the Geological Society,” London, 1859.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_BP_68" id="Footnote_BP_68"></a><a href="#FNanchor_BP_68"><span class="label">[BP]</span></a> <i>Ibid.</i>, 1877.</p></div> - -<p>The first point to which I shall refer, and which will lead to the -other matters to be discussed, is the relation of the characteristic -<i>Lepidodendron</i> of the Devonian of eastern America, <i>L. Gaspianum</i>, -to <i>L. nothum</i> of Unger and of Salter. At the time when I described -this species I had not access to Scottish specimens of <i>Lepidodendron</i> -<span class="pagenum"><a name="Page_99" id="Page_99">« 99 »</a></span> -from the Devonian, but these had been well figured and described -by Salter, and had been identified with <i>L. nothum</i> of Unger, a species -evidently distinct from mine, as was also that figured and described -by Salter, whether identical or not with Unger’s species. In 1870 -I had for the first time an opportunity to study Scottish specimens -in the collection of Mr. Peach; and on the evidence thus afforded I -stated confidently that these specimens represented a species distinct -from <i>L. Gaspianum</i>, perhaps even generically so.<a name="FNanchor_BQ_69" id="FNanchor_BQ_69"></a><a href="#Footnote_BQ_69" class="fnanchor">[BQ]</a> It differs from -<i>L. Gaspianum</i> in its habit of growth by developing small lateral -branches instead of bifurcating, and in its foliage by the absence or -obsolete character of the leaf-bases and the closely placed and somewhat -appressed leaves. If an appearance of swelling at the end of a -lateral branch in one specimen indicates a strobile of fructification, -then its fruit was not dissimilar from that of the Canadian species -in its position and general form, though it may have differed in -details. On these grounds I declined to identify the Scottish species -with <i>L. Gaspianum</i>. The Lepidodendron from the Devonian of -Belgium described and figured by Crepin,<a name="FNanchor_BR_70" id="FNanchor_BR_70"></a><a href="#Footnote_BR_70" class="fnanchor">[BR]</a> has a better claim to such -identification, and would seem to prove that this species existed in -Europe as well as in America. I also saw in Mr. Peach’s collection -in 1870 some fragments which seemed to me distinct from Salter’s -species, and possibly belonging to <i>L. Gaspianum</i>.<a name="FNanchor_BS_71" id="FNanchor_BS_71"></a><a href="#Footnote_BS_71" class="fnanchor">[BS]</a></p> - -<div class="footnote"> - -<p><a name="Footnote_BQ_69" id="Footnote_BQ_69"></a><a href="#FNanchor_BQ_69"><span class="label">[BQ]</span></a> “Report on Devonian Plants of Canada,” 1871.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_BR_70" id="Footnote_BR_70"></a><a href="#FNanchor_BR_70"><span class="label">[BR]</span></a> “Observations sur quelques Plantes Fossiles des dépôts Devoniens.”</p></div> - -<div class="footnote"> - -<p><a name="Footnote_BS_71" id="Footnote_BS_71"></a><a href="#FNanchor_BS_71"><span class="label">[BS]</span></a> “Proceedings of the Geological Society of London,” March, 1871.</p></div> - -<p>In the earliest description of <i>Psilophyton</i> I recognised its probable -generic affinity with Miller’s “dichotomous plants,” with Salter’s -“rootlets,” and with Goeppert’s <i>Haliserites Dechenianus</i>, and stated -that I had “little doubt that materials exist in the Old Red Sandstone -of Scotland for the reconstruction of at least one species of -this genus.” Since, however, Miller’s plants had been referred to -coniferous roots, and to fucoids, and Goeppert’s <i>Haliserites</i> was a -name applicable only to fucoids, and since the structure and fruit -of my plants placed them near to Lycopods, I was under the necessity -of giving them a special generic name, nor could I with certainty -affirm their specific identity with any European species. The -comparison of the Scottish specimens with woody rootlets, though -incorrect, is in one respect creditable to the acumen of Salter, as in -almost any state of preservation an experienced eye can readily perceive -that branchlets of <i>Psilophyton</i> must have been woody rather -<span class="pagenum"><a name="Page_100" id="Page_100">« 100 »</a></span> -than herbaceous, and their appearance is quite different from that -of any true Algæ.</p> - -<p>The type of <i>Psilophyton</i> is my <i>P. princeps</i>, of which the whole -of the parts and structures are well known, the entire plant being -furnished in abundance and in situ in the rich plant-beds of Gaspé. -A second species, <i>P. robustius</i>, has also afforded well-characterised -fructification. <i>P. elegans</i>, whose fruit appears as “oval scales,” no -doubt bore sac-like spore-cases resembling those of the other species, -but in a different position, and perfectly flattened in the specimens -procured. The only other Canadian species, <i>P. glabrum</i>, being somewhat -different in appearance from the others, and not having afforded -any fructification, must be regarded as uncertain.</p> - -<p>The generic characters of the first three species may be stated as -follows:</p> - -<p>Stems dichotomous, with rudimentary subulate leaves, sometimes -obsolete in terminal branchlets and fertile branches; and in decorticated -specimens represented only by punctiform scars. Young -branches circinate. Rhizomata cylindrical, with circular root-areoles. -Internal structure of stem, an axis of scalariform vessels -enclosed in a sheath of imperfect woody tissue and covered with a -cellular bark more dense externally. Fruit, naked sac-like spore-cases, -in pairs or clusters, terminal or lateral.</p> - -<p>The Scottish specimens conform to these characters in so far as -they are known, but not having as yet afforded fruit or internal -structure, they cannot be specifically determined with certainty. -More complete specimens should be carefully searched for, and will -no doubt be found.</p> - -<p>In Belgium, M. Crepin has described a new species from the -Upper Devonian of Condroz under the name <i>P. Condrusianum</i> -(1875). It wants, however, some of the more important characters of -the genus, and differs in having a pinnate ramification, giving it the -aspect of a fern. In a later paper (1876) the author considers this -species distinct from <i>Psilophyton</i>, and proposes for it a new generic -name <i>Rhacophyton</i>.</p> - -<p>The characters given by Mr. Carruthers, in his paper of 1873, for -the species <i>P. Dechenianum</i>, are very few and general: “Lower -branches short and frequently branching, giving the plant an oblong -circumscription.” Yet even these characters do not apply, so far as -known, to Miller’s fucoids or Salter’s rootlets or Goeppert’s <i>Haliserites</i>. -They merely express the peculiar mode of branching already -referred to in Salter’s <i>Lepidodendron nothum</i>. The identification of -the former plants with the <i>Lepidodendron</i> and <i>Lycopodites</i>, indeed, -<span class="pagenum"><a name="Page_101" id="Page_101">« 101 »</a></span> -rests only on mere juxtaposition of fragments, and on the slight resemblance -of the decorticated ends of the branches of the latter plants -to <i>Psilophyton</i>. It is contradicted by the obtuse ends of the -branches of the <i>Lepidodendron</i> and <i>Lycopodites</i>, and by the apparently -strobilaceous termination of some of them.</p> - -<p>Salter’s description of his <i>Lepidodendron nothum</i> is quite definite, -and accords with specimens placed in my hands by Mr. Peach: -“Stems half an inch broad, tapering little, branches short; set on at -an acute angle, blunt at their terminations. Leaves in seven to ten -rows, very short, not a line long, and rather spreading than closely -imbricate.” These characters, however, in so far as they go, are -rather those of the genus <i>Lycopodites</i> than of <i>Lepidodendron</i>, from -which this plant differs in wanting any distinct leaf-bases, and in its -short, crowded leaves. It is to be observed that they apply also to -Salter’s <i>Lycopodites Milleri</i>, and that the difference of the foliage -of that species may be a result merely of different state of preservation. -For these reasons I am disposed to place these two supposed -species together, and to retain for the species the name -<i>Lycopodites Milleri</i>. It may be characterised by the description -above given, with merely the modification that the leaves are sometimes -nearly one-third of an inch long and secund (<a href="#fig17">Fig. 17</a>, <i>supra</i>, -lower figure).</p> - -<p>Decorticated branches of the above species may no doubt be mistaken -for <i>Psilophyton</i>, but are nevertheless quite distinct from it, and -the slender branching dichotomous stems, with terminations which, -as Miller graphically states, are “like the tendrils of a pea,” are too -characteristic to be easily mistaken, even when neither fruit nor -leaves appear. With reference to fructification, the form of <i>L. -Milleri</i> renders it certain that it must have borne strobiles at the -ends of its branchlets, or some substitute for these, and not naked -spore-cases like those of <i>Psilophyton</i>.</p> - -<p>The remarkable fragment communicated by Sir Philip Egerton -to Mr. Carruthers,<a name="FNanchor_BT_72" id="FNanchor_BT_72"></a><a href="#Footnote_BT_72" class="fnanchor">[BT]</a> belongs to a third group, and has, I think, been -quite misunderstood. I am enabled to make this statement with -some confidence, from the fact that the reverse or counterpart of Sir -Philip’s specimen was in the collection of Sir Wyville Thomson, and -was placed by him in my hands in 1870. It was noticed in my -paper on “New Devonian Plants,” in the “Journal of the Geological -Society of London,” and referred to my genus <i>Ptilophyton</i>, as -stated above under Section II., <a href="#Page_86">page 86</a> <i>et seq.</i></p> - -<div class="footnote"> - -<p><a name="Footnote_BT_72" id="Footnote_BT_72"></a><a href="#FNanchor_BT_72"><span class="label">[BT]</span></a> “Journal of Botany,” 1873.</p> - -<p><span class="pagenum"><a name="Page_102" id="Page_102">« 102 »</a></span></p></div> - -<p>Mr. Salter described, in 1857,<a name="FNanchor_BU_73" id="FNanchor_BU_73"></a><a href="#Footnote_BU_73" class="fnanchor">[BU]</a> fragments of fossil wood from the -Scottish Devonian, having the structure of Dadoxylon, though very -imperfectly preserved; and Prof. McNab has proposed<a name="FNanchor_BV_74" id="FNanchor_BV_74"></a><a href="#Footnote_BV_74" class="fnanchor">[BV]</a> the generic -name <i>Palæopitys</i> for another specimen of coniferous wood collected -by Hugh Miller, and referred to by him in the “Testimony of the -Rocks.” From Prof. McNab’s description, I should infer that this -wood may, after all, be generically identical with the woods usually -referred to Dadoxylon of Unger (<i>Araucarioxylon</i> of Kraus). The -description, however, does not mention the number and disposition -of the rows of pores, nor the structure of the medullary rays, and I -have not been able to obtain access to the specimens themselves. I -have described five species of Dadoxylon from the Middle and Upper -Erian of America, all quite distinct from the Lower Carboniferous -species. There is also one species of an allied genus, Ormoxylon. -All these have been carefully figured, and it is much to be desired -that the Scottish specimens should be re-examined and compared -with them.</p> - -<div class="footnote"> - -<p><a name="Footnote_BU_73" id="Footnote_BU_73"></a><a href="#FNanchor_BU_73"><span class="label">[BU]</span></a> “Journal of the London Geological Society.”</p></div> - -<div class="footnote"> - -<p><a name="Footnote_BV_74" id="Footnote_BV_74"></a><a href="#FNanchor_BV_74"><span class="label">[BV]</span></a> “Transactions of the Edinburgh Botanical Society,” 1870.</p></div> - -<p>Messrs. Jack and Etheridge have given an excellent summary -of our present knowledge of the Devonian flora of Scotland, in the -Journal of the London Geological Society (1877). From this it -would appear that species referable to the genera <i>Calamities</i>, <i>Lepidodendron</i>, -<i>Lycopodites</i>, <i>Psilophyton</i>, <i>Arthrostigma</i>, <i>Archæopteris</i>, -<i>Caulopteris</i>, <i>Palæopitys</i>, <i>Araucarioxylon</i>, and <i>Stigmaria</i> have been -recognised.</p> - -<p>The plants described by these gentlemen from the Old Red -Sandstone of Callender, I should suppose, from their figures and -descriptions, to belong to the genus <i>Arthrostigma</i>, rather than to -Psilophyton. I do not attach any importance to the suggestions referred -to by them, that the apparent leaves may be leaf-bases. Long -leaf-bases, like those characteristic of <i>Lepidofloyos</i>, do not occur in -these humbler plants of the Devonian. The stems with delicate -“horizontal processes” to which they refer may belong to <i>Ptilophyton</i> -or to <i>Pinnularia</i>.</p> - -<p>In conclusion, I need scarcely say that I do not share in the -doubts expressed by some British palæontologists as to the distinctness -of the Devonian and Carboniferous floras. In eastern America, -where these formations are mutually unconformable, there is, of -course, less room for doubt than in Ireland and in western America, -where they are stratigraphically continuous. Still, in passing -<span class="pagenum"><a name="Page_103" id="Page_103">« 103 »</a></span> -from the one to the other, the species are for the most part different, -and new generic forms are met with, and, as I have elsewhere -shown, the physical conditions of the two periods were essentially -different.<a name="FNanchor_BW_75" id="FNanchor_BW_75"></a><a href="#Footnote_BW_75" class="fnanchor">[BW]</a></p> - -<div class="footnote"> - -<p><a name="Footnote_BW_75" id="Footnote_BW_75"></a><a href="#FNanchor_BW_75"><span class="label">[BW]</span></a> “Reports on Devonian Plants and Lower Carboniferous Plants of -Canada.”</p></div> - -<p>It is, however, to be observed that since—as Stur and others have -shown—<i>Calamities radiatus</i>, and other forms distinctively Devonian -in America, occur in Europe in the Lower Carboniferous, it is not -unlikely that the Devonian flora, like that of the Tertiary, appeared -earlier in America. It is also probable, as I have shown in the “Reports” -already referred to, that it appeared earlier in the Arctic than -in the temperate zone. Hence an Arctic or American flora, really -Devonian, may readily be mistaken for Lower Carboniferous by a -botanist basing his calculations on the fossils of temperate Europe. -Even in America itself, it would appear, from recent discoveries in -Virginia and Ohio, that certain Devonian forms lingered longer in -those regions than farther to the northeast;<a name="FNanchor_BX_76" id="FNanchor_BX_76"></a><a href="#Footnote_BX_76" class="fnanchor">[BX]</a> and it would not be -surprising if similar plants occurred in later beds in Devonshire or -in the south of Europe than in Scotland. Still, these facts, properly -understood, do not invalidate the evidence of fossil plants as to -geological age, though errors arising from the neglect of them are -still current.</p> - -<div class="footnote"> - -<p><a name="Footnote_BX_76" id="Footnote_BX_76"></a><a href="#FNanchor_BX_76"><span class="label">[BX]</span></a> Andrews, “Palæontology of Ohio,” vol. ii.; Meek, “Fossil Plants -from Western Virginia,” Philosophical Society, Washington, 1875.</p></div> - - -<p class="caption4">VI.—<span class="smcap">Geological Relations of some Plant-bearing Beds of -Eastern Canada.</span><br />(“Report on Erian Plants,” 1871.)</p> - -<p>The Gaspé sandstones have been fully described by Sir W. E. -Logan, in his “Report on the Geology of Canada,” 1863. He there -assigns to them a thickness of seven thousand and thirty-six feet, -and shows that they rest conformably on the Upper Silurian limestones -of the Lower Helderberg group (Ludlow), and are in their -turn overlaid unconformably by the conglomerates which form the -base of the Carboniferous rocks of New Brunswick. I shall add -here merely a few remarks on points in their physical character -connected with the occurrence of plants in them.</p> - -<p><i>Prototaxites</i> (<i>Nematophyton</i>) <i>Logani</i> and other characteristic -Lower Erian plants occur in the base of the sandstones at Little -Gaspé. This fact, along with the occurrence, as stated in my paper -of 1863, of rhizomes of <i>Psilophyton</i> preserving their scalariform -<span class="pagenum"><a name="Page_104" id="Page_104">« 104 »</a></span> -structure, in the upper part of the marine Upper Silurian limestones,<a name="FNanchor_BY_77" id="FNanchor_BY_77"></a><a href="#Footnote_BY_77" class="fnanchor">[BY]</a> -proves the flora of the Devonian rocks to have had its -beginning at least in the previous geological period, and to characterise -the lower as well as the upper beds of the Devonian series. In -this connection I may state that, from their marine fossils, as well -as their stratigraphical arrangement, Sir W. E. Logan and Mr. -Billings regard the lower portions of the Gaspé sandstones as the -equivalents of the Oriskany sandstone of New York. On the other -hand, the great thickness of this formation, the absence of Lower -Devonian fossils from its upper part, and the resemblance of the -upper beds to those of the newer members of the Devonian elsewhere, -render it probable that the Gaspé sandstones, though deficient -in the calcareous members of the system, seen farther to the -westward, represent the whole of the Devonian period.</p> - -<div class="footnote"> - -<p><a name="Footnote_BY_77" id="Footnote_BY_77"></a><a href="#FNanchor_BY_77"><span class="label">[BY]</span></a> The marine fossils of these beds have been determined by Mr. -Billings. They are Upper Silurian, with an intermixture of Lower Devonian -in the upper part. Fragments of <i>Nematophyton</i> occur in beds of -the same age in the Bay des Chaleurs, at Cape Bon Ami.</p></div> - -<p>The Gaspé sandstones, as their name imports, are predominantly -arenaceous, and often coarsely so, the sandstones being frequently -composed of large grains and studded with quartz-pebbles. Grey -and buff are prevalent colours, but red beds also occur, more especially -in the upper portion. There are also interstratified shaly -beds, sometimes occurring in groups of considerable thickness, and -associated with fine-grained and laminated argillaceous sandstone, -the whole having in many places the lithological aspect of the coal-measures. -At one place, near the middle of the series, there is a -bed of coal from one inch to three inches in thickness, associated -with highly bituminous shales abounding in remains of plants, and -also containing fragments of crustaceans and fishes (<i>Pterygotus</i>, -<i>Ctenacanthus ?</i> &c). The beds connected with this coal are grey -sandstones and grey and dark shales, much resembling those of the -ordinary coal formation. The coal is shining and laminated, and -both its roof and floor consist of laminated bituminous shale with -fragments of <i>Psilophyton</i>. It has no true under-clay, and has been, -I believe, a peaty mass of rhizomes of <i>Psilophyton</i>. It occurs near -Tar Point, on the south side of Gaspé Bay, a place so named from -the occurrence of a thick dyke of trap holding petroleum in its -cavities. The coal is of considerable horizontal extent, as in its line -of strike a similar bed has been discovered on the Douglas River, -about four miles distant. It has not been recognised on the north -<span class="pagenum"><a name="Page_105" id="Page_105">« 105 »</a></span> -side of the bay, though we find there beds, probably on very nearly -the same horizon, holding <i>Psilophyton</i> in situ.</p> - -<p>As an illustration of one of the groups of shaly beds, and of the -occurrence of roots of <i>Psilophyton</i>, I may give the following sectional -list of beds seen near “Watering Brook,” on the north shore -of the bay. The order is descending:</p> - -<table summary="bedding"> -<tr> - <td></td> - <td></td> - <td class="tdr">FT.</td> - <td class="tdr">IN.</td> -</tr> -<tr class="row1"> - <td>1.</td> - <td class="tdl">Grey sandstones and reddish pebbly sandstone of great - thickness</td> - <td></td> - <td></td> -</tr> -<tr> - <td>2.</td> - <td class="tdl">Bright-red shale</td> - <td class="tdr">8</td> - <td class="tdr">0</td> -</tr> -<tr class="row1"> - <td>3.</td> - <td class="tdl">Grey shales with stems of <i>Psilophyton</i>, very abundant - but badly preserved</td> - <td class="tdr">0</td> - <td class="tdr">5</td> -</tr> -<tr> - <td>4.</td> - <td class="tdl">Grey incoherent clay, slickensided, and with many - rhizomes and roots of <i>Psilophyton</i></td> - <td class="tdr">0</td> - <td class="tdr">3</td> -</tr> -<tr class="row1"> - <td>5.</td> - <td class="tdl">Hard grey clay or shale, with fragments and roots of - <i>Psilophyton</i></td> - <td class="tdr">4</td> - <td class="tdr">0</td> -</tr> -<tr> - <td>6.</td> - <td class="tdl">Red shale</td> - <td class="tdr">8</td> - <td class="tdr">0</td> -</tr> -<tr class="row1"> - <td>7.</td> - <td class="tdl">Grey and reddish crumbling sandstone</td> - <td></td> - <td></td> -</tr> -</table> - -<p>Groups of beds similar to the above, but frequently much more -rich in fossils, occur in many parts of the section, and evidently include -fossil soils of the nature of under-clays, on which little else -appears to have grown than a dense herbage of <i>Psilophyton</i>, along -with plants of the genus <i>Arthrostigma</i>.</p> - -<p>In addition to these shaly groups, there are numerous examples -of beds of shale of small thickness included in coarse sandstones, -and these beds often occur in detached fragments, as if the remnants -of more continuous layers partially removed by currents of -water. It is deserving of notice that nearly all these patches of -shale are interlaced with roots or stems of <i>Psilophyton</i>, which sometimes -project beyond their limits into the sandstone, as if the vegetable -fibres had preserved the clay from removal. In short, these -lines of patches of shale seem to be remnants of soils on which -<i>Psilophyton</i> has flourished abundantly, and which have been partially -swept away by the currents which deposited the sand. Some -of the smaller patches may even be fragments of tough swamp soils -interwoven with roots, drifted by the agency of the waves or possibly -by ice; such masses are often moved in this way on the borders of -modern swamps on the sea-coast.</p> - -<p>The only remaining point connected with local geology to which -I shall allude is the admirable facilities afforded by the Gaspé coast -both for ascertaining the true geological relations of the beds, and -for studying the Devonian plants, as distinctly exposed on large surfaces -<span class="pagenum"><a name="Page_106" id="Page_106">« 106 »</a></span> -of rock. On the coast of the river St. Lawrence, at Cape -Rozier and its vicinity, the Lower Silurian rocks of the Quebec -group are well exposed, and are overlaid unconformably by the massive -Upper Silurian limestones of Cape Gaspé, which rise into cliffs -six hundred feet in height, and can be seen filled with their characteristic -fossils on both sides of the cape. Resting upon these, and -dipping at high angles toward Gaspé Bay, are the Devonian sandstones, -which are exposed in rugged cliffs slightly oblique to their -line of strike, along a coast-line of ten miles in length, to the head -of the bay. On the opposite side of the bay they reappear; and, -thrown into slight undulations by three anticlinal curves, occupy -a line of coast fifteen miles in length. The perfect manner in which -the plant-bearing beds are exposed in these fine natural sections may -serve to account for the completeness with which the forms and -habits of growth of the more abundant species can be described.</p> - -<p>In the Bay des Chaleurs, similar rocks exist with some local -variations. In the vicinity of Campbellton are calcareous and magnesian -breccia or agglomerate, hard shales, conglomerates and sandstones -of Lower Devonian age. The agglomerate and lower shales -contain abundant remains of fishes of the genera <i>Cephalaspis</i>, <i>Coccosteus</i>, -<i>Ctenacanthus</i>, and <i>Homacanthus</i>, and also fragments of -<i>Pterygotus</i>. The shales and sandstones abound in remains of <i>Psilophyton</i>, -with which are <i>Nematophyton</i>, <i>Arthrostigma</i>, and <i>Leptophleum</i> -of the same species found in the Lower Devonian of Gaspé -Bay. These beds near Campbellton dip to the northward, and the -Restigouche River here occupies a synclinal, for on the opposite side, -at Bordeaux Quarry, there are thick beds of grey sandstone dipping -to the southward, and containing large silicified trunks of Prototaxites, -in addition to <i>Psilophyton</i>. These beds are all undoubtedly -Lower Erian, but farther to the eastward, on the north side of the -river, there are newer and overlying strata. These are best seen at -Scaumenac Bay, opposite Dalhousie, between Cape Florissant and -Maguacha Point, where they consist of laminated and fine-grained -sandstone, with shales of grey colours, but holding some reddish beds -at top, and overlaid unconformably by a great thickness of Lower -Carboniferous red conglomerate and sandstone. In these beds numerous -fossil fishes have been found, among which Mr. Whiteaves -recognises species of <i>Pterichthys</i>, <i>Glyptolepis</i>, <i>Cheirolepis</i>, &c. With -these are found somewhat plentifully four species of fossil ferns, all -of Upper Erian types, of which one is peculiar to this locality; but -the others are found in the Upper Erian of Perry, in Maine, or in -the Cat skill group of New York.</p> - -<p><span class="pagenum"><a name="Page_107" id="Page_107">« 107 »</a></span></p> - -<p>In order that distinct notions may be conveyed as to the geological -horizons of the species, I may state that the typical Devonian -or Erian series of Canada and New York may be divided in descending -order into—1. The Chemung group, including the Chemung and -Portage sandstones and shales. 2. The Hamilton group, including -the Genesee, Hamilton, and Marcellus shales. 3. The Corniferous -limestone and its associated beds. 4 The Oriskany sandstone. As -the Corniferous limestone, which is the equivalent of the Lower -Carboniferous limestone in the Carboniferous period, is marine, and -affords scarcely any plants, we may, as is usually done for like purposes -in the Carboniferous, group it with the Oriskany under the -name Lower Erian. The Hamilton rocks will then be Middle Erian, -and the Chemung group Upper Erian. In the present state of our -knowledge, the series may be co-ordinated with the rocks of Gaspé, -New Brunswick, and Maine, as in the following table:</p> - -<table summary="rock divisions"> -<tr> - <td class="center bdt bdb">Subdivisions.</td> - <td class="center bdt bdb bdl">New York and<br />Western Canada.</td> - <td class="center bdt bdb bdl">Gaspé and<br />Bay des Chaleurs.</td> - <td class="center bdt bdb bdl">Southern<br />New<br />Brunswick.</td> - <td class="center bdt bdb bdl">Coast<br />of<br />Maine.</td> -</tr> -<tr> - <td class="center">Upper<br />Devonian or<br />Erian.</td> - <td class="center bdl">Chemung<br />Group.</td> - <td class="center bdl">Upper<br />Sandstones.<br />Long Cove, &c.<br />Scauminac<br />Beds.</td> - <td class="center bdl">Mispec Group.<br />Shale,<br />Sandstone,<br />and<br />Conglomerate.</td> - <td class="center bdl">Perry<br />Sandstones.</td> -</tr> -<tr> - <td></td> - <td class="bdl"> </td> - <td class="bdl"></td> - <td class="bdl"></td> - <td class="bdl"></td> -</tr> -<tr> - <td class="center">Middle<br />Devonian or<br />Erian.</td> - <td class="center bdl">Hamilton<br />Group.</td> - <td class="center bdl">Middle<br />Sandstones.<br />Bois Brulé,<br />Cape Oiseau,<br />&c.</td> - <td class="center bdl">Little R. Group<br />(including<br />Cordaite<br />Shales and<br />Dadoxylon<br />Sandstone).</td> - <td class="bdl"></td> -</tr> -<tr> - <td></td> - <td class="bdl"> </td> - <td class="bdl"></td> - <td class="bdl"></td> - <td class="bdl"></td> -</tr> -<tr> - <td class="center bdb">Lower<br />Devonian or<br />Erian.</td> - <td class="center bdb bdl">Corniferous<br />and<br />Oriskany groups.</td> - <td class="center bdb bdl">Lower<br />Sandstones.<br />Gaspé Basin,<br />Little Gaspé,<br />&c.<br />Campbellton<br />Beds.</td> - <td class="center bdb bdl">Lower<br />Conglomerates,<br />&c.</td> - <td class="bdb bdl"></td> -</tr> -</table> - -<p>It may be proper, before closing this note, to state the reasons -which have induced me to suggest in the following pages the use of -the term “Erian,” as equivalent to “Devonian,” for the great system -of formations intervening between the Upper Silurian and the -Lower Carboniferous in America. I have been induced to adopt -this course by the following considerations: 1. The great area of -<span class="pagenum"><a name="Page_108" id="Page_108">« 108 »</a></span> -undisturbed and unaltered rocks of this age, including a thickness -in some places of eighteen thousand feet, and extending from east -to west through the Northern States of the Union and western -Canada for nearly seven hundred miles, while it spreads from north -to south from the northern part of Michigan far into the Middle -States, is undoubtedly the most important Devonian area now known -to geologists. 2. This area has been taken by all American geologists -as their typical Devonian region. It is rich in fossils, and -these have been thoroughly studied and admirably illustrated by -the New York and Canadian Surveys. 3. The rocks of this area -surround the basin of Lake Erie, and were named, in the original -reports of the New York Survey, the “<i>Erie Division</i>” 4. Great -difficulties have been experienced in the classification of the European -Devonian, and the uncertainties thus arising have tended to -throw doubt on the results obtained in America in circumstances in -which such difficulties do not occur.</p> - -<p>These reasons are, I think, sufficient to warrant me in holding -the great <i>Erie Division</i> of the New York geologists as the typical -representative of the rocks deposited between the close of the Upper -Silurian and the beginning of the Carboniferous period, and to use -the term Erian as the designation of this great series of deposits as -developed in America, in so far at least as their flora is concerned. -In doing so, I do not wish to introduce a new name merely for the -sake of novelty; but I hope to keep before the minds of geologists -the caution that they should not measure the Erian formations of -America, or the fossils which they contain, by the comparatively -depauperated representatives of this portion of the geological scale -in the Devonian of western Europe.</p> - - -<p class="caption4">VII.—<span class="smcap">On the Relations of the so-called “Ursa Stage” of Bear Island<br /> -with the Palæozoic Flora of North America.</span></p> - -<p>The following note is a verbatim copy of that published by me -in 1873, and the accuracy of which has now been vindicated by the -recent observations of Nathorst:</p> - -<p>The plants catalogued by Dr. Heer, and characterising what he -calls the “Ursa Stage,” are in part representatives of those of the -American flora which I have described as the “Lower Carboniferous -Coal-Measures” (Subcarboniferous of Dana), and whose characteristic -species, as developed in Nova Scotia, I noticed in the “Journal of -the Geological Society” in 1858 (vol. xv.). Dr. Heer’s list, however, -includes some Upper Devonian forms; and I would suggest that -<span class="pagenum"><a name="Page_109" id="Page_109">« 109 »</a></span> -either the plants of two distinct beds, one Lower Carboniferous and -the other Upper Devonian, have been near to or in contact with each -other and have been intermixed, or else that in this high northern -latitude, in which (for reasons stated in my “Report on the Devonian -Flora”<a name="FNanchor_BZ_78" id="FNanchor_BZ_78"></a><a href="#Footnote_BZ_78" class="fnanchor">[BZ]</a>) I believe the Devonian plants to have originated, there -was an actual intermixture of the two floras. In America, at the -base of the Carboniferous of Ohio, a transition of this kind seems -to occur; but elsewhere in northeastern America the Lower Carboniferous -plants are usually unmixed with the Devonian.</p> - -<div class="footnote"> - -<p><a name="Footnote_BZ_78" id="Footnote_BZ_78"></a><a href="#FNanchor_BZ_78"><span class="label">[BZ]</span></a> “Geological Survey of Canada,” 1871.</p></div> - -<p>Dr. Heer, however, proceeds to identify these plants with those -of the American Chemung, and even with those of the Middle Devonian -of New Brunswick, as described by me—a conclusion from -which I must altogether dissent, inasmuch as the latter belong to -beds which were disturbed and partially metamorphosed before the -deposition of the lowest Carboniferous or “Subcarboniferous” beds.</p> - -<p>Dr. Heer’s error seems to have arisen from want of acquaintance -with the rich flora of the Middle Devonian, which, while differing in -species, has much resemblance in its general facies, and especially in -its richness in ferns, to that of the coal-formation.</p> - -<p>To geologists acquainted with the stratigraphy and the accompanying -animal fossils, Dr. Heer’s conclusions will of course appear -untenable; but they may regard them as invalidating the evidence -of fossil plants; and for this reason it is, I think, desirable to give -publicity to the above statements.</p> - -<p>I consider the British equivalent of the lower coal-measures of -eastern America to be the lower limestone shales, the <i>Tweedian -group</i> of Mr. Tate (1858), but which have sometimes been called the -“Calciferous Sandstone” (a name preoccupied for a Cambrian group -in America). This group does not constitute “beds of passage” to -the Devonian, more especially in eastern America, where the lower -coal-formation rests unconformably on the Devonian, and is broadly -distinguished by its fossils.</p> - -<p>The above notes would not have been extended to so great -length, but for the importance of the Erian flora as the precursor -of that of the Carboniferous, and the small amount of attention -hitherto given to it by geologists and botanists.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_110" id="Page_110">« 110 »</a></span></p> - - - - -<p class="caption2"><a name="CHAPTER_IV" id="CHAPTER_IV">CHAPTER IV.</a></p> - -<p class="caption3">THE CARBONIFEROUS FLORA—CULMINATION OF THE -ACROGENS—FORMATION OF COAL.</p> - -<p><span class="smcap">Ascending</span> from the Erian to the Carboniferous system, -so called because it contains the greatest deposits of -anthracite and bituminous coal, we are still within the -limits of the Palæozoic period. We are still within the -reign of the gigantic club-mosses, cordaites, and taxine -pines. At the close of the Erian there had been over -the whole northern hemisphere great changes of level, -accompanied by active volcanic phenomena, and under -these influences the land flora seems to have much diminished. -At length all the old Erian species had become -extinct, and their place was supplied by a meagre group -of lycopods, ferns, and pines of different species from -those of the preceding Erian. This is the flora of the -Lower Carboniferous series, the Tweedian of England, -the Horton series of Nova Scotia, the lower coal-measures -of Virginia, the culm of Germany. But the land -again subsided, and the period of the marine limestone -of the Lower Carboniferous was introduced. In this the -older flora disappeared, and when the land emerged we -find it covered with the rich flora of the coal-formation -proper, in which the great tribes of the lycopods and -cordaites attained their maxima, and the ferns were continued -as before, though under new generic and specific -forms.</p> - -<p><span class="pagenum"><a name="Page_111" id="Page_111">« 111 »</a></span></p> - -<div class="fig_center" style="width: 244px;"> -<a name="fig32" id="fig32"></a> -<img src="images/fig32.png" width="244" height="322" alt="" /> -<div class="fig_caption">Fig. 32.—Foliage from the coal-formation, -<i>a</i>, <i>Alethopteris lonchitica</i>, -fern (Moose River). <i>b</i>, <i>Sphenophyllum -Schlotheimii</i> (Pietou). <i>c</i>, <i>Lepidodendron -binerve</i> (Sydney), <i>d</i>, <i>Asterophyllites -foliosa</i> (_?_) (Sydney). -<i>e</i>, <i>Cordaites</i> (Joggins). <i>f</i>, <i>Neuropteris -rarinervis</i>, fern (Sydney). -<i>g</i>, <i>Odontopteris subcuneata</i>, fern -(Sydney).</div> -</div> - -<p>There is something very striking in this succession of -a new plant world without any material advance. It is -like passing in the modern world from one district to -another, in which we see the same forms of life, only -represented by distinct though allied species. Thus, when -the voyager crosses the Atlantic from Europe to America, -he meets with pines, -oaks, birches, poplars, -and beeches of the same -genera with those he -had left behind; but -the species are distinct. -It is something like this -that meets us in our ascent -into the Carboniferous -world of plants. -Yet we know that this -is a succession in time, -that all our old Erian -friends are dead and -buried long ago, and -that these are new forms -lately introduced (<a href="#fig32">Fig. 32</a>).</p> - -<p>Conveying ourselves, -then, in imagination forward -to the time when -our greatest accumulations -of coal were formed, -and fancying that we are introduced to the American -or European continent of that period, we find ourselves -in a new and strange world. In the Devonian -age, and even in the succeeding Lower Carboniferous, -there was in the interior of America a wide inland sea, -with forest belts clinging to its sides or clothing its islands. -But in the coal period this inland sea had given -<span class="pagenum"><a name="Page_112" id="Page_112">« 112 »</a></span> -place to vast swampy flats, and which, instead of the oil-bearing -shales of the Erian, were destined to produce -those immense and wide-spread accumulations of vegetable -matter which constitute our present beds of bituminous -and anthracite coal. The -atmosphere of these great swamps -is moist and warm. Their vegetation -is most exuberant, but of -forms unfamiliar to modern eyes, -and they swarm with insects, -millipedes, and scorpions, and -with batrachian reptiles large -and small, among which we look -in vain for representatives of the -birds and beasts of the present -day.</p> - -<table summary="Sigillariæ"> -<tr> - <td><div class="fig_left" style="width: 190px;"> - <a name="fig33" id="fig33"></a> - <img src="images/fig33.png" width="190" height="520" alt="" /> - <div class="fig_caption">Fig. 33.—<i>Sigillariæ</i>, restored. - A, <i>Sigillaria Brownii</i>. - B, <i>Sigillaria elegans</i>.</div></div></td> - <td><div class="fig_right" style="width: 367px;"> - <a name="fig34" id="fig34"></a> - <img src="images/fig34.png" width="367" height="497" alt="" /> - <div class="fig_caption">Fig. 34.—<i>Sigillaria Lorwayana</i>, Dawson. <i>a</i>, Zones of fruit-scars. <i>b</i>, Leaf-scar - enlarged, <i>c</i>, Fruit-scar enlarged. See <a href="#Sigillariaceae">appended note</a>.</div></div></td> -</tr> -<tr> - <td><div class="fig_left" style="width: 129px;"> - <a name="fig35" id="fig35"></a> - <img src="images/fig35.png" width="129" height="272" alt="" /> - <div class="fig_caption">Fig. 35.—Stem of <i>Sigillaria - Brownii</i>. reduced. Natural size.</div></div></td> - <td><div class="fig_right" style="width: 261px;"> - <a name="fig36" id="fig36"></a> - <img src="images/fig36.png" width="261" height="259" alt="" /> - <div class="fig_caption">Fig. 36.—Two ribs of <i>Sigillaria Brownii</i>.</div></div></td> -</tr> -</table> - -<div class="fig_left" style="width: 165px;"> -<a name="fig37" id="fig37"></a> -<img src="images/fig37.png" width="165" height="260" alt="" /> -<div class="fig_caption">Fig. 37.—Portion of lower -part of stem of <i>S. Brownii</i>. -Natural size.</div> -</div> - -<p>Prominent among the more -gigantic trees of these swampy -forests are those known to us as -<i>Sigillariæ</i> (<a href="#fig33">Fig. 33</a>). They have -tall, pillar-like trunks, often several -feet in diameter, ribbed like -fluted columns, but in the reverse -way, and spreading at the -top into a few thick branches, -which are clothed with long, -grass-like leaves. They resemble -in some respects the Lepidodendra -of the Erian age, but -are more massive, with ribbed instead -of scaly trunks, and longer -leaves. If we approach one of -them more closely, we are struck with the regular ribs of -its trunk, dotted with rows of scars of fallen leaves, from -which it receives its name <i>Sigillaria</i>, or seal-tree (Figs. <a href="#fig34">34</a>-<a href="#fig37">37</a>). -If we cut into its stem, we find that, instead of -<span class="pagenum"><a name="Page_113" id="Page_113">« 113 »</a></span> -the thin bark and firm wood with which we are familiar -in our modern trees, it has a hard external rind, then a -great thickness of cellular matter with rope-like bands of -fibres, constituting an inner bark, while in the centre is -a firm, woody axis of comparatively small diameter, and -somewhat intermediate in its structures between that of -the Lepidodendra and those of the cycads and the taxine -conifers. Thus a great stem, five feet in diameter, may -consist principally of cellular and bast fibres with very -little true woody matter. The roots of this tree are -<span class="pagenum"><a name="Page_114" id="Page_114">« 114 »</a></span> -perhaps its most singular feature. They usually start -from the stem in four main branches, then regularly -bifurcate several times, and then run out into great -cylindrical cables, running for a long distance, and evidently -intended to anchor the plant firmly in a soft and -oozy soil. They were furnished -with long, cylindrical rootlets -placed regularly in a spiral manner, -and so articulated that when -they dropped off they left regular -rounded scars. They are, -in short, the <i>Stigmariæ</i>, which -we have already met with in -the Erian (Figs. <a href="#fig38">38</a>, <a href="#fig39">39</a>). In -<a href="#fig33">Fig. 33</a> I have endeavoured to -restore these strange trees. It is -not wonderful that such plants -have caused much botanical controversy. -It was long before botanists -could be convinced that -<span class="pagenum"><a name="Page_115" id="Page_115">« 115 »</a></span> -their roots are properly roots at all, and not stems -of some aquatic plant. Then the structure of their -stems is most puzzling, and their fruit is an enigma, -for while some have found connected with them cones -supposed to resemble those of -lycopods, others attribute to -them fruits like those of yew-trees. -For years I have been -myself gathering materials from -the rich coal-formation deposits -of Nova Scotia in aid of the -solution of these questions, and -in the mean time Dr. Williamson, -of Manchester, and Renault -and other botanists in France, -have been amassing and studying -stores of specimens, and it -is still uncertain who may finally -be the fortunate discoverer -to set all controversies at rest. My present belief is, -that the true solution consists in the fact that there are -many kinds of <i>Sigillariæ</i>. While in the modern forests -<span class="pagenum"><a name="Page_116" id="Page_116">« 116 »</a></span> -of America and Europe the species of any of our ordinary -trees, as oaks, birches, or maples, may almost be counted -on one’s fingers, Schimper in his vegetable palæontology -enumerates about eighty species of Carboniferous <i>Sigillariæ</i>; -and while on the one hand many of these are so -imperfectly known that they may be regarded as uncertain, -on the other hand many species must yet remain to -be discovered.<a name="FNanchor_CA_79" id="FNanchor_CA_79"></a><a href="#Footnote_CA_79" class="fnanchor">[CA]</a> Now, in so vast a number of species -there must be a great range of organisation, and, indeed, -it has already been attempted to subdivide them into -several generic groups. The present state of the question -appears to me to be this, that in these <i>Sigillariæ</i> we have -a group divisible into several forms, some of which will -eventually be classed with the Lepidodendra as lycopods, -while others will be found to be naked-seeded phænogams, -allied to the pines and cycads, and to a remarkable -group of trees known as <i>Cordaites</i>, which we must shortly -notice.</p> - -<div class="footnote"> - -<p><a name="Footnote_CA_79" id="Footnote_CA_79"></a><a href="#FNanchor_CA_79"><span class="label">[CA]</span></a> In a recent memoir (Berlin, 1887) Stur has raised the number of -species in one subdivision of the <i>Sigillariæ</i> (the <i>Favulariæ</i>) to forty-seven!</p></div> - -<div class="fig_left" style="width: 452px;"> -<a name="fig38" id="fig38"></a> -<img src="images/fig38.png" width="452" height="246" alt="" /> -<div class="fig_caption">Fig. 38.—<i>Stigmaria</i> root, seen from above, showing its regular divisions.<br /> -From "Acadian Geology".</div> -</div> - -<div class="fig_right" style="width: 183px;"> -<a name="fig39" id="fig39"></a> -<img src="images/fig39.png" width="183" height="239" alt="" /> -<div class="fig_caption">Fig. 39.—Portion of bark of -<i>Stigmaria</i>, showing scars -of attachment of rootlets.</div> -</div> - -<p style="clear: both;">Before considering other forms of Carboniferous vegetation, -let us glance at the accumulation of coal, and the -agency of the forests of <i>Sigillariæ</i> therein. Let us imagine, -in the first instance, such trees as those represented -in the figures, growing thickly together over vast swampy -flats, with quantities of undergrowth of ferns and other -plants beneath their shade, and accumulating from age to -age in a moist soil and climate a vast thickness of vegetable -mould and trunks of trees, and spores and spore-cases, -and we have the conditions necessary for the growth -of coal. Many years ago it was observed by Sir William -Logan that in the coal-field of South Wales it was the -rule with rare exceptions that, under every bed of coal, -there is a bed of clay filled with roots of the <i>Stigmaria</i>, -already referred to as the root of <i>Sigillaria</i>. This discovery -<span class="pagenum"><a name="Page_117" id="Page_117">« 117 »</a></span> -has since been extended to all the coal-fields of -Europe and America, and it is a perfectly conclusive fact -as regards the origin of coal. Each of these “under-clays,” -as they are called, must, in fact, have been a soil -on which grew, in the first instance, Sigillariæ and other -trees having stigmaria-roots. Thus, the growth of a -forest of <i>Sigillariæ</i> was the first step toward the accumulation -of a bed of coal. More than this, in some of the -coarser and more impure coals, where there has been -sufficient earthy matter to separate and preserve impressions -of vegetable forms, we can see that the mass of the -coal is made up of flattened <i>Sigillariæ</i>, mixed with vegetable -<i>débris</i> of all kinds, including sometimes vast quantities -of lepidodendroid spores, and the microscopic study -of the coal gives similar results (<a href="#fig40">Fig. 40</a>). Further, on -the surfaces of many coals, and penetrating the shales or -sandstones which form their roofs, we find erect stumps -of sigillaria and other trees, showing that the accumulation -of the coal terminated as it had begun, by a forest-growth. -I introduce here a section of a few of the numerous -beds of coal exposed in the cliffs of the South -Joggins, in Nova Scotia, in illustration of these facts. -We can thus see how in the slowly subsiding areas of the -coal-swamps successive beds of coal were accumulated, -alternating with beds of sandstone and shale (Figs. <a href="#fig41">41</a>, -<a href="#fig42">42</a>). For other details of this kind I must refer to -papers mentioned in the sequel.</p> - -<div class="fig_center" style="width: 341px;"> -<a name="fig40" id="fig40"></a> -<img src="images/fig40.png" width="341" height="135" alt="" /> -<div class="fig_caption">Fig. 40.—Vegetable tissues from coal. <i>a</i>, <i>Sigillaria</i> and <i>Cordaites</i>. -<i>Calamodendron</i>.</div> -</div> - -<p><span class="pagenum"><a name="Page_118" id="Page_118">« 118 »</a></span></p> - -<p>Returning to the more special subject of this work, I -may remark that the lepidodendroid trees and the ferns, -both the arborescent and herbaceous kinds, are even more -richly represented in the Carboniferous than in the preceding -Erian, I must, however, content myself with -merely introducing a few representatives of some of -the more common -kinds, in an appended -note, and -here give a figure -of a well-known -Lower Carboniferous -lepidodendron, -with its various -forms of leaf-bases, -and its foliage and -fruit (<a href="#fig43">Fig. 43</a>), and -a similar illustration -of an allied -generic form, that -known as <i>Lepidophloios</i><a name="FNanchor_CB_80" id="FNanchor_CB_80"></a><a href="#Footnote_CB_80" class="fnanchor">[CB]</a> -(<a href="#fig44">Fig. 44</a>).</p> - -<div class="footnote"> - -<p><a name="Footnote_CB_80" id="Footnote_CB_80"></a><a href="#FNanchor_CB_80"><span class="label">[CB]</span></a> For full descriptions of these, see “Acadian Geology.”</p></div> - -<table summary="coal"> -<tr> - <td class="center" style="width: 45%"><a name="fig41" id="fig41"></a> - <img src="images/fig41.png" width="295" height="323" alt="" /> - <div class="fig_caption">Fig. 41.—Beds associated with the main coal - (S. Joggins, Nova Scotia). 1, Shale and sandstone—plants - with <i>Spirorbis</i> attached; rain-marks - (?). (2, Sandstone and shale, eight - feet—erect <i>Calamites</i>; 3, Gray sandstone, - seven feet; 4, Gray shale, four feet—an erect - coniferous (?) tree, rooted on the shale, passes - up through fifteen feet of the sandstones and - shale.) 5, Gray sandstone, four feet. 6, Gray - shale, six inches—prostrate and erect trees, - with rootlets, leaves, <i>Naiadites</i>, and <i>Spirorbis</i> - on the plants. 7, Main coal-seam, five - feet of coal in two seams. 8, Underclay, with - rootlets.</div> - </td> - <td class="center" style="width: 45%"><a name="fig42" id="fig42"></a> - <img src="images/fig42.png" width="238" height="371" alt="" /> - <div class="fig_caption">Fig. 42.—Erect <i>Sigillaria</i>, standing - on a coal-seam (S. Joggins, Nova - Scotia).</div> - </td> -</tr> -</table> - -<p>Another group -which claims our -attention is that -of the <i>Calamites</i>. -These are tall, cylindrical, -branchless -stems, with -whorls of branchlets, -bearing needle-like -leaves and spreading in stools from the base, so as to -form dense thickets, like Southern cane-brakes (<a href="#fig46">Fig. 46</a>). -They bear, in habit of growth and fructification, a close -<span class="pagenum"><a name="Page_119" id="Page_119">« 119 »</a></span> -relation to our modern equisetums, or mare’s-tails, but, -as in other cases we have met with, are of gigantic size -and comparatively complex structure. Their stems, in -cross-section, show radiating -bundles of fibres, -like those of exogenous -woods, yet the whole plan -of structure presents some -curious resemblances to -the stems of their humble -successors, the modern -mare’s-tails. It would -seem, from the manner -in which dense brakes of -these <i>Calamites</i> have been -preserved in the coal-formation -of Nova Scotia, -that they spread over low -and occasionally inundated -flats, and formed -fringes on the seaward -sides of the great Sigillaria -forests. In this way -they no doubt contributed -to prevent the invasion of the areas of coal accumulation -by the muddy waters of inundations, and -thus, though they may not have furnished much of the -material of coal, they no doubt contributed to its purity. -Many beautiful plants of the genera Asterophyllites and -<i>Annularia</i> are supposed to have been allied to the <i>Calamites</i>, -or to have connected them with the <i>Rhizocarps</i>. -The stems and fruit of these plants have strong points of -resemblance to those of <i>Sphenophyllum</i>, and the leaves -are broad, and not narrow and angular like those of the -true <i>Calamites</i> (<a href="#fig45">Fig. 45</a>).</p> - -<p><span class="pagenum"><a name="Page_120" id="Page_120">« 120 »</a></span></p> - -<div class="fig_center" style="width: 409px;"> -<a name="fig43" id="fig43"></a> -<img src="images/fig43.png" width="409" height="700" alt="" /> -<div class="fig_caption">Fig. 43.—<i>Lepidodendron corrugatum</i>, Dawson, a tree characteristic of the -Lower Carboniferous, A, Restoration. B, Leaf, natural size, C, Cone -and branch, D, Branch and leaves, E. Various forms of leaf-areoles. -F, <i>Sporangium</i>, I, L, M, Bark, with leaf-scars, N, Bark, with leaf-scars -of old stem, O, Decorticated stem (<i>Knorria</i>).</div> -</div> - -<p><span class="pagenum"><a name="Page_121" id="Page_121">« 121 »</a></span></p> - -<div class="fig_center" style="width: 402px;"> -<a name="fig44" id="fig44"></a> -<img src="images/fig44.png" width="402" height="707" alt="" /> -<div class="fig_caption">Fig. 44.—<i>Lepidophloios Acadianus</i>, Dawson, a lepidodendroid tree of the -coal-formation, A, Restoration. B, Portion of bark (two thirds natural -size), C, Ligneous surface of the same, F, Cone (two thirds natural size). -G, Leaf (natural, size), K, Portion of woody cylinder, showing outer and -inner series of vessels magnified, L, Scalariform vessels (highly magnified), -M, Various forms of leaf-scars and leaf-bases (natural size).</div> -</div> - -<p><span class="pagenum"><a name="Page_122" id="Page_122">« 122 »</a></span></p> - -<div class="fig_center" style="width: 380px;"> -<a name="fig45" id="fig45"></a> -<img src="images/fig45.png" width="380" height="344" alt="" /> -<div class="fig_caption">Fig. 45.—<i>Asterophyllites</i>, <i>Sphenophyllum</i>, and <i>Annularia</i>. A, <i>Asterophyllites -trinerne</i>. A<sup>1</sup>, Leaf enlarged, B, <i>Annularia sphenophylloides</i>. -B<sup>1</sup>, Leaf enlarged, C, <i>Sphenophyllum erosum</i>. C<sup>1</sup>, Leaflet enlarged. -C<sup>2</sup>, Scalariform vessel of <i>Sphenophyllum</i>. D, <i>Pinnularia ramosissima</i>, -probably a root.</div> -</div> - -<p>No one has done more than my friend Dr. Williamson, -of Manchester, to illustrate the structure of Calamites, -and he has shown that these plants, like other -cryptogams of the Carboniferous, had mostly stems with -regular fibrous wedges, like those of exogens. The -structure of the stem is, indeed, so complex, and differs -so much in different stages of growth, and different states -of preservation, that we are in danger of falling into the -greatest confusion in classifying these plants. Sometimes -what we call a Calamite is a mere cast of its pith showing -longitudinal striæ and constrictions at the nodes. Sometimes -we have the form of the outer surface of the woody -cylinder, showing longitudinal ribs, nodes, and marks of -the emission of the branchlets. Sometimes we have the -outer surface of the plant covered with a smooth bark -showing flat ribs, or almost smooth, and having at the -nodes regular articulations with the bases of the verticillate -<span class="pagenum"><a name="Page_123" id="Page_123">« 123 »</a></span> -branchlets, or on the lower part of the stem the -marks of the attachment of the roots. The Calamites -grew in dense clumps, budding off from one another, -sometimes at different levels, as the mud or sand accumulated -about their stems, and in some -species there were creeping rhizomata -or root-stocks (Figs. <a href="#fig46">46</a> to <a href="#fig49">49</a>).</p> - -<table summary="Calamites"> -<tr> - <td><div class="fig_left" style="width: 133px;"> - <a name="fig46" id="fig46"></a> - <img src="images/fig46.png" width="133" height="358" alt="" /> - <div class="fig_caption">Fig. 46.—<i>Calamites</i>. - A, <i>C. Suckovii</i>. B, - <i>C. Cistii</i>. (From - “Acadian Geology.”)</div></div></td> - <td><div class="fig_left" style="width: 145px;"> - <a name="fig47" id="fig47"></a> - <img src="images/fig47.png" width="145" height="372" alt="" /> - <div class="fig_caption">Fig. 47.—Erect <i>Calamites</i>, - with roots attached (Nova Scotia).</div></div></td> - <td><div class="fig_left" style="width: 149px;"> - <a name="fig48" id="fig48"></a> - <img src="images/fig48.png" width="149" height="475" alt="" /> - <div class="fig_caption">Fig. 48.—Node of <i>C. - Cistii</i>, with long leaves (Nova Scotia).</div></div></td> -</tr> -</table> - -<div class="fig_center" style="width: 423px;"> -<a name="fig49" id="fig49"></a> -<img src="images/fig49.png" width="423" height="279" alt="" /> -<div class="fig_caption">Fig. 49.—Erect <i>Calamites</i> (<i>C. Suckovii</i>), showing the mode of growth of -new stems (<i>b</i>), and different forms of the ribs (<i>a</i>, <i>c</i>). (Pictou, Nova -Scotia.) Half natural size.</div> -</div> - -<p>But all Calamites were not alike -in structure. In a recent paper<a name="FNanchor_CC_81" id="FNanchor_CC_81"></a><a href="#Footnote_CC_81" class="fnanchor">[CC]</a> -Dr. Williamson describes three distinct structural types. -What he regards as typical Calamites has in its woody -zone wedges of barred vessels, with thick bands of cellular -tissue separating them. A second type, which -<span class="pagenum"><a name="Page_124" id="Page_124">« 124 »</a></span> -he refers to <i>Calamopitus</i>, has woody bundles composed -of reticulated or multiporous fibres, with their -porous sides parallel to the medullary rays, which are -better developed than in the previous form. The intervening -cellular masses are composed of elongated cells. -This is a decided advance in structure, and is of the type -of those forms having the most woody and largest stems, -which Brongniart named <i>Calamodendron</i> (<a href="#fig50">Fig. 50</a>). A -third form, to which Dr. Williamson seems to prefer to -assign this last name, has the tissue of the woody wedges -barred, as in the first, but the medullary rays are better -developed than in the second. In this third form the -intermediate tissue, or primary medullary rays, is truly -fibrous, and with secondary medullary rays traversing it. -My own observations lead me to infer that there was a -fourth type of calamitean stem, less endowed with woody -matter, and having a larger fistulous or cellular cavity -than any of those described by Dr. Williamson.</p> - -<div class="footnote"> - -<p><a name="Footnote_CC_81" id="Footnote_CC_81"></a><a href="#FNanchor_CC_81"><span class="label">[CC]</span></a> “Memoirs of the Philosophical Society,” Manchester, 1886-'87.</p></div> - -<p>There is every reason to believe that all these various -<span class="pagenum"><a name="Page_125" id="Page_125">« 125 »</a></span> -and complicated stems belonged to higher and nobler -types of mare’s-tails than those of the modern world, and -that their fructification was equisetaceous and of the -form known as <i>Calamostachys</i>.</p> - -<p>We have already seen that noble tree-ferns existed in -the Erian period, and these were continued, and their -number and variety greatly extended, in the Carboniferous. -In regard to the structure of their stems, and the -method of supporting these by aërial roots, the tree-ferns -of all ages have been nearly alike, and the form and -structure of the leaves, except in some comparatively rare -and exceptional types, has also been much the same. -Any ordinary observer examining a collection of coal-formation -ferns recognises at once their kinship to the -familiar brackens of our own time. Their fructification -is, unfortunately, rarely preserved, so that we are not -able, in the case of many species, to speak confidently of -their affinities with modern forms; but the knowledge of -this subject has been constantly extending, and a sufficient -amount of information has been obtained to enable -us to say something as to their probable relationships. -(Figs. <a href="#fig51">51</a> to <a href="#fig55">55</a>.)</p> - -<div class="fig_center" style="width: 396px;"> -<a name="fig50" id="fig50"></a> -<img src="images/fig50.png" width="396" height="191" alt="" /> -<div class="fig_caption">Fig. 50.—Stems of <i>Calamodendron</i> and tissues magnified (Nova Scotia), -<i>a</i>, <i>b</i>, Casts of axis in sandstone, with woody envelope (reduced). -<i>c</i>, <i>d</i>, Woody tissue (highly magnified).</div> -</div> - -<p>The families into which modern ferns are divided are, -it must be confessed, somewhat artificial, and in the case -<span class="pagenum"><a name="Page_126" id="Page_126">« 126 »</a></span> -of fossil ferns, in which the fructification is for the most -part wanting, it is still more so, depending in great part -on the form and venation of the divisions of the fronds. -Of about eight families into which modern ferns are -divided, seven are found in a fossil state, and of these, -four at least, the <i>Cyathaceæ</i>, the <i>Ophioglosseæ</i>, the <i>Hymenophyllaceæ</i>, -and the <i>Marattiaceæ</i>, go back to the coal-formation.<a name="FNanchor_CD_82" id="FNanchor_CD_82"></a><a href="#Footnote_CD_82" class="fnanchor">[CD]</a></p> - -<div class="footnote"> - -<p><a name="Footnote_CD_82" id="Footnote_CD_82"></a><a href="#FNanchor_CD_82"><span class="label">[CD]</span></a> Mr. R. Kidston has recently described very interesting forms of -fern fructification from the coal-formation of Great Britain, and much -has been done by European palæobotanists, and also by Lesquereux and -Fontaine in America.</p></div> - -<div class="fig_center" style="width: 455px;"> -<a name="fig51" id="fig51"></a> -<img src="images/fig51.png" width="455" height="542" alt="" /> -<div class="fig_caption">Fig. 51.—Group of coal-formation ferns, A, <i>Odontopteris subcuneata</i> (Bunbury), -B, <i>Neuropteris cordata</i> (Brongniart). C, <i>Alethopteris lonchitica</i> -(Brongniart). D, <i>Dictyopteris obliqua</i> (Bunbury). E, <i>Phyllopteris antiqua</i> -(Dawson), magnified; E<sup>1</sup>, Natural size, F, <i>Neuropteris cyclopteroides</i> -(Dawson).</div> -</div> - -<p><span class="pagenum"><a name="Page_127" id="Page_127">« 127 »</a></span></p> - -<div class="fig_center" style="width: 405px;"> -<a name="fig52" id="fig52"></a> -<img src="images/fig52.png" width="405" height="392" alt="" /> -<div class="fig_caption">Fig. 52.—<i>Alethopteris grandis</i> (Dawson). Middle coal-formation of Nova Scotia.</div> -</div> - -<div class="fig_center" style="width: 451px;"> -<a name="fig53" id="fig53"></a> -<img src="images/fig53.png" width="451" height="278" alt="" /> -<div class="fig_caption">Fig. 53.—<i>Cyclopteris</i> (<i>Aneimites</i>) <i>Acadica</i> (Dawson), a tree-fern of the -Lower Carboniferous. <i>a</i>, Pinnules. <i>b</i>, Fragment of petiole. <i>c</i>, Remains -of fertile pinnules.</div> -</div> - -<p><span class="pagenum"><a name="Page_128" id="Page_128">« 128 »</a></span></p> - -<div class="fig_center" style="width: 333px;"> -<a name="fig54" id="fig54"></a> -<img src="images/fig54.png" width="333" height="238" alt="" /> -<div class="fig_caption">Fig. 54.—<i>Sphenopteris latior</i>, Dawson. Coal-formation, <i>a</i>, Pinnule -magnified, with traces of fructification.</div> -</div> - -<div class="fig_center" style="width: 359px;"> -<a name="fig55" id="fig55"></a> -<img src="images/fig55.png" width="359" height="117" alt="" /> -<div class="fig_caption">Fig. 55.—Fructification of Palæozoic ferns, <i>a</i>, Thecæ of <i>Archæopteris</i> -(Erian). <i>b</i>, Theca of <i>Senftenbergia</i> (Carboniferous). <i>c</i>, Thecæ of -<i>Asterotheca</i> (Carboniferous).</div> -</div> - -<p><span class="pagenum"><a name="Page_129" id="Page_129">« 129 »</a></span></p> - -<div class="fig_center" style="width: 462px;"> -<a name="fig56" id="fig56"></a> -<img src="images/fig56.png" width="462" height="714" alt="" /> -<div class="fig_caption">Fig. 56.—Tree-ferns of the Carboniferous. A, <i>Megaphyton magnificum</i>, -Dawson, restored. B, Leaf-scar of the same, two thirds natural size. -B<sup>1</sup>, Row of leaf-scars, reduced. C, <i>Palæopteris Harttii</i>, scars half natural -size. D, <i>Acadica</i>, scars half natural size.</div> -</div> - -<p><span class="pagenum"><a name="Page_130" id="Page_130">« 130 »</a></span></p> - -<p>Some of these ferns have the more complex kind of -spore-case, with a jointed, elastic ring. It is to be observed, -however, that those forms which have a simple -spore-case, either netted or membranous, and without -annulus, are most common in the Devonian and lowest -Carboniferous. Some of the forms in these old rocks are -somewhat difficult to place in the system. Of these, the -species of <i>Archæopteris</i>, of the Upper and Middle Erian, -are eminent as examples. This type, however, scarcely -extends as high as the coal-formation.<a name="FNanchor_CE_83" id="FNanchor_CE_83"></a><a href="#Footnote_CE_83" class="fnanchor">[CE]</a> Some of the -tree-ferns of the Carboniferous present very remarkable -features. One of these, of the genus <i>Megaphyton</i>, seems -to have two rows of great leaves, one at each side of the -stem, which was probably sustained by large bundles of -aërial roots (<a href="#fig56">Fig. 56</a>).</p> - -<div class="footnote"> - -<p><a name="Footnote_CE_83" id="Footnote_CE_83"></a><a href="#FNanchor_CE_83"><span class="label">[CE]</span></a> The pretty little ferns of the genus <i>Botrychium</i> (moonwort), so -common in American and European woods, seem to be their nearest modern -allies.</p></div> - -<p>In the Carboniferous, as in the Erian, there are leaves -which have been referred to ferns, but are subject to -doubt, as possibly belonging to broad-leaved taxine trees -allied to the gingko-tree of China. One of these, represented -in <a href="#fig57">Fig. 57</a>, has been -found in the coal-formation of -Nova Scotia, and referred to the -doubtful genus <i>Noeggerathia</i>. -Fontaine has proposed for similar -leaves found in Virginia the -new generic name <i>Saportea</i>.</p> - -<div class="fig_left" style="width: 191px;"> -<a name="fig57" id="fig57"></a> -<img src="images/fig57.png" width="191" height="219" alt="" /> -<div class="fig_caption">Fig. 57.—<i>Noeggerathia disbar</i> -(half natural size).</div> -</div> - -<div class="fig_right" style="width: 262px;"> -<a name="fig58" id="fig58"></a> -<img src="images/fig58.png" width="262" height="455" alt="" /> -<div class="fig_caption">Fig. 58.—<i>Cordaites</i> (<i>Dorycordaites</i>), -Grand d’Eury, reduced.</div> -</div> - -<p>Ferns, as might be inferred -from their great age, are at the -present time dispersed over the -whole world; but their headquarters, -and the regions to -which tree-ferns are confined, -are the more moist climates of the tropics and of the -southern hemisphere. The coal-swamps of the northern -hemisphere seem to have excelled even these favoured -regions of the present world as a paradise for ferns.</p> - -<p>I have already stated that the Carboniferous constitutes -the headquarters of the <i>Cordaites</i> (<a href="#fig58">Fig. 58</a>), of which -a large number of species have been described, both in -<span class="pagenum"><a name="Page_131" id="Page_131">« 131 »</a></span> -Europe and America. We sometimes, though rarely, -find their stems showing structure. In this case we have -a large cellular pith, often divided by horizontal partitions -into flat chambers, and constituting the objects -which, when detached, are called <i>Sternbergiæ</i> (<a href="#fig62">Fig. 62</a>). -These Sternbergia piths, however, occur in true conifers -as well, as they do -in the modern world -in some trees, like our -common butternut, of -higher type; and I -showed many years ago -that the Sternbergia -type may be detected -in the young twigs of -the balsam-fir (<i>Abies -balsamifera</i>). The pith -was surrounded by a -ring of scalariform or -barred tissue, often of -considerable thickness, -and in young stems so -important as to have -suggested lycopodiaceous -affinities. But as -the stem grew in size, -a regular ring of woody -wedges, with tissue having -rounded or hexagonal -pores or discs, -like those of pines, was developed. Outside this was a -bark, often apparently of some thickness. This structure -in many important points resembles that of cycads, -and also approaches to the structure of Sigillaria, while -in its more highly developed forms it approximates to -that of the conifers.</p> - -<p><span class="pagenum"><a name="Page_132" id="Page_132">« 132 »</a></span></p> - -<div class="fig_center" style="width: 477px;"> -<a name="fig59" id="fig59"></a> -<img src="images/fig59.png" width="477" height="547" alt="" /> -<div class="fig_caption">Fig. 59.—Fruits of <i>Cordaites</i> and Taxine Conifers (coal-formation. Nova -Scotia.) A, <i>Antholithes squamosus</i> (two thirds). B, <i>A. rhabdocarpi</i>. -(two thirds). B<sup>1</sup>, Carpel restored. C, <i>A. spinosus</i> (natural size). -D, <i>Trigonocarpum intermedium</i>. E, <i>T. Noeggerathii</i>. F, <i>T. avellanum</i>. -G, <i>Rhabdocarpus insignis</i>, reduced. H, <i>Antholithes pygmæus</i>. -I, <i>Cardiocarpum fluitans</i>. K, <i>Cardiocarpum bisectum</i>. L, <i>Sporangites -papillata</i>, lycopodiaceous macrospores (natural size and magnified).</div> -</div> - -<p>On the stems so constructed were placed long and -often broad many-nerved leaves, with rows of stomata or -breathing-pores, and attached by somewhat broad bases -to the stem and branches. The fruit consisted of racemes, -or clusters of nutlets, which seem to have been provided -<span class="pagenum"><a name="Page_133" id="Page_133">« 133 »</a></span> -with broad lateral wings for flotation in the air, or in -some cases with a pulpy envelope, which flattens into a -film. There seem to have been structures of both these -kinds, though in the state of preservation of these curious -seeds it is extremely difficult to distinguish them. In the -first case they must have been intended for dissemination -by the wind, like the seeds of spruces. In the latter case -they may have been disseminated like the fruits of taxine -trees by the agency of animals, though what these were -it would be difficult to guess. These trees had very great -reproductive power, since they produced numerous seeds, -not singly or a few together, as in modern yews, but in -long spikes or catkins bearing many seeds (<a href="#fig59">Fig. 59</a>).</p> - -<p>It is to be observed that the Cordaites, or the <i>Cordaitinæ</i>, -as they have been called, as a family,<a name="FNanchor_CF_84" id="FNanchor_CF_84"></a><a href="#Footnote_CF_84" class="fnanchor">[CF]</a> constitute -another of those intermediate groups with which we have -already become familiar. On the one hand they approach -closely to the broader-leaved yews like Gingko, Phyllocladus, -and Podocarpus, and, on the other hand, they -have affinities with Cycadaceæ, and even with Sigillariæ. -They were beautiful and symmetrical trees, adding something -to the variety of the rather monotonous Palæozoic -forests. They contributed also somewhat to the accumulation -of coal. I have found that some thin beds are -almost entirely composed of their leaves, and the tissues -of their wood are not infrequent in the mineral charcoal -of the larger coal-seams. There is no evidence that their -roots were of the stigmaroid type, though they evidently -grew in the same swampy flats with the Sigillariæ and -Calamites.</p> - -<div class="footnote"> - -<p><a name="Footnote_CF_84" id="Footnote_CF_84"></a><a href="#FNanchor_CF_84"><span class="label">[CF]</span></a> Engler; Cordaitées of Renault.</p></div> - -<p>It may, perhaps, be well to say here that I believe -there was a considerably wide range of organisation in the -Cordaitinæ as well as in the Calamites and Sigillariæ, and -that it will eventually be found that there were three lines -<span class="pagenum"><a name="Page_134" id="Page_134">« 134 »</a></span> -of connection between the higher cryptogams and the -phænogams, one leading from the lycopods by the Sigillariæ, -another leading by the Cordaites, and the third -leading from the Equisetums by the Calamites. Still -further back the characters afterward separated in the -club-mosses, mare’s-tails, and ferns, were united in the -Rhizocarps, or, as some now, but I think somewhat unreasonably, -prefer to call them, the “heterosporous Filicinæ.” -In the more modern world, all the connecting -links have become extinct and the phænogams stand -widely separated from the higher cryptogams. I do not -make these remarks in a Darwinian sense, but merely to -state what appear to be the lines of natural affinity and -the links wanting to give unity to the system of nature.</p> - -<p>Of all the trees of the modern world, none are perhaps -so widely distributed as the pines and their allies. On -mountain-tops and within the Arctic zone, the last trees -that can struggle against the unfavourable conditions of -existence are the spruces and firs, and in the warm and -moist islands of the tropics they seem equally at home -with the tree-ferns and the palms. We have already seen -that they are a very ancient family, and in the sandstones -of the coal-formation their great trunks are frequently -found, infiltrated with calcareous or silicious matter, and -still retaining their structure in the greatest perfection -(<a href="#fig60">Fig. 60</a>). So far as we know, the foliage of some of them -which constitutes the genera <i>Walchia</i> and <i>Araucarites</i> of -some authors (Figs. <a href="#fig60">60</a>, <a href="#fig63">63</a>) was not dissimilar from that -of modern yews and spruces, though there is reason to -believe that some others had broad, fern-like leaves like -those of the gingko. None of them, so far as yet certainly -known, were cone-bearing trees, their fruit having -probably been similar to that of the yews (<a href="#fig61">Fig. 61</a>). -The minute structures of their stems are nearer to those -of the conifers of the islands of the southern hemisphere -than to that of those in our northern climes—a correlation, -no doubt, to the equable climate of the period. -There is not much evidence that they grew with the Sigillariæ -in the true coal-swamps, though some specimens -have been found in this association. It is more likely -that they were in the main inland and upland trees, and -that in consequence they are mostly known to us by -drifted trunks borne by river inundations into the seas -and estuaries.</p> - -<p><span class="pagenum"><a name="Page_135" id="Page_135">« 135 »</a></span></p> - -<div class="fig_center" style="width: 458px;"> -<a name="fig60" id="fig60"></a> -<img src="images/fig60.png" width="458" height="637" alt="" /> -<div class="fig_caption">Fig. 60.—Coniferous wood and foliage (Carboniferous). A, <i>Araucarites -gracilis</i>, reduced, b, <i>Dadoxylon Acadianum</i> (radial), 90 diams.; -B<sup>1</sup> (tangential), 90 diams; B<sup>2</sup>, cell showing areolation, 250 diams. -C, <i>Dadoxylon materiarium</i> (radial), 90 diams.; C<sup>1</sup> (tangential), 90 -diams. C<sup>2</sup>, cell showing areolation, 250 diams. D, <i>Dadoxylon antiquius</i> -(radial), 90 diams.; D<sup>1</sup> (tangential), 90 diams.; D<sup>2</sup>, cell showing -areolation, 250 diams.</div> -</div> - -<p><span class="pagenum"><a name="Page_136" id="Page_136">« 136 »</a></span></p> - -<div class="fig_center" style="width: 444px;"> -<a name="fig61" id="fig61"></a> -<img src="images/fig61.png" width="444" height="449" alt="" /> -<div class="fig_caption">Fig. 61.—<i>_Trigonocarpum Hookeri</i>, Dawson -from the coal-measures of Cape -Breton. Probably the fruit of a Taxine -tree. A, Broken specimen magnified -twice natural size, B, Section magnified: <i>a</i>, the testa; <i>b</i>, the tegmen; -<i>c</i>, the nucleus; <i>d</i>, the embryo, <i>c</i>, Portion of the surface of the -inner coat more highly magnified.</div> -</div> - -<p>A remarkable fact in connection with them, and showing -also the manner in which the most durable vegetable -structures may perish by decay, is that, like the Cordaites, -they had large piths with transverse partitions, a structure -<span class="pagenum"><a name="Page_137" id="Page_137">« 137 »</a></span> -which, as I have already mentioned, appears on a -minute scale in the twigs of the fir-tree, and that sometimes -casts of these piths in sandstone appear in a separate -form, constituting what have been named <i>Sternbergiæ</i> or -<i>Artisiæ</i>. As Renault well remarks with reference to -Cordaites, the existence of this chambered form of pith -implies rapid elongation of the stem, so that the Cordaites -and conifers of the coal-formation were probably quickly -growing trees (<a href="#fig62">Fig. 62</a>).</p> - -<div class="fig_center" style="width: 457px;"> -<a name="fig62" id="fig62"></a> -<img src="images/fig62.png" width="457" height="195" alt="" /> -<div class="fig_caption">Fig. 62.—<i>Sternbergia</i> pith of <i>Dadoxylon</i>. A, Specimen (natural size), -showing remains of wood at <i>a</i>, <i>a</i>. B, Junction of wood and pith, magnified. -C, Cells of the wood of do., <i>a</i>, <i>a</i>; <i>b</i>, medullary ray; <i>c</i>, areolation.</div> -</div> - -<p>The same general statements may be made as to the -coal-vegetation as in relation to that of the Erian. In -the coal period we have found none of the higher exogens, -and there are only obscure and uncertain indications -of the presence of endogens, which we may reserve -for a future chapter; but gymnosperms abound and are -highly characteristic. On the other hand, we have no -mosses or lichens, and very few Algæ, but a great number -of ferns and Lycopodiaceæ or club-mosses (<a href="#fig63">Fig. 63</a>). -Thus, the coal-formation period is botanically a meeting-place -of the lower phænogams and the higher cryptogams, -and presents many forms which, when imperfectly known, -have puzzled botanists in regard to their position in one -or other series. In the present world, the flora most akin -<span class="pagenum"><a name="Page_138" id="Page_138">« 138 »</a></span> -to that of the coal period is that of warm, temperate regions -in the southern hemisphere. It is not properly a -tropical flora, nor is it the flora of a cold region, but -rather indicative of a moist and equable climate. Still, -we must bear in mind that we may often be mistaken in -reasoning as to the temperature required by extinct -species of plants, differing from those now in existence. -Further, we must not assume that the climatal conditions -of the northern hemisphere were in the coal period at all -similar to those which now prevail. As Sir Charles Lyell -has shown, a less amount of land in the higher latitudes -would greatly modify climates, and there is every reason -to believe that in the coal period there was less land than -now. Further, it has been shown by Tyndall that a very -small additional amount of carbonic acid in the atmosphere -would, by obstructing the radiation of heat from -the earth, produce almost the effect of a glass roof or conservatory, -extending over the whole world. Again, there -is much in the structure of the leaves of the coal-plants, -as well as in the vast amount of carbon which they accumulated -in the form of coal, and the characteristics of -the animal life of the period, to indicate, on independent -<span class="pagenum"><a name="Page_139" id="Page_139">« 139 »</a></span> -grounds, that the carboniferous atmosphere differed from -that of the present world in this way, or in the presence -of more carbonic acid—a substance now existing in the -very minute proportion of one thousandth of the whole—a -quantity adapted to the present requirements of vegetable -and animal life, but probably not to those of the -coal period.</p> - -<div class="fig_center" style="width: 313px;"> -<a name="fig63" id="fig63"></a> -<img src="images/fig63.png" width="313" height="255" alt="" /> -<div class="fig_caption">Fig. 63.—<i>Walchia imbricatula</i>, S. N., Permian, Prince Edward Island.</div> -</div> - -<p>Thus, if we inquire as to any analogous distribution of -plants in the modern world, we find this only in the warmer -insular climates of the southern hemisphere, where -ferns, lycopods, and pines appear under forms somewhat -akin to those of the Carboniferous, but mixed with -other types, some of which are modern, others allied to -those of the next succeeding geological ages of the Mesozoic -and Tertiary; and under these periods it will be -more convenient to make comparisons.</p> - -<p>The readers of recent English popular works on geology -will have observed the statement reiterated that a -large proportion of the material of the great beds of bituminous -coal is composed of the spore-cases of lycopodiaceous -plants—a statement quite contrary to that resulting -from my microscopical examinations of the coal -of more than eighty coal-beds in Nova Scotia and Cape -Breton, as stated in “Acadian Geology” (page 463), and -more fully in my memoir of 1858 on the “Structures in -Coal,”<a name="FNanchor_CG_85" id="FNanchor_CG_85"></a><a href="#Footnote_CG_85" class="fnanchor">[CG]</a> and that of 1866, on the “Conditions of Accumulation -of Coal.”<a name="FNanchor_CH_86" id="FNanchor_CH_86"></a><a href="#Footnote_CH_86" class="fnanchor">[CH]</a> The reason of this mistake is, -that an eminent English naturalist, happening to find in -certain specimens of English coal a great quantity of remains -of spores and spore-cases, though even in his specimens -they constitute only a small portion of the mass, -and being apparently unacquainted with what others had -done in this field, wrote a popular article for the “Contemporary -Review,” in which he extended an isolated and -<span class="pagenum"><a name="Page_140" id="Page_140">« 140 »</a></span> -exceptional fact to all coals, and placed this supposed -origin of coal in a light so brilliant and attractive that he -has been followed by many recent writers. The fact is, -as stated in “Acadian Geology,” that trunks of <i>Sigillariæ</i> -and similar trees constitute a great part of the denser -portion of the coal, and that the cortical tissues of these -rather than the wood remain as coal. But cortical or -epidermal tissues in general, whether those of spore-cases -or other parts of plants, are those which from their resistance -to water-soakage and to decay, and from their -highly carbonaceous character, are best suited to the production -of coal. In point of fact, spore-cases, though -often abundantly present, constitute only an infinitesimal -part of the matter of the great coal-beds. In an article -in “The American Journal of Science,” which appeared -shortly after that above referred to, I endeavoured to correct -this error, though apparently without effect in so far -as the majority of British geological writers are concerned. -From this article I have taken with little change -the following passages, as it is of importance in theoretical -geology that such mistakes, involving as they do the -whole theory of coal accumulation, should not continue -to pass current. The early part of the paper is occupied -with facts as to the occurrence of spores and spore-cases as -partial ingredients in coal. Its conclusions are as follows: -It is not improbable that sporangites, or bodies resembling -them, may be found in most coals; but it -is most likely that their occurrence is accidental rather -than essential to coal accumulation, and that they are -more likely to have been abundant in shales and cannel -coals, deposited in ponds or in shallow waters in the vicinity -of lycopodiaceous forests, than in the swampy -or peaty deposits which constitute the ordinary coals. -It is to be observed, however, that the conspicuous appearance -which these bodies, and also the strips and -fragments of epidermal tissue, which resemble them in -<span class="pagenum"><a name="Page_141" id="Page_141">« 141 »</a></span> -texture, present in slices of coal, may incline an observer, -not having large experience in the examination of coals, -to overrate their importance; and this I think has been -done by most microscopists, especially those who have -confined their attention to slices prepared by the lapidary. -One must also bear in mind the danger arising from mistaking -concretionary accumulations of bituminous matter -for sporangia. In sections of the bituminous shales accompanying -the Devonian coal above mentioned, there -are many rounded yellow spots, which on examination -prove to be the spaces in the epidermis of <i>Psilophyton</i> -through which the vessels passing to the leaves were -emitted. To these considerations I would add the following, -condensed from the paper above referred to -(<a href="#Page_139">p. 139</a>), in which the whole question of the origin of -coal is fully discussed:<a name="FNanchor_CI_87" id="FNanchor_CI_87"></a><a href="#Footnote_CI_87" class="fnanchor">[CI]</a></p> - -<div class="footnote"> - -<p><a name="Footnote_CG_85" id="Footnote_CG_85"></a><a href="#FNanchor_CG_85"><span class="label">[CG]</span></a> “Journal of the Geological Society,” vol. xv.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_CH_86" id="Footnote_CH_86"></a><a href="#FNanchor_CH_86"><span class="label">[CH]</span></a> <i>Ibid.</i>, vol. xxii.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_CI_87" id="Footnote_CI_87"></a><a href="#FNanchor_CI_87"><span class="label">[CI]</span></a> See also “Acadian Geology,” 2d ed., pp. 138, 461, 493.</p></div> - -<p>1. The mineral charcoal or ‘mother coal’ is obviously -woody tissue and fibres of bark, the structure of the varieties -of which, and the plants to which it probably belongs, -I have discussed in the paper above mentioned.</p> - -<p>2. The coarser layers of coal show under the microscope -a confused mass of fragments of vegetable matter -belonging to various descriptions of plants, and including, -but not usually in large quantities, sporangites.</p> - -<p>3. The more brilliant layers of the coal are seen, -when separated by thin laminæ of clay, to have on their -surfaces the markings of <i>Sigillariæ</i> and other trees, of -which they evidently represent flattened specimens, or -rather the bark of such specimens. Under the microscope, -when their structures are preserved, these layers -show cortical tissues more abundantly than any others.</p> - -<p>4. Some thin layers of coal consist mainly of flattened -layers of leaves of <i>Cordaites</i> or <i>Pychnophyllum</i>.</p> - -<p>5. The <i>Stigmaria</i> under-clays and the stumps of -<span class="pagenum"><a name="Page_142" id="Page_142">« 142 »</a></span> -<i>Sigillaria</i> in the coal-roofs equally testify to the accumulation -of coal by the growth of successive forests, more -especially of <i>Sigillariæ</i>. There is, on the other hand, no -necessary connection of sporangite-beds with Stigmarian -soils. Such beds are more likely to be accumulated in -water, and consequently to constitute bituminous shales -and cannels.</p> - -<p>6. <i>Lepidodendron</i> and its allies, to which the spore-cases -in question appear to belong, are evidently much -less important to coal accumulation than <i>Sigillaria</i>, which -cannot be affirmed to have produced spore-cases similar -to those in question, even though the observation of -Goldenberg as to their fruit can be relied on; the accuracy -of which, however, I am inclined to doubt.</p> - -<p>On the whole, then, while giving due credit to those -who have advocated the spore-theory of coal, for directing -attention to this curious and no doubt important constituent -of mineral fuel, and admitting that I may possibly -have given too little attention to it, I must maintain that -sporangite-beds are exceptional among coals, and that -cortical and woody matters are the most abundant ingredients -in all the ordinary kinds; and to this I cannot -think that the coals of England constitute an exception.</p> - -<p>It is to be observed, in conclusion, that the spore-cases -of plants, in their indestructibility and richly carbonaceous -character, only partake of qualities common to -most suberous and epidermal matters, as I have explained -in the publications already referred to. Such epidermal -and cortical substances are extremely rich in carbon and -hydrogen, in this resembling bituminous coal. They are -also very little liable to decay, and they resist more than -other vegetable matters aqueous infiltration—properties -which have caused them to remain unchanged, and to -continue free from mineral additions more than other -vegetable tissues. These qualities are well seen in the -bark of our American white birch. It is no wonder that -<span class="pagenum"><a name="Page_143" id="Page_143">« 143 »</a></span> -materials of this kind should constitute considerable -portions of such vegetable accumulations as the beds of -coal, and that when present in large proportion they -should afford richly bituminous beds. All this agrees -with the fact, apparent on examination of the common -coal, that the greater number of its purest layers consist -of the flattened bark of <i>Sigillariæ</i> and similar trees, just -as any single flattened trunk embedded in shale becomes -a layer of pure coal. It also agrees with the fact that -other layers of coal, and also the cannels and earthy -bitumens, appear under the microscope to consist of -finely comminuted particles, principally of epidermal tissues, -not only from the fruits and spore-cases of plants, -but also from their leaves and stems. These considerations -impress us, just as much as the abundance of spore-cases, -with the immense amount of the vegetable matter -which has perished during the accumulation of coal, in -comparison with that which has been preserved.</p> - -<p>I am indebted to Dr. T. Sterry Hunt for the following -very valuable information, which at once places -in a clear and precise light the chemical relations of -epidermal tissue and spores with coal. Dr. Hunt says: -"The outer bark of the cork-tree, and the cuticle of -many if not all other plants, consists of a highly carbonaceous -matter, to which the name of <i>suberin</i> has been -given. The spores of <i>Lycopodium</i> also approach to this -substance in composition, as will be seen by the following, -one of two analyses by Duconi,<a name="FNanchor_CJ_88" id="FNanchor_CJ_88"></a><a href="#Footnote_CJ_88" class="fnanchor">[CJ]</a> along with which -I give the theoretical composition of pure cellulose or -woody fibre, according to Payen and Mitscherlich, and -an analysis of the suberin of cork, from <i>Quercus suber</i>, -from which the ash and 2·5 per cent of cellulose have -been deducted.<a name="FNanchor_CK_89" id="FNanchor_CK_89"></a><a href="#Footnote_CK_89" class="fnanchor">[CK]</a></p> - -<div class="footnote"> - -<p><a name="Footnote_CJ_88" id="Footnote_CJ_88"></a><a href="#FNanchor_CJ_88"><span class="label">[CJ]</span></a> Liebig and Kopp, “Jahresbuch,” 1847-'48.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_CK_89" id="Footnote_CK_89"></a><a href="#FNanchor_CK_89"><span class="label">[CK]</span></a> Gmelin, “Handbook,” xv., 145.</p> - -<p><span class="pagenum"><a name="Page_144" id="Page_144">« 144 »</a></span></p></div> - -<table summary="stuff"> -<tr> - <td class="bdb"></td> - <td class="bdb bdl center">Cellulose.</td> - <td class="bdb bdl center">Cork.</td> - <td class="bdb bdl center">Lycopodium.</td> -</tr> -<tr> - <td class="tdl">Carbon</td> - <td class="bdl tdr2">44·44</td> - <td class="bdl tdr2">65·73</td> - <td class="bdl tdr2">64·80</td> -</tr> -<tr> - <td class="tdl">Hydrogen</td> - <td class="bdl tdr2">6·17</td> - <td class="bdl tdr2">8·33</td> - <td class="bdl tdr2">8·73</td> -</tr> -<tr> - <td class="tdl">Nitrogen</td> - <td class="bdl tdr2">....</td> - <td class="bdl tdr2">1·50</td> - <td class="bdl tdr2">6·18</td> -</tr> -<tr> - <td class="tdl">Oxygen</td> - <td class="bdl tdr2">49·39</td> - <td class="bdl tdr2">24·44</td> - <td class="bdl tdr2">20·29</td> -</tr> -<tr> - <td class="bdb tdl">Total</td> - <td class="bdt bdb bdl tdr2">100·00</td> - <td class="bdt bdb bdl tdr2">100·00</td> - <td class="bdt bdb bdl tdr2">100·00</td> -</tr> -</table> - - -<p>"This difference is not less striking when we reduce -the above centesimal analyses to correspond with the -formula of cellulose, C<sub>24</sub>H<sub>20</sub>O<sub>20</sub>, and represent cork and -<i>Lycopodium</i> as containing twenty-four equivalents of -carbon. For comparison I give the composition of specimens -of peat, brown coal, lignite, and bituminous coal:<a name="FNanchor_CL_90" id="FNanchor_CL_90"></a><a href="#Footnote_CL_90" class="fnanchor">[CL]</a></p> - -<div class="footnote"> - -<p><a name="Footnote_CL_90" id="Footnote_CL_90"></a><a href="#FNanchor_CL_90"><span class="label">[CL]</span></a> “Canadian Naturalist,” vi., 253.</p></div> - -<table summary="formulae"> -<tr> - <td class="vtop tdl larger">Cellulose</td> - <td class="larger">C<sub>24</sub>H<sub>20</sub>O<sub>20</sub></td> -</tr> -<tr> - <td class="vtop tdl larger">Cork</td> - <td class="larger">C<sub>24</sub>H<sub>18<sup>2</sup>/<sub>10</sub></sub>O<sub>6<sup>7</sup>/<sub>10</sub></sub></td> -</tr> -<tr> - <td class="vtop tdl larger">Lycopodium</td> - <td class="larger">C<sub>24</sub>H<sub>19<sup>4</sup>/<sub>10</sub></sub>NO<sub>5<sup>6</sup>/<sub>10</sub></sub></td> -</tr> -<tr> - <td class="vtop tdl larger">Peat (Vaux)</td> - <td class="larger">C<sub>24</sub>H<sub>14<sup>4</sup>/<sub>10</sub></sub>O<sub>10</sub></td> -</tr> -<tr> - <td class="vtop tdl larger">Brown coal (Schröther)</td> - <td class="larger">C<sub>24</sub>H<sub>14<sup>3</sup>/<sub>10</sub></sub>O<sub>10<sup>6</sup>/<sub>10</sub></sub></td> -</tr> -<tr> - <td class="vtop tdl larger">Lignite (Vaux)</td> - <td class="larger">C<sub>24</sub>H<sub>11<sup>3</sup>/<sub>10</sub></sub>O<sub>6<sup>4</sup>/<sub>10</sub></sub></td> -</tr> -<tr> - <td class="vtop tdl larger">Bituminous coal (Regnault)</td> - <td class="larger">C<sub>24</sub>H<sub>10</sub>O<sub>3<sup>3</sup>/<sub>10</sub></sub></td> -</tr> -</table> - -<p>“It will be seen from this comparison that, in ultimate -composition, cork and <i>Lycopodium</i> are nearer to -lignite than to woody fibre, and may be converted into -coal with far less loss of carbon and hydrogen than the -latter. They in fact approach closer in composition to -resins and fats than to wood, and, moreover, like those -substances repel water, with which they are not easily -moistened, and thus are able to resist those atmospheric -influences which effect the decay of woody tissue.”</p> - -<p>I would add to this only one further consideration. -The nitrogen present in the <i>Lycopodium</i> spores, no doubt, -belongs to the protoplasm contained in them, a substance -which would soon perish by decay; and subtracting this, -the cell-walls of the spores and the walls of the spore-cases -<span class="pagenum"><a name="Page_145" id="Page_145">« 145 »</a></span> -would be most suitable material for the production -of bituminous coal. But this suitableness they share with -the epidermal tissue of the scales of strobiles, and of the -stems and leaves of ferns and lycopods, and, above all, -with the thick, corky envelope of the stems of <i>Sigillariæ</i> -and similar trees, which, as I have elsewhere shown,<a name="FNanchor_CM_91" id="FNanchor_CM_91"></a><a href="#Footnote_CM_91" class="fnanchor">[CM]</a> -from its condition in the prostrate and erect trunks contained -in the beds associated with coal, must have been -highly carbonaceous and extremely enduring and impermeable -to water. In short, if, instead of “spore-cases,” -we read “epidermal tissues in general, including spore-cases,” -all that has been affirmed regarding the latter will -be strictly and literally true, and in accordance with the -chemical composition, microscopical characters, and mode -of occurrence of coal. It will also be in accordance with -the following statement, from my paper on the “Structures -in Coal,” published in 1859:</p> - -<div class="footnote"> - -<p><a name="Footnote_CM_91" id="Footnote_CM_91"></a><a href="#FNanchor_CM_91"><span class="label">[CM]</span></a> “Vegetable Structures in Coal,” “Journal of Geological Society,” -xv., 626. “Conditions of Accumulation of Coal,” <i>ibid.</i>, xxii., 95. “Acadian -Geology,” 197, 464.</p></div> - -<p>“A single trunk of <i>Sigillaria</i> in an erect forest presents -an epitome of a coal-seam. Its roots represent the -<i>Stigmaria</i> under-clay; its bark the compact coal; its -woody axis the mineral charcoal; its fallen leaves (and -fruits), with remains of herbaceous plants growing in its -shade, mixed with a little earthy matter, the layers of -coarse coal. The condition of the durable outer bark of -erect trees concurs with the chemical theory of coal, in -showing the especial suitableness of this kind of tissue for -the production of the purer compact coals. It is also -probable that the comparative impermeability of the bark -to mineral infiltration is of importance in this respect, -enabling this material to remain unaffected by causes -which have filled those layers, consisting of herbaceous -materials and decayed wood, with pyrites and other mineral -substances.”</p> - -<p><span class="pagenum"><a name="Page_146" id="Page_146">« 146 »</a></span></p> - -<p>We need not go far in search of the uses of the coal -vegetation, when .we consider the fact that the greatest -civilised nations are dependent on it for their fuel. Without -the coal of the Carboniferous period and the iron-ore -which is one of the secondary consequences of coal accumulation, -just as bog-ores of iron occur in the subsoils -of modern peats, it would have been impossible either to -sustain great nations in comfort in the colder climates of -the northern hemisphere or to carry on our arts and -manufactures. The coal-formation yields to Great Britain -alone about one hundred and sixty million tons of -coal annually, and the miners of the United States extract -mainly from the same formation nearly a hundred -million tons, while the British colonies and dependencies -produce about five million tons; and it is a remarkable -fact that it is to the English race that the -greatest supply of this buried power and heat and light -has been given.</p> - -<p>The great forests of the coal period, while purifying -the atmosphere of its excess of unwholesome carbonic -acid, were storing up the light and heat of Palæozoic -summers in a form in which they could be recovered in our -human age, so that, independently of their uses to the -animals which were their contemporaries, they are indispensable -to the existence of civilised man.</p> - -<p>Nor can we hope soon to be able to dispense with the -services of this accumulated store of fuel. The forests -of to-day are altogether insufficient for the supply of our -wants, and though we are beginning to apply water-power -to the production of electricity, and though some promising -plans have been devised for the utilisation of the -direct heat and light of the sun, we are still quite as dependent -as any of our predecessors on what has been done -for us in the Palæozoic age.</p> - -<p>In the previous pages I have said little respecting the -physical geography of the Carboniferous age; but, as may -<span class="pagenum"><a name="Page_147" id="Page_147">« 147 »</a></span> -be inferred from the vegetation, this in the northern -hemisphere presented a greater expanse of swampy flats -little elevated above the sea than we find in any other period. -As to the southern hemisphere, less is known, but -the conditions of vegetation would seem to have been essentially -the same.</p> - -<p>Taking the southern hemisphere as a whole, I have -not seen any evidence of a Lower Devonian or Upper Silurian -flora; but in South Africa and Australia there are -remains of Upper Devonian or Lower Carboniferous -plants. These were succeeded by a remarkable Upper -Carboniferous or Permian group, which spread itself all -over India, Australia, and South Africa,<a name="FNanchor_CN_92" id="FNanchor_CN_92"></a><a href="#Footnote_CN_92" class="fnanchor">[CN]</a> and contains -some forms (<i>Vertebraria</i>, <i>Phyllotheca</i>, <i>Glossopteris</i>, &c. ) -not found in rocks of similar age in the northern hemisphere, -so that, if the age of these beds has been correctly -determined, the southern hemisphere was in advance in -relation to some genera of plants. This, however, is to -be expected when we consider that the Triassic and Jurassic -flora of the north contains or consists of intruders -from more southern sites. These beds are succeeded in -India by others holding cycads, &c., of Upper Jurassic -or Lower Cretaceous types (Rajmahal and Jabalpur -groups).</p> - -<div class="footnote"> - -<p><a name="Footnote_CN_92" id="Footnote_CN_92"></a><a href="#FNanchor_CN_92"><span class="label">[CN]</span></a> Wyley, “Journal Geol. Society,” vol. xxiii., p. 172; Daintree, <i>ibid.</i>, -vol. xxviii.; also Clarke and McCoy.</p></div> - -<p>Blanford has shown that there is a very great similarity -in this series all over the Australian and Indian region.<a name="FNanchor_CO_93" id="FNanchor_CO_93"></a><a href="#Footnote_CO_93" class="fnanchor">[CO]</a> -Hartt and Darby have in like manner distinguished -Devonian and Carboniferous forms in Brazil akin -to those of the northern hemisphere. Thus the southern -hemisphere would seem to have kept pace with the northern, -and according to Blanford there is evidence there of -cold conditions in the Permian, separating the Palæozoic -<span class="pagenum"><a name="Page_148" id="Page_148">« 148 »</a></span> -flora from that of the Mesozoic, in the same manner that -Ramsay has supposed a similar period of cold to have done -north of the equator. This would imply a very great -change of climate, since we have evidence of the extension -of the Lower Carboniferous flora at least as far -north as Spitzbergen. The upper coal-formation we -cannot, however, trace nearly so far north; so that a -gradual refrigeration may have been going on before -the Permian. Thus in both hemispheres there was a -general similarity in the later Palæozoic flora, and perhaps -similar conditions leading to its extinction and to -its replacement by that to be described in the next -chapter.</p> - -<div class="footnote"> - -<p><a name="Footnote_CO_93" id="Footnote_CO_93"></a><a href="#FNanchor_CO_93"><span class="label">[CO]</span></a> “Journal Geol. Society,” vol. xxxi.</p></div> - - -<hr class="tb" /> - - -<p class="caption3">NOTES TO CHAPTER IV.</p> - -<p class="caption4"><span class="smcap">I. Characters and Classification of Palæozoic Plants.</span></p> - -<p><span class="smcap">In</span> the space available in this work it would be impossible to -enter fully into the classification of Palæozoic plants; but it may be -well to notice some important points for the guidance of those who -may desire to collect specimens; more especially as much uncertainty -exists as to affinities and very contradictory statements are -made. The statements below may be regarded as the results of -actual observation and of the study of specimens <i>in situ</i> in the rocks, -as well as in the cabinet and under the microscope.</p> - -<p class="caption4"><span class="smcap">Gymnospermeæ</span>.</p> - -<p class="caption4"><i>Family</i> <span class="smcap">Coniferæ</span>; <i>Genus</i> <span class="smcap">Dadoxylon</span>, Endlicher; <span class="smcap">Araucarites</span>, -Goeppert; <span class="smcap">Araucarioxylon</span>, Kraus.</p> - -<p>The trunks of this genus occur from the Middle Devonian to the -Permian inclusive, as drift-logs calcified, silicified, or pyritised. The -only foliage associated with them is of the type of <i>Walchia</i> and -<i>Araucarites</i>—viz., slender branches with numerous small spiral acicular -leaves. Two of the coal-formation species, <i>D. materiarum</i> and -another, had foliage of this type. That of the others is unknown. -They are all distinct from the wood of <i>Cordaites</i>, for which see under -that genus.</p> - -<p><span class="pagenum"><a name="Page_149" id="Page_149">« 149 »</a></span></p> - -<p>The following are North American species:</p> - -<table summary="Species"> -<tr> - <td class="caption3" colspan="4"><i>Trunks.</i></td> -</tr> -<tr> - <td class="tdl"><i>Dadoxylon Ouangondianum</i>, Dn.</td> - <td class="tdl">M. Erian</td> - <td class="tdl" colspan="2">Report, 1871.<a name="FNanchor_CP_94" id="FNanchor_CP_94"></a><a href="#Footnote_CP_94" class="fnanchor">[CP]</a></td> -</tr> -<tr> - <td class="tdl"><i>D. Halli</i>, Dn.</td> - <td class="tdl"> ”</td> - <td class="center" colspan="2">”</td> -</tr> -<tr> - <td class="tdl"><i>D. Newberryi</i>, Dn.</td> - <td class="tdl"> ”</td> - <td class="center" colspan="2">”</td> -</tr> -<tr> - <td class="tdl"><i>D. Clarkii</i>, Dn. (Cordæoxylon ?) </td> - <td class="tdl"> ”</td> - <td class="tdl" colspan="2">Report, 1882.</td> -</tr> -<tr> - <td class="tdl"><i>D. Acadianum</i>, Dn.</td> - <td class="tdl">Coal-formation and<br /> millstone grit.</td> - <td class="tdl" colspan="2">Acadian Geology.</td> -</tr> -<tr> - <td class="tdl"><i>D. Materiarum</i>, Dn.</td> - <td class="tdl">Do. and Permo-Carb.</td> - <td class="center" colspan="2">”</td> -</tr> -<tr> - <td class="tdl"><i>D.</i> (<i>Palæoxylon</i>) <i>antiquius</i>, Dn.</td> - <td class="tdl">L. Carboniferous.</td> - <td class="center" colspan="2">”</td> -</tr> -<tr> - <td class="tdl"><i>D. annulatum</i>, Dn.</td> - <td class="tdl">Coal-formation.</td> - <td class="center" colspan="2">”</td> -</tr> -<tr> - <td class="tdl"><i>Ormoxylon Erianum</i>, Dn.</td> - <td class="tdl">Erian.</td> - <td class="tdl" colspan="2">Report, 1871.</td> -</tr> -<tr> - <td class="caption3" colspan="3"><i>Foliage.</i></td> -</tr> -<tr> - <td class="tdl"><i>Araucarites gracilis</i>, Dn.</td> - <td class="tdl">N. Coal-formation and Permian.</td> - <td class="center" colspan="2">”</td> -</tr> -<tr> - <td class="tdl"><i>Walchia robusta</i>, Dn.</td> - <td class="tdl">Permian.</td> - <td class="tdl" rowspan="2"><img src="images/bracel_60.png" width="11" height="60" alt="{" /></td> - <td class="tdl" rowspan="2">Report on<br />Prince Edward<br />Island.</td> -</tr> -<tr> - <td class="tdl"><i>W. imbricatula</i>, Dn.</td> - <td class="tdl" colspan="2"> ”</td> -</tr> -</table> - -<div class="footnote"> - -<p><a name="Footnote_CP_94" id="Footnote_CP_94"></a><a href="#FNanchor_CP_94"><span class="label">[CP]</span></a> “Geological Survey of Canada: Fossil Plants of Erian and Upper -Silurian Formations,” by J. W. Dawson.</p></div> - -<p>All of the above can be vouched for as good species based upon -microscopic examination of a very large number of trunks from different -parts of North America. The three Erian species of <i>Dadoxylon</i> -and <i>D. antiquius</i> from the Lower Carboniferous have two or more -rows of cells in the medullary rays. The last named has several -rows, and is a true <i>Palæoxylon</i> allied to <i>D. Withami</i> of Great -Britain. <i>D. materiarium</i> is specially characteristic of the upper -coal-formation and Permian, and to it must belong one or both of -the species of foliage indicated above. <i>D. Clarkii</i> has very short, -simple medullary rays of only a few cells superimposed, and has an -inner cylinder of scalariform vessels, approaching in these points to -<i>Cordaites</i>. <i>Ormoxylon</i> has a very peculiar articulated pith and -simple medullary rays.</p> - -<p>Witham in 1833 described several Carboniferous species of pine-wood, -under the generic name Pinites, separating under the name -<i>Pitus</i> species which appeared to have the discs on the cell-walls -<span class="pagenum"><a name="Page_150" id="Page_150">« 150 »</a></span> -separate and in transverse lines. Witham’s name was changed by -Goeppert to <i>Araucarites</i>, to indicate the similarity of these woods to -Araucaria, <i>Pinites</i> being reserved for trees more closely allied to the -ordinary pines. Endlicher, restricting Araucarites to foliage, etc., -of Araucaria-like trees, gave the name <i>Dadoxylon</i> to the wood; and -this, through Unger’s “Genera and Species,” has gained somewhat -general acceptance. Endlicher also gave the name <i>Pissadendron</i> to -the species which Witham had called <i>Pitus</i>; but Brongniart proposed -the name <i>Palæoxylon</i> to include all the species with thick -and complex medullary rays, whatever the arrangement of the discs. -In Schimper’s new work Kraus substitutes <i>Araucarioxylon</i> for Endlicher’s -<i>Dadoxylon</i>, and includes under <i>Pissadendron</i> all the species -placed by Brongniart in <i>Palæoxylon</i>.</p> - -<p>To understand all this confusion, it may be observed that the -characters available in the determination of Palæozoic coniferous -wood are chiefly the form and arrangement of the wood-cells, the -character of the bordered pores or discs of their walls, and the form -and composition of the medullary rays.</p> - -<p>The character on which Witham separated his genus <i>Pitus</i> from -<i>Pinites</i> is, as I have ascertained by examination of slices of one of -his original specimens kindly presented to me by Mr. Sanderson, of -Edinburgh, dependent on state of preservation, the imperfectly preserved -discs or areolations of the walls of the fibre presenting the -appearance of separate and distinct circles, while in other parts of -the same specimens these discs are seen to be contiguous and to assume -hexagonal forms, so that in this respect they do not really -differ from the ordinary species of <i>Dadoxylon</i>. The true character -for subdividing those species which are especially characteristic of -the Carboniferous, is the composite structure of the medullary rays, -which are thick and composed of several radial piles of cells placed -side by side. This was the character employed by Brongniart in -separating the genus <i>Palæoxylon</i>, though he might with convenience -have retained Witham’s name, merely transferring to the genus the -species of Witham’s <i>Pinites</i> which have complex medullary rays. -The Erian rocks present the greatest variety of types, and <i>Palæoxylon</i> -is especially characteristic of the Lower Carboniferous, while species -of <i>Dadoxylon</i> with two rows of bordered pores and simple medullary -rays are especially plentiful in the upper coal-formation and Permo-Carboniferous.</p> - -<p>The following table will clearly show the distinctive characters -and relations of the genera in question, as held by the several authors -above referred to:</p> - -<p><span class="pagenum"><a name="Page_151" id="Page_151">« 151 »</a></span></p> - -<p class="caption3"><i>Wood of Palæozoic Conifers.</i></p> - -<table summary="wood"> -<tr> - <td class="bdt center">Woody fibres.</td> - <td class="bdt bdl center">Medullary rays and pith.</td> - <td class="bdt bdl center">Generic names.</td> - <td class="bdt bdl center">Geological age.</td> -</tr> -<tr> - <td class="tdl bdt">No discs.</td> - <td class="tdl bdt bdl">One or two series of cells.</td> - <td class="tdl bdt bdl"><i>Aporoxylon</i>, Unger.</td> - <td class="tdl bdt bdl">Devonian (Erian).</td> -</tr> -<tr> - <td class="tdl bdt bdb" rowspan="4">Discs in one series<br /> contiguous, or<br /> in several series<br /> spirally arranged.</td> - <td class="tdl bdt bdl">Complex, or of two<br /> or more series<br /> of cells.<br />Pith Sternbergian.</td> - <td class="tdl bdt bdl"> - <table summary="w2"> - <tr> - <td class="tdl"><img src="images/bracel_60.png" width="11" height="60" alt="{" /></td> - <td><i>Pitus</i>, Witham.<br /><i>Palæoxylon</i>, Brongniart.<br /><i>Pissadendron</i>, Endlicher.</td> - </tr> - </table> - </td> - <td class="tdl bdt bdl">Middle and Lower<br /> Carboniferous and<br /> Devonian.</td> -</tr> -<tr> - <td class="tdl bdt bdl">Simple, or of one row of cells.<br />Pith Sternbergian.</td> - <td class="tdl bdt bdl"> - <table summary="w2"> - <tr> - <td class="tdl"><img src="images/bracel_60.png" width="11" height="60" alt="{" /></td> - <td><i>Araucarites</i>, Goeppert.<br /><i>Dadoxylon</i>, Endlicher.<br /><i>Araucarioxylon</i>, Schimper.</td> - </tr> - </table> - </td> - <td class="tdl bdt bdl">Upper Carboniferous<br /> and Permian.</td> -</tr> -<tr> - <td class="tdl bdt bdl">Pith in spherical chambers.</td> - <td class="tdl bdt bdl"><i>Ormoxylon</i>,<a name="FNanchor_CQ_95" id="FNanchor_CQ_95"></a><a href="#Footnote_CQ_95" class="fnanchor">[CQ]</a> Dn.</td> - <td class="tdl bdt bdl">Devonian.</td> -</tr> -<tr> - <td class="tdl bdt bdb bdl">Medullary sheath scalariform.<br />Medullary rays frequent,<br /> simple, short.</td> - <td class="tdl bdt bdb bdl"><i>Dadoxylon</i> (Cordæoxylon),<a name="FNanchor_CR_96" id="FNanchor_CR_96"></a><a href="#Footnote_CR_96" class="fnanchor">[CR]</a> Dn.</td> - <td class="tdl bdt bdb bdl">Devonian.</td> -</tr> -</table> - -<div class="footnote"> - -<p><a name="Footnote_CQ_95" id="Footnote_CQ_95"></a><a href="#FNanchor_CQ_95"><span class="label">[CQ]</span></a> Type <i>O. Erianum</i>, Dn., “Report on Canadian Plants,” 1871.</p> - -<p><a name="Footnote_CR_96" id="Footnote_CR_96"></a><a href="#FNanchor_CR_96"><span class="label">[CR]</span></a> Type <i>D. Clarkii</i>, Dn., “Report on Canadian Plants,” 1882. This may be -wood of Cordaites, to which it approaches very closely.</p> -</div> - - -<p class="caption4"><i>Family</i> <span class="smcap">Cordaites</span>, <i>Genus</i> <span class="smcap">Cordaites</span>, Brongniart.</p> - -<p>Trunks marked by transverse scars of attachment of bases of -leaves; leaves broad, with many parallel veins, and attached by a -broad base; pistillate and staminate catkins of the nature of Antholithes. -Fruit winged or pulpy, of the kind known as <i>Cardiocarpum</i>. -Stem with a Sternbergia pith, usually large, surrounded by -a ring of pseudo-scalariform vessels, and with a cylinder usually -narrow, of woody wedges, with bordered pores in one or more series, -and with simple medullary rays.</p> - -<p>From specimens kindly presented to me by Prof. Renault, I -have been able to ascertain that the stems of some at least of these -plants (Eucordaites) are distinct in structure from all the species of -<i>Dadoxylon</i>, above mentioned, except <i>D. Clarkii</i>, of the Erian. They -may be regarded as intermediate between those of conifers and -cycads, which is indeed the probable position of these remarkable -plants.</p> - -<p>Grand d’Eury has divided the <i>Cordaites</i> into sub-genera, as follows:</p> - -<p>1. <i>Eucordaites.</i>—Leaves spatulate, obovate, elliptical, or lanceolate, -<span class="pagenum"><a name="Page_152" id="Page_152">« 152 »</a></span> -sessile, entire, with rounded apices and of leathery consistency. -The leaves are from twenty to ninety centimetres in -length. The nerves are either equally or unequally strong.</p> - -<p>2. <i>Dorycordaites.</i>—Leaves lanceolate, with sharp points; nerves -numerous, fine, and equal in strength. The leaves attain a length -of from forty to fifty centimetres.</p> - -<p>3. <i>Poacordaites.</i>—Leaves narrow, linear, entire, blunt at the -point, with nerves nearly equally strong. The leaves are as much -as forty centimetres in length.</p> - -<p>To these Renault and Zeiller have added a fourth group, <i>Scutocordaites</i>.</p> - -<p class="caption4"><i>Genus</i> <span class="smcap">Sternbergia</span>.</p> - -<p>This is merely a provisional genus intended to receive casts of -the pith cylinders of various fossil trees. Their special peculiarity -is that, as in the modern <i>Cecropia peltata</i>, and some species of <i>Ficus</i>, -the pith consists of transverse dense partitions which, on the elongation -of the internodes, become separated from each other, so as to -produce a chambered pith cavity, the cast of which shows transverse -furrows. The young twigs of the modern <i>Abies balsamifera</i> present -a similar structure on a minute scale. I have ascertained and -described such pith-cylinders in large stems of <i>Dadoxylon Ouangondianum</i>, -and <i>D. materiarium</i>. They occur also in the stems of -<i>Cordaites</i> and probably of <i>Sigillariæ</i>. I have discussed these curious -fossils at length in “Acadian Geology” and in the “Journal of -the Geological Society of London,” 1860. The following summary -is from the last-mentioned paper:</p> - -<p><i>a.</i> As Prof. Williamson and the writer have shown, many of -the <i>Sternbergia</i> piths belong to coniferous trees of the genus <i>Dadoxylon</i>.</p> - -<p><i>b.</i> A few specimens present multiporous tissue, of the type of -<i>Dictyoxylon</i>, a plant of unknown affinities, and which, according to -Williamson, has a <i>Sternbergia</i> pith.</p> - -<p><i>c.</i> Other examples show a true scalariform tissue, comparable -with that of <i>Lepidodendron</i> or <i>Sigillaria</i>, but of finer texture. Corda -has shown that plants of the type of the former genus (his <i>Lomatophloios</i>) -had <i>Sternbergia</i> piths. Some plants of this group are by -external characters loosely reckoned by botanists as ribless <i>Sigillariæ</i> -(<i>Clathraria</i>); but I believe that they are not related even ordinally -to that genus.</p> - -<p><i>d.</i> Many Carboniferous <i>Sternbergiæ</i> show structures identical -with those described above as occurring in <i>Cordaites</i>, and also in -some of the trees ordinarily reckoned as <i>Sigillariæ</i>.</p> - -<p><span class="pagenum"><a name="Page_153" id="Page_153">« 153 »</a></span></p> - -<p class="caption4"><i>Genus</i> <span class="smcap">Cardiocarpum</span>.</p> - -<p>I have found at least eight species of these fruits in the Erian -and Carboniferous of New Brunswick and Nova Scotia, all of which -are evidently fruits of gymnospermous trees. They agree in having -a dense coaly nucleus of appreciable thickness, even in the -flattened specimens, and surrounded by a thin and veinless wing or -margin. They have thus precisely the appearance of samaras of -many existing forest-trees, some of which they also resemble in the -outline of the margin, except that the wings of samaras are usually -veiny. The character of the nucleus, and the occasional appearance -in it of marks possibly representing cotyledons or embryos, forbids -the supposition that they are spore-cases. They must have been -fruits of phænogams. Whether they were winged fruits or seeds, -or fruits with a pulpy envelope like those of cycads and some -conifers, may be considered less certain. The not infrequent distortion -of the margin is an argument in favour of the latter view, -though this may also be supposed to have occurred in samaras partially -decayed. On the other hand, their being always apparently -flattened in one plane, and the nucleus being seldom, if ever, found -denuded of its margin, are arguments in favour of their having been -winged nutlets or seeds. Until recently I had regarded the latter -view as more probable, and so stated the matter in the second edition -of “Acadian Geology.” I have, however, lately arrived at the -conclusion that the <i>Cardiocarpa</i> of the type of <i>C. cornutum</i> were -gymnospermous seeds, having two cotyledons embedded in an albumen -and covered with a strong membranous or woody tegmen surrounded -by a fleshy outer coat, and that the notch at the apex represents -the foramen or micropyle of the ovule. The structure was -indeed very similar to that of the seeds of <i>Taxus</i> and of <i>Salisburia</i>. -With respect to some of the other species, however, especially those -with very broad margins, it still appears likely that they were winged.</p> - -<p>The <i>Cardiocarpa</i> were borne in racemes or groups, and it seems -certain that some of them at least are the seeds of <i>Cordaites</i>. The -association of some of them and of those of the next genus with -<i>Sigillariæ</i> is so constant that I cannot doubt that some of them -belong to plants of that genus, or possibly to taxine conifers. The -great number of distinct species of these seeds, as compared with -that of known trees which could have produced them, is very remarkable.</p> - -<p class="caption4"><i>Genus</i> <span class="smcap">Trigonocarpum</span>.</p> - -<p>These are large angled nuts contained in a thick envelope, and -showing internal structures resembling those of the seeds of modern -<span class="pagenum"><a name="Page_154" id="Page_154">« 154 »</a></span> -<i>Taxineæ</i>. There are numerous species, as well as allied seeds referred -to the provisional genera <i>Rhabdocarpus</i> and <i>Carpolithes</i>. -In <i>Trigonocarpum Hookeri</i> I have described the internal structure -of one of those seeds, and many fine examples from the coal-field of -St. Etienne, in France, have been described by Brongniart, so that -their internal structure is very well known.</p> - -<p><i>Genus</i> Antholithes.</p> - -<p>This is also a provisional genus, to include spikes of floral -organs, some of which are known to have belonged to <i>Cordaites</i>, -others probably to <i>Sigillariæ</i>.</p> - - -<p class="caption4 smcap"><a name="Sigillariaceae" id="Sigillariaceae"></a>Of Uncertain Affinities.</p> - -<p class="caption4"><i>Family</i> <span class="smcap">Sigillariaceæ</span>.</p> - -<p>Under this name palæobotanists have included a great number -of trees of the Carboniferous system, all of which are characterised -by broad leaf-sears, with three vascular scars, and usually arranged -in vertical rows, and by elongated three-nerved leaves, and roots of -the stigmaria type—that is, with rounded pits, marking the attachment -of rootlets spirally arranged. These trees, however, collected -in the genus Sigillaria by arbitrary characters, which pass into -those of the Lepidodendroid trees, have been involved in almost inextricable -confusion, to disentangle which it will be necessary to consider: -1. The external characters of <i>Sigillariæ</i>, and trees confounded -with them. 2. Subdivision of <i>Sigillariæ</i> by external markings. 3. -The microscopic character of their stems. 4. What is known of -their foliage and fruit.</p> - -<p>1. <i>Characters of Sigillaroid and Lepidodendroid Trunks</i>.</p> - -<p>It may be premised that the modes of determination in fossil -botany are necessarily different from those employed in recent botany. -The palæobotanist must have recourse to characters derived -from the leaves, the scars left by their fall, and the internal structures -of the stem. These parts, held in little esteem by botanists in -describing modern plants, and much neglected by them, must hold -the first place in the regard of the fossil botanist, whereas the fructification, -seldom preserved, and generally obscure, is of comparatively -little service. It is to be remarked also that in such generalised -plants as those of the Palæozoic, remarkable rather for the development -of the vegetative than of the reproductive organs, the -former rise in importance as compared with their value in the study -of modern plants.</p> - -<p><span class="pagenum"><a name="Page_155" id="Page_155">« 155 »</a></span></p> - -<p>In <i>Sigillariæ</i>, <i>Lepidodendra</i>, &c., the following surfaces of the -stem may be presented to our inspection:</p> - -<p>1. The outer surface of the epidermis without its leaves, but -with the leaf-bases and leaf-scars more or less perfectly preserved. -On this surface we may recognise: (1) Cellular swellings or projections -of the bark to which the leaves are attached. These may be -called leaf-bases, and they are sometimes very prominent. (2) The -actual mark of the attachment of the leaf situated in the most -prominent part of the leaf-base. This is the <i>leaf-scar</i>. (3) In the -leaf-scar when well preserved we can see one or more minute punctures -or prominences which are the points where the vascular bundles -passing to the leaf found exit. These are the vascular scars.</p> - -<p>When the leaves are attached, the leaf-scars and vascular scars -cannot be seen, but the leaf-bases can be made out. Hence it is -important, if possible, to secure specimens with and without the -leaves. In flattened specimens the leaf-bases are often distorted by -pressure and marked with furrows which must not be mistaken for -true structural characters. The leaf-bases, which are in relief on the -outer surface of the stem, of course appear as depressions on the -mould in the containing rock, in which the markings often appear -much more distinctly than on the plant itself.</p> - -<p>2. The outer surface of the epidermis may have been removed or -may be destroyed by the coarseness of the containing rock. In this -case the leaf-bases are usually preserved on the surface of the outer -or corky bark, but the leaf-scars and vascular scars have disappeared. -This gives that condition of Lepidodendroid trees to which the name -<i>Knorria</i> has been applied. When plants are in this state careful inspection -may sometimes discover traces of the leaf-scars on portions -of the stem, and thus enable the <i>Knorria</i> to be connected with the -species to which it belongs.</p> - -<p>3. The outer or corky bark may be removed, exposing the surface -of the inner or fibrous and cellular bark, which in the plants in -question is usually of great thickness. In this case neither the leaf-bases -nor the scars are seen, but punctures or little furrows or ridges -appear where the vascular bundles entered the inner bark. Specimens -in this state are usually said to be decorticated, though only -the outer bark is removed. It is often difficult to determine plants -in this condition, unless some portion of the stem can be found still -retaining the bark; but when care is taken in collecting, it will not -infrequently be found that the true outer surface can be recovered -from the containing rock, especially if a coaly layer representing the -outer bark intervenes between this and the inner impression. Specimens -<span class="pagenum"><a name="Page_156" id="Page_156">« 156 »</a></span> -of this kind, taken alone, have been referred to the genera -<i>Knorria</i>, <i>Bothrodendron</i>, and <i>Halonia</i>.</p> - -<p>4. In some cases, though not frequently, the outer surface of the -ligneous cylinder is preserved. It almost invariably presents a -regularly striated or irregularly wrinkled appearance, depending -upon the vertical woody wedges, or the positions of the medullary -rays or vascular bundles. Specimens of this kind constituted some -of the <i>Endogenites</i> of the older botanists, and the genus <i>Schizodendron</i> -of Eichwald appears to include some of them. Many of them -have also been incorrectly referred to Calamites.</p> - -<p>5. In some cases the cast of the medullary cylinder or pith may -alone be preserved. This may be nearly smooch or slightly marked -by vertical striæ, but more usually presents a transverse striation, -and not infrequently the transverse constrictions and septa characteristic -of the genus Sternbergia. Loose <i>Sternbergiæ</i> afford little -means of connecting them with the species to which they belong, -except by the microscopic examination of the shreds of the ligneous -cylinder which often cling to them.<a name="FNanchor_CS_97" id="FNanchor_CS_97"></a><a href="#Footnote_CS_97" class="fnanchor">[CS]</a></p> - -<div class="footnote"> - -<p><a name="Footnote_CS_97" id="Footnote_CS_97"></a><a href="#FNanchor_CS_97"><span class="label">[CS]</span></a> See my paper, “Journal of Geological Society,” vol. xxvii.</p></div> - -<p>These facts being premised, the following general statements -may be made respecting some of the more common Palæozoic genera, -referring, however, principally to the perfect markings as seen on -the epidermis:</p> - -<p><i>Sigillaria.</i>—Leaf-bases hexagonal or elongated, or confluent on -a vertical ridge. Leaf-scars hexagonal or shield-shaped. Vascular -scars three, the two lateral larger than the central. This last character -is constant, depending on the fact that the leaves of Sigillaria -have two or more vascular bundles. All so-called <i>Sigillariæ</i> having -the central vascular scar largest, or only one vascular bundle, should -be rejected from this genus. In young branches of branching <i>Sigillariæ</i> -the leaf-scars sometimes appear to be spiral, but in the older -stems they form vertical rows; interrupted, however, by transverse -rows or bands of <i>fruit-scars</i>, each with a single large central vascular -scar, and which have borne the organs of fructification. <i>Arthrocaulis</i> -of McCoy is founded on this peculiarity.</p> - -<p><i>Syringodendron.</i>—Differs from Sigillaria in the leaf-scars, which -are circular and with a single vascular bundle. It is a matter of -doubt whether these plants were of higher rank than Sigillaria -tending toward the pines, or of lower rank tending toward Cyclostigma. -Their leaf-bases form vertical ridges.</p> - -<p><i>Lepidodendron.</i>—Leaf-bases rhombic, oval, or lanceolate, moderately -<span class="pagenum"><a name="Page_157" id="Page_157">« 157 »</a></span> -prominent. Leaf-scars rhombic or sometimes shield-shaped or -heart-shaped, in the middle or upper part of the leaf-base. Vascular -scars three—the middle one always largest and corresponding to the -single nerve of the leaf; the lateral ones sometimes obsolete.</p> - -<p>In older stems three modes of growth are observed. In some -species the expansion of the bark obliterates the leaf-bases and -causes the leaf-scars to appear separated by wide spaces of more or -less wrinkled bark, which at length becomes longitudinally furrowed -and simulates the ribbed character of Sigillaria. In others the leaf-bases -grow in size as the trunk expands, so that even in large trunks -they are contiguous though much larger than those on the branches. -In others the outer bark, hardening at an early age, is incapable of -either of the above changes, and merely becomes cleft into deep furrows -in the old trunks.</p> - -<p><i>Lepidophloios.</i>—Leaf-bases transverse and prominent—often -very much so. Leaf-scars transversely rhombic or oval with three -vascular scars, the central largest. Leaves very long and one-nerved. -Large strobiles or branchlets borne in two ranks or spirally -on the sides of the stem, and leaving large, round scars (<i>cone-scars</i>), -often with radiating impressions of the basal row of scales.</p> - -<p>Species with long or drooping leaf-bases have been included in -<i>Lepidophloios</i> and <i>Lomatophloios</i>, Species with short leaf-bases and -cone-scars in two rows have been called <i>Ulodendron</i>, and some of -them have been included in Sigillaria (sub-genus <i>Clathraria</i>). Decorticated -stems are Bothrodendron and <i>Halonia</i>. Some of the -species approach near to the last genus, especially to the Lepidodendra -with rhombic leaf-bases like <i>L. tetragonum</i>.</p> - -<p><i>Cyclostigma.</i>—Leaf-bases undeveloped. Leaf-scars circular or -horseshoe-shaped, small, with a central vascular scar. In old trunks -of Cyclostigma the leaf-scars become widely separated, and sometimes -appear in vertical rows. Young branches of Lepidodendron -sometimes have the leaf-scars similar to those of Cyclostigma.</p> - -<p><i>Leptophleum.</i>—Leaf-bases flat, rhombic; leaf-scars obsolete; -vascular scar single, central. The last two genera are characteristically -Devonian.</p> - -<p>In contradistinction from the trees above mentioned, the following -general statements may be made respecting other groups:</p> - -<p>In conifers the leaf-bases are usually elongated vertically, often -scaly in appearance, and with the leaf-scar terminal and round, oval, -or rhombic, and with a single well-marked vascular scar.</p> - -<p>In Calamites, Calamodendron, and Asterophyllites the scars of -the branchlets or leaves are circular or oval, with only a single vascular -<span class="pagenum"><a name="Page_158" id="Page_158">« 158 »</a></span> -scar, and situated in verticils at the top of well-marked nodes -of the stem.</p> - -<p>In tree-ferns the leaf-bases are large and usually without a distinct -articulating surface. The vascular bundles are numerous. -Protopteris has rounded leaf-scars with a large horseshoe-shaped -bundle of vessels above and small bundles below. Caulopteris has -large elliptic or oval leaf-scars with vascular scars disposed concentrically. -Palæopteris,<a name="FNanchor_CT_98" id="FNanchor_CT_98"></a><a href="#Footnote_CT_98" class="fnanchor">[CT]</a> of Geinitz, has the leaf-scars transversely -oval and the vascular bundles confluent in a transverse band with an -appendage or outlying bundle below. Stemmatopteris has leaf-scars -similar to those of Caulopteris, but the vascular bundles united -into a horseshoe-shaped band.</p> - -<div class="footnote"> - -<p><a name="Footnote_CT_98" id="Footnote_CT_98"></a><a href="#FNanchor_CT_98"><span class="label">[CT]</span></a> This name, preoccupied by Geinitz, has been inadvertently misapplied -to the Devonian ferns of the genus <i>Archæopteris</i>.</p></div> - - -<p>2. <i>Subdivision of Sigillariæ in Accordance with their Markings</i>.</p> - -<p>The following groups may be defined in this way; but, being -based on one character only, they are of course in all probability far -from natural:</p> - -<p>1. <i>Sigillaria</i>, Brongniart. Type, <i>Sigillaria reniformis</i>, Brongniart, -or <i>S. Brounii</i>, Dawson.—Stem with broad ribs, usually much -broader than the usually oval or elliptical tripunctate areoles, but -disappearing at base, owing to expansion of the stem. Leaves narrow, -long, three-nerved.</p> - -<p>2. <i>Rhytidolepis</i>, Sternberg. Type, <i>S. scutellata</i>, Brongniart.—Ribs -narrow, and often transversely striate. Areoles large, hexagonal -or shield-shaped, tripunctate. Leaves as in last group. Kings -of rounded scars on the stems and branches mark attachment of -fruit. It is possible that some of the smaller stems of this group -may be branches of trees of group first.</p> - -<p>3. <i>Syringodendron</i>, Sternberg. Type, <i>S. organum</i>, L. and H., -<i>S. oculata</i>, Brongniart.—Stems ribbed; areoles small and round, -and apparently with a single scar, or three closely approximated. -These are rare, and liable to be confounded with decorticated examples -of other groups; but I have some specimens which unquestionably -represent the external surface.</p> - -<p>4. <i>Favularia</i>, Sternberg. Type, <i>Sigillaria elegans</i> of Brongniart.—Leaf-bases -hexagonal, or in young branches elliptical, in vertical -rows, but without distinct ribs, except in old or decorticated stems. -Fruit borne in verticils on the branches bearing transverse rows of -rounded scars. Leaves somewhat broad and longitudinally striate.</p> - -<p><span class="pagenum"><a name="Page_159" id="Page_159">« 159 »</a></span></p> - -<p>5. <i>Leioderma</i>, Goldenberg. Type, <i>S. Sydnensis</i>, Dawson.—Ribs -obsolete. Cortical and ligneous surfaces striate. Vascular -scars double, elongate longitudinally, and alike on cortical and inner -surfaces. Areoles in rows and distinct; stigmaria-roots striate, with -small and distinct areoles.</p> - -<p>6. <i>Clathraria</i>, Brongniart. Type, <i>S. Menardi</i>, Brongniart.—Areoles -hexagonal, not in distinct rows, but having a spiral appearance. -Some of the plants usually referred to this group are probably -branches of <i>Favularia</i>. Others are evidently fragments of plants -of the genus <i>Lepidophloios</i>.</p> - - -<p>3. <i>Internal Structures of Sigillaria-Stems</i>.</p> - -<p>I long ago pointed out, on the evidence of the external markings -and mode of growth, that the stems of <i>Sigillariæ</i> must have been -exogenous, and this conclusion has now been fully confirmed by the -microscopic researches of Williamson, not only in the case of <i>Sigillariæ</i>, -but of <i>Lepidodendra</i> and <i>Calamodendra</i> as well. Confining -myself to my own observations, three types of <i>Sigillariæ</i> are known -to me by their internal structures, though I cannot certainly correlate -all of these with the external markings referred to above.</p> - -<p>1. <i>Diploxylon</i>, in which the stem consists of a small internal -axis surrounded by a very thick inner bark and a dense outer cortex. -A fine example from the South Joggins is thus described:<a name="FNanchor_CU_99" id="FNanchor_CU_99"></a><a href="#Footnote_CU_99" class="fnanchor">[CU]</a></p> - -<div class="footnote"> - -<p><a name="Footnote_CU_99" id="Footnote_CU_99"></a><a href="#FNanchor_CU_99"><span class="label">[CU]</span></a> “Journal of the Geological Society of London,” November, 1877.</p></div> - -<p>"The axis of the stem is about six centimetres in its greatest -diameter, and consists of a central pith-cylinder and two concentric -coats of scalariform tissue. The pith-cylinder is replaced -by sandstone, and is about one centimetre in diameter. The inner -cylinder of scalariform tissue is perfectly continuous, not radiated, -and about one millimetre in thickness. Its vessels are somewhat -crushed, but have been of large diameter. Its outer surface, which -readily separates from that of the outer cylinder, is striated longitudinally. -The outer cylinder, which constitutes by much the -largest part of the whole, is also composed of scalariform tissue; -but this is radially arranged, with the individual cells quadrangular -in cross-section. The cross-bars are similar on all the sides and -usually simple and straight, but sometimes branching or slightly -reticulated. The wall intervening between the bars has extremely -delicate longitudinal waving lines of ligneous lining, in the manner -first described by Williamson as occurring in the scalariform tissue -of certain <i>Lepidodendra</i>. A few small radiating spaces, partially -<span class="pagenum"><a name="Page_160" id="Page_160">« 160 »</a></span> -occupied with pyrites, obscurely represent the medullary rays, which -must have been very feebly developed. The radiating bundles -passing to the leaves run nearly horizontally; but their structure -is very imperfectly preserved. The stem being old and probably -long deprived of its leaves, they may have been partially disorganised -before it was fossilised. The outer surface of the axis is striated -longitudinally, and in some places marked with impressions of tortuous -fibres, apparently those of the inner bark. In the cross-section, -where weathered, it shows concentric rings; but under the -microscope these appear rather as bands of compressed tissue than -as proper lines of growth. They are about twenty in number. This -tree has an erect, ribbed trunk, twelve feet in height and fifteen -inches in diameter, swelling to about two feet at the base."</p> - -<p>2. <i>Favularia Type.</i>—This has been well described by Brongniart -and by Renault,<a name="FNanchor_CV_100" id="FNanchor_CV_100"></a><a href="#Footnote_CV_100" class="fnanchor">[CV]</a> and differs from the above chiefly in the fact that -the outer exogenous woody zone is composed of reticulated instead -of scalariform tissue, and the inner zone is of the peculiar form -which I have characterised as pseudo-scalariform.</p> - -<div class="footnote"> - -<p><a name="Footnote_CV_100" id="Footnote_CV_100"></a><a href="#FNanchor_CV_100"><span class="label">[CV]</span></a> “Botanique Fossile,” Paris, 1881.</p></div> - -<p>3. <i>Sigillaria Proper.</i>—This I have illustrated in my paper in -the “Journal of the Geological Society” for May, 1871, and it appears -to represent the highest and most perfect type of the larger -ribbed <i>Sigillaria</i>. This structure I have described as follows, basing -my description on a very fine axis found in an erect stem, and -on the fragments of the woody axis found in the bases of other erect -stems:</p> - -<p><i>a.</i> A dense cellular outer bark, usually in the state of compact -coal—but when its structure is preserved, showing a tissue of thickened -parenchymatous cells.</p> - -<p><i>b.</i> A very thick inner bark, which has usually in great part -perished, or been converted into coal, but which, in old trunks, contained -a large quantity of prosenchymatous tissue, very tough and -of great durability. This “bast-tissue” is comparable with that of -the inner bark of modern conifers, and constitutes much of the mineral -charcoal of the coal-seams.</p> - -<p><i>c.</i> An outer ligneous cylinder, composed of wood-cells, either -with a single row of large bordered pores,<a name="FNanchor_CW_101" id="FNanchor_CW_101"></a><a href="#Footnote_CW_101" class="fnanchor">[CW]</a> in the manner of pines -<span class="pagenum"><a name="Page_161" id="Page_161">« 161 »</a></span> -and cycads, or with two, three, or four rows of such pores sometimes -inscribed in hexagonal areoles in the manner of Dadoxylon. This -woody cylinder is traversed by medullary rays, which are short, and -composed of few rows of cells superimposed. It is also traversed by -oblique radiating bundles of pseudo-scalariform tissue proceeding to -the leaves. In some <i>Sigillariæ</i> this outer cylinder was itself in part -composed of pseudo-scalariform tissue, as in Brongniart’s specimen -of <i>S. elegans</i>; and in others its place may have been taken by multiporous -tissue, as in a case above referred to; but I have no reason -to believe that either of these variations occurred in the typical -ribbed species now in question. The woody fibres of the outer -cylinder may be distinguished most readily from those of conifers, -as already mentioned, by the thinness of their walls, and the more -irregular distribution of the pores. Additional characters are furnished -by the medullary rays and the radiating bundles of scalariform -tissue when these can be observed.</p> - -<div class="footnote"> - -<p><a name="Footnote_CW_101" id="Footnote_CW_101"></a><a href="#FNanchor_CW_101"><span class="label">[CW]</span></a> These are the same with the wood-cells elsewhere called discigerous -tissue, and to which I have applied the terms uniporous and multiporous. -The markings on the walls are caused by an unlined portion of the cell-wall -placed in a disk or depression, and this often surrounded by an -hexagonal rim of thickened wall; but in all cases these structures are -less pronounced than in <i>Dadoxylon</i>, and less regular in the walls of the -same cell, as well as in different layers of the tissues of the axis.</p></div> - -<p><i>d.</i> An inner cylinder of pseudo-scalariform tissue. I have -adopted the term pseudo-scalariform for this tissue, from the conviction -that it is not homologous with the scalariform ducts of ferns -and other acrogens, but that it is merely a modification of the discigerous -wood-cells, with pores elongated transversely, and sometimes -separated by thickened bars, corresponding to the hexagonal areolation -of the ordinary wood-cells. A similar tissue exists in cycads, -and is a substitute for the spiral vessels existing in ordinary exogens.</p> - -<p><i>e.</i> A large medulla, or pith, consisting of a hollow cylinder of -cellular tissue, from which proceed numerous thin diaphragms towards -the centre of the stem.</p> - -<p>These structures of the highest type of <i>Sigillaria</i> are on the -one hand scarcely advanced beyond those of Calamopitus, as described -by Williamson, and on the other approach to those of -<i>Cordaites</i>, as seen in specimens presented to me by Renault.</p> - -<p>Finally, as to the fruit of <i>Sigillariæ</i>, I have no new facts to -offer. The strobiles or spikes associated with these trees have been -variously described as gymnospermous (Renault) or cryptogamous -(Groldenberg and Williamson). 1 have never seen them in place. -Two considerations, however, have always weighed with me in reference -to this subject. One is the constant abundance of Trigonocarpa -<span class="pagenum"><a name="Page_162" id="Page_162">« 162 »</a></span> -and Cardiocarpa in the soil of the Sigiliaria forests, as I have studied -this at the South Joggins. The other is that the rings of fruit-scars -on the branches of Sigiliaria are homologous with leaf-scars, not -with branches, and therefore should have borne single carpels and -not cones or spikes of inflorescence. These are merely suggestions, -but I have no doubt they will be vindicated by future discoveries, -which will, I have no doubt, show that in the family <i>Sigillariaceæ</i> -we have really two families, one possibly of gymnospermous rank, -or at least approaching to this, the other allied to the Lepidodendra.</p> - - -<p class="caption3 smcap">Cryptogamia.</p> - -<p class="caption4">(<i>Acrogenes.</i>)</p> - -<p class="caption4"><i>Family</i> <span class="smcap">Lepidodendreæ</span>; <i>Genus</i> <span class="smcap">Lepidodendron</span>, Sternberg.</p> - -<p>These are arboreal Lycopods having linear one-nerved leaves, -stems branching dichotomously, and with ovate or rhombic leaf-bases -bearing rhombic leaf-scars, often very prominent. The fruit is in -scaly strobiles, terminal or lateral, and there are usually, if not -always, macrospores and microspores in each strobile. The young -branches and stems have a central pith, a cylinder of scalariform -tubes sending out ascending bundles to the leaves through a thick -cellular and fibrous inner bark, and externally a dense cortex confluent -with or consisting of the leaf-bases. Older stems have a second or -outer layer of scalariform fibres in wedges with medullary rays, and -strengthening the stem by a true exogenous growth, much as in the -Diploxylon type of Sigiliaria. The development of this exogenous -cylinder is different in amount and rate in different species.<a name="FNanchor_CX_102" id="FNanchor_CX_102"></a><a href="#Footnote_CX_102" class="fnanchor">[CX]</a> This -different development of the exogenous axis is accompanied with -appropriate external appearances in the stems, and the changes -which take place in their markings. These are of three kinds. In -some species the areoles, at first close together, become, in the process -of the expansion of the stem, separated by intervening spaces of -bark in a perfectly regular manner; so that in old stems, while widely -separated, they still retain their arrangement, while in young stems -they are quite close to one another. This is the case in <i>L. corrugatum</i>. -In other species the leaf-scars or bases increase in size in the -old stems, still retaining their forms and their contiguity to each -other. This is the case in <i>L. undulatum</i>, and generally in those -<i>Lepidodendra</i> which have large leaf-bases. In these species the -<span class="pagenum"><a name="Page_163" id="Page_163">« 163 »</a></span> -continued vitality of the bark is shown by the occasional production -of lateral strobiles on large branches, in the manner of the modern -red pine of America. In other species the areoles neither increase in -size nor become regularly separated by growth of the intervening -bark; but in old stems the bark splits into deep furrows, between -which may be seen portions of bark still retaining the areoles in -their original dimensions and arrangement. This is the case with -<i>L. Pictoense</i>. This cracking of the bark no doubt occurs in very old -trunks of the first two types, but not at all to the same extent.</p> - -<div class="footnote"> - -<p><a name="Footnote_CX_102" id="Footnote_CX_102"></a><a href="#FNanchor_CX_102"><span class="label">[CX]</span></a> See “Memoirs of Dr. Williamson,” in “Philosophical Transactions,” -for ample details.</p></div> - -<p>As a type of Lepidodendron, I may describe one of the oldest -Carboniferous species characteristic of the Lower Carboniferous in -America, and corresponding to <i>L. Veltheimianum</i> of Europe.</p> - -<p>Lepidodendron Corrugatum, Dawson.—(See <a href="#fig43">Fig. 43</a>, <i>supra</i>.) -“Quarterly Journal of Geological Society,” vol. xv.; “Acadian Geology,” -page 451.</p> - -<p><i>Habit of Growth.</i>—Somewhat slender, with long branches and -long, slender leaves having a tendency to become horizontal or -drooping.</p> - -<p><i>Markings of Stem.</i>—Leaf-bases disposed in quincunx or spirally, -elongate, ovate, acute at both ends, but more acute and slightly -oblique at the lower end; most prominent in the upper third, and -with a slight vertical ridge. Leaf-scars small, rounded, and showing -only a single punctiform vascular scar. The leaf-scar on the outer -surface is in the upper third of the base; but the obliquity of the -vascular bundle causes it to be nearly central on the inside of the -epidermis. In young succulent shoots the leaf-scars are contiguous -and round as in Cyclostigma, without distinct leaf-bases. In this -state it closely resembles <i>L. Olivieri</i>, Eichwald.<a name="FNanchor_CY_103" id="FNanchor_CY_103"></a><a href="#Footnote_CY_103" class="fnanchor">[CY]</a></p> - -<div class="footnote"> - -<p><a name="Footnote_CY_103" id="Footnote_CY_103"></a><a href="#FNanchor_CY_103"><span class="label">[CY]</span></a> Lethæa Rossica, Plate Y, Figs. 12, 13.</p></div> - -<p>In the ordinary young branches the leaf-scars are contiguous, -and closely resemble those of <i>L. elegans</i>, Brongt. (<a href="#fig43">Fig. 43 C</a>). As the -branches increase in diameter the leaf-scars slightly enlarge and -sometimes assume a verticillate appearance (<a href="#fig43">Fig. 43 D</a>). As they -still further enlarge they become separated by gradually increasing -spaces of bark, marked with many waving striæ or wrinkles -(<a href="#fig43">Fig. 43 I, N</a>). At the base of old stems the bark assumes a generally -wrinkled appearance without distinct scars.</p> - -<p><i>Knorria or Decorticated States.</i>—Of these there is a great variety, -depending on the state of preservation, and the particular longitudinal -ridges. <a href="#fig43">Fig. 43 D</a> shows a form in which the vascular bundles -appear as cylindrical truncate projections. Other forms show -<span class="pagenum"><a name="Page_164" id="Page_164">« 164 »</a></span> -the leaf-bases prominent, or have an appearance of longitudinal ribbing -produced by the expansion of the bark.</p> - -<p><i>Structure of Stem.</i>—This is not perfectly preserved in any of -my specimens, but one flattened specimen shows a central medulla -with a narrow ring of scalariform vessels surrounding it, and constituting -the woody axis. The structure is thus similar to that of <i>L. -Harcourtii</i>, which I regard as probably the same with the closely -allied European species L. Veltheimianum.</p> - -<p><i>Leaves.</i>—These are narrow, one-nerved, curving somewhat rapidly -outward (<a href="#fig43">Figs. 43, B, C, D</a>). They vary from one to two inches -in length.</p> - -<p><i>Roots.</i>—I have not seen these actually attached, but they occur -very abundantly in the under-clays of some erect forests of these -plants at Horton Bluff, and are of the character of Stigmariæ (Figs. <a href="#fig30">30</a>, <a href="#fig31">31</a>). -In some of the under-clays the long, flattened rootlets are excessively -abundant, and show the mark of a central vascular bundle.</p> - -<p><i>Fructification.</i>—Cones terminal, short, with many small, acute -imbricate scales. Spore-cases globular, smooth (<a href="#fig43">Fig. 43 C</a>). On -the surface of some shales and sandstones at Horton there are innumerable -round spore-cases of this tree about the size of mustard-seed -(<a href="#fig43">Fig. 43 F</a>). Large slabs are sometimes covered with these, and thin -layers of shale are filled with flattened specimens.</p> - -<p>This is the characteristic species of the Lower Carboniferous coal-measures, -occurring in great profusion at Horton Bluff and its -vicinity, also at Sneid’s Mills near Windsor, Noel and Five-Mile -River, at Norton Creek and elsewhere in New Brunswick (Matthew’s -collection), and at Antigonish (Honeyman’s collection).</p> - -<p>I have received from the lowest Carboniferous beds of Ohio specimens -of this species.<a name="FNanchor_CZ_104" id="FNanchor_CZ_104"></a><a href="#Footnote_CZ_104" class="fnanchor">[CZ]</a> According to Rogers and Lesquereux similar -forms occur in the Vespertine of Pennsylvania and in the Lower -Carboniferous of Illinois. <i>L. Veltheimianum</i> of western Europe -and <i>L. glincanum</i> of Russia are closely allied Lower Carboniferous -species.<a name="FNanchor_DA_105" id="FNanchor_DA_105"></a><a href="#Footnote_DA_105" class="fnanchor">[DA]</a></p> - -<div class="footnote"> - -<p><a name="Footnote_CZ_104" id="Footnote_CZ_104"></a><a href="#FNanchor_CZ_104"><span class="label">[CZ]</span></a> “Journal of Geological Society,” November, 1862, p. 313.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_DA_105" id="Footnote_DA_105"></a><a href="#FNanchor_DA_105"><span class="label">[DA]</span></a> For comparisons of these see “Report on Plants of Lower Carboniferous -of Canada,” p. 21.</p></div> - -<p>A very different type is furnished by a new species from the -middle coal-formation of Clifton, New Brunswick.</p> - -<p><span class="smcap">Lepidodendron Cliftonense</span>, Dawson.—<i>Habit of Growth</i>.—Robust, -with thick branches, and leaves several inches in length. -Terminal branches becoming slender, with shorter leaves.</p> - -<p><span class="pagenum"><a name="Page_165" id="Page_165">« 165 »</a></span></p> - -<p><i>Markings of Stem.</i>—Leaf-bases long oval, pointed at ends, enlarging -with growth of stem. Leaf-scars central, rhombic, transverse.</p> - -<p><i>Leaves.</i>—One-nerved, acutely pointed, from four inches in length -on the larger branches to one inch or less on the branchlets.</p> - -<p><i>Fructification.</i>—Cones large, cylindrical or long oval, with large -scales of trigonal form, and not elongated but lying close to the surface. -Borne on lateral, slender branchlets, with short leaves.</p> - -<p class="caption4"><i>Genus</i> <span class="smcap">Lepidophloios</span>, Sternberg; <span class="smcap">Ulodendron</span>, L. and H.; -<span class="smcap">Lomatophloios</span>, Corda.</p> - -<p><i>Lepidophloios.</i>—Under this generic name, established by Sternberg, -I include those lycopodiaceous trees of the coal-measures -which have thick branches, transversely elongated leaf-scars, each -with three vascular points and placed on elevated or scale-like protuberances, -long one-nerved leaves, and large lateral strobiles in vertical -rows or spirally disposed. Their structure resembles that of -<i>Lepidodendron</i>, consisting of a <i>Sternbergia</i> pith, a slender axis of -large scalariform vessels, giving off from its surface bundles of -smaller vessels to the leaves, a very thick cellular bark, and a thin -dense outer bark, having some elongated cells or bast-tissue on its -inner side. In these trees the exogenous outer cylinder is less developed -than in the Lepidodendra, and is sometimes wanting in -stems or branches of some thickness.</p> - -<p>Regarding <i>L. laricinum</i> of Sternberg as the type of the genus, -and taking in connection with this the species described by Goldenberg, -and my own observations on numerous specimens found in -Nova Scotia, 1 have no doubt that <i>Lomatophloios crassicaulis</i> of -Corda, and other species of that genus described by Goldenberg, -<i>Ulodendron</i> and <i>Bothrodendron</i> of Lindley, <i>Lepidodendron ornatissimum</i> -of Brongniart, and <i>Halonia punctata</i> of Geinitz, all belong -to this genus, and differ from each other only in conditions of -growth and preservation. Several of the species of <i>Lepidostrobus</i> -and <i>Lepidophyllum</i> also belong to <i>Lepidophloios</i>.</p> - -<p>The species of <i>Lepidophloios</i> are readily distinguished from -<i>Lepidodendron</i> by the form of the areoles, and by the round scars on -the stem, which usually mark the insertion of the large strobiles, -though in barren stems they may also have produced branches; still, -the fact of my finding the strobiles <i>in situ</i> in one instance, the accurate -resemblance which the scars bear to those left by the cones of -the red pine when borne on thick branches, and the actual impressions -of the radiating scales in some specimens, leave no doubt in my -<span class="pagenum"><a name="Page_166" id="Page_166">« 166 »</a></span> -mind that they are usually the marks of cones; and the great size of -the cones of <i>Lepidophloios</i> accords with this conclusion.</p> - -<p>The species of <i>Lepidophloios</i> are numerous, and individuals are -quite abundant in the coal formation, especially toward its upper -part. Their flattened bark is frequent in the coal-beds and their -roofs, affording a thin layer of pure coal, which sometimes shows the -peculiar laminated or scaly character of the bark when other characters -are almost entirely obliterated. The leaves also are nearly as -abundant as those of Sigillaria in the coal-shales. They can readily -be distinguished by their strong, angular midrib.</p> - -<p>The markings of <i>Lepidophloios</i> may easily be mistaken for those -of the <i>Clathraria</i> type of <i>Sigillaria</i>. When the stem only is seen, -they can be distinguished by the length of the leaf-bases in <i>Lepidophloios</i>, -and by the dominant central vascular scar; also by the -one-nerved and ribbed leaves. Where the large, round marks of the -cones are present, these are an infallible guide, never being present -in <i>Sigillaria</i>. As the cones grew on the upper sides of the branches, -the impression of the lower side often shows no cone-scars, or only -two lateral rows, whereas on the upper side of the same branch they -appear spirally arranged. I may describe as an example—</p> - -<p><i>Lepidophloios Acadianus</i>, Dawson. Leaf-bases broadly rhombic, -or in old stems regularly rhombic, prominent, ascending, terminated -by very broad rhombic scars having a central point and two -lateral obscure points. Outer bark laminated or scaly. Surface of -inner bark with single points or depressions. Leaves long, linear, -with a strong keel on one side, five inches or more in length. Cone-scars -sparsely scattered on thick branches, either in two rows or -spirally, both modes being sometimes seen on the same branch. -Scalariform axis scarcely an inch in diameter in a stem five inches -thick. Fruit, an ovate strobile with numerous acute scales covering -small globular spore-cases. This species is closely allied to <i>Ulodendron -majus</i> and <i>Lepidophloios laricinus</i>, and presents numerous -varieties of marking. Coal-formation, Nova Scotia.</p> - -<p class="caption4"><i>Family</i> <span class="smcap">Calamiteæ</span>; <i>Genus</i> <span class="smcap">Calamites</span>, Suckow.</p> - -<p>The plants of this genus are unquestionably allied to the modern -<i>Equisetaceæ</i>, but excel these so much in variety of form and -structure, and are so capricious in their states of preservation, and so -liable to be mistaken for parts of plants generically different, that -they have given rise to much controversy. The following considerations -will enable us to arrive at some certainty.</p> - -<p>The genus <i>Calamites</i> was originally founded in the longitudinally -<span class="pagenum"><a name="Page_167" id="Page_167">« 167 »</a></span> -ribbed and jointed stems so frequent in the coal-formation, -and of which the common <i>C. Suckovii</i> is a typical form. The most -perfect of these stems represent the outer surface immediately within -the epidermis, in which case transverse lines or constrictions -mark the nodes, and at the nodes there are rounded spots, sometimes -indicating radial processes of the pith, first described by -Williamson; in other cases, the attachment of branchlets, or in some -specimens both. But some specimens show the outer surface of the -epidermis, in which case the transverse nodal lines are usually invisible, -though the scars of branchlets may appear. In still other -examples the whole of the outer tissues have perished, and the so-called -Calamite is a cast of the interior of the stem, showing merely -longitudinal ribbing and transverse nodal constrictions. In studying -these plants <i>in situ</i> in the erect Calamite brakes of the coal-formation -of Nova Scotia, one soon becomes familiar with these appearances, -but they are evidently unknown to the majority of palæobotanists, -though described in detail more than twenty years ago.</p> - -<p>When the outer surface is preserved it is sometimes seen to bear -verticils of long needle-like leaves (<i>C. Cistii</i>), or of branchlets with -secondary whorls of similar leaves (<i>C. Suckovii</i> and <i>C. undulatus</i>). -No Calamite known to me bears broad one-nerved leaves like those -of <i>Asterophyllites</i> and <i>Annularia</i>, though the larger stems of these -plants have been described as Calamites, and the term <i>Calamocladus</i> -has been used to include both groups. The base of the Calamite -stem usually terminates in a blunt point, and may be attached to a -rhizome, or several stems may bud out from each other in a group or -stool. The roots are long and cylindrical, sometimes branching. -The fruit consists of spikes of spore-cases, borne in whorls and subtended -by linear floral leaves. To these strobiles the name Calamostachys -has been given.</p> - -<p>Williamson has shown that the stem of Calamites consists of a -central pith or cavity of large size surrounded by a cylinder consisting -of alternate wedges of woody and cellular matter, with vertical -canals at the inner sides of the wedges, and slender medullary -rays. The thick cellular wedges intervening between the woody -wedges he calls primary medullary rays; the smaller medullary -rays in the wedges, secondary medullary rays. There is thus a -highly complex exogenous stem based on the same principle with -the stem of a common <i>Equisetum</i>, but with much greater strength -and complexity.</p> - -<p>Williamson has also shown that there are different sub-types of -these stems. More especially he refers to the three following:</p> - -<p><span class="pagenum"><a name="Page_168" id="Page_168">« 168 »</a></span></p> - -<p>(<i>a</i>) <i>Calamites</i> proper, which has the woody wedges of scalariform -or barred tissue with thin medullary rays, and the thick primary -medullary rays are cellular.</p> - -<p>(<i>b</i>) <i>Calamopitus</i> has reticulated or multiporous tissue in the -woody wedges with medullary rays, and the primary medullary -wedges are composed of elongated cells.</p> - -<p>(<i>c</i>) <i>Calamodendron</i> has the woody wedges of barred tissue as in -<i>a</i>, with medullary rays, but has the intervening medullary wedges -of an elongated tissue approaching to woody fibre, and also with -medullary rays.</p> - -<p>To these I would add a fourth type, which I have described, from -the coal-formation of Nova Scotia.<a name="FNanchor_DB_106" id="FNanchor_DB_106"></a><a href="#Footnote_DB_106" class="fnanchor">[DB]</a></p> - -<div class="footnote"> - -<p><a name="Footnote_DB_106" id="Footnote_DB_106"></a><a href="#FNanchor_DB_106"><span class="label">[DB]</span></a> “Quarterly Journal of the Geological Society,” 1871.</p></div> - -<p>(<i>d</i>) <i>Eucalamodendron</i> differs from <i>Calamodendron</i> in having -true bordered pores or pseudo-scalariform slit-pored tissue, and corresponds -to the highest type of calamitean stem.</p> - -<p>I would also add that under <i>a</i> and <i>b</i> there are some species in -which the woody cylinder is very thin in comparison to the size of -the stem. In <i>c</i> and <i>d</i> the woody cylinder is thick and massive, and -the stems are often large and nodose.</p> - -<p>As an example of an ordinary Calamite in which the external -surface and foliage are preserved, I may quote the following from -my report on the “Flora of the Lower Carboniferous and Millstone -Grit,” 1873:</p> - -<p><span class="smcap">Calamites Undulatus</span>, Brongniart.—This species is stated by -Brongniart to be distinguished from the <i>C. Suckovii</i>, the characteristic -Calamite of the middle coal-formation, by its undulated ribs -marked with peculiar cellular reticulation. He suggests that it may -be merely a variety of <i>C. Suckovii</i>, an opinion in which Schimper -coincides; but since I have received large additional collections from -Mr. Elder, containing not only the stems and branches, but also the -leaves and rhizomes, I am constrained to regard it as a distinct -though closely allied species.</p> - -<p>The rhizomata are slender, being from one to two inches in -diameter, and perfectly flattened. They are beautifully covered with -a cellular reticulation on the thin bark, and show occasional round -areoles marking the points of exit of the rootlets. I have long been -familiar with irregular flattened stems thus reticulate, but have only -recently been able to connect them with this species of Calamite.</p> - -<p>The main stems present a very thin carbonaceous bark reticulated -like the rhizomes. They have flat, broad ribs separated by deep -<span class="pagenum"><a name="Page_169" id="Page_169">« 169 »</a></span> -and narrow furrows, and undulated in a remarkable manner even -when the stems are flattened. This undulation is, however, perhaps an -indication of vertical pressure while the plant was living, as it seems -to have had an unusually thin and feeble cortical layer, and the undulations -are apparently best developed in the lower part of the stem. -At the nodes the ribs are often narrowed and gathered together, -especially in the vicinity of the rounded radiating marks which appear -to indicate the points of insertion of the branches. At the top -of each rib we have the usual rounded areole, probably marking the -insertion of a primary branchlet.</p> - -<p>The branches have slender ribs and distant nodes, from which -spring secondary branchlet s in whorls, these bearing in turn small -whorls of acicular leaflets much curved upward, and which are apparently -round in cross section and delicately striate. They are -much shorter than the leaves of <i>Calamites Suckovii</i>, and are less -dense and less curved than those of <i>C. nodosus</i>, which I believe to be -the two most closely allied species.</p> - -<p>Lesquereux notices this species as characteristic of the lower part -of the Carboniferous in Arkansas.</p> - -<p>It will be observed that I regard the striated and ribbed stems not -as internal axes, but as representing the outer surface of the plants. -This was certainly the case with the present species and with <i>C. -Suckovii</i> and <i>C. nodosus</i>. Other species, and especially those which -belonged to Calamodendron, no doubt had a smooth or irregularly -wrinkled external bark; but this gives no good ground for the manner -in which some writers on this subject confound Calamites with -Calamodendra, and both with Asterophyllites and Sphenophyllum. -With this no one who has studied these plants, rooted in their native -soils, and with their appendages still attached, can for a moment -sympathise. One of the earliest geological studies of the writer was -a bed of these erect Calamites, which he showed to Sir C. Lyell in -1844, and described in the “Proceedings of the Geological Society” -in 1851, illustrating the habit of growth as actually seen well exposed -in a sandstone cliff. Abundant opportunities of verifying -the conclusions formed at that time have since occurred, the results -of which have been summed up in the figures in Acadian Geology, -which, though they have been treated by some botanists as merely -restorations, are in reality representations of facts actually observed.</p> - -<p>On these subjects, without entering into details, and referring -for these to the elaborate discussions of Schimper, Williamson, and -McNab, and to my paper on the subject, “Journal of the Geological -Society,” vol. xxvii, p. 54, I may remark:</p> - -<p><span class="pagenum"><a name="Page_170" id="Page_170">« 170 »</a></span></p> - -<p>1. That the aërial stems of ordinary Calamites had a thin cortical -layer, with lacunæ and fibrous bundles and multiporous vessels—the -whole not differing much from the structure of modern Equiseta.</p> - -<p>2. Certain arborescent forms, perhaps allied to the true Calamites, -as well as possibly the old underground stems of ordinary species<a name="FNanchor_DC_107" id="FNanchor_DC_107"></a><a href="#Footnote_DC_107" class="fnanchor">[DC]</a> -assumed a thick-walled character in which the tissues resembled the -wedges of an exogen, and abundance of pseudo-scalariform fibres were -developed, while the ribbing of the external surface became obsolete -or was replaced by a mere irregular wrinkling.</p> - -<div class="footnote"> - -<p><a name="Footnote_DC_107" id="Footnote_DC_107"></a><a href="#FNanchor_DC_107"><span class="label">[DC]</span></a> Williamson, “Transactions of the Royal Society.” McNab, in -“Proceedings of the Edinburgh Botanical Society.”</p></div> - -<p>3. Sufficient discrimination has not been exercised in separating -casts of the internal cavities of Calamites and Calamodendron from -those representing other surfaces and the proper external surface.</p> - -<p>4. There is no excuse for attributing to Calamites the foliage of -Annularia, Asterophyllites, and Sphenophyllum, since these leaves -have not been found attached to true Calamite stems, and since the -structure of the stems of Asterophyllites as described by Williamson, -and that of Sphenophyllum as described by the writer,<a name="FNanchor_DD_108" id="FNanchor_DD_108"></a><a href="#Footnote_DD_108" class="fnanchor">[DD]</a> are essentially -different from those of Calamites.</p> - -<div class="footnote"> - -<p><a name="Footnote_DD_108" id="Footnote_DD_108"></a><a href="#FNanchor_DD_108"><span class="label">[DD]</span></a> “Journal of the Geological Society,” 1866.</p></div> - -<p>5. As the species above described indicates, good external characters -can be found for establishing species of this genus, and these -species are of value as marks of geological age.</p> - -<p class="caption4"><i>Genus</i> <span class="smcap">Archæocalamites</span>, Sternberg.</p> - -<p>This genus has been established to include certain Calamites of -the Devonian and Lower Carboniferous, in which the furrows on the -stem do not alternate at the nodes or joints, and the leaves in one -species at least bifurcate. <i>C. radiatus</i>, Brongniart, is the typical -species. In North America it occurs in the Erian, probably as low -as the Middle Erian. In Europe it has so far been recognised in the -Lower Carboniferous only. I have, however, seen stems from alleged -Devonian beds in Devonshire which may have belonged to this species.</p> - -<p class="caption4"><i>Family</i> <span class="smcap">Asterophylliteæ</span>; <i>Genus</i> <span class="smcap">Asterophyllites</span>, Brongniart.</p> - -<p>Stems ribbed and jointed like the <i>Calamites</i>, but with inflated -nodes and a stout internal woody cylinder, which has been described -by Williamson. From the joints proceeded whorls of leaves or of -branchlets, bearing leaves which differed from those of <i>Calamites</i> in -their having a distinct middle rib or vein. The fructification consisted -<span class="pagenum"><a name="Page_171" id="Page_171">« 171 »</a></span> -of long slender cones or spikes, having whorls of scales bearing -the spore-cases. Some authors speak of <i>Asterophyllites</i> as only -branches and leaves of <i>Calamites</i>; but though at first sight the resemblance -is great, a close inspection shows that the leaves of Asterophyllites -have a true midrib, which is wanting in <i>Calamites</i>.</p> - -<p><i>Genus</i> <span class="smcap">Annularia</span>.—It is perhaps questionable whether these -plants should be separated from <i>Asterophyllites</i>, The distinction is -that they produce branches in pairs, and that their whorls of leaves -are one-sided and usually broader than those of <i>Asterophyllites</i>, and -united into a ring at their insertion on the stem. One little species, -<i>A. sphenophylloides</i>, is very widely distributed.</p> - -<p><span class="smcap">Pinnularia</span>—a provisional genus—-includes slender roots or stems -branching in a pinnate manner, and somewhat irregularly. They -are very abundant in the coal shales, and were probably not independent -plants, but aquatic roots belonging to some of the plants -last mentioned. The probability of this is farther increased by their -resemblance in miniature to the roots of <i>Calamites</i>. They are always -flattened, but seem originally to have been round, with a slender -thread-like axis of scalariform vessels, enclosed in a soft, smooth, -cellular bark.</p> - -<p class="caption4"><i>Family</i> <span class="smcap">Rhizocarpeæ</span>; <i>Genus</i> <span class="smcap">Sphenophyllum</span>.</p> - -<p>Leaves in whorls, wedge-shaped, with forking veins. Fructification -on spikes, with verticils of sporocarps. These plants are -by some regarded as allied to the <i>Calamiteæ</i> and <i>Asterophylliteæ</i>, by -others as a high grade of Rhizocarps of the type of Marsilia. The -stem had a star-shaped central bundle of scalariform or reticulato-scalariform -vessels.</p> - -<p class="caption4"><i>Genus</i> <span class="smcap">Sporangites</span>. (<i>Sporocarpon</i>, Williamson.)</p> - -<p>Under this name we may provisionally include those rounded -spherical bodies found in the coal and its accompanying beds, and -also in the Erian, which may be regarded as Macrospores or Sporocarps -of Protosalvinia, or other Rhizocarpean plants akin to those described -above in <a href="#CHAPTER_III">Chapter III</a>, which see for description.</p> - -<p><i>Genus</i> <span class="smcap">Protosalvinia</span>.—Under this we include sporocarps allied -to those of <i>Salvinia</i>, as described in <a href="#CHAPTER_III">Chapter III</a>.</p> - - -<p class="caption4"><i>Family</i> <span class="smcap">Filices</span>.</p> - -<p>Under this head I shall merely refer to a few groups of special -interest, and to the provisional arrangement adopted for the fronds -of ferns when destitute of fructification.</p> - -<p><span class="pagenum"><a name="Page_172" id="Page_172">« 172 »</a></span></p> - -<p>The external appearances of trunks of tree-ferns have been already -referred to.</p> - -<p>With respect to tree ferns, the oldest known examples are those -from the Middle Devonian of New York and Ohio, which I have described -in the “Journal of the Geological Society,” 1871 and 1881. -As these are of some interest, I have reproduced their descriptions -in a <a href="#NOTES_TO_CHAPTER_III">note</a> appended to Chapter III, which see.</p> - -<p>The other forms most frequently occurring in the Carboniferous -are <i>Caulopteris</i>, <i>Palæopteris</i>, and <i>Megaphyton</i><a name="FNanchor_DE_109" id="FNanchor_DE_109"></a><a href="#Footnote_DE_109" class="fnanchor">[DE]</a> Stems showing -merely masses of aërial roots are known by the name <i>Psaronius</i>.</p> - -<div class="footnote"> - -<p><a name="Footnote_DE_109" id="Footnote_DE_109"></a><a href="#FNanchor_DE_109"><span class="label">[DE]</span></a> See my “Acadian Geology,” also below.</p></div> - -<p>With reference to the classification of Palæozoic ferns, this has -hitherto been quite arbitrary, being based on mere form and venation -of fronds, but much advance has recently been made in the -knowledge of their fructification, warranting a more definite attempt -at classification. The following are provisional genera usually -adopted:</p> - -<p>1. <i>Cyclopteris</i>, Brongniart.—Leaflets more or less rounded or -wedge-shaped, without midrib, the nerves spreading from the point -of attachment. This group includes a great variety of fronds evidently -of different genera, were their fructification known; and some -of them probably portions of fronds, the other parts of which may -be in the next genus.</p> - -<p>2. <i>Neuropteris</i>, Brongniart.—Fronds pinnate, and with the -leaflets narrowed at the base; midrib often not distinct, and disappearing -toward the apex. Nervures equal, and rising at an acute -angle. Ferns of this type are among the most abundant in the coal-formation.</p> - -<p>3. <i>Odontopteris</i>, Brongniart.—In these the frond is pinnate, and -the leaflets are attached by their whole base, with the nerves either -proceeding wholly from the base, or in part from an indistinct midrib, -which soon divides into nervures.</p> - -<p>4. <i>Dictyopteris</i>, Gutbier.—This is a beautiful style of fern, with -leaflets resembling those of <i>Neuropteris</i>, but the veins arranged in a -network of oval spaces. Only a few species are known in the coal-formation.</p> - -<p>5. <i>Lonchopteris</i>, Brongniart.—Ferns with netted veins like the -above, but with a distinct midrib, and the leaflets attached by the -whole base. Of this, also, we can boast but few species.</p> - -<p>6. <i>Sphenopteris</i>, Brongniart.—These are elegant ferns, very numerous -in species, and most difficult to discriminate. Their most -<span class="pagenum"><a name="Page_173" id="Page_173">« 173 »</a></span> -distinctive characters are leaflets narrowed at the base, often lobed, -and with nervures dividing in a pinnate manner from the base.</p> - -<p>7. <i>Phyllopteris</i>, Brongniart.—These are pinnate, with long lanceolate -pinnules, having a strong and well-defined midrib, and -nerves proceeding from it very obliquely, and dividing as they proceed -toward the margin. The ferns of this genus are for the most -part found in formations more recent than the Carboniferous; but I -have referred to it, with some doubt, one of our species.</p> - -<p>8. <i>Alethopteris</i>, Brongniart.—This genus includes many of the -most common coal-formation ferns, especially the ubiquitous <i>A. lonchitica</i>, -which seems to have been the common brake of the coal-formation, -corresponding to <i>Pteris aquilina</i> in modern Europe and -America. These are brake-like ferns, pinnate, with leaflets often -long and narrow, decurrent on the petiole, adherent by their whole -base, and united at base to each other. The midrib is continuous to -the point, and the nervures run off from it nearly at right angles. -In some of these ferns the fructification is known to have been marginal, -as in <i>Pteris</i>.</p> - -<p>9. <i>Pecopteris</i>, Brongniart.—This genus is intermediate between -the last and <i>Neuropteris</i>. The leaflets are attached by the whole -base, but not usually attached to each other; the midrib, though -slender, attains to the summit; the nervures are given off less obliquely -than in <i>Neuropteris</i>. This genus includes a large number of -our most common fossil ferns.</p> - -<p>10. <i>Beinertia</i>, Goeppert.—A genus established by Goeppert for a -curious Pecopteris-like fern, with flexuous branching oblique nervures -becoming parallel to the edge of the frond.</p> - -<p>11. <i>Hymenophyllites</i>, Goeppert.—These are ferns similar to -Sphenopteris, but divided at the margin into one-nerved lobes, in the -manner of the modern genus <i>Hymenophyllum</i>.</p> - -<p>12. <i>Palæopteris</i>, Geinitz.—This is a genus formed to include certain -trunks of tree-ferns with oval transverse scars of leaves.</p> - -<p>13. <i>Caulopteris</i>, Lindley and Hutton.—Is another genus of fossil -trunks of tree-ferns, but with elongate scars of leaves.</p> - -<p>14. <i>Psaronius</i>, Cotta.—Includes other trunks of tree-ferns with -alternate scars or thick scales, and ordinarily with many aërial roots -grouped round them, as in some modern tree-ferns.</p> - -<p>15. <i>Megaphyton</i>, Artis.—Includes trunks of tree-ferns which -bore their fronds, which were of great size, in two rows, one on each -side of the stem. These were very peculiar trees, less like modern -ferns than any of the others. My reasons for regarding them as -ferns are stated in the following extract from a recent paper:</p> - -<p><span class="pagenum"><a name="Page_174" id="Page_174">« 174 »</a></span></p> - -<p>“Their thick stems, marked with linear scars and having two -rows of large depressed areoles on the sides, suggest no affinities to -any known plants. They are usually ranked with <i>Lepidodendron</i> -and <i>Ulodendron</i>, but sometimes, and probably with greater reason, -are regarded as allied to tree-ferns. At the Joggins a very fine -species (<i>M. magnificum</i>) has been found, and at Sydney a smaller -species (<i>M. humile</i>); but both are rare and not well preserved. If -the large scars bore cones and the smaller bore leaves, then, as Brongniart -remarks, the plant would much resemble <i>Lepidophloios</i>, in -which the cone-scars are thus sometimes distichous. But the scars -are not round and marked with radiating scales as in <i>Lepidophloios</i>; -they are reniform or oval, and resemble those of tree-ferns, for which -reason they may be regarded as more probably leaf-scars; and in -that case the smaller linear scars would indicate ramenta, or small -aërial roots. Further, the plant described by Corda as <i>Zippea disticha</i> -is evidently a <i>Megaphyton</i>, and the structure of that species is -plainly that of a tree-fern of somewhat peculiar type. On these -grounds I incline to the opinion of Geinitz that these curious trees -were allied to ferns, and bore two rows of large fronds, the trunks -being covered with coarse hairs or small aërial roots. At one time I -was disposed to suspect that they may have crept along the ground; -but a specimen from Sydney shows the leaf-stalks proceeding from -the stem at an angle so acute that the stem must, I think, have been -erect. From the appearance of the scars it is probable that only a -pair of fronds were borne at one time at the top of the stem; and, if -these were broad and spreading, it would be a very graceful plant. -To what extent plants of this type contributed to the accumulation -of coal I have no means of ascertaining, their tissues in the state of -coal not being distinguishable from those of ferns and <i>Lycopodiaceæ</i>.”</p> - -<p>16. For descriptions of the genus <i>Archæopteris</i> and other Erian -ferns, see <a href="#CHAPTER_III">Chapter III</a>.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_175" id="Page_175">« 175 »</a></span></p> - - - - -<p class="caption2"><a name="CHAPTER_V" id="CHAPTER_V">CHAPTER V.</a></p> - -<p class="caption3">THE FLORA OF THE EARLY MESOZOIC.</p> - - -<p><span class="smcap">Great</span> physical changes occurred at the close of the -Carboniferous age. The thick beds of sediment that had -been accumulating in long lines along the primitive continents -had weighed down the earth’s crust. Slow subsidence -had been proceeding from this cause in the coal-formation -period, and at its close vast wrinklings occurred, -only surpassed by those of the old Laurentian time. -Hence in the Appalachian region of America we have the -Carboniferous beds thrown into abrupt folds, their shales -converted into hard slates, their sandstones into quartzite -and their coals into anthracite, and all this before the -deposition of the Triassic Red Sandstones which constitute -the earliest deposit of the great succeeding Mesozoic -period. In like manner the coal-fields of Wales and -elsewhere in western Europe have suffered similar treatment, -and apparently at the same time.</p> - -<p>This folding is, however, on both sides of the Atlantic -limited to a band on the margin of the continents, and to -certain interior lines of pressure, while in the middle, as -in Ohio and Illinois in America, and in the great interior -plains of Europe, the coal-beds are undisturbed and unaltered. -In connection with this we have an entire -change in the physical character of the deposits, a great -elevation of the borders of the continents, and probably -a considerable deepening of the seas, leading to the establishment -of general geographical conditions which still -remain, though they have been temporarily modified by -subsequent subsidences and re-elevations.</p> - -<p><span class="pagenum"><a name="Page_176" id="Page_176">« 176 »</a></span></p> - -<p>Along with this a great change was in progress in -vegetable and animal life. The flora and fauna of the -Palæozoic gradually die out in the Permian and are replaced -in the succeeding Trias by those of the Mesozoic -time. Throughout the Permian, however, the remains -of the coal-formation flora continue to exist, and some -forms, as the <i>Calamites</i>, even seem to gain in importance, -as do also certain types of coniferous trees. The Triassic, -as well as the Permian, was marked by physical disturbances, -more especially by great volcanic eruptions discharging -vast beds and dykes of lava and layers of volcanic -ash and agglomerate. This was the case more especially -along the margins of the Atlantic, and probably also on -those of the Pacific. The volcanic sheets and dykes associated -with the Red Sandstones of Nova Scotia, Connecticut, -and New Jersey are evidences of this.</p> - -<p>At the close of the Permian and beginning of the -Trias, in the midst of this transition time of physical -disturbance, appear the great reptilian forms characteristic -of the age of reptiles, and the earliest precursors of -the mammals, and at this time the old Carboniferous -forms of plants finally pass away, to be replaced by a -flora scarcely more advanced, though different, and consisting -of pines, cycads, and ferns, with gigantic equiseta, -which are the successors of the genus <i>Calamites</i>, a genus -which still survives in the early Trias. Of these groups -the conifers, the ferns, and the equiseta are already familiar -to us, and, in so far as they are concerned, a botanist -who had studied the flora of the Carboniferous would -have found himself at home in the succeeding period. -The cycads are a new introduction. The whole, however, -come within the limits of the cryptogams and the -gymnosperms, so that here we have no advance.<a name="FNanchor_DF_110" id="FNanchor_DF_110"></a><a href="#Footnote_DF_110" class="fnanchor">[DF]</a></p> - -<div class="footnote"> - -<p><a name="Footnote_DF_110" id="Footnote_DF_110"></a><a href="#FNanchor_DF_110"><span class="label">[DF]</span></a> Fontaine’s “Early Mesozoic Flora of Virginia” gives a very good -summary of this flora in America.</p> - -<p><span class="pagenum"><a name="Page_177" id="Page_177">« 177 »</a></span></p></div> - -<div class="fig_center" style="width: 463px;"> -<a name="fig64" id="fig64"></a> -<img src="images/fig64.png" width="463" height="499" alt="" /> -<div class="fig_caption">Fig. 64.—Jurassic vegetation. Cycads and pines. (After Saporta.)</div> -</div> - -<p>As we ascend, however, in the Mesozoic, we find new -and higher types. Even within the Jurassic epoch, the -next in succession to the Trias, there are clear indications -of the presence of the endogens, in species allied to -the screw-pines and grasses; and the palms appear a -little later, while a few exogenous trees have left their -remains in the Lower Cretaceous, and in the Middle and -Upper Cretaceous these higher plants come in abundantly -and in generic forms still extant, so that the dawn -of the modern flora belongs to the Middle and Upper -<span class="pagenum"><a name="Page_178" id="Page_178">« 178 »</a></span> -Cretaceous. It will thus be convenient to confine ourselves -in this chapter to the flora of the earlier Mesozoic.</p> - -<p>Passing over for the present the cryptogamous plants -already familiar in older deposits, we may notice the new -features of gymnospermous and phænogamous life, as they -present themselves in this earlier part of the great reptilian -age, and as they extended themselves with remarkable -uniformity in this period over all parts of the world. -For it is a remarkable fact that, if we place together in -our collections fossil plants of this period from Australia, -India, China, Siberia, Europe, or even from Greenland, -we find wonderfully little difference in their aspect. This -uniformity we have already seen prevailed in the Palæozoic -flora; and it is perhaps equally marked in that of -the Mesozoic. Still we must bear in mind that some -of the plants of these periods, as the ferns and pines, -for example, are still -world-wide in their -distribution; but this -does not apply to others, -more especially -the cycads (<a href="#fig65">Fig. 65</a>).</p> - -<div class="fig_center" style="width: 274px;"> -<a name="fig65" id="fig65"></a> -<img src="images/fig65.png" width="274" height="282" alt="" /> -<div class="fig_caption">Fig. 65.—<i>Podozamites lanceolatus</i>, Sternb. -L. Cretaceous.</div> -</div> - -<p>The cycads constitute -a singular and exceptional -type in the -modern world, and -are limited at present -to the warmer climates, -though very -generally distributed -in these, as they occur -in Africa, India, -Japan, Australia, Mexico, Florida, and the West Indies. -In the Mesozoic age, however, they were world-wide in -their distribution, and are found as far north as Greenland, -though most of the species found in the Cretaceous -<span class="pagenum"><a name="Page_179" id="Page_179">« 179 »</a></span> -of that country are of small size/ and may have been of -low growth, so that they may have been protected by the -snows of winter. The cycads have usually simple or unbranching -stems, pinnate leaves borne in a crown at top, -and fruits which, though somewhat various in structure -and arrangement, are all of the simpler form of gymnospermous -type. The stems are exogenous in structure, -but with slender wood and thick bark, and barred tissue, -or properly as tissue intermediate between this and the -disc-bearing fibres of the pines.</p> - -<p>Though the cycads have a considerable range of organisation -and of fructification, and though some points -in reference to the latter might assign them a higher -place, on the whole they seem to occupy a lower position -than the conifers or the cordaiteæ of the Carboniferous. -In the Carboniferous some of the fern-like leaves assigned -to the genus <i>Noeggerathia</i> have been shown by Stur and -Weiss to have been gymnosperms, probably allied to -cycads, of which they may be regarded at least as precursors. -Thus the cycadean type does not really constitute -an advance in grade of organisation in the Mesozoic, -any further than that, in the period now in question, it -becomes much more developed in number and variety of -forms. But the conifers would seem to have had precedence -of it for a long time in the Palæozoic, and it replaces -in the Mesozoic the <i>Cordaites</i>, which in many respects -excelled it in complexity.</p> - -<p>The greater part of the cycads of the Mesozoic age -would seem to have had short stems and to have constituted -the undergrowth of woods in which conifers attained -to greater height. An interesting case of this is -the celebrated dirt-bed of the quarries of the Isle of Portland, -long ago described by Dean Buckland. In this -fossil soil trunks of pines, which must have attained to -great height, are interspersed with the short, thick stems -of cycads, of the genus named <i>Cycadoidea</i> by Buckland, -<span class="pagenum"><a name="Page_180" id="Page_180">« 180 »</a></span> -and which from their appearance are called “fossil -birds' nests” by the quarrymen. Some, however, must -have attained a considerable height so as to resemble -palms.</p> - -<p>The cycads, with their simple, thick trunks, usually -marked with rhombic scars, and bearing broad spreading -crowns of large, elegantly formed pinnate leaves, must -have formed a prominent part of the vegetation of the -northern hemisphere during the whole of the Mesozoic -period. A botanist, had there been such a person at the -time, would have found this to be the case everywhere -from the equator to Spitzbergen, and probably in the -southern hemisphere as well, and this throughout all the -long periods from the Early Trias to the Middle Cretaceous. -In a paper published in the “Linnæan Transactions” -for 1868, Dr. Carruthers enumerates twenty species -of British Mesozoic cycads, and the number might -now be considerably increased.</p> - -<div class="fig_center" style="width: 197px;"> -<a name="fig66" id="fig66"></a> -<img src="images/fig66.png" width="197" height="149" alt="" /> -<div class="fig_caption">Fig. 66.—<i>Salisburia</i> (Gingko) -<i>Sibirica</i>, Heer. L. Cretaceous, -Siberia and North -America.</div> -</div> - -<p>The pines present some features of interest. We have -already seen their connection with the broad-leaved <i>Cordaites</i>, -and in the Permian there are some additional -types of broad-leaved coniferæ. -In the Mesozoic we have great -numbers of beautiful trees, -with those elegant fan-shaped -leaves characteristic of but one -living species, the Salisburia, -or gingko-tree of China. It is -curious that this tree, though -now limited to eastern Asia, -will grow, though it rarely -fruits, in most parts of temperate -Europe, and in America as far north as Montreal, -and that in the Mesozoic period it occupied all these regions, -and even Siberia and Greenland, and with many -and diversified species (<a href="#fig66">Fig. 66</a>).</p> - -<p><span class="pagenum"><a name="Page_181" id="Page_181">« 181 »</a></span></p> - -<p><i>Salisburia</i> belongs to the yews, but an equally curious -fact applies to the cypresses. The genus <i>Sequoia</i>, limited -at present to two species, both Californian, and one of -them the so-called “big tree,” celebrated for the gigantic -size to which it attains, is represented by species found as -far back at least as the Lower Cretaceous, and in every -part of the northern hemisphere.<a name="FNanchor_DG_111" id="FNanchor_DG_111"></a><a href="#Footnote_DG_111" class="fnanchor">[DG]</a> -It seems to have -thriven in all these regions -throughout the Mesozoic -and early Kainozoic, and -then to have disappeared, -leaving only a small remnant -to represent it in -modern days. A number -of species have been described -from the Mesozoic -and Tertiary, all of them -closely related to those now -existing (<a href="#fig67">Fig. 67</a>).</p> - -<div class="footnote"> - -<p><a name="Footnote_DG_111" id="Footnote_DG_111"></a><a href="#FNanchor_DG_111"><span class="label">[DG]</span></a> In the Eocene of Australia.</p></div> - -<div class="fig_right" style="width: 237px;"> -<a name="fig67" id="fig67"></a> -<img src="images/fig67.png" width="237" height="466" alt="" /> -<div class="fig_caption">Fig. 67.—<i>Sequoia Smithiana</i>, Heer. -L. Cretaceous.</div> -</div> - -<p>The following notice of -these trees is for the most -part translated, with some -modifications and abridgment, -from a paper read -by the late Prof. Heer before -the Botanical Section -of the Swiss Natural History -Society:</p> - -<p>The name itself deserves -consideration. It is that -of an Indian of the Cherokee tribe, Sequo Yah, who invented -an alphabet without any aid from the outside world -of culture, and taught it to his tribe by writing it upon -<span class="pagenum"><a name="Page_182" id="Page_182">« 182 »</a></span> -leaves. This came into general use among the Cherokees, -before the white man had any knowledge of it; and -afterward, in 1828, a periodical was published in this -character by the missionaries. Sequo Yah was banished -from his home in Alabama, with the rest of his tribe, and -settled in New Mexico, where he died in 1843.</p> - -<p>When Endlicher was preparing his synopsis of the -conifers, in 1846, and had established a number of new -genera, Dr. Jacbon Tschudi, then living with Endlicher, -brought before his notice this remarkable man, and asked -him to dedicate this red-wooded tree to the memory of a -literary genius so conspicuous among the red men of -America. Endlicher consented to do so, and only endeavored -to make the name pronounceable by changing -two of its letters.</p> - -<p>Endlicher founded the genus on the redwood of the -Americans, <i>Taxodium sempervirens</i> of Lamb; and named -the species <i>Sequoia sempervirens</i>. These trees form large -forests in California, which extend along the coast as far -as Oregon. Trees are there met with of 300 feet in height -and 20 feet in diameter. The seeds have been brought -to Europe a number of years ago, and we already see in -upper Italy and around the Lake of Geneva, and in England, -high trees; but, on the other hand, they have not -proved successful around Zurich.</p> - -<p>In 1852, a second species of Sequoia was discovered in -California, which, under the name of big tree, soon attained -a considerable celebrity. Lindley described it, in -1853, as <i>Wellingtonia gigantea</i>; and, in the following -year, Decaisne and Torrey proved that it belonged to -Sequoia, and that it accordingly should be called <i>Sequoia -gigantea</i>.</p> - -<p>While the <i>Sequoia sempervirens</i>, in spite of the destructiveness -of the American lumbermen, still forms -large forests along the coast, the <i>Sequoia gigantea</i> is confined -to the isolated clumps which are met with inland at -<span class="pagenum"><a name="Page_183" id="Page_183">« 183 »</a></span> -a height of 5,000 to 7,000 feet above sea-level, and are -much sought after by tourists as one of the wonders of -the country. Reports came to Europe concerning the -largest of them which were quite fabulous, but we have -received accurate accounts of them from Prof. Whitney. -The tallest tree measured by him has a height of 325 -feet, and in the case of one of the trees the number of the -rings of growth indicated an age of about 1,300 years. -It had a girth of 50 to 60 feet.</p> - -<p>We know only two living species of <i>Sequoia</i>, both of -which are confined to California. The one (<i>S. sempervirens</i>) -is clothed with erect leaves, arranged in two rows, -very much like our yew-tree, and bears small, round -cones; the other (<i>S. gigantea</i>) has smaller leaves, set -closely against the branches, giving the tree more the appearance -of the cypress. The cones are egg-shaped, and -much larger. These two types are therefore sharply defined.</p> - -<p>Both of these trees have an interesting history. If we -go back into the Tertiary, this same genus meets us with -a long array of species. Two of these species correspond -to those living at present: the <i>S. Langsdorfii</i> to the <i>S. -sempervirens</i>, and the <i>S. Couttsiæ</i> to the <i>S. gigantea</i>.<a name="FNanchor_DH_112" id="FNanchor_DH_112"></a><a href="#Footnote_DH_112" class="fnanchor">[DH]</a> -But, while the living species are confined to California, in -the Tertiary they are spread over several quarters of the -globe.</p> - -<div class="footnote"> - -<p><a name="Footnote_DH_112" id="Footnote_DH_112"></a><a href="#FNanchor_DH_112"><span class="label">[DH]</span></a> <i>S. Couttsiæ</i> has leaves like <i>S. gigantea</i>, and cones like those of <i>8. -sempervirens</i>.</p></div> - -<p>Let us first consider the <i>Sequoia Langsdorfii</i>. This -was first discovered in the lignite of Wetterau, and was -described as <i>Taxites langsdorfii</i>. Heer found it in the -upper Rhone district, and there lay beside the twigs -the remains of a cone, which showed that the <i>Taxites -Langsdorfii</i> of Brongniart belonged to the Californian -genus Sequoia established by Endlicher. He afterward -<span class="pagenum"><a name="Page_184" id="Page_184">« 184 »</a></span> -found much better preserved cones, together with seeds, -along with the plants of east Greenland, which fully -confirmed the determination. At Atanekerdluk in -Greenland (about 70° north latitude) this tree is very -common. The leaves, and also the flowers and numerous -cones, leave no doubt that it stands very near to the -modern redwood. It differs from it, however, in having -a much larger number of scales in the cone. The tree -is also found in Spitzbergen at nearly 78° north latitude, -where Nordenskiöld has collected, at Cape Lyell, wonderfully -preserved branches. From this high latitude the -species can be followed down through the whole of Europe -as far as the middle of Italy (at Senegaglia, Gulf of -Spezia). In Asia, also,, we can follow it to the steppes -of Kirghisen, to Possiet, and to the coast of the Sea of -Japan, and across to Alaska and Sitka. It is recognized -by Mr. Starkie Gardner as one of the species found in -the Eocene of Mull in the Hebrides.<a name="FNanchor_DI_113" id="FNanchor_DI_113"></a><a href="#Footnote_DI_113" class="fnanchor">[DI]</a> It is thus known -in Europe, Asia, and America, from 43° to 78° north -latitude, while its most nearly related living species, perhaps -even descended from it, is now confined to California.</p> - -<div class="footnote"> - -<p><a name="Footnote_DI_113" id="Footnote_DI_113"></a><a href="#FNanchor_DI_113"><span class="label">[DI]</span></a> It is <i>Fareites Campbelli</i> of Forbes.</p></div> - -<p>With this <i>S. Langsdorfii</i>, three other Tertiary species -are nearly related (<i>S. brevifolia</i>, Hr., <i>S. disticha</i>, Hr., -and <i>S. Nordenskiöldi</i>, Hr.). These have been met with in -Greenland and Spitzbergen, and one of them has lately -been found in the United States. Three other species, in -addition to these, have been described by Lesquereux, -which appear to belong to the group of the <i>S. Langsdorfii</i>, -viz., <i>S. longifolia</i>, Lesq., <i>S. angustifolia</i>, and <i>S. acuminata</i>, -Lesq. Several species also occur in the Cretaceous -and Eocene of Canada.</p> - -<p>These species thus answer to the living <i>Sequoia sempervirens</i>; -but we can also point to Tertiary representatives -<span class="pagenum"><a name="Page_185" id="Page_185">« 185 »</a></span> -of the <i>S. gigantea</i>. Their leases are stiff and -sharp-pointed, are thinly set round the branches, and lie -forward in the same way: the egg-shaped cones are in -some cases similar.</p> - -<p>There are, however, in the early Tertiary six species, -which fill up the gap between <i>S. sempervirens</i> and <i>S. -gigantea</i>. They are the <i>S. Couttsiæ</i>, <i>S. affinis</i>, Lesq., -<i>S. imbricata</i>, Hr., <i>S. sibirica</i>, Hr., <i>S. Heerii</i>, Lesq., and -<i>S. biformis</i>, Lesq. Of these, <i>S. Couttsiæ</i>, Hr., is the -most common and most important species. It has short -leaves, lying along the branch, like <i>S. gigantea</i>, and -small, round cones, like <i>S. Langsdorfii</i> and <i>sempervirens</i>. -Bovey Tracey in Devonshire has afforded splendid specimens -of cones, seeds, and twigs, which have been described -in the “Philosophical Transactions.” More lately, Count -Saporta has described specimens of cones and twigs from -Armissan. Specimens of this species have also been found -in the older Tertiary of Greenland, so that it must have -had a wide range. It is very like to the American <i>S. -affinis</i>, Lesq.</p> - -<p>In the Tertiary there have been already found fourteen -well-marked species, which thus include representatives -of the two living types, <i>S. sempervirens</i> and <i>S. gigantea</i>.</p> - -<p>We can follow this genus still further back. If we go -back to the Cretaceous age, we find ten species, of which -five occur in the Urgon of the Lower Cretaceous, two in -the Middle, and three in the Upper Cretaceous. Among -these, the Lower Cretaceous exhibits the two types of the -Sequoia sempervirens and <i>S. gigantea</i>. To the former -the <i>S. Smithiana</i> answers, and to the latter, the <i>Reichenbachii</i>, -Gein. The <i>S. Smithiana</i> stands indeed uncommonly -near the <i>S. Langsdorfii</i>, both in the appearance of -the leaves on the twigs and in the shape of the cones. -These are, however, smaller, and the leaves do not become -narrower toward the base. The <i>S. pectina</i>, Hr., of the -Upper Cretaceous, has its leaves arranged in two rows, and -<span class="pagenum"><a name="Page_186" id="Page_186">« 186 »</a></span> -presents a similar appearance. The <i>S. Reichenbachii</i> is a -type more distinct from those now living and those in -the Tertiary. It has indeed stiff, pointed leaves, lying -forward, but they are arcuate, and the cones are smaller. -This tree has been known for a long time, and it serves -in the Cretaceous as a guiding star, which we can follow -from the Urgonian of the Lower Cretaceous up to the -Cenomanian. It is known in France, Belgium, Bohemia, -Saxony, Greenland, and Spitzbergen (also in Canada and -the United States). It has been placed in another genus—Geinitzia—but -we can recognise, by the help of the -cones, that it belongs to Sequoia.</p> - -<p>Below this, there is found in Greenland a nearly related -species, the <i>S. ambigua</i>, Hr., of which the leaves -are shorter and broader, and the cones round and somewhat -smaller.</p> - -<p>The connecting link between <i>S. Smithiana</i> and <i>Reichenbachii</i> -is formed by <i>S. subulata</i>, Hr., and <i>S. rigida</i>, -Hr., and three species (<i>S. gracilis</i>, Hr., <i>S. fastigiata</i> and -<i>S. Gardneriana</i>, Carr.), with leaves lying closely along the -branch, and which come very near to the Tertiary species -<i>S. Couttsiæ</i>. We have therefore in the Cretaceous quite -an array of species, which fill up the gap between the <i>S. -sempervirens</i> and <i>gigantea</i>, and show us that the genus -Sequoia had already attained a great development in the -Cretaceous. This was still greater in the Tertiary, in -which it also reached its maximum of geographical distribution. -Into the present world the two extremes of -the genus have alone continued; the numerous species -forming its main body have fallen out in the Tertiary.</p> - -<p>If we look still further back, we find in the Jura a -great number of conifers, and, among them, we meet in -the genus Pinus with a type which is highly developed, -and which still survives; but for Sequoia we have till now -looked in vain, so that for the present we can not place -the rise of the genus lower than the Urgonian of the Cretaceous, -<span class="pagenum"><a name="Page_187" id="Page_187">« 187 »</a></span> -however remarkable we may think it that in that -period it should have developed into so many species; and -it is still more surprising that two species already make -their appearance which approach so near to the living -<i>Sequoia sempervirens</i> and <i>S. gigantea</i>.</p> - -<p>Altogether, we have become acquainted, up to the -present time, with twenty-six species of Sequoia. Fourteen -of these species are found in the Arctic zone, and -have been described and figured in the “Fossil Flora -of the Arctic Regions.” Sequoia has been recognised by -Ettingshausen even in Australia, but there in the Eocene.</p> - -<p>This is, perhaps, the most remarkable record in the -whole history of vegetation. The Sequoias are the giants -of the conifers, the grandest representatives of the family, -and the fact that, after spreading over the whole northern -hemisphere and attaining to more than twenty specific -forms, their decaying remnant should now be confined to -one limited region in western America and to two species -constitutes a sad memento of departed greatness.<a name="FNanchor_DJ_114" id="FNanchor_DJ_114"></a><a href="#Footnote_DJ_114" class="fnanchor">[DJ]</a> The -small remnant of <i>S. gigantea</i> still, however, towers above -all competitors, as eminently the “big trees ”; but, had -they and the allied species failed to escape the Tertiary -continental submergences and the disasters of the glacial -period, this grand genus would have been to us an extinct -type. In like manner the survival of the single gingko -of eastern Asia alone enables us to understand that -great series of taxine trees with fern-like leaves of which -it is the sole representative.</p> - -<div class="footnote"> - -<p><a name="Footnote_DJ_114" id="Footnote_DJ_114"></a><a href="#FNanchor_DJ_114"><span class="label">[DJ]</span></a> The writer has shown that much of the material of the great lignite -beds of the Canadian Northwest consists of wood of Sequoia of both the -modern types.</p></div> - -<p>Besides these peculiar and now rare forms, we have in -the Mesozoic many others related closely to existing yews, -cypresses, pines, and spruces, so that the conifers were -probably in greater abundance and variety than they are -at this day.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_188" id="Page_188">« 188 »</a></span></p> - -<p>In this period, also, we find the earliest representatives -of the endogenous plants. It is true that some plants -found in the coal-formation have been doubtfully referred -to these, but the earliest certain examples would -seem to be some bamboo-like and screw-pine-like plants -occurring in the Jurassic rocks. Some of these are, it is -true, doubtful forms, but of others there seems to be no -question. The modern <i>Pandanus</i> or screw-pine of the -tropical regions, which is not a pine, however, but a -humble relation of the palms, is a stiffly branching tree, -of a candelabra-like form, and with tufts of long leaves -on its branches, and nuts or great hard berries for fruit, -borne sometimes in large masses, and so protected as to -admit of their drifting uninjured on the sea. The stems -are supported by masses of aërial roots like those which -strengthen the stems of tree-ferns. These structures and -habits of growth fit the Pandanus for its especial habitat -on the shores of tropical islands, to which its masses of -nuts are drifted by the winds and currents, and on whose -shores it can establish itself by the aid of its aërial roots.</p> - -<p>Some plants referred to the cycads have proved veritable -botanical puzzles. One of these, the <i>Williamsonia -gigas</i> of the English oölite, originally discovered by my -friend Dr. Williamson, and named by him <i>Zamia gigas</i>, a -very tall and beautiful species, found in rocks of this age in -various parts of Europe, has been claimed by Saporta for -the Endogens, as a plant allied to <i>Pandanus</i>. Some -other botanists have supposed the flowers and fruits to be -parasites on other plants, like the modern <i>Rafflesia</i> of -Sumatra, but it is possible that after all it may prove to -have been an aberrant cycad.</p> - -<p>The tree-palms are not found earlier than the Middle -Cretaceous, where we shall notice them in the next chapter. -In like manner, though a few Angiosperms occur -in rocks believed to be Lower or Lower Middle Cretaceous -in Greenland and the northwest territory of Canada, and -<span class="pagenum"><a name="Page_189" id="Page_189">« 189 »</a></span> -in Virginia, these are merely precursors of those of the -Upper Cretaceous, and are not sufficient to redeem the -earlier Cretaceous from being a period of pines and cycads.</p> - -<p>On the whole, this early Mesozoic flora, so far as -known to us, has a monotonous and mean appearance. -It no doubt formed vast forests of tall pines, perhaps resembling -the giant Sequoias of California; but they must -for the most part have been dark and dismal woods, -probably tenanted by few forms of life, for the great reptiles -of this age must have preferred the open and sunny -coasts, and many of them dwelt in the waters. Still we -must not be too sure of this. The berries and nuts of the -numerous yews and cycads were capable of affording -much food. We know that in this age there were many -great herbivorous reptiles, like <i>Iguanodon</i> and <i>Hadrosaurus</i>, -some of them fitted by their structure to feed upon -the leaves and fruits of trees. There were also several -kinds of small herbivorous mammals, and much insect -life, and it is likely that few of the inhabitants of the -Mesozoic woods have been preserved as fossils. We may -yet have much to learn of the inhabitants of these forests -of ferns, cycads, and pines. We must not forget in this -connection that in the present day there are large islands, -like New Zealand, destitute of mammalia, and having a -flora comparable with that of the Mesozoic in the northern -hemisphere, though more varied. We have also the remarkable -example of Australia, with a much richer flora -than that of the early Mesozoic, yet inhabited only by -non-placental mammals, like those of the Mesozoic.</p> - -<p>The principal legacy that the Mesozoic woods have -handed down to our time is in some beds of coal, locally -important, but of far less extent than those of the Carboniferous -period. Still, in America, the Richmond coal-field -in Virginia is of this age, and so are the anthracite -beds of the Queen Charlotte Islands, on the west coast of -Canada, and the coal of Brora in Sutherlandshire. Valuable -<span class="pagenum"><a name="Page_190" id="Page_190">« 190 »</a></span> -beds of coal, probably of this age, also exist in China, -India, and South Africa; and jet, which is so extensively -used for ornament, is principally derived from the carbonised -remains of the old Mesozoic pines.</p> - -<p>In the next chapter we have to study a revolution in -vegetable life most striking and unique, in the advent of -the forest-trees of strictly modern types.</p> - -<hr class="tb" /> - - -<p class="caption3">NOTE TO CHAPTER V.</p> - -<p><span class="smcap">I append</span> to this chapter a table showing the plant-bearing series -of the Cretaceous and Laramie of North America, from a paper in -“Trans. R. S. C,” 1885, which see for further details:</p> - -<p class="center">(<span class="smcap">In Descending Order.</span>)</p> - -<table summary="plants"> -<tr> - <td class="bdt bdb center">Periods.</td> - <td class="bdt bdb bdl center">Floras and sub-floras.</td> - <td class="bdt bdb bdl center" colspan="2">References.</td> -</tr> -<tr> - <td class="bdb tdl">Transition<br /> Eocene to<br /> Cretaceous.</td> - <td class="bdb bdl tdl">Upper Laramie or Porcupine Hill. Fort Union<br /> group, U. S. territory.</td> - <td class="bdb bdl tdl"><img src="images/bracel_60.png" width="11" height="60" alt="" /></td> - <td class="bdb tdl">Platanus beds of Souris River and<br /> Calgary. Report of Geol. Survey<br /> of Canada for 1879, and Memoir of 1885.</td> -</tr> -<tr> - <td class="bdb tdl" rowspan="6">Upper<br /> Cretaceous<br /> (Danian and<br /> Senonian).</td> - <td class="bdl tdl">Middle Laramie or Willow Creek beds.</td> - <td class="bdl"></td> - <td></td> -</tr> -<tr> - <td class="bdl tdl">Lower Laramie or St. Mary River.</td> - <td class="bdl tdl"><img src="images/bracel_60.png" width="11" height="60" alt="" /></td> - <td class="tdl">Lemna and Pistia beds of bad lands<br /> of 49th parallel, Red Deer River,<br /> &c., with lignites. Report 49th<br /> Parallel and Memoir of 1885.</td> -</tr> -<tr> - <td class="bdl tdl">Fox Hill series</td> - <td class="bdl tdl" colspan="2">Marine.</td> -</tr> -<tr> - <td class="bdl tdl">Fort Pierre series</td> - <td class="bdl tdl" colspan="2">Marine.</td> -</tr> -<tr> -<td class="bdl tdl">Belly River</td> - <td class="bdl tdl"><img src="images/bracel_60.png" width="11" height="60" alt="" /></td> - <td class="tdl">Sequoia and Brasenia beds of S.<br /> Saskatchewan, Belly River, &c.<br /> with lignites. Memoir of 1885.</td> -</tr> -<tr> - <td class="bdl bdb tdl">Coal measures of Nanaimo,<br /> B.C., probably here.</td> - <td class="bdl bdb tdl"><img src="images/bracel_60.png" width="11" height="60" alt="" /></td> - <td class="bdb tdl">Memoir of 1883. Many dicotyledons,<br /> palms, &c.</td> -</tr> -<tr> - <td class="bdb tdl" rowspan="2">Middle<br /> Cretaceous<br /> (Turonian and<br /> Cenomanian).</td> - <td class="bdl tdl">Dunvegan series of Peace<br /> River. Dakota group,<br /> U. S. Amboy clays, U. S.</td> - <td class="bdl tdl"><img src="images/bracel_60.png" width="11" height="60" alt="" /></td> - <td class="tdl">Memoir of 1883. Many dicotyledons,<br /> cycads, &c.</td> -</tr> -<tr> - <td class="bdb bdl tdl">Mill Creek beds of Rocky Mountains.</td> - <td class="bdb bdl tdl"><img src="images/bracel_60.png" width="11" height="60" alt="" /></td> - <td class="bdb tdl">Dicotyledonous leaves, similar to<br /> Dakota group of the U. S.<br /> Memoir of 1885.</td> -</tr> -<tr> - <td class="bdb tdl" rowspan="2">Lower<br /> Cretaceous<br /> (Neocomian.&c).</td> - <td class="bdl tdl">Suskwa River beds and Queen Charlotte Island<br /> coal series. Intermediate<br /> beds of Rocky<br /> Mountains. Potomac<br /> series of Virginia.</td> - <td class="bdl tdl"><img src="images/bracel_60.png" width="11" height="60" alt="" /></td> - <td class="tdl">Cycads, pines, a few dicotyledons.<br /> Report Geol.Survey. Memoir of 1885.</td> -</tr> -<tr> - <td class="bdb bdl tdl">Kootanie series of Rocky<br /> Mountains.</td> - <td class="bdb bdl tdl"><img src="images/bracel_60.png" width="11" height="60" alt="" /></td> - <td class="bdb tdl">Cycads, pines, and ferns. Memoir<br /> of 1885.</td> -</tr> -</table> - - - -<p><span class="pagenum"><a name="Page_191" id="Page_191">« 191 »</a></span></p> - - -<p class="caption2"><a name="CHAPTER_VI" id="CHAPTER_VI">CHAPTER VI.</a></p> - -<p class="caption3">THE REIGN OF ANGIOSPERMS IN THE LATER CRETACEOUS AND KAINOZOIC.</p> - - -<div class="fig_right" style="width: 179px;"> -<a name="fig68" id="fig68"></a> -<img src="images/fig68.png" width="179" height="251" alt="" /> -<div class="fig_caption">Fig. 68.—<i>Populus primæva</i>, -Heer. Cretaceous, of -Greenland. One of the -oldest known Angiosperms.</div> -</div> - -<p><span class="smcap">It</span> is a remarkable fact in geological chronology that -the culmination of the vegetable kingdom antedates that -of the animal. The placental mammals, the highest -group of the animal kingdom, are not known till the beginning -of the Eocene Tertiary. The dicotyledonous -Angiosperms, which correspond -to them in the vegetable kingdom, -occur far earlier—in the -beginning of the Upper Cretaceous -or close of the Lower -Cretaceous. The reign of cycads -and pines holds throughout -the Lower Cretaceous, but -at the close of that age there is -a sudden incoming of the higher -plants, and a proportionate -decrease, more especially of the -cycads.</p> - -<p>I have already referred to the -angiospermous wood supposed -to be Devonian, but I fear to -rest any conclusion on this isolated -fact. Beyond this, the earliest indications of -plants of this class have been found in the Lower -Cretaceous. Many years ago Heer described and figured -the leaves of a poplar (<i>Populus primæva</i>) from -<span class="pagenum"><a name="Page_192" id="Page_192">« 192 »</a></span> -the supposed Lower Cretaceous of Komé, in Greenland -(<a href="#fig68">Fig. 68</a>). Two species, a <i>Sterculia</i> and a <i>Laurus</i> or -<i>Salix</i>, occur among fossils described by me in the upper -part of the Kootanie series of the Rocky Mountains, and -Fontaine has recently found in the Potomac group of -Virginia—believed to be of Neocomian age—several angiospermous -species (<i>Sassafras</i>, <i>Menispermites</i>, <i>Sapindus</i>, -<i>Aralia</i>, <i>Populus</i>, &c.) mixed with a rich flora of cycads -and pines. These are the early forerunners of the modern -angiospermous flora; but so far as known they do -not occur below the Cretaceous, and in its lower portions -only very rarely. When, however, we ascend into the -Upper Cretaceous, whether of Europe or America, there -is a remarkable incoming of the higher plants, under -generic forms similar to those now existing. This is, in -truth, the advent of the modern flora of the temperate -regions of the earth. A very interesting tabular view of -its early distribution is given by Ward, in the “American -Journal of Science” for 1884, of which the following is a -synopsis, with slight emendations. I may add that the -new discoveries made since 1884 would probably tend to -increase the proportionate number of dicotyledons in the -newer groups.</p> - -<p class="center smcap">Dicotyledonous Trees in the Cretaceous.</p> - -<table summary="trees"> -<tr> - <td class="tdl"><i>Upper Senonian</i><br /> - (Fox Hill group of America.)</td> - <td class="tdr vtop">179</td> - <td class="tdl vtop">species.</td> -</tr> -<tr> - <td class="tdl"><i>Lower Senonian</i><br /> - Upper white chalk of Europe; Fort Pierre<br /> - group of America; coal-measures of Nanaimo?</td> - <td class="tdr vtop">81</td> - <td class="tdl vtop">species.</td> -</tr> -<tr> - <td class="tdl"><i>Turonian</i><br /> - Lower white chalk; New Jersey marls;<br /> - Belly R. group.</td> - <td class="tdr vtop">20</td> - <td class="tdl vtop">species.</td> -</tr> -<tr> - <td class="tdl"><i>Cenomanian.</i><br /> - (Chalk-marl, greensand, and Gault, Niobrara<br /> - and Dakota groups of America); Dunvegan<br /> - group of Canada; Amboy clays of New Jersey.</td> - <td class="tdr vtop">357</td> - <td class="tdl vtop">species.</td> -</tr> -<tr> - <td class="tdl"><i>Neocomian</i><br /> - (Lower greensand and Speeton clay, Wealden<br /> - and Hastings sands, Kootanie and Queen<br /> - Charlotte groups of Canada.)</td> - <td class="tdr vtop">20</td> - <td class="tdl vtop">species.<a name="FNanchor_DK_115" id="FNanchor_DK_115"></a><a href="#Footnote_DK_115" class="fnanchor">[DK]</a></td> -</tr> -</table> - -<div class="footnote"> - -<p><a name="Footnote_DK_115" id="Footnote_DK_115"></a><a href="#FNanchor_DK_115"><span class="label">[DK]</span></a> Including an estimate of Fontaine’s undescribed species.</p> - -<p><span class="pagenum"><a name="Page_193" id="Page_193">« 193 »</a></span></p></div> - -<p>Thus we have a great and sudden inswarming of the -higher plants of modern types at the close of the Lower -Cretaceous. In relation to this, Saporta, one of the most -enthusiastic of evolutionists, is struck by this phenomenon -of the sudden appearance of so many forms, and -some of them the most highly differentiated of dicotyledonous -plants. The early stages of their evolution may, -he thinks, have been obscure and as yet unobserved, or -they may have taken place in some separate region, or -mother country as yet undiscovered, or they may have -been produced by a rapid and unusual multiplication of -flower-haunting insects! Or it is even conceivable that -the apparently sudden elevation of plants may have been -due to causes still unknown. This last seems, indeed, -the only certain inference in the case, since, as Saporta -proceeds to say in conclusion: “Whatever hypothesis -one may prefer, the fact of the rapid multiplication of -dicotyledons, and of their simultaneous appearance in -a great number of places in the northern hemisphere at -the beginning of the Cenomanian epoch, cannot be disputed.”<a name="FNanchor_DL_116" id="FNanchor_DL_116"></a><a href="#Footnote_DL_116" class="fnanchor">[DL]</a></p> - -<div class="footnote"> - -<p><a name="Footnote_DL_116" id="Footnote_DL_116"></a><a href="#FNanchor_DL_116"><span class="label">[DL]</span></a> “Monde des Plantes,” p. 197.</p></div> - -<p>The leaves described by Heer, from the Middle Cretaceous -of Greenland, are those of a poplar (<i>P. primæva</i>). -Those which I have described from a corresponding horizon -in the Rocky Mountains are a <i>Sterculites</i> (<i>S. vetustula</i>), -probably allied to the mallows, and an elongated -leaf, <i>Laurophyllum</i> (<i>L. crassinerve</i>) (<a href="#fig69">Fig. 69</a>), which -may, however, have belonged to a willow rather than a -laurel. These are certainly older than the Dakota group -<span class="pagenum"><a name="Page_194" id="Page_194">« 194 »</a></span> -of the United States and the corresponding formations -in Canada. On the eastern side of the American continent, -in Virginia, the Potomac series is supposed to be -of Lower Cretaceous age, -and here Fontaine, as -already stated, has found -an abundant flora of cycads, -conifers, and ferns, -with a few angiospermous -leaves, which have -not yet been described.</p> - -<div class="fig_center" style="width: 233px;"> -<a name="fig69" id="fig69"></a> -<img src="images/fig69.png" width="233" height="255" alt="" /> -<div class="fig_caption">Fig. 69.—<i>Stercalia</i> and <i>Laurophyllum</i> -or Salix, the oldest Angiosperms -Known in the Cretaceous of Canada.</div> -</div> - -<p>In the Canadian Rocky -Mountains, a few hundreds -of feet above the -beds holding the beforementioned -species, are the -shales of the Mill Creek -series, rich in many species -of dicotyledonous -leaves, and corresponding in age with the Dakota group, -whose fossils have been so well described, first by Heer -and Capellini, and afterward by Lesquereux. We may -take this Dakota group and the quader-sand stone of Germany -as types of the plant-bearing Cenomanian, and may -notice the forms occurring in them.</p> - -<p>In the first place, we recognise here the successors of -our old friends, the ferns and the pines, the latter represented -by such genera as <i>Taxites</i>, <i>Sequoia</i>, <i>Glyptostrobus</i>, -<i>Gingko</i>, and even <i>Pinus</i> itself. We also have a few -cycads, but not so dominant as in the previous ages. -The fan-palms are well represented, both in America and -in the corresponding series in Europe, especially by the -genus <i>Sabal</i>, which is the characteristic American type of -fan-palm, and there is one genus which Saporta regards -as intermediate between the fan-palms and the pinnately -leaved species. There are also many fragments of stems -<span class="pagenum"><a name="Page_195" id="Page_195">« 195 »</a></span> -and leaves of carices and grasses, so that these plants, now -so important to the nourishment of man and his companion -animals, were already represented.</p> - -<div class="fig_right" style="width: 440px;"> -<a name="fig70" id="fig70"></a> -<img src="images/fig70.png" width="440" height="506" alt="" /> -<div class="fig_caption">Fig. 70.—Vegetation of Later Cretaceous. Exogens and palms. (After -Saporta.)</div> -</div> - -<p>But the great feature of the time was its dicotyledonous -forests, and I have only to enumerate the genera -supposed to be represented in order to show the richness -of the time in plants of this type. It may be necessary -to explain here that the generic names used are mostly -based on leaves, and consequently cannot be held as being -<span class="pagenum"><a name="Page_196" id="Page_196">« 196 »</a></span> -absolutely certain, since we know that at present one -genus may have considerable variety in its leaves, and, on -the other hand, that plants of different genera may be -very much alike in their foliage. There is, however, undoubtedly -a likeness in plan or type of structure in leaves -of closely allied plants, and, therefore, if judiciously -studied, they can be determined with at least approximate -certainty.<a name="FNanchor_DM_117" id="FNanchor_DM_117"></a><a href="#Footnote_DM_117" class="fnanchor">[DM]</a> More especially we can attain to much -certainty when the fruits as well as the leaves are found, -and when we can obtain specimens of the wood, showing -its structure. Such corroboration is not wanting, though -unfortunately the leaves of trees are generally found -drifted away from the other organs once connected with -them. In my own experience, however, I have often -found determinations of the leaves of trees confirmed by -the discovery of their fruits or of the structure of their -stems. Thus, in the rich cretaceous plant-beds of the -Dunvegan series we have beech-nuts associated in the -same beds with leaves referred to <i>Fagus</i>. In the Laramie -beds I determined many years ago nuts of the <i>Trapa</i> -or water-chestnut, and subsequently Lesquereux found, -in beds in the United States, leaves which he referred to -the same genus. Later, I found in collections made on -the Red Deer River of Canada my fruits and Lesquereux’s -leaves on the same slab. The presence of trees of the -genera <i>Carya</i> and <i>Juglans</i> in the same formation was inferred -from their leaves, and specimens have since been -obtained of silicified wood, with the microscopic structure -of the modern butternut. Still we are willing to admit -that determinations from leaves alone are liable to doubt.</p> - -<div class="footnote"> - -<p><a name="Footnote_DM_117" id="Footnote_DM_117"></a><a href="#FNanchor_DM_117"><span class="label">[DM]</span></a> Great allowance has to be made for the variability of leaves of the -same species. The modern hazel (<i>C. rostrata</i>) is a case in point. Its -leaves, from different parts of the same plant, are so dissimilar in form -and size that they might readily be regarded as of different species.</p></div> - -<p>In the matter of names of fossil leaves, I sympathise -very strongly with Dr. Nathorst, of Stockholm, in his -<span class="pagenum"><a name="Page_197" id="Page_197">« 197 »</a></span> -objection to the use of modern generic names for mere -leaves, and would be quite content to adopt some non-committal -termination, as that of “<i>phyllum</i>” or “<i>ites</i>” -suggested by him. I feel, however, that almost as much -is taken for granted if a plant is called Corylophyllum or -<i>Corylites</i>, as if called <i>Corylus</i>. In either case a judgment -is expressed as to its affinities, which if wrong under the -one term is wrong under the other; and after so much has -been done by so many eminent botanists, it seems inexpedient -to change the whole nomenclature for so small -and questionable an advantage. I wish it, however, to -be distinctly understood that plants catalogued on the -evidence of leaves alone are for the most part referred to -certain genera on grounds necessarily imperfect, and -their names are therefore subject to correction, as new -facts may be obtained.</p> - -<p>The more noteworthy modern genera included in the -Dakota flora, as catalogued by Lesquereux, are the following: -<i>Liquidambar</i>, the sweet-gum, is represented both in -America and Europe, the leaves resembling those of the -modern species, but with entire edges, which seems to be -a common peculiarity of Cretaceous foliage.<a name="FNanchor_DN_118" id="FNanchor_DN_118"></a><a href="#Footnote_DN_118" class="fnanchor">[DN]</a> <i>Populus</i> -(poplar), as already stated, appears very early in Greenland, -and continues with increasing number of species -throughout the Cretaceous and Tertiary. <i>Salix</i> (willow) -appears only a little later and continues. Of the family -<i>Cupuliferæ</i> we have <i>Fagus</i> (beech), <i>Quercus</i> (oak), and -<i>Castanea</i> (chestnut), which appear together in the Dakota -group and its equivalents. Fruits of some of the species -are known, and also wood showing structure. -<span class="pagenum"><a name="Page_198" id="Page_198">« 198 »</a></span><i>Betula</i> -(birch) is represented by a few species, and specimens of -its peculiar bark are also common. <i>Alnus</i> (alder) appears -in one species at least. The genus Plat anus (<a href="#fig71">Fig. 71</a>), -that of the plane-trees, represented at present by one -European and one American species, has several species -in the Cretaceous, though the plane-trees seem to culminate -in the early part of the succeeding Eocene, where -there are several species with immense leaves. The large -<span class="pagenum"><a name="Page_199" id="Page_199">« 199 »</a></span> -leaves, known as <i>Credneria</i>, found in the Cenomanian of -Europe, and those called <i>Protophyllum</i> (<a href="#fig72">Fig. 72</a>) in -America, appear to be nearer to the plane-trees than to -any others, though representing an extinct type. The -laurels are represented in this age, and the American -genus Sassafras, which has now only one species, has not -one merely but several species in the Cretaceous. <i>Diospyros</i>, -the persimmon-tree, was also a Cretaceous genus.</p> - -<div class="footnote"> - -<p><a name="Footnote_DN_118" id="Footnote_DN_118"></a><a href="#FNanchor_DN_118"><span class="label">[DN]</span></a> With reference to this, something may be learned from the leaves -of modern trees. In these, young shoots have leaves often less toothed -and serrated than those of the adult tree. A remarkable instance is the -<i>Populus grandidentatus</i> of America, the young shoots of which have entire -leaves, quite unlike except in venation those of the parent tree, and -having an aspect very similar to that of the Cretaceous poplars.</p></div> - -<div class="fig_center" style="width: 384px;"> -<a name="fig71" id="fig71"></a> -<img src="images/fig71.png" width="384" height="525" alt="" /> -<div class="fig_caption">Fig. 71.—<i>Platanus nobilis</i>, Newberry, variety <i>basilobata</i>. Laramie. -Much reduced.</div> -</div> - -<div class="fig_center" style="width: 375px;"> -<a name="fig72" id="fig72"></a> -<img src="images/fig72.png" width="375" height="320" alt="" /> -<div class="fig_caption">Fig. 72.—<i>Protophyllum boreale</i>, Dawson, reduced. Upper Cretaceous, -Canada.</div> -</div> - -<p>The single species of the beautiful <i>Liriodendron</i>, or tulip-tree, -is a remnant of a genus which had several Cretaceous -species (Figs. <a href="#fig74">74</a>, <a href="#fig75">75</a>). The magnolias, still well represented -in the American flora, were equally plentiful in the -Cretaceous (<a href="#fig73">Fig. 73</a>). The walnut family were well represented -by species of <i>Juglans</i> (butternut) and <i>Carya</i>, or -hickory. In all, no less than forty-eight genera are present -belonging to at least twenty-five families, running -through the whole range of the dicotyledonous exogens. -This is a remarkable result, indicating a sudden profusion -<span class="pagenum"><a name="Page_200" id="Page_200">« 200 »</a></span> -of forms of these plants of a very striking character. It -is further to be observed that some of the genera have -many species in the Cretaceous -and dwindle toward -the modern. In -others the reverse is the -case—they have expanded -in modern times. In -a number there seems to -have been little change.</p> - -<div class="fig_center" style="width: 242px;"> -<a name="fig73" id="fig73"></a> -<img src="images/fig73.png" width="242" height="668" alt="" /> -<div class="fig_caption">Fig. 73.—<i>Magnolia magnifica</i>, Dawson, -reduced. Upper Cretaceous, Canada.</div> -</div> - -<p>Dr. Newberry has -given, in the “Bulletin -of the Torrey Botanical -Club” an interesting -<i>résumé</i> of the history -of the beautiful <i>Liriodendron</i>, -or tulip-tree, -which may be taken as -an example of a genus -which has gone down -in importance in the -course of its geological -history.</p> - -<p>"The genus <i>Liriodendron</i>, -as all botanists -know, is represented -in the present flora -by a single species, ‘the -tulip-tree’ which is confined -to eastern America, -but grows over all -the area lying between -the Lakes and the Gulf, -the Mississippi and the -Atlantic. It is a magnificent -tree, on the -<span class="pagenum"><a name="Page_201" id="Page_201">« 201 »</a></span> -whole, the finest in our forests. Its cylindrical trunk, -sometimes ten feet in diameter, carries it beyond all its -associates in size, while the beauty of its glossy, lyre-shaped -leaves and tulip-like -flowers is only surpassed -by the flowers and -foliage of its first cousin, -<i>Magnolia grandiflora</i>. -That a plant so splendid -should stand quite alone in the vegetation of the present -day excited the wonder of the earlier botanists, but the -sassafras, the sweet-gum, and the great Sequoias of the far -West afford similar examples of isolation, and the latter -are still more striking illustrations of solitary grandeur." -(Figs. <a href="#fig74">74</a> and <a href="#fig75">75</a>.)</p> - -<div class="fig_right" style="width: 133px;"> -<a name="fig74" id="fig74"></a> -<img src="images/fig74.png" width="133" height="195" alt="" /> -<div class="fig_caption">Fig. 74.—<i>Liriodendron Meekii</i>, -Heer. (After Lesquereux.)</div> -</div> - -<div class="fig_right" style="width: 241px;"> -<a name="fig75" id="fig75"></a> -<img src="images/fig75.png" width="241" height="308" alt="" /> -<div class="fig_caption">Fig. 75.—<i>Liriodendron primævum</i>, -Newberry. (After Newberry.)</div> -</div> - -<p>"Three species of <i>Liriodendron</i> are indicated by leaves -found in the Amboy clays—Middle Cretaceous—of New -Jersey, and others have been obtained from the Dakota -group in the West, and from the Upper Cretaceous strata -of Greenland. Though differing considerably among -themselves in size and form, all these have the deep sinus -of the upper extremity so characteristic of the genus, -and the nervation is also essentially the same. Hence, -we must conclude that the genus <i>Liriodendron</i>, now represented -<span class="pagenum"><a name="Page_202" id="Page_202">« 202 »</a></span> -by a single species, was in the Cretaceous age -much more largely developed, having many species, and -those scattered throughout many lands. In the Tertiary -age the genus continued to exist, but the species seem to -have been reduced to one, which is hardly to be distinguished -from that now living. In many parts of Europe -leaves of the tulip-tree have been found, and it extended -as far south as Italy. Its presence there was first made -known by Unger, in his ‘Synopsis,’ page 232, and in his -‘Genera et Species,’ page 443, where he describes it -under the name of <i>Liriodendron procaccinii</i>. The genus -has also been noticed in Europe by Massalongo, Heer, and -Ettingshausen, and three species have been distinguished. -All these are, however, so much like the living species -that they should probably be united with it. We here -have a striking illustration of the wide distribution of a -species which has retained its characters both of fruit and -leaf quite unchanged through long migrations and an -enormous lapse of time.</p> - -<p>“In Europe the tulip-tree, like many of its American -associates, seems to have been destroyed by the cold of -the Ice period, the Mediterranean cutting off its retreat, -but in America it migrated southward over the southern -extension of the continent and returned northward again -with the amelioration of the climate.”</p> - -<p>Leaves of <i>Liriodendron</i> have been recognised in the -Cretaceous of Greenland, though it is now a tree of -the warm temperate region, and Lesquereux describes -several species from the Dakota group. But the genus -has not yet been recognised in the Laramie or in the -Upper Cretaceous of British Columbia. In the paper -above quoted, Newberry describes three new species -from the Amboy clays, one of which he considers identical -with a Greenland form referred by Heer to <i>L. -Meekii</i> of the Dakota group. Thus, if all Lesquereux’s -species are to be accepted, the genus begins -<span class="pagenum"><a name="Page_203" id="Page_203">« 203 »</a></span> -in the Middle Cretaceous with at least nine American -species.</p> - -<p>In New Jersey the Amboy clays are referred to the -same age with the Dakota beds of the West. In these -Dr. Newberry has found a rich flora, including many -angiosperms. The following is condensed from a preliminary -notice in the “Bulletin of the Torrey Botanical -Club”:<a name="FNanchor_DO_119" id="FNanchor_DO_119"></a><a href="#Footnote_DO_119" class="fnanchor">[DO]</a></p> - -<div class="footnote"> - -<p><a name="Footnote_DO_119" id="Footnote_DO_119"></a><a href="#FNanchor_DO_119"><span class="label">[DO]</span></a> March, 1886.</p></div> - -<p>"The flora of the Amboy clays is closely related to -that of the Dakota group—most of the genera and some -of the species being identical—so that we may conclude -they were nearly contemporaneous, though the absence in -New Jersey of the Fort Benton and Niobrara groups of -the upper Missouri and the apparent synchronism of the -New Jersey marls and the Pierre group indicate that the -Dakota is a little the older.</p> - -<p>“At least one-third of the species of the Amboy clays -seem to be identical with leaves found in the Upper Cretaceous -clays of Greenland and Aachen (Aix la Chapelle), -which not only indicates a chronological parallelism, but -shows a remarkable and unexpected similarity in the vegetation -of these widely separated countries in the middle -and last half of the Cretaceous age. The botanical character -of the flora of the Amboy clays will be seen from the -following brief synopsis:</p> - -<p>“<i>Algæ.</i>—A small and delicate form, allied to Chondrites.</p> - -<p>“<i>Ferns.</i>—Twelve species, generally similar and in -part identical with those described by Heer from the -Cretaceous beds of Greenland, and referred to the genera -<i>Dicksonia</i>, <i>Gleichenia</i>, and <i>Aspidium</i>.</p> - -<p>“<i>Cycads.</i>—Two species, probably identical with the -forms from Greenland described by Heer under the -names of <i>Podozamites marginatus</i> and <i>P. tenuinervis</i>.</p> - -<p><span class="pagenum"><a name="Page_204" id="Page_204">« 204 »</a></span></p> - -<p>“<i>Conifers.</i>—Fourteen species, belonging to the genera -<i>Moriconia</i>, <i>Brachyphyllum</i>, <i>Cunninghamites</i>, <i>Pinus</i>, <i>Sequoia</i>, -and others referred by Heer to <i>Juniperus</i>, <i>Libocedrus</i>, -<i>Frenelopsis</i>, <i>Thuya</i>, and <i>Dammara</i>. Of these, -the most abundant and most interesting are <i>Moriconia -cyclotoxon</i>—the most beautiful of conifers—and <i>Cunninghamites -elegans</i>, both of which occur in the Cretaceous -clays of Aachen, Prussia, and Patoot, Greenland. The -<i>Brachyphyllum</i> was a large and strong species, with imbricated -cones, eight inches in length.</p> - -<p>“The angiosperms form about seventy species, which -include three of <i>Magnolia</i>, four of <i>Liriodendron</i>, three or -four of <i>Salix</i>, three of <i>Celastrophyllum</i> (of which one is -identical with a Greenland species), one <i>Celastrus</i> (also -found in Greenland), four or five <i>Aralias</i>, two <i>Sassafras</i>, -one <i>Cinnamomum</i>, one <i>Hedera</i>; with leaves that are apparently -identical with those described by Heer as belonging -to <i>Andromeda</i>, <i>Cissites</i>, <i>Cornus</i>, <i>Dewalquea</i>, <i>Diospyros</i>, -<i>Eucalyptus</i>, <i>Ficus</i>, <i>Ilex</i>, <i>Juglans</i>, <i>Laurus</i>, <i>Menispermites</i>, -<i>Myrica</i>, <i>Myrsine</i>, <i>Prunus</i>, <i>Rhamnus</i>, and -others not yet determined.</p> - -<p>“Some of the Aralias had palmately-lobed leaves, -nearly a foot in diameter, and two of the tulip-trees -(<i>Liriodendron</i>) had leaves quite as large as those of the -living species. One of these had deeply lobed leaves, like -those of the white oak. Of the other, the leaves resembled -those of the recent tulip-tree, but were larger. Both -had the peculiar emargination and the nervation of <i>Liriodendron</i>.</p> - -<p>“Among the most interesting plants of the collection -are fine species of <i>Bauhinia</i> and <i>Hymenæa</i>. Of these, -the first is represented by a large number of leaves, some -of which are six or seven inches in diameter. They are -deeply bilobed, and have the peculiar and characteristic -form and nervation of the leaves of this genus. <i>Bauhinia</i> -is a leguminous genus allied to <i>Cercis</i>, and now inhabits -<span class="pagenum"><a name="Page_205" id="Page_205">« 205 »</a></span> -tropical and warm temperate climates in both -hemispheres. Only one species occurs in the United -States, <i>Bauhinia lunarioides</i>, Gray, found by Dr. Bigelow -on the Rio Grande.</p> - -<p>“<i>Hymenæa</i> is another of the leguminosæ, and inhabits -tropical America. A species of this genus has been -found in the Upper Cretaceous of France, but quite different -from the one before us, in which the leaves are -much larger, and the leaflets are united in a common -petiole, which is winged; this is a modification not found -in the living species, and one which brings it nearer to -<i>Bauhinia</i>.</p> - -<p>“But the most surprising discovery yet made is that -of a number of quite large helianthoid flowers, which I -have called <i>Palæanthus</i>. These are three to four inches -in diameter, and exhibit a scaly involucre, enclosing what -much resembles a fleshy receptacle with achenia. From -the border of this radiate a number of ray florets, one to -two inches in length, which are persistent and must have -been scarious, like those of <i>Helichrysum</i>. Though these -flowers so much resemble those of the compositæ, we are -not yet warranted in asserting that such is certainly their -character. In the Jurassic rocks of Europe and India -some flowers not very unlike these have been found, which -have been named <i>Williamsonia</i>, and referred to cycads by -Carruthers. A similar fossil has been found in the Cretaceous -rocks of Greenland, and named by Heer <i>Williamsonia -cretacea</i>, but he questions the reference of the genus -to the Cycadeæ, and agrees with Nathorst in considering -all the species of <i>Williamsonia</i> as parasitic flowers, allied -to <i>Brugmansia</i> or <i>Rafflesia</i>. The Marquis of Saporta -regards them as monocotyledons, similar to <i>Pandanus</i>. -More specimens of the flowers now exhibited will perhaps -prove—what we can now only regard as probable—that -the Compositæ, like the <i>Leguminosæ</i>, <i>Magnoliaceæ</i>, <i>Celastraceæ</i>, -and other highly organised plants, formed part -<span class="pagenum"><a name="Page_206" id="Page_206">« 206 »</a></span> -of the Cretaceous flora. No composite flowers have before -been found in the fossil state, and, as these are among -the most complex and specialised forms of florescence, it -has been supposed that they belonged only to the recent -epoch, where they were the result of a long series of formative -changes.”</p> - -<p>The above presents some interesting new types not -heretofore found in the Middle Cretaceous. More especially -the occurrence of large flowers of the composite -type presents a startling illustration of the early appearance -of a very elevated and complex form. Great interest -also attaches to these Amboy beds, as serving, with those -of Aix and Greenland, to show that the margins of the -Atlantic were occupied with a flora similar to that occurring -at the same time in the interior plateau of North -America and on the Pacific slope.</p> - -<p>The beds at Aix-la-Chapelle are, however, probably -somewhat newer than the Dakota or Amboy beds, and -correspond more nearly in age with those of the Cretaceous -coal-field of Vancouver Island, where there is a very -rich Upper Cretaceous flora, which I have noticed in detail -in the “Transactions of the Royal Society of Canada.”<a name="FNanchor_DP_120" id="FNanchor_DP_120"></a><a href="#Footnote_DP_120" class="fnanchor">[DP]</a> -In these Upper Cretaceous beds there are fan-palms -as far north at least as the latitude of 49°, indicating -a very mild climate at this period. This inference is -corroborated by the Upper Cretaceous flora of Atané and -Patoot in Greenland, as described by Heer.</p> - -<div class="footnote"> - -<p><a name="Footnote_DP_120" id="Footnote_DP_120"></a><a href="#FNanchor_DP_120"><span class="label">[DP]</span></a> Vol. ii., 1884.</p></div> - -<p>The dicotyledonous plants above referred to are trees -and shrubs. Of the herbaceous exogens of the period we -know less. Obviously their leaves are less likely to find -their way into aqueous deposits than the leaves of trees. -They are, besides, more perishable, and in densely wooded -countries there are comparatively few herbaceous plants. -I have examined the beds of mud deposited at the mouth -<span class="pagenum"><a name="Page_207" id="Page_207">« 207 »</a></span> -of a woodland streamlet, and have found them stored with -the fallen leaves of trees, but it was in vain to search for -the leaves of herbaceous plants.</p> - -<div class="fig_center" style="width: 256px;"> -<a name="fig76" id="fig76"></a> -<img src="images/fig76.png" width="256" height="163" alt="" /> -<div class="fig_caption">Fig. 76.—<i>Brasenia antiqua</i>. Upper Cretaceous, -South Saskatchewan River. -Natural size, <i>a</i>, <i>b</i>, Diagrams of venation, -slightly enlarged.</div> -</div> - -<p>The climate of North America and Europe, represented -by the Cenomanian vegetation, is not tropical but warm -temperate; but the flora was more uniform than at present, -indicating a very equable climate and the possibility -of temperate genera existing within the Arctic circle, and -it would seem to have become warmer toward the close of -the period.</p> - -<p>The flora of the Cenomanian is separated in most -countries from that of the Senonian, or uppermost Cretaceous, -by a marine formation holding few plants. This -depends on great movements of elevation and depression, -to which we must refer in the sequel. In a few regions, -however, as in the vicinity of the Peace River in Canada, -there are plant-bearing beds which serve to bridge over -the interval between the -Early Cenomanian and -the later Cretaceous.<a name="FNanchor_DQ_121" id="FNanchor_DQ_121"></a><a href="#Footnote_DQ_121" class="fnanchor">[DQ]</a></p> - -<div class="footnote"> - -<p><a name="Footnote_DQ_121" id="Footnote_DQ_121"></a><a href="#FNanchor_DQ_121"><span class="label">[DQ]</span></a> See paper by the author in the “Transactions of the Royal Society -of Canada,” 1882.</p></div> - -<p>To this interval also -would seem to belong -the Belly River series of -western Canada, which -contains important beds -of Coal, but is Closely associated -with the marine -Fort Pierre series. A -very curious herbaceous -plant of this group, which I have named <i>Brasenia antiqua</i>, -occurs in the beds associated with one of the coals. -It is a close ally of the modern <i>B. peltata</i>, an aquatic -plant which occurs in British Columbia and in eastern -<span class="pagenum"><a name="Page_208" id="Page_208">« 208 »</a></span> -America, and is also said to be found in Japan, Australia, -and India, a width of distribution appropriate to so old -a type (<a href="#fig76">Fig. 76</a>).</p> - -<p>In so far as vegetable life is concerned, the transition -from the Upper Cretaceous to the Tertiary or Kainozoic -is easy, though in many parts of the world, and more -especially in western Europe, there is a great gap in the -deposits between the upper Chalk and the lowest Eocene. -With reference to fossil plants, Schimper recognises in -the Kainozoic, beginning with the oldest, five formations—Palæocene, -Eocene, Oligocene, Miocene, and Pliocene. -Throughout these a flora, similar to that of the Cretaceous -on the one hand and the modern on the other, -though with important local peculiarities, extends. There -is evidence, however, of a gradual refrigeration, so that -in the Pliocene the climates of the northern hemisphere -were not markedly different from their present character.</p> - -<p>In the first instance an important error was committed -by palæobotanists, in referring to the Miocene -many deposits really belonging to the Eocene. This -arose from the early study of the rich plant-bearing -Miocene beds of Switzerland, and from the similarity of -the flora all the way from the Middle Cretaceous to the -later Tertiary. The differences are now being worked -out, and we owe to Mr. Starkie Gardner the credit of -pointing these out in England, and to the Geological -Survey of Canada that of collecting the material for -exhibiting them in the more northern part of America.</p> - -<p>In the great interior plain of America there rests -on the Cretaceous a series of clays and sandstones with -beds of lignite, some of them eighteen feet in thickness. -This was formerly known as the lignitic or lignite Tertiary, -but more recently as the Laramie series. These -beds were deposited in fresh or brackish water, in an -internal sea or group of lakes and swamps, when the -continent was lower than at present. They have been -<span class="pagenum"><a name="Page_209" id="Page_209">« 209 »</a></span> -studied both in the United States<a name="FNanchor_DR_122" id="FNanchor_DR_122"></a><a href="#Footnote_DR_122" class="fnanchor">[DR]</a> and Canada; and, -though their flora was originally referred by mistake to -the Miocene, it is now known to be Eocene or Palæocene, -or even in part a transition group between the latter and -the Cretaceous. The following remarks, taken chiefly -from recent papers by the author,<a name="FNanchor_DS_123" id="FNanchor_DS_123"></a><a href="#Footnote_DS_123" class="fnanchor">[DS]</a> will serve to illustrate -this:</p> - -<div class="footnote"> - -<p><a name="Footnote_DR_122" id="Footnote_DR_122"></a><a href="#FNanchor_DR_122"><span class="label">[DR]</span></a> See more especially the elaborate and valuable reports by Lesquereux -and Newberry, and a recent memoir by Ward on “Types of the -Laramie Flora,” “Bulletins of the United States Geological Survey,” -1887.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_DS_123" id="Footnote_DS_123"></a><a href="#FNanchor_DS_123"><span class="label">[DS]</span></a> “Transactions of the Royal Society of Canada,” 1886-'87.</p></div> - -<p>On the geological map of Canada the Laramie series, -formerly known as the lignitic or lignite Tertiary, occurs, -with the exception of a few outliers, in two large -areas west of the 100th meridian, and separated from each -other by a tract of older Cretaceous rocks, over which the -Laramie beds may have extended, before the later denudation -of the region.</p> - -<p>The most eastern of these areas, that of the Souris -River and Wood Mountain, extends for some distance -along the United States boundary, between the 102d and -109th meridians, and reaches northward to about thirty -miles south of the “elbow” of the South Saskatchewan -River, which is on the parallel of 51° north. In this -area the lowest beds of the Laramie are seen to rest on -those of the Fox Hill group of the Upper Cretaceous, -and at one point on the west they are overlaid by beds of -Miocene Tertiary age, observed by Mr. McConnell, of -the Geological Survey, in the Cypress Hills, and referred -by Cope, on the evidence of mammalian remains, to the -White River division of the United States geologists, -which is regarded by them as Lower Miocene.<a name="FNanchor_DT_124" id="FNanchor_DT_124"></a><a href="#Footnote_DT_124" class="fnanchor">[DT]</a> The age -of the Laramie beds is thus stratigraphically determined -to be between the Fox Hill Cretaceous and the Lower -<span class="pagenum"><a name="Page_210" id="Page_210">« 210 »</a></span> -Miocene. They are also undoubtedly continuous with -the Fort Union group of the United States geologists on -the other side of the international boundary, and they -contain similar fossil plants. They are divisible into two -groups—a lower, mostly argillaceous, and to which the -name of “Bad Lands beds” may be given, from the “bad -lands” of Wood Mountain, where they are well exposed, -and an upper, partly arenaceous member, which may be -named the Souris River or Porcupine Creek division. -In the lower division are found reptilian remains of Upper -Cretaceous type, with some fish remains more nearly akin -to those of the Eocene.<a name="FNanchor_DU_125" id="FNanchor_DU_125"></a><a href="#Footnote_DU_125" class="fnanchor">[DU]</a> Neither division has as yet -afforded mammalian remains.</p> - -<div class="footnote"> - -<p><a name="Footnote_DT_124" id="Footnote_DT_124"></a><a href="#FNanchor_DT_124"><span class="label">[DT]</span></a> “Report of the Geological Survey of Canada,” 1885.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_DU_125" id="Footnote_DU_125"></a><a href="#FNanchor_DU_125"><span class="label">[DU]</span></a> Cope, in Dr. G. M. Dawson’s “Report on the 49th Parallel.”</p></div> - -<p>The western area is of still larger dimensions, and extends -along the eastern base of the Rocky Mountains from -the United States boundary to about the 55th parallel of -latitude, and stretches eastward to the 111th meridian. -In this area, and more especially in its southern part, the -officers of the Geological Survey of Canada have recognised -three divisions, as follows: (1) The Lower Laramie -or St. Mary River series, corresponding in its character -and fossils to the Lower or Bad Lands division of the -other area. (2) A middle division, the Willow Creek -beds, consisting of clays, mostly reddish, and not recognised -in the other area. (3) The Upper Laramie or -Porcupine Hills division, corresponding in fossils, and to -some extent in mineral character, to the Souris River -beds of the eastern area.</p> - -<p>The fossil plants collected by Dr. G. M. Dawson in -the eastern area were noticed by the author in an appendix -to Dr. Dawson’s report on the 49th parallel, in 1875, -and a collection subsequently made by Dr. Selwyn was -described in the “Report of the Geological Survey of -Canada” for 1879-'80. Those of the western area, and -<span class="pagenum"><a name="Page_211" id="Page_211">« 211 »</a></span> -especially collections made by myself near Calgary in -1883, and by officers of the Geological Survey in 1884, -have been described in the “Transactions of the Royal -Society of Canada” vols. iii. and iv.</p> - -<p>In studying these fossil plants, I have found that -there is a close correspondence between those of the -Lower and Upper Laramie in the two areas above referred -to respectively, and that the flora of the Lower -Laramie is somewhat distinct from that of the Upper, -the former being especially rich in certain aquatic plants, -and the latter much more copious on the whole, and -much more rich in remains of forest-trees. This is, however, -possibly an effect rather of local conditions than of -any considerable change in the flora, since some Upper -Laramie forms recur as low as the Belly River series of the -Cretaceous, which is believed on stratigraphical grounds -to be considerably older than the Lower Laramie.</p> - -<p>With reference to the correlation of these beds with -those of the United States, some difficulty has arisen from -the tendency of palæobotanists to refer the plants of the -Upper Laramie to the Miocene age, although in the reports -of Mr. Clarence King, the late director of the -United States Geological Survey, these beds are classed, -on the evidence of stratigraphy and animal fossils, as -Upper Cretaceous. More recently, however, and partly -perhaps in consequence of the views maintained by the -writer since 1875, some change of opinion has occurred, -and Dr. Newberry and Mr. Lesquereux seem now inclined -to admit that what in Canada we recognise as -Upper Laramie is really Eocene, and the Lower Laramie -either Cretaceous or a transition group between this and -the Eocene. In a recent paper <a name="FNanchor_DV_126" id="FNanchor_DV_126"></a><a href="#Footnote_DV_126" class="fnanchor">[DV]</a> Dr. Newberry gives a -comparative table, in which he correlates the Lower -<span class="pagenum"><a name="Page_212" id="Page_212">« 212 »</a></span> -Laramie with the Upper Cretaceous of Vancouver Island -and the Faxoe and Maestricht beds of Europe, while he -regards the Upper Laramie as equivalent to European -Eocene. Except in so far as the equivalence of the -Lower Laramie and Vancouver Island beds is concerned, -this corresponds very nearly with the conclusions of the -writer in a paper published last year<a name="FNanchor_DW_127" id="FNanchor_DW_127"></a><a href="#Footnote_DW_127" class="fnanchor">[DW]</a>—namely, that we -must either regard the Laramie as a transition Cretaceo-Eocene -group, or must institute our line of separation in -the Willow Creek or Middle Laramie division, which has, -however, as yet afforded no fossil plants. I doubt, however, -the equivalence of the Vancouver beds and the -Lower Laramie, except perhaps in so far as the upper -member of the former is concerned. I have also to observe -that in the latest report of Mr. Lesquereux he still -seems to retain in the Miocene certain formations in the -West, which from their fossil plants I should be inclined -to regard as Eocene.<a name="FNanchor_DX_128" id="FNanchor_DX_128"></a><a href="#Footnote_DX_128" class="fnanchor">[DX]</a></p> - -<div class="footnote"> - -<p><a name="Footnote_DV_126" id="Footnote_DV_126"></a><a href="#FNanchor_DV_126"><span class="label">[DV]</span></a> Newberry, “Transactions of the New Fork Academy,” February, -1886.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_DW_127" id="Footnote_DW_127"></a><a href="#FNanchor_DW_127"><span class="label">[DW]</span></a> “Transactions of the Royal Society of Canada,” vol. ii.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_DX_128" id="Footnote_DX_128"></a><a href="#FNanchor_DX_128"><span class="label">[DX]</span></a> While these sheets were going through the press I received a very -valuable report of Mr. Lester F. Ward upon the Laramie of the United -States. I have merely had time to glance at this report, but can see that -the views of the author agree closely with those above expressed.</p></div> - -<p>Two ferns occurring in these beds are remarkable as -evidence of the persistence of species, and of the peculiarities -of their ancient and modern distribution. <i>Onoclea -sensibilis</i>, the very common sensitive fern of eastern -America, is extremely abundant in the Laramie beds over -a great area in the West. Mr. Starkie Gardner and Dr. -Newberry have also shown that it is identical with the -<i>Filicites Hebridicus</i> of Forbes, from the early Eocene beds -of the Island of Mull, in Scotland. Thus we have a -species once common to Europe and America, but now -restricted to the latter, and which has continued to exist -over all the vast ages between the Cretaceous and the -present day. In the Laramie beds I have found associated -<span class="pagenum"><a name="Page_213" id="Page_213">« 213 »</a></span> -with this species another and more delicate fern, -the modern <i>Davallia</i> (<i>Stenloma</i>) <i>tenuifolia</i>, but this, unlike -its companion, no longer occurs in America, but is -found in the mountains of Asia. This is a curious illustration -of the fact that frail and delicate plants may be -more ancient than the mountains or plains on which -they live.</p> - -<p>There are also some very interesting and curious facts -in connection with the conifers of the Laramie. One of -the most common of these is a <i>Thuja</i> or arbor vitæ (the -so-called “cedar” of Canada). The Laramie species has -been named <i>T. interrupta</i> by Newberry, but it approaches -very closely in its foliage to <i>T. occidentalis</i>, of eastern -Canada, while its fruit resembles that of the western -species, <i>T. gigantea</i>.</p> - -<p>Still more remarkable are the Sequoias to which we -have already referred, but which in the Laramie age seem -to have been spread over nearly all North America. The -fossil species are of two types, representing respectively -the modern <i>S. gigantea</i> and <i>S. sempervirens</i>, and their -wood, as well as that of Thuja, is found in great abundance -in the lignites, and also in the form of silicified -trunks, and corresponds with that of the recent species. -The Laramie contains also conifers of the genera <i>Glyptostrobus</i>, -<i>Taxodium</i>, and <i>Taxus</i>; and the genus <i>Salisburia</i> -or gingko—so characteristic of the Jurassic and Cretaceous—is -still represented in America as well as in Europe -in the early Eocene.</p> - -<p>We have no palms in the Canadian or Scottish Palæocene, -though I believe they are found further south. The -dicotyledonous trees are richly represented. Perhaps the -most conspicuous were three species of <i>Platanus</i>, the -leaves of which sometimes fill the sandstones, and one of -which, <i>P. nobilis</i>, Newberry, sometimes attains the gigantic -size of a foot or more in diameter of its blade. -The hazels are represented by a large-leaved species, -<span class="pagenum"><a name="Page_214" id="Page_214">« 214 »</a></span> -<i>C. Macquarrii</i>, and by leaves not distinguishable from those -of the modern American species, <i>C. Americana</i> and <i>C. -rostrata</i>. There are also chestnuts and oaks. But the -poplars and willows are specially abundant, being represented -by no less than six species, and it would seem -that all the modern types of poplar, as indicated by the -forms and venation of the leaves, existed already in the -Laramie, and most of them even in the Upper Cretaceous. -<i>Sassafras</i> is represented by two species, and the beautiful -group of <i>Viburnum</i>,, to which the modern tree-cranberry -belongs, has several fine species, of some of which both -leaves and berries have been found. The hickories and -butternuts are also present, the horse-chestnut, the <i>Catalpa</i> -and <i>Sapindus</i>, and some curious leaves which seem -to indicate the presence of the modern genus <i>Symphorocarpus</i>, -the snow-berry tribe.</p> - -<p>The above may suffice to give an idea of the flora of -the older Eocene in North America, and I may refer for -details to the works of Newberry, Lesquereux, and Ward, -already cited. I must now add that the so-called Miocene -of Atanekerdluk, Greenland, is really of the same -age, as also the “Miocene” of Mull, in Scotland, of -Antrim, in Ireland, and of Bovey Tracey, in the south of -England, and the Gelinden, or “Heersian” beds, of Belgium, -described by Saporta. In comparing the American -specimens with the descriptions given by Gardner of the -leaf-beds at Ardtown, in Mull, we find, as already stated, -<i>Onoclea sensibilis</i>, common to both. The species of -<i>Sequoia</i>, <i>Gingko</i>, <i>Taxus</i>, and <i>Glyptostrobus</i> are also identical -or closely allied, and so are many of the dicotyledonous -leaves. For example, <i>Platanoides Hebridicus</i> is -very near to <i>P. nobilis</i>, and <i>Corylus Macquarrii</i> is common -to both formations, as well as <i>Populus Arctica</i> and -<i>P. Richardsoni</i>. I may add that ever since 1875-'76, -when I first studied the Laramie plants, I have maintained -their identity with those of the Fort Union group -<span class="pagenum"><a name="Page_215" id="Page_215">« 215 »</a></span> -of the United States, and of the so-called Miocene of -McKenzie River and Greenland, and that the whole are -Paleocene; and this conclusion has now been confirmed -by the researches of Gardner in England, and by the discovery -of true Lower Miocene beds in the Canadian northwest, -overlying the Laramie or lignite series.</p> - -<p>In a bulletin of the United States Geological Survey -(1886), Dr. White has established in the West the -continuous stratigraphical succession of the Laramie and -the Wahsatch Eocene, thus placing the Laramie conformably -below the Lower Eocene of that region. Cope -has also described as the Puerta group a series of beds -holding vertebrate fossils, and forming a transition from -the Laramie to the Wahsatch. White also testifies that a -number of fresh-water mollusks are common to the Wahsatch -and the Laramie. This finally settles the position -of the Laramie so far as the United States geologists are -concerned, and shows that the flora is to be regarded as -Eocene if not Upper Cretaceous, in harmony with what -has been all along maintained in Canada. An important -<i>résumé</i> of the flora has just been issued by Ward in the -bulletins of the United States Geological Survey (1887).</p> - -<p>Before leaving this part of the subject, I would deprecate -the remark, which I see occasionally made, that fossil -plants are of little value in determining geological horizons -in the Cretaceous and Tertiary. I admit that in -these periods some allowance must be made for local -differences of station, and also that there is a generic -sameness in the flora of the northern hemisphere, from -the Cenomanian to the modern, yet these local differences -and general similarity are not of a nature to invalidate -inferences as to age. No doubt, so long as -palæobotanists seemed obliged, in deference to authority, -and to the results of investigations limited to a few European -localities, to group together, without distinction, -all the floras of the later Cretaceous and earlier Tertiary, -<span class="pagenum"><a name="Page_216" id="Page_216">« 216 »</a></span> -irrespective of stratigraphical considerations, the subject -lost its geological importance. But, when a good series -has been obtained in any one region of some extent, the -case becomes different. Though there is still much imperfection -in our knowledge of the Cretaceous and Tertiary -floras of Canada, I think the work already done is -sufficient to enable any competent observer to distinguish -by their fossil plants the Lower, Middle, and Upper Cretaceous, -and the latter from the Tertiary; and, with the -aid of the work already done by Lesquereux and Newberry -in the United States, to refer approximately to its -true geological position any group of plants from beds of -unknown age in the West.</p> - -<p>An important consequence arising from the above -statements is that the period of warm climate which -enabled a temperate flora to exist in Greenland was that -of the later Cretaceous and early Eocene rather than, as -usually stated, the Miocene. It is also a question admitting -of discussion whether the Eocene flora of latitudes -so different as those of Greenland, Mackenzie River, northwest -Canada, and the United States, were strictly contemporaneous, -or successive within a long geological -period in which climatal changes were gradually proceeding. -The latter statement must apply at least to -the beginning and close of the period; but the plants -themselves have something to say in favour of contemporaneity. -The flora of the Laramie is not a tropical -but a temperate flora, showing no doubt that a much -more equable climate prevailed in the more northern -parts of America than at present. But this equability -of climate implies the possibility of a great geographical -range on the part of plants. Thus it is quite possible -and indeed highly probable that in the Laramie age a -somewhat uniform flora extended from the Arctic seas -through the great central plateau of America far to the -south, and in like manner along the western coast of -<span class="pagenum"><a name="Page_217" id="Page_217">« 217 »</a></span> -Europe. It is also to be observed that, as Gardner points -out, there are some differences indicating a diversity of -climate between Greenland and England, and even between -Scotland and Ireland and the south of England, -and we have similar differences, though not strongly-marked, -between the Laramie of northern Canada and -that of the United States. When all our beds of this -age from the Arctic sea to the 49th parallel have been -ransacked for plants, and when the palæobotanists of the -United States shall have succeeded in unravelling the -confusion which now exists between their Laramie and -the Middle Tertiary, the geologist of the future will be -able to restore with much certainty the distribution of -the vast forests which in the early Eocene covered the -now bare plains of interior America. Further, since the -break which in western Europe separates the flora of the -Cretaceous from that of the Eocene does not exist in -America, it will then be possible to trace the succession -from the Mesozoic flora of the Trias and of the Queen -Charlotte Islands and Kootanie series of the Lower Cretaceous -up to the close of the Eocene; and to determine, -for America at least, the manner and conditions -under which the angiospermous flora of the later Cretaceous -succeeded to the pines and cycads which characterised -the beginning of the Cretaceous period. In so -far as Europe is concerned, this may be more difficult, -since the want of continuity of land from north to south -seems there to have been fatal to the continuance of some -plants during changes of climate, and there were also -apparently in the Kainozoic period invasions at certain -times of species from the south and east, which did not -occur to the same extent in America.</p> - -<p>In recent reports on the Tertiary floras of Australia -and New Zealand,<a name="FNanchor_DY_129" id="FNanchor_DY_129"></a><a href="#Footnote_DY_129" class="fnanchor">[DY]</a> Ettingshausen holds that the flora of -<span class="pagenum"><a name="Page_218" id="Page_218">« 218 »</a></span> -the Tertiary, as a whole, was of a generalised character; -forms now confined to the southern and northern hemispheres -respectively being then common to both. It -would thus seem that the present geographical diversities -must have largely arisen from the great changes in climate -and distribution of land and water in the later -Tertiary.</p> - -<div class="footnote"> - -<p><a name="Footnote_DY_129" id="Footnote_DY_129"></a><a href="#FNanchor_DY_129"><span class="label">[DY]</span></a> “Geological Magazine,” August, 1887.</p></div> - -<p>The length of our discussion of the early angiospermous -flora does not permit us to trace it in detail through -the Miocene and Pliocene, but we may notice the connection -through these in the next chapter, and may refer -to the magnificent publications of Heer and Lesquereux -on the Tertiary floras of Europe and America respectively.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_219" id="Page_219">« 219 »</a></span></p> - - - - -<p class="caption2"><a name="CHAPTER_VII" id="CHAPTER_VII">CHAPTER VII.</a></p> - -<p class="caption3">PLANTS FROM THE TERTIARY TO THE MODERN PERIOD.</p> - - -<p><span class="smcap">It</span> may be well to begin this chapter with a sketch of -the general physical and geological conditions of the period -which was characterised by the advent and culmination -of the dicotyledonous trees.</p> - -<p>In the Jurassic and earliest Cretaceous periods the -prevalence, over the whole of the northern hemisphere -and for a long time, of a monotonous assemblage of gymnospermous -and acrogenous plants, implies a uniform -and mild climate, and facility for intercommunication in -the north. Toward the end of the Jurassic and beginning -of the Cretaceous, the land of the northern hemisphere was -assuming greater dimensions, and the climate probably -becoming a little less uniform. Before the close of the -Lower Cretaceous period the dicotyledonous flora seems -to have been introduced, under geographical conditions -which permitted a warm temperate climate to extend as -far north as Greenland.</p> - -<p>In the Cenomanian or Middle Cretaceous age we find -the northern hemisphere tenanted with dicotyledonous -trees closely allied to those of modern times, though still -indicating a climate much warmer than that which at -present prevails. In this age, extensive but gradual submergence -of land is indicated by the prevalence of chalk -and marine limestones over the surface of both continents; -but a circumpolar belt seems to have been maintained, -protecting the Atlantic and Pacific basins from -<span class="pagenum"><a name="Page_220" id="Page_220">« 220 »</a></span> -floating ice, and permitting a temperate flora of great -richness to prevail far to the north, and especially along -the southern margins and extensions of the circumpolar -land. These seem to have been the physical conditions -which terminated the existence of the old Mesozoic flora -and introduced that of the Middle Cretaceous.</p> - -<p>As time advanced the quantity of land gradually increased, -and the extension of new plains along the older -ridges of land was coincident with the deposition of the -great Laramie series, and with the origination of its peculiar -flora, which indicates a mild climate and considerable -variety of station in mountain, plain, and swamp, -as well as in great sheets of shallow and weedy fresh -water.</p> - -<p>In the Eocene and Miocene periods, the continents -gradually assumed their present form, and the vegetation -became still more modern in aspect. In that period of -the Eocene, however, in which the great nummulitic -limestones were deposited, a submergence of land occurred -on the eastern continent which must have assimilated its -physical conditions to those of the Middle Cretaceous. -This great change, affecting materially the flora of Europe, -was not equally great in America, which also by the -north and south extension of its mountain-chains permitted -movements of migration not possible in the Old -World. From the Eocene downward, the remains of -land-animals and plants are found chiefly in lake-basins -occupying the existing depressions of the land, though -more extensive than those now remaining. It must also -be borne in mind that the great foldings and fractures of -the crust of the earth which occurred at the close of the -Eocene, and to which the final elevation of such ranges -as the Alps and the Rocky Mountains belongs, permanently -modified and moulded the forms of the continents.</p> - -<p>These statements raise, however, questions as to the -precise equivalence in time of similar floras found in different -<span class="pagenum"><a name="Page_221" id="Page_221">« 221 »</a></span> -latitudes. However equable the climate, there -must have been some appreciable difference in proceeding -from north to south. If, therefore, as seems in -every way probable, the new species of plants originated -on the Arctic land and spread themselves southward, -this latter process would occur most naturally in -times of gradual refrigeration or of the access of a -more extreme climate—that is, in times of the elevation -of land in the temperate latitudes, or, conversely, of -local depression of land in the Arctic, leading to invasions -of northern ice. Hence, the times of the prevalence of -particular types of plants in the far north would precede -those of their extension to the south, and a flora found -fossil in Greenland might be supposed to be somewhat -older than a similar flora when found farther south. It -would seem, however, that the time required for the extension -of a new flora to its extreme geographical limit is -so small, in comparison with the duration of an entire -geological period, that, practically, this difference is of -little moment, or at least does not amount to antedating -the Arctic flora of a particular type by a whole period, -but only by a fraction of such period.</p> - -<p>It does not appear that, during the whole of the Cretaceous -and Eocene periods, there is any evidence of such -refrigeration as seriously to interfere with the flora, but -perhaps the times of most considerable warmth are those -of the Dunvegan group in the Middle Cretaceous, and -those of the later Laramie and oldest Eocene.</p> - -<p>It would appear that no cause for the mild temperature -of the Cretaceous needs to be invoked, other than -those mutations of land and water which the geological -deposits themselves indicate. A condition, for example, -of the Atlantic basin in which the high land of Greenland -should be reduced in elevation, and at the same time the -northern inlets of the Atlantic closed against the invasion -of Arctic ice, would at once restore climatic conditions -<span class="pagenum"><a name="Page_222" id="Page_222">« 222 »</a></span> -allowing of the growth of a temperate flora in Greenland. -As Dr. Brown has shown,<a name="FNanchor_DZ_130" id="FNanchor_DZ_130"></a><a href="#Footnote_DZ_130" class="fnanchor">[DZ]</a> and as I have elsewhere -argued, the absence of light in the Arctic winter is no -disadvantage, since, during the winter, the growth of -deciduous trees is in any case suspended; while the constant -continuance of light in the summer is, on the contrary, -a very great stimulus and advantage.</p> - -<div class="footnote"> - -<p><a name="Footnote_DZ_130" id="Footnote_DZ_130"></a><a href="#FNanchor_DZ_130"><span class="label">[DZ]</span></a> “Florula Discoana.”</p></div> - -<p>It is a remarkable phenomenon in the history of genera -of plants in the later Mesozoic and Tertiary, that the -older genera appear at once in a great number of specific -types, which become reduced as well as limited in range -down to the modern. This is, no doubt, connected with -the greater differentiation of local conditions in the modern; -but it indicates also a law of rapid multiplication of -species in the early life of genera. The distribution of the -species of <i>Salisburia</i>, <i>Sequoia</i>, <i>Platanus</i>, <i>Sassafras</i>, <i>Liriodendron</i>, -<i>Magnolia</i>, and many other genera, affords remarkable -proofs of this.</p> - -<p>Gray, Saporta, Heer, Newberry, Lesquereux, and -Starkie Gardner have all ably discussed these points; but -the continual increase of our knowledge of the several -floras, and the removal of error as to the dates of their -appearance, must greatly conduce to clearer and more -definite ideas. In particular, the prevailing opinion that -the Miocene was the period of the greatest extension of -warmth and of a temperate flora into the Arctic, must -be abandoned in favour of the later Cretaceous and -Eocene; and, if I mistake not, this will be found to accord -better with the evidence of general geology and of -animal fossils.</p> - -<p>In these various revolutions of the later Cretaceous -and Kainozoic periods, America, as Dr. Gray has well -pointed out, has had the advantage of a continuous stretch -of high land from north to south, affording a more sure -<span class="pagenum"><a name="Page_223" id="Page_223">« 223 »</a></span> -refuge to plants in times of submergence, and means of -escape to the south in times of refrigeration. Hence, -the greater continuity of American vegetation and the -survival of genera like <i>Sequoia</i> and <i>Liriodendron</i>, which -have perished in the Old World. Still, there are some exceptions -to this, for the gingko-tree is a case of survival in -Asia of a type once plentiful in America, but now extinct -there. Eastern Asia has had, however, some considerable -share of the same advantage possessed by America, with -the addition, referred to by Gray, of a better and more -insular climate.</p> - -<p>But our survey of these physical conditions can not be -considered complete till we shall have considered the -great Glacial age of the Pleistocene. It is certain that -throughout the later Miocene and Pliocene the area of land -in the northern hemisphere was increasing, and the large -and varied continents were tenanted by the noblest vegetation -and the grandest forms of mammalian life that the -earth has ever witnessed. As the Pliocene drew to a -close, a gradual diminution of warmth came on, and -more especially a less equable climate, and this was accompanied -with a subsidence of the land in the temperate -regions and with changes of the warm ocean-currents. -Thus gradually the summers became cooler and the -winters longer and more severe, the hill-tops became -covered with permanent snows, glaciers ploughed their -way downward into the plains, and masses and fields of -floating ice cooled the seas. In these circumstances the -richer and more delicate forms of vegetation must have -been chilled to death or obliged to remove farther south, -and in many extensive regions, hemmed in by the advance -of the sea on the one hand and land-ice on the other, they -must have altogether perished.</p> - -<p>Yet even in this time vegetation was not altogether -extinct. Along the Gulf of Mexico in America, and in -the Mediterranean basin in Europe, there were still some -<span class="pagenum"><a name="Page_224" id="Page_224">« 224 »</a></span> -remains of a moderate climate and certain boreal and -arctic forms moving southward continued to exist here -and there in somewhat high latitudes, just as similar -plants now thrive in Grinnell Land within sight of the -snows of the Greenland mountains. A remarkable summary -of some of these facts as they relate to England was -given by an eminent English botanist, Mr. Carruthers, in -his address as President of the Biological Section of the -British Association at Birmingham in 1886. At Cromer, -on the coast of Norfolk, the celebrated forest-bed of newer -Pliocene age, and containing the remains of a copious -mammalian fauna, holds also remains of plants in a state -admitting of determination. These have been collected -by Mr. Reid, of the Geological Survey, and were reported -on by Carruthers, who states that they represent a somewhat -colder temperature than that of the present day. I -quote the following details from the address.</p> - -<p>With reference to the plants of the forest-bed or -newer Pliocene he remarks as follows:</p> - -<p>"Only one species (<i>Trapa natans</i>, Willd.) has disappeared -from our islands. Its fruits, which Mr. Reid -found abundantly in one locality, agree with those of the -plants found until recently in the lakes of Sweden. Four -species (<i>Prunus speciosa</i>, L., <i>Œnanthe Tichenalii</i>, Sm., -<i>Potamogeton pterophyllus</i>, Sch., and <i>Pinus abies</i>, L.) -are found at present only in Europe, and a fifth (<i>Potamogeton -trichoides</i>, Cham.) extends also to North America; -two species (<i>Peucedanum palustre</i>, Moench, and -<i>Pinus sylvestris</i>, L.) are found also in Siberia, while six -more (<i>Sanguisorba officinalis</i>, L., <i>Rubus fruticosus</i>, L., 5 -<i>Cornus sanguinea</i>, L., <i>Euphorbia amygdaloides</i>, L., -<i>Quercus robur</i>, L., and <i>Potamogeton crispus</i>, L.) extend -into western Asia, and two (<i>Fagus sylvatica</i>, L., and -<i>Alnus glutinosa</i>, L.) are included in the Japanese flora. -Seven species, while found with the others, enter also into -the Mediterranean flora, extending to North Africa: these -<span class="pagenum"><a name="Page_225" id="Page_225">« 225 »</a></span> -are <i>Thalictrum minus</i>, L., <i>Thalictrum flavum</i>, L., <i>Ranunculus -repens</i>, L., <i>Stellaria aquatica</i>, Scop., <i>Corylus -avellana</i>, L., <i>Yannichellia palustris</i>, L., and <i>Cladium -mariscus</i>, Br. With a similar distribution in the Old -World, eight species (<i>Bidens tripartita</i>, L., <i>Myosotis -cæspitosa</i>, Schultz, <i>Suæda maritima</i>, Dum., <i>Ceratophyllum -demersum</i>,, L., <i>Sparganium ramosum</i>, Huds., <i>Potamogeton -pectinatus</i>, L., <i>Carex paludosa</i>, Good., and <i>Osmunda -regalis</i>, L.) are found also in North America. Of -the remainder, ten species (<i>Nuphar luteum</i>, Sm., <i>Menyanthes -trifoliata</i>, L., <i>Stachys palustris</i>, L., <i>Rumex maritimus</i>, -L., <i>Rumex acetosella</i>, L., <i>Betula alba</i>, L., <i>Scirpus -pauciflorus</i>, Lightf., <i>Taxus baccata</i>, L., and <i>Isoetes lacustris</i>, -L.) extend round the north temperate zone, while -three (<i>Lycopus europæus</i>, L., <i>Alisma plantago</i>, L., and -<i>Phragmites communis</i>, Trim), having the same distribution -in the north, are found also in Australia, and one -(<i>Hippuris vulgaris</i>, L.) in the south of South America. -The list is completed by <i>Ranunculus aquatilis</i>, L., distributed -over all the temperate regions of the globe, and -<i>Scirpus lacustris</i>, L., which is found in many tropical -regions as well."</p> - -<p>He remarks that these plants, while including species -now very widely scattered, present no appreciable change -of characters.</p> - -<p>Above this bed are glacial clays, which hold other -species indicating an extremely cold climate. They are -few in number, only <i>Salix polaris</i>, a thoroughly arctic -species, and its ally, <i>S. cinerea</i>, L., and a moss, <i>Hypnum -turgescens</i>, Schimp., no longer found in Britain, but an -Alpine and arctic species. This bed belongs to the beginning -of the Glacial period, the deposits of which have as -yet afforded no plants in England. But plants occur in -post-glacial and upper-glacial beds in different parts of -England, to which Carruthers thus refers:</p> - -<p>"The period of great cold, during which arctic ice -<span class="pagenum"><a name="Page_226" id="Page_226">« 226 »</a></span> -extended far into temperate regions, was not favorable to -vegetable life. But in some localities we have stratified -clays with plant-remains later than the Glacial epoch, -yet indicating that the great cold had not then entirely -disappeared. In the lacustrine beds at Holderness is -found a small birch (<i>Betula nana</i>, L.), now limited in -Great Britain to some of the mountains of Scotland, but -found in the arctic regions of the Old and New World -and on Alpine districts in Europe, and with it <i>Prunus -padus</i>, L., <i>Quercus robur</i>, L., <i>Corylus avellana</i>, L., -<i>Alnus glutinosa</i>, L., and <i>Pinus sylvestris</i>, L. In the -white clay-beds at Bovey Tracey of the same age there -occur the leaves of <i>Arctostaphylos uva-ursi</i>, L., three -species of willow, viz., <i>Salix cinerea</i>, L., <i>S. myrtilloides</i>, -L., and <i>S. polaris</i>, Wahl., and in addition to our Alpine -<i>Betula nana</i>, L., the more familiar <i>B. alba</i>, L. Two of -these plants have been lost to our flora from the change -of climate that has taken place, viz., <i>Salix myrtilloides</i>, -L., and <i>S. polaris</i>, Wahl.; and <i>Betula nana</i>, L., has retreated -to the mountains of Scotland. Three others -(<i>Dryas octopetala</i>, L., <i>Arctostaphylos uva-ursi</i>, L., and -<i>Salix herbacea</i>, L.) have withdrawn to the mountains of -northern England, Wales, and Scotland, while the remainder -are still found scattered over the country. Notwithstanding -the diverse physical conditions to which -these plants have been subjected, the remains preserved -in these beds present no characters by which they can -be distinguished from the living representatives of the -species."</p> - -<p>One of the instances referred to is very striking. At -Bovey Tracey the arctic beds rest directly on those holding -the rich, warm temperate flora of the Eocene; so -that here we have the evidence of fossil plants to show the -change from the climate of the Eocene to that of arctic -lands, and the modern vegetation to indicate the return -of a warm temperature.</p> - -<p><span class="pagenum"><a name="Page_227" id="Page_227">« 227 »</a></span></p> - -<p>In Canada, in the Pleistocene beds known as the Leda -clays, intervening between the lower boulder clay and -the Saxicava sand, which also holds boulders, there are -beds holding fossil plants, in some places intermixed with -sea-shells and bones of marine fishes, showing that they -were drifted into the sea at a time of submergence. -These remains are boreal rather than arctic in character, -and with the remains of drift-wood often found in the -boulder deposits serve to indicate that there were at all -times oases of hardy life in the glacial deserts, just as we -find these in polar lands at the present day. I condense -from a paper on these plants<a name="FNanchor_EA_131" id="FNanchor_EA_131"></a><a href="#Footnote_EA_131" class="fnanchor">[EA]</a> the following facts, with a -few additional notes:</p> - -<div class="footnote"> - -<p><a name="Footnote_EA_131" id="Footnote_EA_131"></a><a href="#FNanchor_EA_131"><span class="label">[EA]</span></a> “Canadian Naturalist,” 1866.</p></div> - -<p>The importance of all information bearing on the -temperature of the Post-pliocene period invests with -much interest the study of the land-plants preserved in -deposits of this age. Unfortunately, these are few in number, -and often not well preserved. In Canada, though -fragments of the woody parts of plants occasionally occur -in the marine clays and sands, there is only one locality -which has afforded any considerable quantity of remains -of their more perishable parts. This is the well-known -deposit of Leda clay at Green’s Creek, on the Ottawa, -celebrated for the perfection in which the skeletons of -the capelin and other fishes are preserved in the calcareous -nodules imbedded in the clay. In similar nodules, contained -apparently in a layer somewhat lower than that -holding the ichthyolites, remains of land-plants are somewhat -abundant, and, from their association with shells of -<i>Leda glacialis</i>, seem to have been washed down from the -land into deep water. The circumstances would seem to -have been not dissimilar from those at present existing -in the northeast arm of Gaspé Basin, where I have dredged -from mud now being deposited in deep water, living -<span class="pagenum"><a name="Page_228" id="Page_228">« 228 »</a></span> -specimens of <i>Leda limatula</i>, mixed with remains of land-plants.</p> - -<p>The following are the species of plants recognised in -these nodules:</p> - -<p>1. <i>Drosera rotundifolia</i>, Linn. In a calcareous nodule -from Green’s Creek, the leaf only preserved. This plant -is common in bogs in Canada, Nova Scotia, and Newfoundland, -and thence, according to Hooker, to the Arctic -circle. It is also European.</p> - -<p>2. <i>Acer spicatum</i>, Lamx. (<i>Acer montanum</i>, Aiton.) -Leaf in a nodule from Green’s Creek. Found in Nova -Scotia and Canada, also at Lake Winnipeg, according to -Richardson.</p> - -<p>3. <i>Potentilla Canadensis</i>, Linn. In nodules from -Green’s Creek; leaves only preserved. I have had some -difficulty in determining these, -but believe they must be referred -to the species above named, or -to <i>P. simplex</i>, Michx., supposed -by Hooker and Gray to be a variety. -It occurs in Canada and -New England, but I have no information -as to its range northward.</p> - -<p>4. <i>Gaylussaccia resinosa</i>, Torrey -and Gray. Leaf in nodule -at Green’s Creek. Abundant in -New England and in Canada, -also on Lake Huron and the Saskatchewan, according to -Richardson (<a href="#fig77">Fig. 77</a>).</p> - -<p>5. <i>Populus balsamifera</i>, Linn. Leaves and branches -in nodules at Green’s Creek. This is by much the most -common species, and its leaves are of small size, as if from -trees growing in cold and exposed situations. The species -is North American and Asiatic, and abounds in New England -and Canada. It extends to the Arctic circle, and is -<span class="pagenum"><a name="Page_229" id="Page_229">« 229 »</a></span> -abundant on the shores of the Great Slave Lake and on -the McKenzie River, and according to Richardson constitutes -much of the drift timber of the Arctic coast -(<a href="#fig78">Fig. 78</a>).</p> - -<table summary="leaves"> -<tr> - <td class="center" style="width: 45%;"><a name="fig77" id="fig77"></a> - <img src="images/fig77.png" width="189" height="204" alt="" /> - <div class="fig_caption">Fig. 77.—<i>Gaylussaccia resinosa</i>. - Pleistocene, Canada.</div> - </td> - <td class="center" style="width: 45%;"><a name="fig78" id="fig78"></a> - <img src="images/fig78.png" width="374" height="272" alt="" /> - <div class="fig_caption">Fig. 78.—<i>Populus balsamifera</i>. Pleistocene, Canada.</div> - </td> -</tr> -</table> - -<p>6. <i>Thuja occidentalism</i> Linn. Trunks and branches -in the Leda clay at Montreal. This tree occurs in New -England and Canada, and extends northward into the -Hudson Bay territories. It is a northern though not -arctic species in its geographical range. According to -Lyell it occurs associated with the bones of Mastodon in -New Jersey. From the great durability of its wood, it is -one of the trees most likely to be preserved in aqueous -deposits.</p> - -<p>7. <i>Potamogeton perfoliatus</i>, Linn. Leaves and seeds -in nodules at Green’s Creek. Inhabits streams of the -Northern States and Canada, and according to Richardson -extends to Great Slave Lake.</p> - -<p>8. <i>Potamogeton pusillus.</i> Quantities of fragments -which I refer to this species occur in nodules at Green’s -Creek. They may possibly belong to a variety of <i>P. -hybridus</i> which, together with <i>P. natans</i>, now grows in -<span class="pagenum"><a name="Page_230" id="Page_230">« 230 »</a></span> -the river Ottawa, where it flows over the beds containing -these fossils.</p> - -<p>9. <i>Cariceæ and Gramineæ.</i> Fragments in nodules -from Green’s Creek appear to belong to plants of these -groups, but I cannot venture to determine their species.</p> - -<p>10. <i>Equisetum scirpoides</i>, Michx. Fragments in nodules, -Green’s Creek. This is a widely distributed species, -occurring in the Northern States and Canada.</p> - -<p>11. <i>Fontinalis.</i> In nodules at Green’s Creek there -occur, somewhat plentifully, branches of a moss apparently -of the genus <i>Fontinalis</i>.</p> - -<div class="fig_center" style="width: 243px;"> -<a name="fig79" id="fig79"></a> -<img src="images/fig79.png" width="243" height="302" alt="" /> -<div class="fig_caption">Fig. 79.—Frond of <i>Fucus</i>. Pleistocene, -Canada.</div> -</div> - -<p>12. <i>Algæ.</i> With the -plants above mentioned, -both at Green’s Creek -and at Montreal, there -occur remains of sea-weeds -(<a href="#fig79">Fig. 79</a>). They -seem to belong to the -genera <i>Fucus</i> and <i>Ulva</i>, -but I cannot determine -the species. A thick -stem in one of the nodules -would seem to indicate -a large <i>Laminaria</i>. -With the above there are -found at Green’s Creek a -number of fragments of leaves, stems, and fruits, which -I have not been able to refer to their species, principally -on account of their defective state of preservation.</p> - -<p>None of the plants above mentioned is properly arctic -in its distribution, and the assemblage may be characterised -as a selection from the present Canadian flora of some -of the more hardy species having the most northern -range. Green’s Creek is in the central part of Canada, -near to the parallel of 46°, and an accidental selection -<span class="pagenum"><a name="Page_231" id="Page_231">« 231 »</a></span> -from its present flora, though it might contain the same -species found in the nodules, would certainly include with -these, or instead of some of them, more southern forms. -More especially the balsam poplar, though that tree occurs -plentifully on the Ottawa, would not be so predominant. -But such an assemblage of drift-plants might -be furnished by any American stream flowing in the latitude -of 50° to 55° north. If a stream flowing to the -north, it might deposit these plants in still more northern -latitudes, as the McKenzie River does now. If flowing -to the south, it might deposit them to the south of 50°. -In the case of the Ottawa, the plants could not have been -derived from a more southern locality, nor probably from -one very far to the north. We may therefore safely assume -that the refrigeration indicated by these plants -would place the region bordering the Ottawa in nearly the -same position with that of the south coast of Labrador -fronting on the Gulf of St. Lawrence at present. The -absence of all the more arctic species occurring in Labrador -should perhaps induce us to infer a somewhat -milder climate than this.</p> - -<p>The moderate amount of refrigeration thus required -would in my opinion accord very well with the probable -conditions of climate deducible from the circumstances in -which the fossil plants in question occur. At the time -when they were deposited the sea flowed up the Ottawa -valley to a height of 200 to 400 feet above its present -level, and the valley of the St. Lawrence was a wide arm -of the sea, open to the arctic current. Under these conditions -the immense quantities of drift-ice from the -northward, and the removal of the great heating surface -now presented by the low lands of Canada and New England, -must have given for the Ottawa coast of that period -a summer temperature very similar to that at present experienced -on the Labrador coast, and with this conclusion -the marine remains of the Leda clay, as well as the few -<span class="pagenum"><a name="Page_232" id="Page_232">« 232 »</a></span> -land molluscs whose shells have been found in the beds -containing the plants, and which are species still occurring -in Canada, perfectly coincide.</p> - -<p>The climate of that portion of Canada above water at -the time when these plants were imbedded may safely be -assumed to have been colder in summer than at present, -to an extent equal to about 5° of latitude, and this refrigeration -may be assumed to correspond with the requirements -of the actual geographical changes implied. -In other words, if Canada was submerged until the -Ottawa valley was converted into an estuary inhabited by -species of <i>Leda</i>, and frequented by capelin, the diminution -of the summer heat consequent on such depression -would be precisely suitable to the plants occurring in -these deposits, without assuming any other cause of -change of climate.</p> - -<p>I have arranged elsewhere the Post-pliocene deposits -of the central part of Canada, as consisting of, in ascending -order: (1) The boulder clay; (2) a deep-water deposit, -the Leda clay; and (3) a shallow-water deposit, the -Saxicava sand. But, although I have placed the boulder -clay in the lowest position, it must be observed that I do -not regard this as a continuous layer of equal age in all -places. On the contrary, though locally, as at Montreal, -under the Leda clay, it is in other places and at other -levels contemporaneous with or newer than that deposit, -which itself also locally contains boulders.</p> - -<p>At Green’s Creek the plant-bearing nodules occur in -the lower part of the Leda clay, which contains a few -boulders, and is apparently in places overlaid by large -boulders, while no distinct boulder clay underlies it. -The circumstances which accumulated the thick bed of -boulder clay near Montreal were probably absent in the -Ottawa valley. In any case we must regard the deposits -of Green’s Creek as coeval with the Leda clay of Montreal, -and with the period of the greatest abundance of -<span class="pagenum"><a name="Page_233" id="Page_233">« 233 »</a></span> -<i>Leda glacialis</i>, the most exclusively arctic shell of these deposits. -In other words, I regard the plants above mentioned -as probably belonging to the period of greatest refrigeration -of which we have any evidence, of course not -including that mythical period of universal incasement in -ice, of which, as I have elsewhere endeavoured to show, -in so far as Canada is concerned, there is no evidence -whatever.<a name="FNanchor_EB_132" id="FNanchor_EB_132"></a><a href="#Footnote_EB_132" class="fnanchor">[EB]</a></p> - -<div class="footnote"> - -<p><a name="Footnote_EB_132" id="Footnote_EB_132"></a><a href="#FNanchor_EB_132"><span class="label">[EB]</span></a> Notes on Post-Pliocene of Canada, “Canadian Naturalist,” 1872.</p></div> - -<p>The facts above stated in reference to Post-pliocene -plants concur, with all the other evidence I have been -able to obtain, in the conclusion that the refrigeration of -Canada in the Post-pliocene period consisted of a diminution -of the summer heat, and was of no greater amount -than that fairly attributable to the great depression of the -land and the different distribution of the ice-bearing -arctic current.</p> - -<p>In connection with the plants above noticed, it is interesting -to observe that at Green’s Creek, at Pakenham -Mills, at Montreal, and at Clarenceville on Lake Champlain, -species of Canadian <i>Pulmonata</i> have been found in -deposits of the same age with those containing the plants. -The species which have been noticed belong to the genera -<i>Lymnea</i> and <i>Planorbis</i>.</p> - -<p>The Glacial age was, fortunately, not of very long duration, -though its length has been much exaggerated by -certain schools of geologists,<a name="FNanchor_EC_133" id="FNanchor_EC_133"></a><a href="#Footnote_EC_133" class="fnanchor">[EC]</a> It passed away, and a returning -cosmic spring gladdened the earth, and was ushered -in by a time of great rainfall and consequent denudation -and deposit, which has been styled the “Pluvial -Period” The remains of the Pliocene forests then returned—with -somewhat diminished numbers of species—from -<span class="pagenum"><a name="Page_234" id="Page_234">« 234 »</a></span> -the south and again occupied the land, though they -have not been able, in their decimated condition, to restore -the exuberance of the flora of the earlier Tertiary. -In point of fact, as we shall see in the next chapter, it is -the floras originating within the polar circle and coming -down from the north that are rich and copious. Those -that, after periods of cold or submergence, return from -the south, are comparatively poor. Hence the modern -flora is far inferior to that of the Middle Kainozoic. In -America, however, and in eastern Asia, for reasons already -stated, the return was more abundant than in -Europe.</p> - -<div class="footnote"> - -<p><a name="Footnote_EC_133" id="Footnote_EC_133"></a><a href="#FNanchor_EC_133"><span class="label">[EC]</span></a> This I have long maintained on grounds connected with Pleistocene -fossils, amount of denudation and deposit, &c., and I am glad to see that -Prestwich, the best English authority on such subjects, has recently announced -similar conclusions, based on independent reasons.</p></div> - -<p>Simultaneously with the return of the old temperate -flora, the arctic plants that had overspread the land retreated -to mountain-tops, now bared of ice and snow, and -back to the polar lands whence they came; and so it happens -that, on the White Mountains, the Alps, and the -Himalayas, we have insular patches of the same groups of -plants that exist around the pole.</p> - -<p>These changes need not have required a very long -time, for the multiplication and migration of plants are -very rapid, especially when aided by the agency of migratory -animals. Many parts of the land must, indeed, have -been stocked with plants from various sources, and by -agencies—as that of the sea—which might at first sight -seem adverse to their distribution. The British Islands, -for example, have no indigenous plants. Their flora -consists mainly of Germanic plants, which must have -migrated to Britain in that very late period of the Post-glacial -when the space now occupied by the North Sea -was mostly dry land. Other portions of it are Scandinavian -plants, perhaps survivors of the Glacial age, or -carried by migratory birds; and still another element -consists of Spanish plants, brought north by spring migrants, -and establishing themselves in warm and sheltered -spots, just as the arctic plants do on the bleak hill-tops. -<span class="pagenum"><a name="Page_235" id="Page_235">« 235 »</a></span> -The Bermudas, altogether recent islands, have one hundred -and fifty species of native plants, all of which are -West Indian and American, and must have been introduced -by the sea-currents or by migratory birds.</p> - -<p>And so the earth became fitted for the residence of -modern man. Yet it is not so good or Edenic a world as -it once was, or as it may yet become, were another revolution -to restore a mild climate to the arctic regions, and -to send down a new swarm of migratory species to renew -the face of the earth and restore it to its pristine fertility -of vegetable life.</p> - -<p>Thus closes this long history of the succession of -plants, reaching from the far back Laurentian to the -present day. It has, no doubt, many breaks, and much -remains to be discovered. Yet it may lead us to some -positive conclusions regarding the laws of the introduction -of plants.</p> - -<p>One of these, and perhaps the most remarkable of all, -is that certain principles were settled very far back, and -have remained ever since. We have seen that in the -earliest geological periods all that pertains to the structure, -powers, and laws of the vegetable cell was already -fixed and settled. When we consider how much this -implies of mechanical structure and chemical and vital -property, the profound significance of this statement becomes -apparent. The relations in these respects between -the living cell and the soil, the atmosphere and the sunshine, -were apparently as perfect in the early Palæozoic -as in any subsequent time. The same may be said of the -structures of the leaf and of the stem. In such old forms -as Nematophyton these were, it is true, peculiar and rudimentary, -but in the Devonian and Carboniferous the -structure of leaves and stems embodied all the parts and -principles that we find at present. In regard to fructification -there has been more progress, for, so far as we -know, the highest and most complex forms of flowery, -<span class="pagenum"><a name="Page_236" id="Page_236">« 236 »</a></span> -fruits, and seeds belong to the more recent periods, and -simpler forms were at least dominant in the older times. -Yet even in this respect the great leading laws and structures -of bisexual reproduction were perfected in the early -Palæozoic, and the improvements introduced in the gymnosperm -and the angiosperm of later periods have consisted -mainly in additions of accessory parts, and in modifications -and refinements suited to the wants of the higher -and more complex types.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_237" id="Page_237">« 237 »</a></span></p> - - - - -<p class="caption2"><a name="CHAPTER_VIII" id="CHAPTER_VIII">CHAPTER VIII.</a></p> - -<p class="caption3">GENERAL LAWS OF ORIGIN AND MIGRATIONS OF PLANTS.—RELATIONS -OF RECENT AND FOSSIL FLORAS.</p> - - -<p><span class="smcap">The</span> origination of the successive floras which have -occupied the northern hemisphere in geological time, -not, as one might at first sight suppose, in the sunny -climes of the south, but under the arctic skies, is a fact -long known or suspected. It is proved by the occurrence -of fossil plants in Greenland, in Spitzbergen, and in Grinnell -Land, under circumstances which show that these -were their primal homes. The fact bristles with physical -difficulties, yet is fertile of the most interesting theoretical -deductions, to reach which we may well be content to -wade through some intricate questions. Though not at -all a new fact, its full significance seems only recently to -have dawned on the minds of geologists, and within the -last few years it has produced a number of memoirs and -addresses to learned societies, besides many less formal -notices.<a name="FNanchor_ED_134" id="FNanchor_ED_134"></a><a href="#Footnote_ED_134" class="fnanchor">[ED]</a></p> - -<div class="footnote"> - -<p><a name="Footnote_ED_134" id="Footnote_ED_134"></a><a href="#FNanchor_ED_134"><span class="label">[ED]</span></a> Saporta, “Ancienne Végétation Polaire”; Hooker, “Presidential -Address to Royal Society,” 1878; Thistleton Dyer, “Lecture on Plant -Distribution”; Mr. Starkie Gardner, “Letters in ‘Nature,’” 1878, &c. -The basis of most of these brochures is to be found in Heer’s “Flora -Fossilis Arctica.”</p></div> - -<p>The earliest suggestion on the subject known to the -writer is that of Prof. Asa Gray, in 1867, with reference -to the probable northern source of the related floras of -North America and eastern Asia. With the aid of the -new facts disclosed by Heer and Lesquereux, Gray returned -<span class="pagenum"><a name="Page_238" id="Page_238">« 238 »</a></span> -to the subject in 1872, and more fully developed -this conclusion with reference to the Tertiary floras,<a name="FNanchor_EE_135" id="FNanchor_EE_135"></a><a href="#Footnote_EE_135" class="fnanchor">[EE]</a> -and he has recently still further discussed these questions -in an able lecture on “Forest Geography and Archæology.”<a name="FNanchor_EF_136" id="FNanchor_EF_136"></a><a href="#Footnote_EF_136" class="fnanchor">[EF]</a> -In this he puts the case so well and tersely that -we may quote the following sentences as a text for what -follows:</p> - -<div class="footnote"> - -<p><a name="Footnote_EE_135" id="Footnote_EE_135"></a><a href="#FNanchor_EE_135"><span class="label">[EE]</span></a> Address to American Association.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_EF_136" id="Footnote_EF_136"></a><a href="#FNanchor_EF_136"><span class="label">[EF]</span></a> “American Journal of Science,” xvi., 1818.</p></div> - -<p>“I can only say, at large, that the same species (of -Tertiary fossil plants) have been found all round the -world; that the richest and most extensive finds are in -Greenland; that they comprise most of the sorts which I -have spoken of, as American trees which once lived in -Europe—magnolias, sassafras, hickories, gum-trees, our -identical southern cypress (for all we can see of difference), -and especially <i>Sequoias</i>, not only the two which -obviously answer to the two big-trees now peculiar to -California, but several others; that they equally comprise -trees now peculiar to Japan and China, three kinds -of gingko-trees, for instance, one of them not evidently -distinguishable from the Japan species which alone survives; -that we have evidence, not merely of pines and -maples, poplars, birches, lindens, and whatever else characterise -the temperate zone forests of our era, but also of -particular species of these, so like those of our own time -and country that we may fairly reckon them as the ancestors -of several of ours. Long genealogies always deal -more or less in conjecture; but we appear to be within -the limits of scientific inference when we announce that -our existing temperate trees came from the north, and -within the bounds of nigh probability when we claim not -a few of them as the originals of present species. Remains -of the same plants have been found fossil in our temperate -region as well as in Europe.”</p> - -<p><span class="pagenum"><a name="Page_239" id="Page_239">« 239 »</a></span></p> - -<p>Between 1860 and 1870 the writer was engaged in -working out all that could be learned of the Devonian -plants of eastern America, the oldest known flora of any -richness, and which consists almost exclusively of gigantic, -and to us grotesque, representatives of the club-mosses, -ferns, and mares'-tails, with some trees allied to the cycads -and pines. In this pursuit nearly all the more important -localities were visited, and access was had to the large -collections of Prof. Hall and Prof. Newberry, in New -York and Ohio, and to those made in the remarkable -plant-bearing beds of New Brunswick by Messrs. Matthew -and Hartt. In the progress of these researches, which -developed an unexpectedly rich assemblage of species, the -northern origin of this old flora seemed to be established -by its earlier culmination in the northeast, in connection -with the growth of the American land to the southward, -which took place after the great Upper Silurian subsidence, -by elevations beginning in the north while those -portions of the continent to the southwest still remained -under the sea. The same result was indicated by the -persistence in the Carboniferous of the south and west of -old Erian forms, like <i>Megalopteris</i>.</p> - -<p>When, in 1870, the labours of those ten years were -brought before the Royal Society of London, in the -Bakerian lecture of that year, and in a memoir illustrating -no less than one hundred and twenty-five species of -plants older than the great Carboniferous system, these -deductions were stated in connection with the conclusions -of Hall, Logan, and Dana, as to the distribution of sediment -along the northeast side of the American continent, -and the anticipation was hazarded that the oldest Palæozoic -floras would be discovered to the north of Newfoundland. -Mention was also made of the apparent earlier -and more copious birth of the Devonian flora in America -than in Europe, a fact which is itself connected with the -greater northward extension of this continent.</p> - -<p><span class="pagenum"><a name="Page_240" id="Page_240">« 240 »</a></span></p> - -<p>The memoir containing these results was not published -by the Royal Society, but its publication was secured in a -less complete form in the reports of the “Geological Survey -of Canada.” The part of the memoir relating to Canadian -fossil plants, with a portion of the theoretical deductions, -was published in a report issued in 1871.<a name="FNanchor_EG_137" id="FNanchor_EG_137"></a><a href="#Footnote_EG_137" class="fnanchor">[EG]</a> In this -report the following language was used:</p> - -<div class="footnote"> - -<p><a name="Footnote_EG_137" id="Footnote_EG_137"></a><a href="#FNanchor_EG_137"><span class="label">[EG]</span></a> “Fossil Plants of the Devonian and Upper Silurian Formations of -Canada,” pp. 92, twenty plates, Montreal, 1871.</p></div> - -<p>"In eastern America, from the Carboniferous period -onward, the centre of plant distribution has been the Appalachian -chain. From this the plants and sediments -extended westward in times of elevation, and to this they -receded in times of depression. But this centre was nonexistent -before the Devonian period, and the centre for -this must have been to the northeast, whence the great -mass of older Appalachian sediment was derived. In the -Carboniferous period there was also an eastward distribution -from the Appalachians, and links of connection in -the Atlantic bed between the floras of Europe and America. -In the Devonian such connection can have been only -far to the northeast. It is therefore in Newfoundland, -Labrador, and Greenland that we are to look for the -oldest American flora, and in like manner on the border -of the old Scandinavian nucleus for that of Europe.</p> - -<p>"Again, it must have been the wide extension of the -sea of the corniferous limestone that gave the last blow -to the remaining flora of the Lower Devonian; and the -re-elevation in the middle of that epoch brought in the -Appalachian ridges as a new centre, and established a -connection with Europe which introduced the Upper -Devonian and Carboniferous floras. Lastly, from the -comparative richness of the later Erian<a name="FNanchor_EH_138" id="FNanchor_EH_138"></a><a href="#Footnote_EH_138" class="fnanchor">[EH]</a> flora in eastern -America, especially in the St. John beds, it might be a -<span class="pagenum"><a name="Page_241" id="Page_241">« 241 »</a></span> -fair inference that the northeastern end of the Appalachian -ridge was the original birthplace or centre of creation -of what we may call the later Palæozoic flora, or of -a large part of that flora."</p> - -<div class="footnote"> - -<p><a name="Footnote_EH_138" id="Footnote_EH_138"></a><a href="#FNanchor_EH_138"><span class="label">[EH]</span></a> See <a href="#Page_107">pages 107 and 108</a>.</p></div> - -<p>When my paper was written I had not seen the account -published by the able Swiss palæobotanist Heer, of -the remarkable Devonian flora of Bear Island, near Spitzbergen.<a name="FNanchor_EI_139" id="FNanchor_EI_139"></a><a href="#Footnote_EI_139" class="fnanchor">[EI]</a> -From want of acquaintance with the older -floras of America and western Europe, Heer fell into the -unfortunate error of regarding the whole of Bear Island -plants as Lower Carboniferous, a mistake which his great -authority has tended to perpetuate, and which has even -led to the still graver error of some European geologists, -who do not hesitate to regard as Carboniferous the fossil -plants of the American deposits from the Hamilton to -the Chemung groups inclusive, though these belong to -formations underlying the oldest Carboniferous, and characterised -by animal remains of unquestioned Devonian -age. In 1872 I addressed a note to the Geological Society -of London on the subject of the so-called “Ursa stage” -of Heer, showing that, though it contained some forms -not known at so early a date in temperate Europe, it was -clearly, in part at least, Devonian when tested by North -American standards; but that in this high latitude, in -which, for reasons stated in the report above referred to, -I believed the Devonian plants to have originated, there -might be an intermixture of the two floras. But such a -mixed group should in that latitude be referred to a -lower horizon than if found in temperate regions. Dr. -Nathorst, as already stated, has recently obtained new -facts which go to show that plants of two distinct horizons -may have been intermixed in the collections submitted -to Heer.</p> - -<div class="footnote"> - -<p><a name="Footnote_EI_139" id="Footnote_EI_139"></a><a href="#FNanchor_EI_139"><span class="label">[EI]</span></a> “Transactions of the Swedish Academy” 1871; “Journal of the -London Geological Society,” vol. xxviii.</p> - -<p><span class="pagenum"><a name="Page_242" id="Page_242">« 242 »</a></span></p></div> - -<p>Between 1870 and 1873 my attention was turned to -the two sub-floras intermediate between those of the Devonian -and the coal-formation, the floras of the Lower -Carboniferous (Subcarboniferous of some American geologists) -and the Millstone Grit, and in a report upon -these<a name="FNanchor_EJ_140" id="FNanchor_EJ_140"></a><a href="#Footnote_EJ_140" class="fnanchor">[EJ]</a> similar deductions were expressed. It was stated -that in Newfoundland the coal-beds seem to belong to -the Millstone Grit series, and as we proceed southward -they belong to progressively newer portions of the Carboniferous -system. The same fact is observed in the -coal-beds of Scotland, as compared with those of England, -and it indicates that the coal-formation flora, like -that of the Devonian, spread itself from the north, and -this accords with the somewhat extensive occurrence of -Lower Carboniferous rocks and fossils in the Parry Islands -and elsewhere in the arctic regions.</p> - -<div class="footnote"> - -<p><a name="Footnote_EJ_140" id="Footnote_EJ_140"></a><a href="#FNanchor_EJ_140"><span class="label">[EJ]</span></a> “Fossil Plants of Lower Carboniferous and Millstone Grit Formations -of Canada,” pp. 47, ten plates, Montreal, 1873.</p></div> - -<p>Passing over the comparatively poor flora of the earlier -Mesozoic, consisting largely of cycads, pines, and ferns, -and as yet little known in the arctic, and which may -have originated in the south, though represented, according -to Heer, by the supposed Jurassic flora of Siberia, we -find, especially at Komé and Atané in Greenland, an interesting -occurrence of those earliest precursors of the -truly modern forms of plants which appear in the Cretaceous, -the period of the English chalk and of the New -Jersey greensands. There are two plant-groups of this -age in Greenland; one, that of Komé, consists almost entirely -of ferns, cycads, and pines, and is of decidedly -Mesozoic aspect. This is called Lower Cretaceous. The -other, that of Atané, holds remains of many modern temperate -genera, as <i>Populus</i>, <i>Myrica</i>, <i>Ficus</i>, <i>Sassafras</i>, and -<i>Magnolia</i>. This is regarded as Upper Cretaceous. Resting -upon these Upper Cretaceous beds, without the intervention -<span class="pagenum"><a name="Page_243" id="Page_243">« 243 »</a></span> -of any other formation,<a name="FNanchor_EK_141" id="FNanchor_EK_141"></a><a href="#Footnote_EK_141" class="fnanchor">[EK]</a> are beds rich in plants -of much more modern appearance, and referred by Heer -to the Miocene period, a reference, as we have seen, not -warranted by comparison with the Tertiary plants of Europe -or of America. Still farther north this so-called -Miocene assemblage of plants appears in Spitzbergen and -Grinnell Land; but there, owing to the predominance of -trees allied to the spruces, it has a decidedly more boreal -character than in Greenland, as might be anticipated from -its nearer approach to the pole.<a name="FNanchor_EL_142" id="FNanchor_EL_142"></a><a href="#Footnote_EL_142" class="fnanchor">[EL]</a></p> - -<div class="footnote"> - -<p><a name="Footnote_EK_141" id="Footnote_EK_141"></a><a href="#FNanchor_EK_141"><span class="label">[EK]</span></a> Nordenskiöld, “Expedition to Greenland,” “Geological Magazine,” -1872.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_EL_142" id="Footnote_EL_142"></a><a href="#FNanchor_EL_142"><span class="label">[EL]</span></a> Yet even here the bald cypress (<i>Taxodium distichum</i>), or a tree -nearly allied to it, is found, though this species is now limited to the -Southern States. Fielden and De Ranee, “Journal of the Geological Society,” 1878.</p></div> - -<p>If now we turn to the Cretaceous and Tertiary floras -of western America, as described by Lesquereux, Newberry, -and others, we find in the lowest Cretaceous rocks -there known—those of the Dakota group—which may be -in the lower part of the Middle Cretaceous, a series of -plants<a name="FNanchor_EM_143" id="FNanchor_EM_143"></a><a href="#Footnote_EM_143" class="fnanchor">[EM]</a> essentially similar to those of the so-called Upper -Cretaceous of Greenland. They occur in beds indicating -land and fresh-water conditions as prevalent at the time -over great areas of the interior of America. But overlying -this plant-bearing formation we have an oceanic -limestone (the Niobrara), corresponding in many respects -to the European chalk, and extending far north into the -British territory,<a name="FNanchor_EN_144" id="FNanchor_EN_144"></a><a href="#Footnote_EN_144" class="fnanchor">[EN]</a> indicating that the land of the Lower -Cretaceous was replaced by a vast Mediterranean Sea, -filled with warm water from the equatorial currents, and -not invaded by cold waters from the north. This is succeeded -by thick Upper Cretaceous deposits of clay and -sandstone, with marine remains, though very sparsely -<span class="pagenum"><a name="Page_244" id="Page_244">« 244 »</a></span> -distributed; and these show that further subsidence or -denudation in the north had opened a way for the arctic -currents, killing out the warm-water animals of the Niobrara -group, and rilling up the Mediterranean of that -period. Of the flora of these Upper Cretaceous periods, -which must have been very long, we know something in -the interior regions, from the discovery of a somewhat -rich flora in the Dunvegan beds of the Peace River district, -on the northern shore of the great Cretaceous Mediterranean;<a name="FNanchor_EO_145" id="FNanchor_EO_145"></a><a href="#Footnote_EO_145" class="fnanchor">[EO]</a> -and on the coast of British Columbia we -have the remarkable Cretaceous coal-field of Vancouver -Island, which holds the remains of plants of modern -genera, and, indeed, of almost as modern aspect as those -of the so-called Miocene of Greenland. They indicate, -however, a warmer climate as then prevalent on the Pacific -coast, and in this respect correspond with a peculiar -transition flora, intermediate between the Cretaceous and -Eocene or earliest Tertiary of the interior regions, and -which is described by Lesquereux as the Lower Lignitic.</p> - -<div class="footnote"> - -<p><a name="Footnote_EM_143" id="Footnote_EM_143"></a><a href="#FNanchor_EM_143"><span class="label">[EM]</span></a> Lesquereux, “Report on Cretaceous Flora.”</p></div> - -<div class="footnote"> - -<p><a name="Footnote_EN_144" id="Footnote_EN_144"></a><a href="#FNanchor_EN_144"><span class="label">[EN]</span></a> G. M. Dawson, “Report on Forty-ninth Parallel.”</p></div> - -<div class="footnote"> - -<p><a name="Footnote_EO_145" id="Footnote_EO_145"></a><a href="#FNanchor_EO_145"><span class="label">[EO]</span></a> “Reports of Dr. G. M. Dawson, Geological Survey of Canada.” Also, -“Transactions of the Royal Society of Canada,” vol. i.</p></div> - -<p>Immediately above these Upper Cretaceous beds we -have the great Lignite Tertiary of the West—the Laramie -group of recent American reports—abounding in fossil -plants, at one time regarded as Miocene, but now known -to be Lower Eocene, though farther south extending upward -toward the Miocene age.<a name="FNanchor_EP_146" id="FNanchor_EP_146"></a><a href="#Footnote_EP_146" class="fnanchor">[EP]</a> These beds, with their -characteristic plants, have been traced into the British -territory north of the forty-ninth parallel, and it has been -shown that their fossils are identical with those of the -<span class="pagenum"><a name="Page_245" id="Page_245">« 245 »</a></span> -McKenzie River valley, described by Heer as Miocene, -and probably also with those of Alaska, referred to the -same age.<a name="FNanchor_EQ_147" id="FNanchor_EQ_147"></a><a href="#Footnote_EQ_147" class="fnanchor">[EQ]</a> Now this truly Eocene flora of the temperate -and northern parts of America has so many species in -common with that called Miocene in Greenland that its -identity can scarcely be doubted. These facts have led -to scepticism as to the Miocene age of the upper plant-bearing -beds of Greenland, and more especially Mr. J. -Starkie Gardner has ably argued, from comparison with -the Eocene flora of England and other considerations, -that they are really of that earlier date.<a name="FNanchor_ER_148" id="FNanchor_ER_148"></a><a href="#Footnote_ER_148" class="fnanchor">[ER]</a></p> - -<div class="footnote"> - -<p><a name="Footnote_EP_146" id="Footnote_EP_146"></a><a href="#FNanchor_EP_146"><span class="label">[EP]</span></a> Lesquereux’s “Tertiary Flora”; “White on the Laramie Group”; -Stevenson, “Geological Relations of Lignitic Groups,” American Philosophical -Society, June, 1875; Dawson, “Transactions of the Royal Society -of Canada,” vol. iv.; Ward, “Bulletin of United States Geological -Survey.”</p></div> - -<div class="footnote"> - -<p><a name="Footnote_EQ_147" id="Footnote_EQ_147"></a><a href="#FNanchor_EQ_147"><span class="label">[EQ]</span></a> G. M. Dawson, “Report on the Geology of the Forty-ninth Parallel,” -where full details on these points may be found. “Transactions of the -Royal Society of Canada,” vol. iv.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_ER_148" id="Footnote_ER_148"></a><a href="#FNanchor_ER_148"><span class="label">[ER]</span></a> “Nature,” December 12, 1878.</p></div> - -<p>In looking at this question, we may fairly assume that -no climate, however equable, could permit the vegetation -of the neighbourhood of Disco in Greenland to be -exactly identical with that of Colorado and Missouri, at a -time when little difference of level existed in the two -regions. Either the southern flora migrated north in -consequence of a greater amelioration of climate, or the -northern flora moved southward as the climate became -colder. The same argument, as Gardner has ably shown, -applies to the similarity of the Tertiary plants of temperate -Europe to those of Greenland. If Greenland required -a temperature of about 50°, as Heer calculates, to maintain -its Eocene flora, the temperature of England and -that of the Southwestern States must have been higher, -though probably more equable, than at present.</p> - -<p>We cannot certainly affirm anything respecting the -migrations of these floras, but there are some probabilities -which deserve attention. The ferns and cycads of the -so-called Lower Cretaceous of Greenland are nothing but -a continuation of the previous Jurassic flora. Now this -was established at an equally early date in the Queen -<span class="pagenum"><a name="Page_246" id="Page_246">« 246 »</a></span> -Charlotte Islands,<a name="FNanchor_ES_149" id="FNanchor_ES_149"></a><a href="#Footnote_ES_149" class="fnanchor">[ES]</a> and still earlier in Virginia,<a name="FNanchor_ET_150" id="FNanchor_ET_150"></a><a href="#Footnote_ET_150" class="fnanchor">[ET]</a> The -presumption is, therefore, that it came from the south. -It has, indeed, the facies of a southern hemisphere and -insular flora, and probably spread itself northward as far -as Greenland, at a time when our northern continents -were groups of islands, and when the ocean currents were -carrying warm water far toward the arctic regions. The -flora which succeeds this in the sections at Atané has no -special affinities with the southern hemisphere, and is of -a more temperate and continental character.<a name="FNanchor_EU_151" id="FNanchor_EU_151"></a><a href="#Footnote_EU_151" class="fnanchor">[EU]</a> It is not -necessarily Upper Cretaceous, since it is similar to that -of the Dakota group farther south, and this is at least -Middle Cretaceous. This flora must have originated -either somewhere in temperate America or within the -Arctic circle, and it must have replaced the older one by -virtue of increasing coolness and continental character of -climate. It must, therefore, have been connected with -that elevation of the land which took place at the beginning -of the Cretaceous. During this elevation it spread -over all western America at one time or another, and, as -the land again subsided under the sea of the Niobrara -chalk, it assumed an aspect more suited to a warm climate, -but still held its place on such islands as remained -above water along the Pacific coast and in the north, and -it continued to exist on these islands till the colder seas -<span class="pagenum"><a name="Page_247" id="Page_247">« 247 »</a></span> -of the Upper Cretaceous had again given place to the -warm plains and land-locked brackish seas or fresh-water -lakes of the Laramie period (Eocene). Thus the true -Upper Cretaceous marks a cool period intervening between -the so-called Upper Cretaceous (really Middle Cretaceous) -and the so-called Miocene (really Lower Eocene) -floras of Greenland.</p> - -<div class="footnote"> - -<p><a name="Footnote_ES_149" id="Footnote_ES_149"></a><a href="#FNanchor_ES_149"><span class="label">[ES]</span></a> “Reports of the Geological Survey of Canada.”</p></div> - -<div class="footnote"> - -<p><a name="Footnote_ET_150" id="Footnote_ET_150"></a><a href="#FNanchor_ET_150"><span class="label">[ET]</span></a> Fontaine has well described the Mesozoic flora of Virginia, “American -Journal of Science,” January, 1879, and “Report on Early Mesozoic -Floras.”</p></div> - -<div class="footnote"> - -<p><a name="Footnote_EU_151" id="Footnote_EU_151"></a><a href="#FNanchor_EU_151"><span class="label">[EU]</span></a> In the “Proceedings of the Royal Society of Tasmania,” 1887, Mr. -R. M. Johnston, F. L. S., states that in the Miocene beds of Tasmania trees -of European genera abound. The Mesozoic flora of that island is of the -usual conifero-cycadean type. Ettingshausen makes a similar statement -in the “Geological Magazine” respecting the Tertiary flora of Australia -and New Zealand, stating that, like the Tertiary floras of Europe, they -have a mixed character, being partly of types now belonging to the northern -hemisphere.</p></div> - -<p>This latter established itself in Greenland, and probably -all around the Arctic circle, in the warm period of -the earliest Eocene, and, as the climate of the northern -hemisphere became gradually reduced from that time till -the end of the Pliocene, it marched on over both continents -to the southward, chased behind by the modern -arctic flora, and eventually by the frost and snow of the -Glacial age. This history may admit of correction in details; -but, so far as present knowledge extends, it is in -the main not far from the truth.</p> - -<p>Perhaps the first great question which it raises is that -as to the causes of the alternations of warm and cold climates -in the north, apparently demanded by the vicissitudes -of the vegetable kingdom. Here we may set aside -the idea that in former times plants were suited to endure -greater cold than at present. It is true that some of the -fossil Greenland plants are of unknown genera, and many -are species new to us; but we are on the whole safe in -affirming that they must have required conditions similar -to those necessary to their modern representatives, except -within such limits as we now find to hold in similar cases -among existing plants. Still we know that at the present -time many species found in the equable climate of England -will not live in Canada, though species to all appearance -similar in structure are native here. There is also -some reason to suppose that species when new may have -greater hardiness and adaptability than when in old age -and verging toward extinction. In any case these facts -can account for but a small part of the phenomena, which -<span class="pagenum"><a name="Page_248" id="Page_248">« 248 »</a></span> -require to be explained by physical changes affecting the -earth as a whole, or at least the northern hemisphere. -Many theoretical views have been suggested on this subject, -and perhaps the most practical way of disposing of -these will be first to set aside a number which are either -precluded by the known facts, incapable of producing -the effects, or altogether uncertain as to their possible -occurrence.</p> - -<p>1. In this class we may place the theory that the poles -of the earth have changed their position. Independently -of astronomical objections, there is good geological evidence -that the poles of the earth must have been nearly -in their present places from the dawn of life until now. -From the Laurentian upward, those organic limestones -which mark the areas where warm and shallow equatorial -water was spreading over submerged continents are so -disposed as to prove the permanence of the poles. In -like manner all the great foldings of the crust of the earth -have followed lines which are parts of great circles tangent -to the existing polar circles. So, also, from the Cambrian -age the great drift of sediment from the north has followed -the line of the existing Arctic currents from the -northeast to the southwest, throwing itself, for example, -along the line of the Appalachian uplifts in eastern -America, and against the ridge of the Cordilleras in the -west.</p> - -<p>2. Some of the above considerations, along with astronomical -evidence, prevent us from assuming any considerable -change in the obliquity of the axis of the earth -during geological time.</p> - -<p>3. That the earth and the sun have diminished in -heat during geological time seems probable; but physical -and geological facts alike render it certain that this influence -could have produced no appreciable effect, even in -the times of the earliest floras, and certainly not in the -case of Tertiary vegetation.</p> - -<p><span class="pagenum"><a name="Page_249" id="Page_249">« 249 »</a></span></p> - -<p>4. It has been supposed that the earth may have at -different times traversed more or less heated zones of -space, giving alternations of warm and cold temperature. -No such differences in space are, however, known, nor -does there seem any good ground for imagining their existence.</p> - -<p>5. The heat of the sun is known to be variable, and -the eleven years' period of sun-spots has recently attracted -much attention as producing appreciable effects on the -seasons. There may possibly be longer cycles of solar -energy, or the sun may be liable, like some variable stars, -to paroxysms of increased energy. Such changes are -possible, and may fairly be taken into the account, provided -that we fail to find known causes sufficient to account -for the phenomena.</p> - -<p>Of well-known causes there seem to be but three. -These are: First, that urged by Lyell—viz., the varying -distribution of land and water along with that of marine -currents; secondly, the varying eccentricity of the earth’s -orbit, along with the precession of the equinoxes, and the -effects of this on oceanic circulation, as illustrated by -Croll; thirdly, the different conditions of the earth’s -atmosphere with reference to radiation, as argued by Tyndall -and Hunt. As these causes are all founded on known -facts, and not exclusive of each other, we may consider -them together. I shall take the Lyellian theory first, regarding -it as the most important, and the best supported -by geological facts.</p> - -<p>We know that the present distribution of land and -water greatly influences climate, more especially by affecting -that of the ocean currents and of the winds, and -by the different action of land as compared with water in -the reception and radiation of heat. The present distribution -of land gives a large predominance to the arctic -and sub-arctic regions, as compared with the equatorial -and with the antarctic; and we might readily imagine -<span class="pagenum"><a name="Page_250" id="Page_250">« 250 »</a></span> -other distributions that would give very different results. -But this is not an imaginary case. We know that, while -the forms and positions of the great continents have been -fixed from a very early date, they have experienced many -great submergences and re-elevations, and that these have -occurred in somewhat regular sequence, as evidenced by -the cyclical alternations of organic limestones and earthy -sediments in successive geological formations.</p> - -<p>An example bearing on our present subject may serve -to illustrate this. In the latter part of the Upper Silurian -period (the Lower Helderberg age), vast areas of the -American continent<a name="FNanchor_EV_152" id="FNanchor_EV_152"></a><a href="#Footnote_EV_152" class="fnanchor">[EV]</a> were covered with an ocean in -which were deposited organic limestones whose fossils -show that this great interior sea was pervaded by equatorial -waters bringing food and warmth, while the incipient -ranges of the Appalachians on the east, and the -Cordilleras on the west, and the Laurentian axis on the -north, fenced off from it the colder arctic waters. How -different must the climate of America and of the region -north of it have been in these circumstances from that -which prevails at present, or from that which prevailed -in certain other periods, when it was open to the incursions -of the arctic ice-laden currents, bearing loads of fine -sediment!<a name="FNanchor_EW_153" id="FNanchor_EW_153"></a><a href="#Footnote_EW_153" class="fnanchor">[EW]</a> It was in these circumstances, and in the -similar circumstances in which the great Corniferous -limestone of the Devonian was deposited—a limestone -showing in its rich coral fauna even warmer waters than -those of the Lower Helderberg—that the Devonian flora -<span class="pagenum"><a name="Page_251" id="Page_251">« 251 »</a></span> -took its origin in the north and advanced southward over -new lands in process of emergence from the sea. The -somewhat similar condition evidenced by the Lower Carboniferous -limestone preceded the advent of the great and -rich flora of the coal-formation.</p> - -<div class="footnote"> - -<p><a name="Footnote_EV_152" id="Footnote_EV_152"></a><a href="#FNanchor_EV_152"><span class="label">[EV]</span></a> See a memoir and map by Prof. Hall, “Reports of the Regents of -New York,” 1874-'75.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_EW_153" id="Footnote_EW_153"></a><a href="#FNanchor_EW_153"><span class="label">[EW]</span></a> It seems certain that the faunæ of the old limestones, like the Trenton, -Niagara, Lower Helderberg, and Corniferous, belong to warm and -sheltered sea areas, and that those rich in graptolites and trilobites, enclosed -in muddy sediments, belong to the colder arctic waters. Such -arctic faunæ are those of the Quebec group and of the Utica shale, and -to some extent that of the Hamilton group.</p></div> - -<p>Lyell’s theory on this subject has, I think, in some recent -publications, been somewhat misapprehended. It -is true that he stated hypothetically two contrasted conditions -of distribution, in one of which all the land was -equatorial, in another all polar; but he did not suppose -that these conditions had actually occurred; and even in -his earlier editions, before the recent discoveries and discussions -as to ocean currents, he was always careful to attach -due value to these in connection with subsidences -and elevations.<a name="FNanchor_EX_154" id="FNanchor_EX_154"></a><a href="#Footnote_EX_154" class="fnanchor">[EX]</a> In his later editions he introduced -more full references to current action, and also stated -Croll’s theory, but still maintained the validity of his -original conclusions.</p> - -<div class="footnote"> - -<p><a name="Footnote_EX_154" id="Footnote_EX_154"></a><a href="#FNanchor_EX_154"><span class="label">[EX]</span></a> See “Principles of Geology,” edition of 1840, chapter vii.</p></div> - -<p>The sufficiency of this Lyellian theory to account for -the facts, in so far as plants are concerned, may, I think, -be inferred from the course of the isothermal lines at -present. The south end of Greenland is on the latitude -of Christiania in Norway on the one hand, and of Fort -Liard in the Peace River region on the other; and while -Greenland is clad in ice and snow, wheat and other grains, -and the ordinary trees of temperate climates, grow at the -latter places,<a name="FNanchor_EY_155" id="FNanchor_EY_155"></a><a href="#Footnote_EY_155" class="fnanchor">[EY]</a> It is evident, therefore, that only exceptionally -unfavourable circumstances prevent the Greenland -area from still possessing a temperate flora, and these unfavourable -circumstances possibly tell even on the localities -with which we have compared it. Further, the -mouth of the McKenzie River is in the same latitude with -<span class="pagenum"><a name="Page_252" id="Page_252">« 252 »</a></span> -Disco, near which are some of the most celebrated localities -of fossil Cretaceous and Tertiary plants. Yet the -mouth of the McKenzie River enjoys a much more favourable -climate and has a much more abundant flora than -Disco. If north Greenland were submerged, and low -land reaching to the south terminated at Disco, and if -from any cause either the cold currents of Baffin’s Bay -were arrested, or additional warm water thrown into the -North Atlantic by the Gulf Stream, there is nothing to -prevent a mean temperature of 45° Fahr. from prevailing -at Disco; and the estimate ordinarily formed of the requirements -of its extinct floras is 50°,<a name="FNanchor_EZ_156" id="FNanchor_EZ_156"></a><a href="#Footnote_EZ_156" class="fnanchor">[EZ]</a> which is probably -above rather than below the actual temperature required.</p> - -<div class="footnote"> - -<p><a name="Footnote_EY_155" id="Footnote_EY_155"></a><a href="#FNanchor_EY_155"><span class="label">[EY]</span></a> See “Macoun’s Report,” “Geological Survey of Canada,” and Richardson’s -“Boat Voyage.”</p></div> - -<div class="footnote"> - -<p><a name="Footnote_EZ_156" id="Footnote_EZ_156"></a><a href="#FNanchor_EZ_156"><span class="label">[EZ]</span></a> Heer. See, also, papers by Prof. Haughton and by Gardner in -“Nature” for 1878.</p></div> - -<p>Since, then, geological facts assure us of mutations of -the continents much greater than those apparently required -to account for the changes of climate implied in -the existence of the ancient arctic floras, it does not seem -absolutely necessary to invoke any others.<a name="FNanchor_FA_157" id="FNanchor_FA_157"></a><a href="#Footnote_FA_157" class="fnanchor">[FA]</a> If, however, -there are other true causes which might either aid or -counteract those above referred to, it may be well to -consider them.</p> - -<div class="footnote"> - -<p><a name="Footnote_FA_157" id="Footnote_FA_157"></a><a href="#FNanchor_FA_157"><span class="label">[FA]</span></a> Sir William Thomson, “Transactions of the Geological Society of -Glasgow,” February 22, 1878.</p></div> - -<p>Mr. Croll has, in his valuable work “Climate and -Time” and in various memoirs, brought forward an ingenious -astronomical theory to account for changes of -climate. This theory, as stated by himself in a recent -paper,<a name="FNanchor_FB_158" id="FNanchor_FB_158"></a><a href="#Footnote_FB_158" class="fnanchor">[FB]</a> is that when the eccentricity of the earth’s orbit -is at a high value, and the northern winter solstice is in -perihelion, agencies are brought into operation which -make the southeast trade-winds stronger than the northeast, -and compel them to blow over upon the northern -<span class="pagenum"><a name="Page_253" id="Page_253">« 253 »</a></span> -hemisphere as far as the Tropic of Cancer. The result is -that all the great equatorial currents of the ocean are impelled -into the northern hemisphere, which thus, in consequence -of the immense accumulation of warm water, -has its temperature raised, so that ice and snow must to a -great extent disappear from the arctic regions. In the -prevalence of the converse conditions, the arctic zone becomes -clad in ice, and the southern has its temperature -raised.</p> - -<div class="footnote"> - -<p><a name="Footnote_FB_158" id="Footnote_FB_158"></a><a href="#FNanchor_FB_158"><span class="label">[FB]</span></a> “Cataclysmic Theories of Geological Climate,” “Geological Magazine,” May, 1878.</p></div> - -<p>At the same time, according to Croll’s calculations, -the accumulation of ice on either pole would tend, by -shifting the earth’s centre of gravity, to raise the level of -the ocean and submerge the land on the colder hemisphere. -Thus a submergence of land would coincide with a cold -condition, and emergence with increasing warmth. Facts -already referred to, however, show that this has not always -been the case, but that in many cases submergence -was accompanied with the influx of warm equatorial -waters and a raised temperature, this apparently depending -on the question of local distribution of land and -water; and this in its turn being regulated not always by -mere shifting of the centre of gravity, but by foldings occasioned -by contraction, by equatorial subsidences resulting -from the retardation of the earth’s rotation, and by the excess -of material abstracted by ice and frost from the arctic -regions, and drifted southward along the lines of arctic -currents. This drifting must in all geological times have -greatly exceeded, as it certainly does at present, the denudation -caused by atmospheric action at the equator, -and must have tended to increase the disposition to equatorial -collapse occasioned by retardation of rotation.<a name="FNanchor_FC_159" id="FNanchor_FC_159"></a><a href="#Footnote_FC_159" class="fnanchor">[FC]</a></p> - -<div class="footnote"> - -<p><a name="Footnote_FC_159" id="Footnote_FC_159"></a><a href="#FNanchor_FC_159"><span class="label">[FC]</span></a> Croll, in “Climate and Time,” and in a note read before the British -Association in 1876, takes an opposite view; but this is clearly contrary -to the facts of sedimentation, which show a steady movement of <i>débris</i> -toward the south and southwest.</p></div> - -<p>While such considerations as those above referred to -<span class="pagenum"><a name="Page_254" id="Page_254">« 254 »</a></span> -tend to reduce the practical importance of Mr. Croll’s -theory., on the other hand they tend to remove one of the -greatest objections against it—namely, that founded on -the necessity of supposing that glacial periods recur with -astronomical regularity in geological time. They cannot -do so if dependent on other causes inherent in the earth -itself, and producing important movements of its crust.</p> - -<p>The third great cause of warmer climates in the past -is the larger proportion of carbon dioxide, or carbonic-acid -gas, in the atmosphere in early geological times, as -proved by the immense amount of carbon now sealed up in -limestone and coal, and which must at one time have been -in the air. It has been shown that a very small additional -quantity of this substance would so obstruct radiation of -heat from the earth as to act almost like a glass roof. If, -however, the quantity of carbonic acid, great at first, was -slowly and regularly removed, even if, as suggested by -Hunt, small additional supplies were gradually added -from space, this cause could have affected only the very -oldest floras. But it is known that some comets and -meteorites contain carbonaceous matter, and this allows -us to suppose that accessions of carbon may have been -communicated at irregular intervals. If so, there may -have been cycles of greater and less abundance of this -substance, and an atmosphere rich in carbon dioxide -might at one and the same time afford warmth and abundance -of food to plants.</p> - -<p>It thus appears that the causes of ancient vicissitudes -of climate are somewhat complex, and when two or more -of them happened to coincide very extreme changes might -result, having most important bearings on the distribution -of plants.</p> - -<p>This may help us to deal with the peculiarities of the -great Glacial age, which may have been rendered exceptionally -severe by the combination of several of the causes -of refrigeration. We must not suppose, however, that -<span class="pagenum"><a name="Page_255" id="Page_255">« 255 »</a></span> -the views of those extreme glacialists who suppose continental -ice-caps reaching half way to the equator are borne -out by facts. In truth, the ice accumulating round the -pole must have been surrounded by water, and there must -have been tree-clad islands in the midst of the icy seas, -even in the time of greatest refrigeration. This is proved -by the fact that, in the Leda clay of eastern Canada, -which belongs to the time of greatest submergence, and -whose fossil shells show sea-water almost at the freezing-point, -there are leaves of poplars and other plants which -must have been drifted from neighbouring shores. Similar -remains occur in clays of like origin in the basin of -the great lakes and in the West. These have been called -“interglacial,” but there is no evidence to prove that they -are not truly glacial. Thus, while we need not suppose -that plants existed within the Arctic circle in the Glacial -age, we have evidence that those of the cold temperate -and sub-arctic zones continued to exist pretty far north. -At the same time the warm temperate flora would be -driven to the south, except where sustained in insular -spots warmed by the equatorial currents. It would return -northward on the re-elevation of the land and the renewal -of warmth.</p> - -<p>If, however, our modern flora is thus one that has returned -from the south, this would account for its poverty -in species as compared with those of the early Tertiary. -Groups of plants descending from the north have been -rich and varied. Returning from the south they are like -the shattered remains of a beaten army. This, at least, -has been the case with such retreating floras as those of -the Lower Carboniferous, the Permian, and the Jurassic, -and possibly that of the Lower Eocene of Europe.</p> - -<p>The question of the supply of light to an arctic flora -is much less difficult than some have imagined. The -long summer day is in this respect a good substitute for -a longer season of growth, while a copious covering of -<span class="pagenum"><a name="Page_256" id="Page_256">« 256 »</a></span> -winter snow not only protects evergreen plants from those -sudden alternations of temperature which are more destructive -than intense frost, and prevents the frost from -penetrating to their roots, but, by the ammonia which it -absorbs, preserves their greenness. According to Dr. -Brown, the Danish ladies of Disco long ago solved this -problem.<a name="FNanchor_FD_160" id="FNanchor_FD_160"></a><a href="#Footnote_FD_160" class="fnanchor">[FD]</a> He informs us that they cultivate in their -houses most of our garden flowers—as roses, fuchsias, and -geraniums—showing that it is merely warmth and not -light that is required to enable a sub-tropical flora to -thrive in Greenland. Even in Canada, which has a flora -richer in some respects than that of temperate Europe, -growth is effectually arrested by cold for nearly six -months, and though there is ample sunlight there is no -vegetation. It is, indeed, not impossible that in the -plans of the Creator the continuous summer sun of the -arctic regions may have been made the means for the introduction, -or at least for the rapid growth and multiplication, -of new and more varied types of plants.</p> - -<div class="footnote"> - -<p><a name="Footnote_FD_160" id="Footnote_FD_160"></a><a href="#FNanchor_FD_160"><span class="label">[FD]</span></a> “Florula Discoana,” Botanical Society of Edinburgh, 1868.</p></div> - -<p>Much, of course, remains to be known of the history -of the old floras, whose fortunes I have endeavoured to -sketch, and which seem to have been driven like shuttle-cocks -from north to south, and from south to north, -especially on the American continent, whose meridional -extension seems to have given a field specially suited for -such operations.</p> - -<p>This great stretch of the western continent, from -north to south, is also connected with the interesting fact -that, when new floras are entering from the arctic regions, -they appear earlier in America than in Europe, -and that in times when old floras are retreating from the -south old genera and species linger longer in America. -Thus, in the Devonian and Cretaceous new forms of those -periods appear in America long before they are recognized -<span class="pagenum"><a name="Page_257" id="Page_257">« 257 »</a></span> -in Europe, and in the modern epoch forms that would be -regarded in Europe as Miocene still exist. Much confusion -in reasoning as to the geological ages of the fossil floras -has arisen from want of attention to this circumstance.</p> - -<p>What we have learned respecting this wonderful history -has served strangely to change some of our preconceived -ideas. We must now be prepared to admit that -an Eden can be planted even in Spitzbergen, that there -are possibilities in this old earth of ours which its present -condition does not reveal to us; that the present state of -the world is by no means the best possible in relation to -climate and vegetation; that there have been and might -be again conditions which could convert the ice-clad arctic -regions into blooming paradises, and which at the -same time would moderate the fervent heat of the tropics. -We are accustomed to say that nothing is impossible with -God; but how little have we known of the gigantic possibilities -which lie hidden under some of the most common -of his natural laws!</p> - -<p>These facts have naturally been made the occasion of -speculations as to the spontaneous development of plants -by processes of varietal derivation. It would, from this -point of view, be a nice question to calculate how many -revolutions of climate would suffice to evolve the first land-plant; -what are the chances that such plant would be so -dealt with by physical changes as to be preserved and -nursed into a meagre flora like that of the Upper Silurian -or the Jurassic; how many transportations to Greenland -would suffice to promote such meagre flora into the rich -and abundant forests of the Upper Cretaceous, and to -people the earth with the exuberant vegetation of the -early Tertiary. Such problems we may never be able to -solve. Probably they admit of no solution, unless we invoke -the action of an Almighty mind, operating through -long ages, and correlating with boundless power and wisdom -all the energies inherent in inorganic and organic -<span class="pagenum"><a name="Page_258" id="Page_258">« 258 »</a></span> -nature. Even then we shall perhaps be able to comprehend -only the means by which, after specific types have -been created, they may, by the culture of their Maker, -be “sported” into new varieties or subspecies, and thus -fitted to exist under different conditions or to occupy -higher places in the economy of nature.</p> - -<p>Before venturing on such extreme speculations as -some now current on questions of this kind, we would -require to know the successive extinct floras as perfectly -as those of the modern world, and to be able to ascertain -to what extent each species can change either spontaneously -or under the influence of struggle for existence or -expansion under favourable conditions, and under arctic -semi-annual days and nights, or the shorter days of the -tropics. Such knowledge, if ever acquired, it may take -ages of investigation to accumulate.</p> - -<p>As to the origin and mode of introduction of successive -floras, I am, for the reasons above stated, not disposed -to dogmatise, or to adopt as final any existing theory of -the development of the vegetable kingdom. Still, some -laws regulating the progress of vegetable life may be -recognised, and I propose to state these in connection -with the Palæozoic floras, to which my own studies have -chiefly related.</p> - -<p>Fossil plants are almost proverbially uncertain with -reference to their accurate determination, and have been -regarded as of comparatively little utility in the decision -of general questions of palæontology. This results principally -from the fragmentary condition in which they -have been studied, and from the fact that fragments of -animal structures are more definite and instructive than -corresponding portions of plants.</p> - -<p>It is to be observed, however, that our knowledge of -fossil plants becomes accurate in proportion to the extent -to which we can carry the study of specimens in the beds -in which they are preserved, so as to examine more perfect -<span class="pagenum"><a name="Page_259" id="Page_259">« 259 »</a></span> -examples than those usually to be found in museums. -When structures are taken into the account, as well as -external forms, we can also depend more confidently on -our results. Further, the abundance of specimens to be -obtained in particular beds often goes far to make up for -their individual imperfection. The writer of these pages -has been enabled to avail himself very fully of these advantages; -and on this account, if on no other, feels entitled -to speak with some authority on theoretical questions.</p> - -<p>It is an additional encouragement to pursue the subject, -that, when we can obtain definite information as to -the successive floras of any region, we thereby learn much -as to climate and vicissitudes in regard to the extent of -land and water; and that, with reference to such points, -the evidence of fossil plants, when properly studied, is, -from the close relation of plants to those stations and -climates, even more valuable than that of animal fossils.</p> - -<p>It is necessary, however, that in pursuing such inquiries -we should have some definite views as to the -nature and permanence of specific forms, whether with -reference to a single geological period or to successive -periods; and I may be excused for stating here some general -principles, which I think important for our guidance.</p> - -<p>1. Botanists proceed on the assumption, vindicated by -experience, that, within the period of human observation, -species have not materially varied or passed into each -other. We may make, for practical purposes, the same -assumption with regard to any given geological period, -and may hold that for each such period there are specific -types which, for the time at least, are invariable.</p> - -<p>2. When we inquire what constitutes a good species -for any given period, we have reason to believe that many -names in our lists represent merely varietal forms or erroneous -determinations. This is the case even in the -modern flora; and in fossil floras, through the poverty of -specimens, their fragmentary condition, and various states -<span class="pagenum"><a name="Page_260" id="Page_260">« 260 »</a></span> -of preservation, it is still more likely to occur. Every -revision of any group of fossils detects numerous synonyms, -and of these many are incapable of detection -without the comparison of large suites of specimens.</p> - -<p>3. We may select from the flora of any geological period -certain forms, which I shall call <i>specific types</i>, which -may for such period be regarded as unchanging. Having -settled such types, we may compare them with similar -forms in other periods, and such comparisons will not be -vitiated by the uncertainty which arises from the comparison -of so-called species which may, in many cases, be -mere varietal forms, as distinguished from specific types. -Our types may be founded on mere fragments, provided -that these are of such a nature as to prove that they belong -to distinct forms which cannot pass into each other, -at least within the limits of one geological period.</p> - -<p>4. When we compare the specific types of one period -with those of another immediately precedent or subsequent, -we shall find that some continue unchanged -through long intervals of geological time, that others are -represented by allied forms regarded either as varietal or -specific, and as derived or otherwise, according to the -view which we may entertain as to the permanence of -species. On the other hand, we also find new types not -rationally deducible on any theory of derivation from -those known in other periods. Further, in comparing -the types of a poor period with those of one rich in species, -we may account for the appearance of new types in -the latter by the deficiency of information as to the former; -where many new types appear in the poorer period -this conclusion seems less probable. For example, new -types appearing in poor formations, like the Lower Erian -and Lower Carboniferous, have greater significance than if -they appeared in the Middle Erian or in the Coal Measures.</p> - -<p>5. When specific types disappear without any known -successors, under circumstances in which it seems unlikely -<span class="pagenum"><a name="Page_261" id="Page_261">« 261 »</a></span> -that we should have failed to discover their continuance, -we may fairly assume that they have become -extinct, at least locally; and where the field of observation -is very extensive, as in the great coal-fields of Europe -and America, we may esteem such extinction as practically -general, at least for the northern hemisphere. -When many specific types become extinct together, or in -close succession, we may suppose that such extinction -resulted from physical changes; but where single types -disappear, under circumstances in which others of similar -habit continue, we may not unreasonably conjecture that, -as Pictet has argued in the case of animals, such types -may have been in their own nature limited in duration, -and may have died out without any external cause.</p> - -<p>6. With regard to the <i>introduction</i> of specific types -we have not as yet a sufficient amount of information. -Even if we freely admit that ordinary specific forms, as -well as mere varieties, may result from derivation, this by -no means excludes the idea of primitive specific types -originating in some other way. Just as the chemist, after -analysing all compounds and ascertaining all allotropic -forms, arrives at length at certain elements not mutually -transmutable or derivable, so the botanist and zoölogist -must expect sooner or later to arrive at elementary -specific types, which, if to be accounted for at all, must -be explained on some principle distinct from that of -derivation. The position of many modern biologists, in -presence of this question, may be logically the same with -that of the ancient alchemists with reference to the -chemical elements, though the fallacy in the case of fossils -may be of more difficult detection. Our business at -present, in the prosecution of palæobotany, is to discover, -if possible, what are elementary or original types, and, having -found these, to enquire as to the law of their creation.</p> - -<p>7. In prosecuting such questions geographical relations -must be carefully considered. When the floras of -<span class="pagenum"><a name="Page_262" id="Page_262">« 262 »</a></span> -two successive periods have existed in the same region, -and under circumstances that render it probable that -plants have continued to grow on the same or adjoining -areas throughout these periods, the comparison becomes -direct, and this is the case with the Erian and Carboniferous -floras in northeastern America. But, when the -areas of the two formations are widely separated in space -as well as in time, any resemblances of facies that we may -observe may have no connection whatever with an unbroken -continuity of specific types.</p> - -<p>I desire, however, under this head, to affirm my conviction -that, with reference to the Erian and Carboniferous -floras of North America and of Europe, the doctrine -of “homotaxis,” as distinct from actual contemporaneity, -has no place. The succession of formations in the Palæozoic -period evidences a similar series of physical phenomena -on the grandest scale throughout the northern hemisphere. -The succession of marine animals implies the -continuity of the sea-bottoms on which they lived. The -headquarters of the Erian flora in America and Europe -must have been in connected or adjoining areas in the -North Atlantic. The similarity of the Carboniferous flora -on the two sides of the Atlantic, and the great number of -identical species, proves a still closer connection in that -period. These coincidences are too extensive and too frequently -repeated to be the result of any accident of similar -sequence at different times, and this more especially as -they extend to the more minute differences in the features -of each period, as, for instance, the floras of the -Lower and Upper Devonian, and of the Lower, Middle, -and Upper Carboniferous.</p> - -<p>8. Another geographical question is that which relates -to centres of dispersion. In times of slow subsidence of -extensive areas, the plants inhabiting such areas must be -narrowed in their range and often separated from one -another in detached spots, while, at the same time, important -<span class="pagenum"><a name="Page_263" id="Page_263">« 263 »</a></span> -climatal changes must also occur. On the re-emergence -of the land such of these species as remained would -again extend themselves over their former areas of distribution, -in so far as the new climatal and other conditions -would permit. We would naturally suppose that the first -of the above processes would tend to the elimination of -varieties, the second, to their increase; but, on the other I -hand, the breaking up of a continental flora into that of -distinct islets, and the crowding together of many forms, -might be a process fertile in the production of some varieties -if fatal to others.</p> - -<p>Further, it is possible that these changes of subsidence -may have some connection with the introduction, as well -as with the extinction, even of specific types. It is certain, -at least, in the case of land-plants, that such types -come in most plentifully immediately after elevation, -though they are most abundantly preserved in periods of -slow subsidence. I do not mean, however, that this connection -is one of cause and effect; there are, indeed, indications -that it is not so. One of these is, that in some -cases the enlargement of the area of the land seems to be -as injurious to terrestrial species as its diminution.</p> - -<p>9. Another point on which I have already insisted, and -which has been found to apply to the Tertiary as well as -to the Palæozoic floras, is the appearance of new types -within the arctic and boreal areas, and their migration -southward. Periods in which the existence of northern -land coincided with a general warm temperature of the -northern hemisphere seem to have been those most favourable -to the introduction of new forms of land-plants. -Hence, there has been throughout geological time a general -movement of new floras from the Palæarctic and -Nearctic regions to the southward.</p> - -<p>Applying the above considerations to the Erian and -Carboniferous floras of North America, we obtain some -data which may guide us in arriving at general conclusions. -<span class="pagenum"><a name="Page_264" id="Page_264">« 264 »</a></span> -The Erian flora is comparatively poor, and its -types are in the main similar to those of the Carboniferous. -Of these types a few only reappear in the middle -coal-formation under identical forms; a great number appear -under allied forms; some altogether disappear. The -Erian flora of New Brunswick and Maine occurs side by -side with the Carboniferous of the same region; so does -the Erian of New York and Pennsylvania with the Carboniferous -of those States. Thus we have data for the -comparison of successive floras in the same region. In -the Canadian region we have, indeed, in direct sequence, -the floras of the Upper Silurian, the Lower, Middle, and -Upper Erian, and the Lower, Middle, and Upper Carboniferous, -all more or less distinct from each other, and -affording an admirable series for comparison in a region -whose geographical features are very broadly marked. -All these floras are composed in great part of similar -types, and probably do not indicate very dissimilar general -physical conditions, but they are separated from each -other by the great subsidences of the Corniferous limestone -and the Lower Carboniferous limestone, and by the -local but intense subterranean action which has altered -and disturbed the Erian beds toward the close of that -period. Still, these changes were not universal. The -Corniferous limestone is absent in Gaspé, and probably in -New Brunswick, where, consequently, the Erian flora -could continue undisturbed during that long period. -The Carboniferous limestone is absent from the slopes of -the Appalachians in Pennsylvania, where a retreat may -have been afforded to the Upper Erian and Lower Carboniferous -floras. The disturbances at the close of the -Erian were limited to those eastern regions where the -great limestone-producing subsidences were unfelt, and, -on the other hand, are absent in Ohio, where the subsidences -and marine conditions were almost at a maximum.</p> - -<p><span class="pagenum"><a name="Page_265" id="Page_265">« 265 »</a></span></p> - -<p>Bearing in mind these peculiarities of the area in -question, we may now group in a tabular form the distinct -specific types recognised in the Erian system, indicating, -at the same time, those which are represented by -identical species in the Carboniferous, those represented -by similar species of the same general type, and those not -represented at all. For example, <i>Calamites cannæformis</i> -extends as a species into the Carboniferous; <i>Asterophyllites -latifolia</i> does not so extend, but is represented by -closely allied species of the same type; <i>Nematophyton</i> -disappears altogether before we reach the Carboniferous.</p> - -<p class="center"><i>Table of Erian and Carboniferous Specific Types.</i></p> - -<table summary="types"> -<tr> - <td class="vtop"> -<table summary="col1"> -<tr> - <td class="bdt bdb center" colspan="2">Erian types. Represented in<br /> - Carboniferous—</td> - <td class="bdt bdr bdb bdl center">By identical<br />types.</td> - <td class="bdt bdr bdb bdl center">By related<br />forms.</td> -</tr> -<tr> - <td class="tdr">1.</td> - <td class="tdl">Syringoxylon mirabile ?</td> - <td class="bdl"></td> - <td class="bdr bdl"></td> -</tr> -<tr> - <td class="tdr">2.</td> - <td class="tdl">Nematoxylon</td> - <td class="bdl"></td> - <td class="bdr bdl"></td> -</tr> -<tr> - <td class="tdr">3.</td> - <td class="tdl">Nematophyton</td> - <td class="bdl"></td> - <td class="bdr bdl"></td> -</tr> -<tr> - <td class="tdr">4.</td> - <td class="tdl">Aporoxylon</td> - <td class="bdl"></td> - <td class="bdr bdl"></td> -</tr> -<tr> - <td class="tdr">5.</td> - <td class="tdl">Ormoxylon</td> - <td class="bdl"></td> - <td class="bdr bdl"></td> -</tr> -<tr> - <td class="tdr">6.</td> - <td class="tdl">Dadoxylon</td> - <td class="bdl"></td> - <td class="bdr bdl center">*</td> -</tr> -<tr> - <td class="tdr">7.</td> - <td class="tdl">Sigillaria Vanuxemii</td> - <td class="bdl"></td> - <td class="bdr bdl center">*</td> -</tr> -<tr> - <td class="tdr">8.</td> - <td class="tdl">S. palpebra</td> - <td class="bdl"></td> - <td class="bdr bdl center">*</td> -</tr> -<tr> - <td class="tdr">9.</td> - <td class="tdl">Didymophyllum</td> - <td class="bdl"></td> - <td class="bdr bdl"></td> -</tr> -<tr> - <td class="tdr">10.</td> - <td class="tdl">Calamodendron</td> - <td class="bdl"></td> - <td class="bdr bdl center">*</td> -</tr> -<tr> - <td class="tdr">11.</td> - <td class="tdl">Calamites transitionis</td> - <td class="bdl center">*</td> - <td class="bdr bdl"></td> -</tr> -<tr> - <td class="tdr">12.</td> - <td class="tdl">C. cannæformis</td> - <td class="bdl center">*</td> - <td class="bdr bdl"></td> -</tr> -<tr> - <td class="tdr">13.</td> - <td class="tdl">Asterophyllites scutigera</td> - <td class="bdl"></td> - <td class="bdr bdl"></td> -</tr> -<tr> - <td class="tdr">14.</td> - <td class="tdl">A. latifolia</td> - <td class="bdl"></td> - <td class="bdr bdl center">*</td> -</tr> -<tr> - <td class="tdr">15.</td> - <td class="tdl">Annularia laxa</td> - <td class="bdl"></td> - <td class="bdr bdl"></td> -</tr> -<tr> - <td class="tdr">16.</td> - <td class="tdl">Sphenophyllum antiquum</td> - <td class="bdl"></td> - <td class="bdr bdl center">*</td> -</tr> -<tr> - <td class="tdr">17.</td> - <td class="tdl">Cyclostigma</td> - <td class="bdl"></td> - <td class="bdr bdl"></td> -</tr> -<tr> - <td class="tdr">18.</td> - <td class="tdl">Arthrostigma</td> - <td class="bdl"></td> - <td class="bdr bdl"></td> -</tr> -<tr> - <td class="tdr">19.</td> - <td class="tdl">Lepidodendron Gaspianum</td> - <td class="bdl"></td> - <td class="bdr bdl center">*</td> -</tr> -<tr> - <td class="tdr">20.</td> - <td class="tdl">L. corrugatum</td> - <td class="bdl center">*</td> - <td class="bdr bdl"></td> -</tr> -<tr> - <td class="tdr">21.</td> - <td class="tdl">Lycopodites Matthewi</td> - <td class="bdl"></td> - <td class="bdr bdl center">*</td> -</tr> -<tr> - <td class="tdr">22.</td> - <td class="tdl">L. Richardsoni</td> - <td class="bdl"></td> - <td class="bdr bdl"></td> -</tr> -<tr> - <td class="tdr">23.</td> - <td class="tdl">Ptilophyton Vanuxemii</td> - <td class="bdl"></td> - <td class="bdr bdl"></td> -</tr> -<tr> - <td class="tdr">24.</td> - <td class="tdl">Lepidophloios antiquus</td> - <td class="bdl"></td> - <td class="bdr bdl center">*</td> -</tr> -<tr> - <td class="tdr">25.</td> - <td class="tdl">Psilophyton princeps</td> - <td class="bdl"></td> - <td class="bdr bdl"></td> -</tr> -<tr> - <td class="bdb tdr">26.</td> - <td class="bdb tdl">P. robustius</td> - <td class="bdb bdl"></td> - <td class="bdr bdb bdl"></td> -</tr> -</table> - </td> - <td class="vtop"> -<table summary="col2"> -<tr> - <td class="bdt bdb bdl center" colspan="2">Erian types. Represented in<br />Carboniferous—</td> - <td class="bdt bdb bdl center">By identical<br />types.</td> - <td class="bdt bdb bdl center">By related<br />forms.</td> -</tr> -<tr> - <td class="bdl tdr">27.</td> - <td class="tdl">Cordaites Robbii</td> - <td class="bdl"></td> - <td class="bdl center">*</td> -</tr> -<tr> - <td class="bdl tdr">28.</td> - <td class="tdl">C. angustifolia</td> - <td class="bdl"></td> - <td class="bdl"></td> -</tr> -<tr> - <td class="bdl tdr">29.</td> - <td class="tdl">Archæopteris Jacksoni</td> - <td class="bdl"></td> - <td class="bdl"></td> -</tr> -<tr> - <td class="bdl tdr">30.</td> - <td class="tdl">Aneimites obtusa</td> - <td class="bdl"></td> - <td class="bdl center">*</td> -</tr> -<tr> - <td class="bdl tdr">31.</td> - <td class="tdl">Platyphyllum Brownii</td> - <td class="bdl"></td> - <td class="bdl"></td> -</tr> -<tr> - <td class="bdl tdr">32.</td> - <td class="tdl">Cyclopteris varia</td> - <td class="bdl"></td> - <td class="bdl center">*</td> -</tr> -<tr> - <td class="bdl tdr">33.</td> - <td class="tdl">C. obtusa</td> - <td class="bdl"></td> - <td class="bdl"></td> -</tr> -<tr> - <td class="bdl tdr">34.</td> - <td class="tdl">Neuropteris polymorpha</td> - <td class="bdl"></td> - <td class="bdl center">*</td> -</tr> -<tr> - <td class="bdl tdr">35.</td> - <td class="tdl">N. serrulata</td> - <td class="bdl"></td> - <td class="bdl center">*</td> -</tr> -<tr> - <td class="bdl tdr">36.</td> - <td class="tdl">N. retorquata</td> - <td class="bdl"></td> - <td class="bdl center">*</td> -</tr> -<tr> - <td class="bdl tdr">37.</td> - <td class="tdl">N. resecta</td> - <td class="bdl"></td> - <td class="bdl"></td> -</tr> -<tr> - <td class="bdl tdr">38.</td> - <td class="tdl">Megalopteris Dawsoni</td> - <td class="bdl"></td> - <td class="bdl"></td> -</tr> -<tr> - <td class="bdl tdr">39.</td> - <td class="tdl">Sphenopteris Hœninghausi</td> - <td class="bdl center">*</td> - <td class="bdl"></td> -</tr> -<tr> - <td class="bdl tdr">40.</td> - <td class="tdl">S. Harttii</td> - <td class="bdl"></td> - <td class="bdl center">*</td> -</tr> -<tr> - <td class="bdl tdr">41.</td> - <td class="tdl">Hymenophyllites curtilobus</td> - <td class="bdl"></td> - <td class="bdl"></td> -</tr> -<tr> - <td class="bdl tdr">42.</td> - <td class="tdl">H. obtusilobus</td> - <td class="bdl"></td> - <td class="bdl center">*</td> -</tr> -<tr> - <td class="bdl tdr">43.</td> - <td class="tdl">Alethopteris discrepans</td> - <td class="bdl"></td> - <td class="bdl center">*</td> -</tr> -<tr> - <td class="bdl tdr">44.</td> - <td class="tdl">Pecopteris serrulata</td> - <td class="bdl"></td> - <td class="bdl center">*</td> -</tr> -<tr> - <td class="bdl tdr">45.</td> - <td class="tdl">P. preciosa</td> - <td class="bdl"></td> - <td class="bdl"></td> -</tr> -<tr> - <td class="bdl tdr">46.</td> - <td class="tdl">Trichomanites</td> - <td class="bdl"></td> - <td class="bdl center">*</td> -</tr> -<tr> - <td class="bdl tdr">47.</td> - <td class="tdl">Callipteris</td> - <td class="bdl"></td> - <td class="bdl center">*</td> -</tr> -<tr> - <td class="bdl tdr">48.</td> - <td class="tdl">Cardiocarpum</td> - <td class="bdl"></td> - <td class="bdl center">*</td> -</tr> -<tr> - <td class="bdl tdr">49.</td> - <td class="tdl">C. Crampii</td> - <td class="bdl"></td> - <td class="bdl"></td> -</tr> -<tr> - <td class="bdl tdr">50.</td> - <td class="tdl">Antholithes</td> - <td class="bdl"></td> - <td class="bdl center">*</td> -</tr> -<tr> - <td class="bdl tdr">51.</td> - <td class="tdl">Trigonocarpum</td> - <td class="bdl"></td> - <td class="bdl center">*</td> -</tr> -<tr> - <td class="bdb bdl"> </td> - <td class="bdb"></td> - <td class="bdb bdl"></td> - <td class="bdb bdl"></td> -</tr> -</table> - </td> -</tr> -</table> - -<p><span class="pagenum"><a name="Page_266" id="Page_266">« 266 »</a></span></p> - -<p>Of the above forms, fifty-one in all, found in the Erian -of eastern America, all, except the last four, are certainly -distinct specific types. Of these only four reappear in the -Carboniferous under identical species, but no less than -twenty-six reappear under representative or allied forms, -some at least of which a derivationist might claim as -modified descendants. On the other hand, nearly one -half of the Devonian types are unknown in the Carboniferous, -while there remain a very large number of Carboniferous -types not accounted for by anything known in -the Devonian. Further, a very poor flora, including only -two or three types, is the predecessor of the Erian flora in -the Upper Silurian, and the flora again becomes poor in -the Upper Devonian and Lower Carboniferous. Every -new species discovered must more or less modify the above -statements, and the whole Erian flora of America, as well -as the Carboniferous, requires a thorough comparison with -that of Europe before general conclusions can be safely -drawn. In the mean time I may indicate the direction in -which the facts seem to point by the following general -statements:</p> - -<p>1. Some of the forms reckoned as specific in the Devonian -and Carboniferous may be really derivative races. -There are indications that such races may have originated -in one or more of the following ways: (1) By a natural -tendency in synthetic types to become specialised in the -direction of one or other of their constituent elements. -In this way such plants as <i>Arthrostigma</i> and <i>Psilophyton</i> -may have assumed new varietal forms. (2) By embryonic -retardation or acceleration,<a name="FNanchor_FE_161" id="FNanchor_FE_161"></a><a href="#Footnote_FE_161" class="fnanchor">[FE]</a> whereby certain species -may have had their maturity advanced or postponed, thus -giving them various grades of perfection in reproduction -and complexity of structure. The fact that so many -Erian and Carboniferous plants seem to be on the confines -<span class="pagenum"><a name="Page_267" id="Page_267">« 267 »</a></span> -of the groups of Acrogens and Gymnosperms may -be supposed favourable to such exchanges. (3) The contraction -and breaking up of floras, as occurred in the -Middle Erian and Lower Carboniferous, may have been -eminently favourable to the production of such varietal -forms as would result from what has been called the -“struggle for existence.” (4) The elevation of a great -expanse of new land at the close of the Middle Erian and -the beginning of the coal period would, by permitting -the extension of species over wide areas and fertile soils, -and by removing the pressure previously existing, be -eminently favourable to the production of new, and especially -of improved, varieties.</p> - -<div class="footnote"> - -<p><a name="Footnote_FE_161" id="Footnote_FE_161"></a><a href="#FNanchor_FE_161"><span class="label">[FE]</span></a> In the manner illustrated by Hyatt and Cope.</p></div> - -<p>2. Whatever importance we may attach to the above -supposed causes of change, we still require to account -for the origin of our specific types. This may forever -elude our observation, but we may at least hope to ascertain -the external conditions favourable to their production. -In order to attain even to this it will be necessary -to inquire critically, with reference to every acknowledged -species, what its claims to distinctness are, so that -we may be enabled to distinguish specific types from -mere varieties. Having attained to some certainty in -this, we may be prepared to inquire whether the conditions -favourable to the appearance of new varieties were -also those favourable to the creation of new types, or the -reverse—whether these conditions were those of compression -or expansion, or to what extent the appearance of -new types may be independent of any external conditions, -other than those absolutely necessary for their -existence. I am not without hope that the further study -of fossil plants may enable us thus to approach to a comprehension -of the laws of the creation, as distinguished -from those of the continued existence of species.</p> - -<p>3. In the present state of our knowledge we have no -good ground either to limit the number of specific types -<span class="pagenum"><a name="Page_268" id="Page_268">« 268 »</a></span> -beyond what a fair study of our material may warrant, -or to infer that such primitive types must necessarily -have been of low grade, or that progress in varietal forms -has always been upward. The occurrence of such an -advanced and specialised type as that of <i>Dadoxylon</i> -in the Middle Devonian should guard us against these -errors. The creative process may have been applicable -to the highest as well as to the lowest forms, and subsequent -deviations must have included degradation as well -as elevation. I can conceive nothing more unreasonable -than the statement sometimes made that it is illogical or -even absurd to suppose that highly organised beings -could have been produced except by derivation from previously -existing organisms. This is begging the whole -question at issue, depriving science of a noble department -of inquiry on which it has as yet barely entered, and anticipating -by unwarranted assertions conclusions which -may perhaps suddenly dawn upon us through the inspiration -of some great intellect, or may for generations to -come baffle the united exertions of all the earnest promoters -of natural science. Our present attitude should -not be that of dogmatists, but that of patient workers -content to labour for a harvest of grand generalisations -which may not come till we have passed away, but which, -if we are earnest and true to Nature and its Creator, may -reward even some of us.</p> - -<p>Within the human period great changes of distribution -of plants have occurred, chiefly through the agency -of man himself, and we have had ample evidence that -plants are able to establish themselves and prosper in -climates and conditions to which unaided they could not -have transported themselves, as, for instance, in the case -of European weeds naturalised in Australia and New Zealand. -There is, however, no reason to believe that any -specific change has occurred to any plant within the Pleistocene -or modern period.</p> - -<p><span class="pagenum"><a name="Page_269" id="Page_269">« 269 »</a></span></p> - -<p>In a recent address, delivered to the biological section -of the British Association, Mr. Carruthers has discussed -this question, and has shown that the earliest vegetable -specimens described by Dr. Schweinfurth from the Egyptian -tombs present no appearance of change. This fact -appears also in the leaves and other organs of plants preserved -in the nodules in the Pleistocene clays of the Ottawa, -and in specimens of similar age found in various -places in Britain and the continent of Europe.<a name="FNanchor_FF_162" id="FNanchor_FF_162"></a><a href="#Footnote_FF_162" class="fnanchor">[FF]</a></p> - -<div class="footnote"> - -<p><a name="Footnote_FF_162" id="Footnote_FF_162"></a><a href="#FNanchor_FF_162"><span class="label">[FF]</span></a> “Proceedings British Association,” 1886, “Pleistocene Plants of -Canada,” Canadian Naturalist, 1866.</p></div> - -<p>The difficulties attending the ordinary theories of -evolution as applied to plants have been well set forth by -the same able botanist in his “Presidential Address to -the Geological Association in 1877,” a paper which deserves -careful study. One of his illustrations is that -ancient willow, <i>Salix polaris</i>, referred to in a previous -chapter, which now lives in the arctic regions, and is -found fossil in the Pleistocene beds at Cromer and at -Bovey Tracey.</p> - -<p>He notes the fact that the genus <i>Salix</i> is a very variable -one, including 19 subgeneric groups and 160 species, -with no less than 222 varieties and 70 hybrids. <i>Salix -polaris</i> belongs to a subgeneric group containing 29 -species, which are arranged in four sections, that to -which <i>S. polaris</i> belongs containing six species. Now it -is easy to construct a theoretical phylogeny of the derivation -of the willows from a supposed ancestral source, -but when we take our little <i>S. polaris</i> we find that this -one twig of our ancestral tree takes us back without -change to the Glacial period. The six species would take -us still farther, and the sections, sub-genera, and genus -at the same rate would require an incalculable amount of -past time. He concludes the inquiry in the following -terms:</p> - -<p><span class="pagenum"><a name="Page_270" id="Page_270">« 270 »</a></span></p> - -<p>"But when we have reached the branch representing -the generic form we have made but little progress in the -phylogenesis of <i>Salix</i>. With <i>Populus</i> this genus forms -a small order, Salicineæ, The two genera are closely -allied, yet separated by well-marked characters; it is -not, however, difficult to conceive of both having sprung -from a generalised form. But there is no record of such -a form. The two genera appear together among the -earliest known dicotyledons, the willows being represented -by six and the poplars by nine species. The ordinal -form, if it ever existed, must necessarily be much -older than the period of the Upper Cretaceous rocks, -that is, than the period to which the earliest known -dicotyledons belong.</p> - -<p>“The Salicineæ are related to five other natural -orders, in all of which the apetalous flowers are arranged -in catkins. These different though allied orders must -be led up by small modifications to a generalised amentiferous -type, and thereafter the various groups of apetalous -plants by innumerable eliminations of differentiating -characters until the primitive form of the apetalous plant -is reached. Beyond this the uncurbed imagination will -have more active work in bridging over the gap between -Angiosperms and Gymnosperms, in finding the intermediate -forms that led up to the vascular cryptogams, and -on through the cellular plants to the primordial germ. -Every step in this phylogenetic tree must be imagined. -The earliest dicotyledon takes us not a step farther back -in the phylogenetic history of <i>Salix</i> than that supplied -by existing vegetation. All beyond the testimony of our -living willows is pure imagination, unsupported by a -single fact. So that here, also, the evidence is against -evolution, and there is none in favour of it.”</p> - -<p>It is easy to see that similar difficulties beset every -attempt to trace the development of plants on the principle -of slow and gradual evolution, and we are driven -<span class="pagenum"><a name="Page_271" id="Page_271">« 271 »</a></span> -back on the theory of periods of rapid origin, as we have -already seen suggested by Saporta in the case of the Cretaceous -dicotyledons. Such abrupt and plentiful introduction -of species over large areas at the same time, by -whatever cause effected—and we are at present quite ignorant -of any secondary causes—becomes in effect something -not unlike the old and familiar idea of creation. Science -must indeed always be baffled by questions of ultimate -origin, and, however far it may be able to trace the chain -of secondary causation and development, must at length -find itself in the presence of the great Creative Mind, -who is “before all things and in whom all things consist.”</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_272" id="Page_272">« 272 »</a><br /><a name="Page_273" id="Page_273">« 273 »</a></span></p> - - - - -<p class="caption2"><a name="APPENDIX_I" id="APPENDIX_I"></a>APPENDIX.</p> - - -<p class="caption2"> -I.—COMPARATIVE VIEW OF THE SUCCESSIVE PALÆOZOIC<br /> -FLORAS OF NORTHEASTERN AMERICA AND<br /> -GREAT BRITAIN.<br /> -</p> - -<p><span class="smcap">In</span> eastern Canada there is a very complete series of fossil plants, -extending from the Silurian to the Permian, and intermediate in its -species between the floras of interior America and of Europe. I may -use this succession, mainly worked out by myself,<a name="FNanchor_FG_163" id="FNanchor_FG_163"></a><a href="#Footnote_FG_163" class="fnanchor">[FG]</a> to summarise the -various Palæozoic floras and sub-floras, in order to give a condensed -view of this portion of the history of the vegetable kingdom, and to -direct attention to the important fact, too often overlooked, that -there is a definite succession of fossil plants as well as of animals, -and that this is important as a means of determining geological -horizons. A British list for comparison has been kindly prepared -for me by Mr. R. Kidston, F. Gr. S. For lists referring to the western -and southern portions of America, I may refer to the reports of -Lesquereux and Fontaine and White.<a name="FNanchor_FH_164" id="FNanchor_FH_164"></a><a href="#Footnote_FH_164" class="fnanchor">[FH]</a></p> - -<div class="footnote"> - -<p><a name="Footnote_FG_163" id="Footnote_FG_163"></a><a href="#FNanchor_FG_163"><span class="label">[FG]</span></a> “Acadian Geology,” “Reports on Fossil Plants of Canada,” Geological -Survey of Canada.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_FH_164" id="Footnote_FH_164"></a><a href="#FNanchor_FH_164"><span class="label">[FH]</span></a> “Geological Surveys of Pennsylvania, Ohio, and Illinois.”</p></div> - -<p>In this connection I am reminded, by an excellent little paper of -M. Zeiller,<a name="FNanchor_FI_165" id="FNanchor_FI_165"></a><a href="#Footnote_FI_165" class="fnanchor">[FI]</a> on Carboniferous plants from the region of the Zambesi, -in Africa, that the flora which in the Carboniferous period extended -over the temperate portions of the northern hemisphere and far into -the arctic, also passed across the equator and prevailed in the southern -hemisphere. Of eleven species brought from the Zambesi by M. -Lapierre and examined by M. Zeiller, all were identical with European -<span class="pagenum"><a name="Page_274" id="Page_274">« 274 »</a></span> -species of the upper coal-formation, and the same fact has been -observed in the coal flora of the Cape Colony.<a name="FNanchor_FJ_166" id="FNanchor_FJ_166"></a><a href="#Footnote_FJ_166" class="fnanchor">[FJ]</a> These facts bear -testimony to the remarkable uniformity of climate and vegetation in -the coal period, and I perfectly agree with Zeiller that they show, -when taken in connection with other parallelisms in fossils, an actual -contemporaneousness of the coal flora over the whole world.</p> - -<div class="footnote"> - -<p><a name="Footnote_FI_165" id="Footnote_FI_165"></a><a href="#FNanchor_FI_165"><span class="label">[FI]</span></a> Paris, 1883.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_FJ_166" id="Footnote_FJ_166"></a><a href="#FNanchor_FJ_166"><span class="label">[FJ]</span></a> Grey, “Journal of the Geological Society,” vol. xxvii.</p></div> - - -<p class="caption3">1. Carboniferous Flora.</p> - -<p class="p0">(1) <i>Permo-Carboniferous Sub-Flora</i>:</p> - -<p>This occurs in the upper member of the Carboniferous system of -Nova Scotia and Prince Edward Island, originally named by the -writer the Newer Coal-formation, and more recently the Permo-Carboniferous, -and the upper beds of which may not improbably be -contemporaneous with the Lower Permian or Lower Dyas of Europe. -In this formation there is a predominance of red sandstones and -shales, and it contains no productive beds of coal. Its fossil plants -are for the most part of species found in the Middle or Productive -Coal-formation, but are less numerous, and there are a few new forms -akin to those of the European Permian. The most characteristic -species of the upper portion of the formation, which has the most -decidedly Permian aspect, are the following:</p> - -<table summary="table"> -<tr> - <td></td> - <td class="tdl"><i>Dadoxylon materiarium</i>, Dawson.</td> -</tr> -<tr> - <td>*</td> - <td class="tdl"><i>Walchia</i> (<i>Araucarites</i>) <i>robusta</i>, Dn.</td> -</tr> -<tr> - <td>*</td> - <td class="tdl"><i>W.</i> (<i>A.</i>) <i>gracilis</i>, Dn.</td> -</tr> -<tr> - <td>*</td> - <td class="tdl"><i>W. imbricatula</i>, Dn.</td> -</tr> -<tr> - <td></td> - <td class="tdl"><i>Calamites Suckovii</i>, Brongt.</td> -</tr> -<tr> - <td></td> - <td class="tdl"><i>C. Cistii</i>, Brongt.</td> -</tr> -<tr> - <td>*</td> - <td class="tdl"><i>C. gigas</i>, Brongt.</td> -</tr> -<tr> - <td></td> - <td class="tdl"><i>Neuropteris rarinervis</i>, Bunbury.</td> -</tr> -<tr> - <td></td> - <td class="tdl"><i>Alethopteris nervosa</i>, Brongt.</td> -</tr> -<tr> - <td></td> - <td class="tdl"><i>Pecopteris arborescens</i>, Brongt.</td> -</tr> -<tr> - <td>*</td> - <td class="tdl"><i>P. rigida</i>, Dn.</td> -</tr> -<tr> - <td></td> - <td class="tdl"><i>P. oreopteroides</i>, Brongt.</td> -</tr> -<tr> - <td>*</td> - <td class="tdl"><i>Cordaites simplex</i>, Dn.</td> -</tr> -</table> - -<p>Of these species, those marked with an asterisk have not yet been -found in the middle or lower members of the Carboniferous system. -They will be found described, and several of them figured, in my -“Report on the Geology of Prince Edward Island.”<a name="FNanchor_FK_167" id="FNanchor_FK_167"></a><a href="#Footnote_FK_167" class="fnanchor">[FK]</a> The others are -<span class="pagenum"><a name="Page_275" id="Page_275">« 275 »</a></span> -common and widely diffused Carboniferous species, some of which -have extended to the Permian period in Europe as well. From the -upper beds, characterised by these and a few other species, there is a -gradual passage downward into the productive coal-measures, and a -gradually increasing number of true coal-formation species.</p> - -<div class="footnote"> - -<p><a name="Footnote_FK_167" id="Footnote_FK_167"></a><a href="#FNanchor_FK_167"><span class="label">[FK]</span></a> 1871.</p></div> - -<p>It is worthy of remark here that the association in the Permo-Carboniferous -of numerous trunks of <i>Dadoxylon</i> with the branches -of <i>Walchia</i> and with fruits of the character of <i>Trigonocarpa</i>, seems -to show that these were parts of one and the same plant.</p> - -<p>This formation represents the Upper Barren Measures of West -Virginia, which are well described by Fontaine and White,<a name="FNanchor_FL_168" id="FNanchor_FL_168"></a><a href="#Footnote_FL_168" class="fnanchor">[FL]</a> and the -reasons which these authors adduce for considering the latter equivalent -to the European Permian will apply to the more northern and -eastern deposits as well, though these have afforded fewer species of -plants, and are apparently less fully developed.</p> - -<div class="footnote"> - -<p><a name="Footnote_FL_168" id="Footnote_FL_168"></a><a href="#FNanchor_FL_168"><span class="label">[FL]</span></a> “Report on the Permian Flora of Western Virginia and South -Pennsylvania,” 1880.</p></div> - -<p class="p0">(2) <i>Coal-formation Sub-Flora</i>:</p> - -<p>The Middle or Productive Coal-formation, containing all the beds -of coal which are mined in Nova Scotia and Cape Breton, is the headquarters -of the Carboniferous flora. From this formation I have -catalogued<a name="FNanchor_FM_169" id="FNanchor_FM_169"></a><a href="#Footnote_FM_169" class="fnanchor">[FM]</a> one hundred and thirty-five species of plants; but, as -several of these are founded on imperfect specimens, the number of -actual species may be estimated at one hundred and twenty. Of -these more than one half are species common to Europe and America. -No less than nineteen species are <i>Sigillariæ</i>, and about the same -number are <i>Lepidodendra</i>. About fifty are ferns and thirteen are -<i>Calamites</i>, <i>Asterophyllites</i>, and <i>Sphenophylla</i>. The great abundance -and number of species of Sigillariæ, Lepidodendra, and ferns are -characteristic of this sub-flora; and among the ferns certain species -of <i>Neuropteris</i>, <i>Pecopteris</i>, <i>Alethopteris</i>, and <i>Sphenopteris</i> greatly -preponderate.</p> - -<div class="footnote"> - -<p><a name="Footnote_FM_169" id="Footnote_FM_169"></a><a href="#FNanchor_FM_169"><span class="label">[FM]</span></a> “Acadian Geology,” and “Report on Flora of Lower Carboniferous,” 1873.</p></div> - -<p>These beds are the equivalents of the Middle Coal-measures, or -Productive Coal-measures of Pennsylvania, Ohio, &c., and of the -coal-formation proper of various European countries. Very many -of the species are common to Nova Scotia and Pennsylvania; but in -proceeding westward the number of identical species seems to diminish.</p> - -<p><span class="pagenum"><a name="Page_276" id="Page_276">« 276 »</a></span></p> - -<p class="p0">(3) <i>The Millstone Grit Sub-Flora</i>:</p> - -<p>In this formation the abundance of plants and the number of -species are greatly diminished.<a name="FNanchor_FN_170" id="FNanchor_FN_170"></a><a href="#Footnote_FN_170" class="fnanchor">[FN]</a> Trunks of coniferous trees of the -species <i>Dadoxylon Acadianum</i>, having wide wood-cells with three -or more series of discs and complex medullary rays, become characteristic. -<i>Calamites undulatum</i> is abundant and seems to replace <i>C. -Suckovii</i>, though <i>C. cannæformis</i> and <i>C. cistii</i> continue. <i>Sigillariæ</i> -become very rare, and the species of Lepidodendron are few, and -mostly those with large leaf-bases. <i>Lepidophloios</i> still continues, and -<i>Cordaites</i> abounds in some beds. The ferns are greatly reduced, -though a few characteristic coal-formation species occur, and the -genus <i>Cardiopteris</i> appears. Beds of coal are rare in this formation; -but where they occur there is in connection with them a remarkable -anticipation of the rich coal-formation flora, which would thus seem -to have existed locally in the Millstone Grit period, but to have -found itself limited by generally unfavorable conditions. In America, -as in Europe, it is in the north that this earlier development of -the coal-flora occurs, while in the south there is a lingering of old -forms in the newer beds. In Newfoundland and Cape Breton, for -instance, as well as in Scotland, productive coal-beds and a greater -variety of species of plants occur in this formation.</p> - -<div class="footnote"> - -<p><a name="Footnote_FN_170" id="Footnote_FN_170"></a><a href="#FNanchor_FN_170"><span class="label">[FN]</span></a> “Report on Fossil Plants of the Lower Carboniferous and Millstone -Grit of Canada,” 1873.</p></div> - -<p>The following would appear to be the equivalents of this formation, -in flora and geological position:</p> - -<p>1. The Seral Conglomerate of Rogers in Pennsylvania, &c.</p> - -<p>2. The Lower Coal-formation Conglomerate and Chester groups -of Illinois (Worthen).</p> - -<p>3. The Lower Carboniferous Sandstone of Kentucky, Alabama, -and Virginia.</p> - -<p>4. The Millstone Grit and Yoredale rocks of northern England, -and the Culmiferous of Devonshire.</p> - -<p>5. The Moor rock and Lower Coal-measures of Scotland.</p> - -<p>6. Flagstones and Lower Shales of the south of Ireland, and Millstone -Grit of the north of Ireland.</p> - -<p>7. The Jüngste Grauwacke of the Hartz, Saxony, and Silesia.</p> - -<p class="p0">(4) <i>The Carboniferous Limestone Series</i>:</p> - -<p>This affords few fossil plants in eastern America, and in so far as -known they are similar to those of the next group. In Scotland it -is richer in plants, but, according to Mr. Kidston, these are largely -<span class="pagenum"><a name="Page_277" id="Page_277">« 277 »</a></span> -similar to those of the underlying beds, though with some species -which extend upward into the Millstone Grit. In Scotland the alga -named <i>Spirophyton</i> and <i>Archæocalamites radiatus</i>—which in America -are Erian—appear in this formation.</p> - -<p class="p0">(5) <i>The Lower Carboniferous Sub-Flora</i>:</p> - -<p>This group of plants is best seen in the shales of the Horton -series, under the Lower Carboniferous marine limestones. It is -small and peculiar. The most characteristic species are the following:</p> - -<p><i>Dadoxylon</i> (<i>Palæoxylon</i>) <i>antiquius</i>, Dn.—A species with large -medullary rays of three or more series of cells.</p> - -<p><i>Lepidodendron corrugatum</i>, Dn.—A species closely allied to <i>L. -Veltheimianum</i> of Europe, and which is its American representative. -This is perhaps the most characteristic plant of the formation. It -is very abundant, and presents very protean appearances, in its old -stems, branches, twigs, and <i>Knorria</i> forms. It had well-characterised -stigmaria roots, and constitutes the oldest erect forest known in -Nova Scotia.</p> - -<p><i>Lepidodendron tetragonum</i>, Sternberg.</p> - -<p><i>L. obovatum</i>, Sternb.</p> - -<p><i>L. aculeatum</i>, Sternb.</p> - -<p><i>L. dichotomum</i>, Sternb.</p> - -<p>The four species last mentioned are comparatively rare, and the -specimens are usually too imperfect to render their identification -certain, but Lepidodendra are especially characteristic trees of this -horizon.</p> - -<p><i>Cyclopteris</i> (<i>Aneimites</i>) <i>Acadica</i>, Dn.—A very characteristic fern, -allied in the form of its fronds to <i>C. tenuifolia</i> of Goeppert, to <i>C. -nana</i> of Eichwald, and to <i>Adiantites antiquus</i> of Stur. Its fructification, -however, is nearer to that of <i>Aneimia</i> than to that of <i>Adiantum</i>.</p> - -<p>Ferns of the genera Cardiopteris and <i>Hymenophyllites</i> also occur, -though rarely.</p> - -<p><i>Ptilophyton plumula</i>, Dn.—This is the latest appearance of this -Erian genus, which also occurs in the Lower Carboniferous of Europe -and of the United States.</p> - -<p><i>Cordaites borassifolia</i>, Brongt.</p> - -<p>On the whole, this small flora is markedly distinct from that of -the Millstone Grit and true coal-formation, from which it is separated -by the great length of time required for the deposition of the -marine limestones and their associated beds, in which no land-plants -<span class="pagenum"><a name="Page_278" id="Page_278">« 278 »</a></span> -have been found; nor is this gap filled up by the conglomerates and -coarse arenaceous beds which, as I have explained in “Acadian Geology,” -in some localities take the place of the limestones, as they do -also in the Appalachian region farther south.</p> - -<p>The palæobotanical and stratigraphical equivalents of this series -abroad would seem to be the following:</p> - -<p>1. The Vespertine group of Rogers in Pennsylvania.</p> - -<p>2. The Kinderhook group of Worthen in Illinois.</p> - -<p>3. The Marshall group of Winchell in Michigan.</p> - -<p>4. The Waverley sandstone (in part) of Ohio.</p> - -<p>5. The Lower or False Coal-measures of Virginia.</p> - -<p>6. The Calciferous sandstones of McLaren, or Tweedian group of -Tate in Scotland.</p> - -<p>7. The Lower Carboniferous slate and Coomhala grits of Jukes -in Ireland.</p> - -<p>8. The Culm and Culm Grauwacke of Germany.</p> - -<p>9. The Graywacke or Lower Coal-measures of the Vosges, as described -by Schimper.</p> - -<p>10. The Older Coal-formation of the Ural, as described by Eichwald.</p> - -<p>11. The so-called “Ursa Stage” of Heer includes this, but he has -united it with Devonian beds, so that the name cannot be used except -for the local development of these beds at Bear Island, Spitsbergen. -The Carboniferous plants of arctic America, Melville Island, -&c., as well as those of Spitzbergen, appear all to be Lower -Carboniferous.<a name="FNanchor_FO_171" id="FNanchor_FO_171"></a><a href="#Footnote_FO_171" class="fnanchor">[FO]</a></p> - -<div class="footnote"> - -<p><a name="Footnote_FO_171" id="Footnote_FO_171"></a><a href="#FNanchor_FO_171"><span class="label">[FO]</span></a> “Notes on Geological Map of the Northern Portion of the Dominion -of Canada,” by Dr. G. M. Dawson, 1887.</p></div> - -<p>All of the above groups of rocks are characterised by the prevalence -of <i>Lepidodendra</i> of the type of <i>L. corrugatum</i>, <i>L. Veltheimianum</i>, -and <i>L. Glincanum</i>; pines of the sub-genus <i>Pitus</i> of Witham, -<i>Palæoxylon</i> of Brongniart, and peculiar ferns of the genera <i>Cyclopteris</i>, -<i>Cardiopteris</i>, <i>Triphyllopteris</i>, and <i>Sphenopteris</i>. In all the -regions above referred to they form the natural base of the great -Carboniferous system.</p> - -<p>In Virginia, according to Fontaine and White, types, such as -Archæopteris, which in the north are Upper Erian, occur in this -group. Unless there have been some errors in fixing the lower limit -of the Vespertine, this would indicate a longer continuance of old -forms in the south.</p> - -<p><span class="pagenum"><a name="Page_279" id="Page_279">« 279 »</a></span></p> - -<p class="caption3">2. Erian Flora.</p> - -<p class="p0">(1) <i>Upper Erian Sub-Flora</i>:</p> - -<p>This corresponds to the Catskill and Chemung of the New York -series, and to the Upper Devonian of Europe.</p> - -<p>The flora of this formation, which consists mostly of sandstones, -is not rich. Its most distinctive species on both sides of the Atlantic -seem to be the ferns of the genus <i>Archæopteris</i>, along with species -referred to the genus <i>Cyclopteris</i>, but which, in so far as their barren -fronds are concerned, for the most part resemble <i>Archæopteris</i>.</p> - -<p>The characteristic American species are <i>Archæopteris Jacksoni</i>, -<i>A. Rogersi</i>, and <i>A. Gaspiensis</i>. <i>Cyclopteris obtusa</i> and <i>C.</i> (<i>Platyphyllum</i>) -<i>Brownii</i> are also very characteristic species. In Europe, -<i>Archæopteris Hibernica</i> is a prevalent species.</p> - -<p><i>Leptophleum rhombicum</i> and fragments of <i>Psilophyton</i> are also -found in the Upper Erian. There is evidence of the existence of -vast numbers of <i>Rhizocarps</i> in this period, in the deposits of spore-cases -(<i>Sporangites Huronensis</i>) in the shales of Kettle Point, Lake -Huron; and in deposits of similar character in Ohio and elsewhere -in the West.</p> - -<p>The Upper Erian flora is thus very distinct from that of the -Lower Carboniferous, and the unconformable relation of the beds in -the Northeast may perhaps indicate a considerable lapse of time. -Still, even in localities where there appears to be a transition from -the Carboniferous into the Devonian, as in the Western States and -in Ireland, the characteristic flora of each formation may be distinguished, -though, as already stated, there is apparently some mixture -in the South.</p> - -<p class="p0">(2) <i>Middle Erian Sub-Flora</i>:</p> - -<p>Both in Canada and the United States that part of the great -Erian system which may be regarded as its middle division, the -Hamilton and Marcellus shales of New York, the Cordaites shales of -St. John, New Brunswick, and the middle shales and sandstones of -the Gaspé series, presents conditions more favourable to the abundant -growth of land-plants than either the upper or lower member. In -the St. John beds, in particular, there is a rich fern flora, comparable -with that of the coal-formation, and numerous stipes of ferns and -trunks of tree-ferns have been found in the Hamilton and Corniferous -series in the West, as well as trunks of <i>Dadoxylon</i>. It is, however, -distinguished by a prevalence of small and delicate species, and -by such forms as <i>Hymenophyllites</i> and the smaller Sphenopterids, -and also by some peculiar ferns, as <i>Archæopteris</i> and <i>Megalopteris</i>. -<span class="pagenum"><a name="Page_280" id="Page_280">« 280 »</a></span> -In addition to ferns, it has small <i>Lepidodendra</i>, of which <i>L. Gaspianum</i> -is the chief. <i>Calamiteæ</i> occur, <i>Archæocalamites radiatus</i> being -the dominant species. This plant, which in Europe appears to reach -up into the Lower Carboniferous, is so far strictly Erian in northeast -America. <i>Sigillariæ</i> scarcely appear, but <i>Cordaites</i> is abundant, -and the earliest known species of <i>Dadoxylon</i> appear, while the -Psilophyton, so characteristic of the Lower Erian, still continues, -and the remarkable aquatic plants of the genus <i>Ptilophyton</i> are -locally abundant.</p> - -<p class="p0">(3) <i>Lower Erian Sub-Flora</i>:</p> - -<p>This belongs to the Lower Devonian sandstones and shales, and -is best seen in that formation at Gaspé and the Bay des Chaleurs. It -is equivalent to the Oriskany sandstone, so far as its animal fossils -and mineral character are concerned. It is characterised by the absence -of true ferns, <i>Calamites</i> and <i>Sigillariæ</i>, and by the presence -of such forms as <i>Psilophyton</i>, <i>Arthrostigma</i>, <i>Leptophleum</i>, and <i>Nematophyton</i>. -<i>Lepidodendron Gaspianum</i> and <i>Leptophleum</i> already -occur, though not nearly so abundant as Psilophyton.</p> - -<p>The Lower Erian plants have an antique and generalised aspect -which would lead us to infer that they are near the beginning of the -land-flora, or perhaps in part belong to the close of an earlier flora -still in great part unknown and few indications of land-plants have -been found earlier.</p> - -<p>At Campbellton and Scaumenac Bay, on the Bay des Chaleurs, -fossil fishes of genera characteristic of the Lower and Upper Devonian -horizons respectively, occur in association with fossil plants -of these horizons, and have been described by Mr. Whiteaves.<a name="FNanchor_FP_172" id="FNanchor_FP_172"></a><a href="#Footnote_FP_172" class="fnanchor">[FP]</a></p> - -<div class="footnote"> - -<p><a name="Footnote_FP_172" id="Footnote_FP_172"></a><a href="#FNanchor_FP_172"><span class="label">[FP]</span></a> “Transactions of the Royal Society of Canada.”</p></div> - -<p>It is interesting to note that, as Fontaine and White have observed, -certain forms which are Erian in the northeast are found in -the Lower members of the Carboniferous in West Virginia, indicating -the southward march of species in these periods.</p> - -<p class="caption3">3. The Silurian Flora and still Earlier Indications of -Plants.</p> - -<p>In the upper beds of the Silurian, those of the Helderberg series, -we still find <i>Psilophyton</i> and <i>Nematophyton</i>; but below these we -know no land-plants in Canada. In the United States, Lesquereux -and Claypole have described remains which may indicate the existence -of lycopodiaceous and annularian types as far back as the beginning -<span class="pagenum"><a name="Page_281" id="Page_281">« 281 »</a></span> -of the Upper Silurian, or even as low as the Hudson River -group, and Hicks has found <i>Nematophyton</i> and <i>Psilophyton</i> in beds -about as old in Wales, along with the uncertain stems named <i>Berwynia</i>. -In the Lower Silurian the <i>Protannularia</i> of the Skiddaw -series in England may represent a land-plant, but this is uncertain, -and no similar species has been found in Canada.</p> - -<p>The Cambrian rocks are so far barren of land-plants; the so-called -<i>Eophyton</i> being evidently nothing but markings, probably -produced by crustaceans and other aquatic animals. In the still -older Laurentian the abundant beds of graphite probably indicate -the existence of plants, but whether aquatic or terrestrial it is impossible -to decide at present.</p> - -<p>It would thus appear that our certain knowledge of land-vegetation -begins with the Upper Silurian or the Silurio-Cambrian, and -that its earliest forms were Acrogens allied to Lycopods, and prototypal -trees, forerunners of the Acrogens or the gymnosperms. In -the Lower Devonian little advance is made. In the Middle Devonian -this meagre flora had been replaced by one rivalling that of the Carboniferous, -and including pines, tree-ferns, and arboreal forms of -Lycopods and of equisetaceous plants, as well as numerous herbaceous -plants. At the close of the Erian the flora again became -meagre, and continued so in the Lower Carboniferous. It again became -rich and varied in the Middle Carboniferous, to decay in the -succeeding Permian.</p> - - - -<hr class="chap" /> -<p class="caption2"><a name="APPENDIX_II" id="APPENDIX_II"></a>II.—HEER’S LATEST RESULTS IN THE GREENLAND FLORA.</p> - - -<p><span class="smcap">A very</span> valuable report of Prof. Steenstrup, published in Copenhagen -in 1883, the year in which Heer died, contains the results of -his last work on the Greenland plants, and is so important that a -summary of its contents will be interesting to all students of fossil -botany or of the vicissitudes of climate which the earth has undergone.<a name="FNanchor_FQ_173" id="FNanchor_FQ_173"></a><a href="#Footnote_FQ_173" class="fnanchor">[FQ]</a></p> - -<div class="footnote"> - -<p><a name="Footnote_FQ_173" id="Footnote_FQ_173"></a><a href="#FNanchor_FQ_173"><span class="label">[FQ]</span></a> Meddelelser om Gronland, Hefte V., Copenhagen, 1883.</p></div> - -<p>The plant-bearing beds of Greenland are as follows, in ascending -order:</p> - -<p class="caption3">1. <span class="smcap">Cretaceous</span>.</p> - -<p>1. The <i>Komé</i> series, of black shales resting on the Laurentian -gneiss. These beds are found at various other localities, but the -<span class="pagenum"><a name="Page_282" id="Page_282">« 282 »</a></span> -name above given is that by which they are generally known. Their -flora is limited to ferns, cycads, conifers, and a few endogens, with -only <i>Populus primæva</i> to represent the dicotyledons. These beds -are regarded as Lower Cretaceous (Urgonian), but the animal fossils -would seem to give them a rather higher position. They may be -regarded as equivalent to the Kootanie and Queen Charlotte beds in -Canada, and the Potomac series in Virginia.</p> - -<p>2. The <i>Atané</i> series. These also are black shales with dark-coloured -sandstones. They are best exposed at Upernavik and -Waigat. Here dicotyledonous leaves abound, amounting to ninety -species, or more than half the whole number of species found. -The fossil plants resemble those of the Dakota series of the United -States and the Dunvegan series of Canada, and the animal fossils -indicate the horizon of the Fort Pierre or its lower part. They may -be regarded as representing the lower part of the Upper Cretaceous. -The genera <i>Populus</i>, <i>Myrica</i>, <i>Quercus</i>, <i>Ficus</i>, <i>Platanus</i>, <i>Sassafras</i>, -<i>Laurus</i>, <i>Magnolia</i>, and <i>Liriodendron</i> are among those represented -in these beds, and the peculiar genera <i>Macclintockia</i> and <i>Credneria</i> -are characteristic. The genus <i>Pinus</i> is represented by five species, -<i>Sequoia</i> by five, and <i>Salisburia</i> by two, with three of the allied -genus <i>Baiera</i>. There are many ferns and cycads.</p> - -<p>3. The <i>Patoot</i> series. These are yellow and red shales, which -seem to owe their colour to the spontaneous combustion of pyritous -lignite, in the manner observed on the South Saskatchewan and the -Mackenzie rivers. Their age is probably about that of the Fox-Hill -group or Senonian, and the Upper Cretaceous of Vancouver Island, -and they afford a large proportion of dicotyledonous leaves. The -genera of dicotyledons are not dissimilar from those of Atané, but -we now recognise <i>Betula</i> and <i>Alnus</i>, <i>Comptonia</i>, <i>Planera</i>, <i>Sapotacites</i>, -<i>Fraxinus</i>, <i>Viburnum</i>, <i>Cornus</i>, <i>Acer</i>, <i>Celastrus</i>, <i>Paliurus</i>, -<i>Ceanothus</i>, <i>Zizyphus</i>, and <i>Cratægus</i> as new genera of modern aspect.</p> - -<p>On the whole there have been found in all these beds 335 species, -belonging to 60 families, of which 36 are dicotyledonous, and represent -all the leading types of arborescent dicotyledons of the temperate -latitudes. The flora is a warm temperate one, with some remarkable -mixtures of sub-tropical forms, among which perhaps the -most remarkable are <i>Kaidocarpum</i> referred to the <i>Pandaneæ</i>, and -such exogens as <i>Ficus</i> and <i>Cinnamomum</i>.</p> - -<p class="caption3">2. <span class="smcap">Tertiary</span>.</p> - -<p>4. The <i>Unartok</i> series. This is believed to be Eocene. It consists -of sandstone, which appears on the shores of Disco Island, and -<span class="pagenum"><a name="Page_283" id="Page_283">« 283 »</a></span> -possibly at some other places on the coast. The beds rest directly -and apparently conformably on the Upper Cretaceous, and have afforded -only eleven species of plants. <i>Magnolia</i> is represented by -two species, <i>Laurus</i> by two, <i>Platanus</i> by two, and one of these said -to be identical with a species found by Lesquereux in the Laramie,<a name="FNanchor_FR_174" id="FNanchor_FR_174"></a><a href="#Footnote_FR_174" class="fnanchor">[FR]</a> -<i>Viburnum</i>, <i>Juglans</i>, <i>Quercus</i>, each by one species; the ubiquitous -<i>Sequoias</i> by <i>S. Langsdorfii</i>. This is pretty clearly a Lower Laramie -flora.</p> - -<div class="footnote"> - -<p><a name="Footnote_FR_174" id="Footnote_FR_174"></a><a href="#FNanchor_FR_174"><span class="label">[FR]</span></a> <i>Viburnum marginatum</i> of Lesquereux.</p></div> - -<p>5. The <i>Atanekerdluk</i> series, consisting of shaly beds, with limestone -intercalated between great sheets of basalt, much like the -Eocene of Antrim and the Hebrides. These beds have yielded 187 -species, principally in bands and concretions of siderite, and often -in a good state of preservation. They are referred to the Lower -Miocene, but, as explained in the text, the flora is more nearly akin -to that of the Eocene of Europe and the Laramie of America. The -animal fossils are chiefly fresh-water shells. <i>Onoclea sensibilis</i>, -several conifers, as <i>Taxites</i> <i>Olriki</i>, <i>Taxodium distichum</i>, <i>Glyptostrobus -Europæus</i>, and <i>Sequoia Langsdorfii</i>, and 42 of the dicotyledons -are recognised as found also in American localities. Of these, a -large proportion of the more common species occur in the Laramie -of the Mackenzie River and elsewhere in northwest Canada, and in -the western United States. It is quite likely also that several species -regarded as distinct may prove to be identical.</p> - -<p>It would seem that throughout the whole thickness of these -Tertiary beds the flora is similar, so that it is probable it belongs altogether -to the Eocene rather than to the Miocene.</p> - -<p>No indication has been observed of any period of cold intervening -between the Lower Cretaceous and the top of the Tertiary deposits, -so that, in all the vast period which these formations represent, the -climate of Greenland would seem to have been temperate. There -is, however, as is the case farther south, evidence of a gradual diminution -of temperature. In the Lower Cretaceous the probable mean -annual temperature in latitude 71° north is stated as 21° to 22° -centigrade, while in the early Tertiary it is estimated at 12° centigrade. -Such temperatures, ranging from 71° to 53° of Fahrenheit, -represent a marvellously warm climate for so high a latitude. In -point of fact, however, the evidence of warm climates in the arctic -regions, in the Palæozoic as well as in the Mesozoic and early Tertiary, -should perhaps lead us to conclude that, relatively to the whole -of geological time, the present arctic climate is unusually severe, and -<span class="pagenum"><a name="Page_284" id="Page_284">« 284 »</a></span> -that a temperate climate in the arctic regions has throughout geological -time been the rule rather than the exception.</p> - - - -<hr class="chap" /> -<p class="caption2"><a name="APPENDIX_III" id="APPENDIX_III"></a>III.—MINERALISATION OF FOSSIL PLANTS.</p> - - -<p>The state of preservation of fossil plants has been referred to -incidentally in several places in the text; but the following more -definite statements may be of service to the reader.</p> - -<p>I. Organic remains imbedded in aqueous deposits may occur in -an unchanged condition, or only more or less altered by decay. This -is often the case with such enduring substances as bark and wood, -and even with leaves, which appear as thin carbonaceous films when -the layers containing them are split open. In the more recent deposits -such remains occur little modified, or perhaps only slightly -changed by partial decay of their more perishable parts. In the -older formations, however, they are usually found in a more or -less altered condition, in which their original substance has been -wholly or in part changed into coaly, or bituminous, or anthracitic -or graphitic matter, so that leaves are sometimes represented by stains -of graphite, as if drawn on stone with a lead-pencil. Yet even in -this case some portion of the original substance remains, and without -any introduction of foreign material.</p> - -<p>II. On the other hand, such remains are often mineralised by the -filling of their pores or the replacement of their tissues with mineral -matter, so that they become hard and stony, and sometimes retain -little or nothing of their original substance. The more important -of these changes, in so far as they affect fossil plants, may be arranged -under the following heads:</p> - -<p>(<i>a</i>) <i>Infiltration</i> of mineral matter which has penetrated the pores -of the fossil in a state of solution. Thus the pores of fossil wood -are often filled with calcite, quartz, oxide of iron, or sulphide of iron, -while the woody walls of the cells and vessels remain in a carbonised -state, or converted into coaly matter. When wood is preserved in -this way it has a hard and stony aspect; but we can sometimes dissolve -away the mineral matter, and restore the vegetable tissue to a -condition resembling that before mineralisation. This is especially -the case when calcite is the mineralising substance. We sometimes -find, on microscopic examination, that even cavities so small as those -of vegetable cells and vessels have been filled with successive coats -of different kinds of mineral matter.</p> - -<p>(<i>b</i>) Organic matters may be entirely <i>replaced</i> by mineral substances. -In this case the cavities and pores have been first filled, -<span class="pagenum"><a name="Page_285" id="Page_285">« 285 »</a></span> -and then—the walls or solid parts being removed by decay or solution—mineral -matter, either similar to that filling the cavities, or -differing in colour or composition, has been introduced. Silicified -wood often occurs in this condition. In the case of silicified wood, -it sometimes happens that the cavities of the fibers have been filled -with silica, and the wood has been afterward removed by decay, -leaving the casts of the tubular fibers as a loose filamentous substance. -Some of the Tertiary coniferous woods of California are in -this state, and look like asbestus, though they show the minute -markings of the tissue under the microscope. In the case of silicified -or agatized woods, it would seem that the production of carbon dioxide -from the decaying wood has caused the deposition of silica in -its place, from alkaline solutions of that substance, and thus the -carbon has been replaced, atom by atom, by silicon, until the whole -mass has been silicified, yet retaining perfectly its structure.</p> - -<p>(<i>c</i>) The cavities left by fossils which have decayed may be filled -with clay, sand, or other foreign matter, and this, becoming subsequently -hardened into stone, may constitute a <i>cast</i> of the fossils. -Trunks of trees, roots, &c., are often preserved in this way, appearing -as stony casts, often with the outer bark of the plant forming a carbonaceous -coating on their surfaces. In connection with this state -may be mentioned that in which, the wood having decayed, an entire -trunk has been flattened so as to appear merely as a compressed film -of bark, yet retaining its markings; and that in which the whole of -the vegetable matter having been removed, a mere impression of -the form remains.</p> - -<p>Fossils preserved in either of the modes, (<i>a</i>) or (<i>b</i>), usually show -more or less of their minute structures under the microscope. These -may be observed:—(1) By breaking off small splinters or flakes and -examining them, either as opaque or as transparent objects. (2) By -treating the material with acids, so as to dissolve out the mineral -matters, or portions of them. This method is especially applicable -to fossil woods mineralised with calcite or pyrite. (3) By grinding -thin sections. These are first polished on one face on a coarse stone -or emery hone, and then on a fine hone, then attached by the polished -face to glass slips with a transparent cement or Canada balsam, and -ground on the opposite face until they become so thin as to be translucent. -In most cities there are lapidaries who prepare slices of this -kind; but the amateur can readily acquire the art by a little practice, -and the necessary appliances can be obtained through dealers -in minerals or in microscopic materials. Very convenient cutting -and polishing machines, some of them quite small and portable, are -<span class="pagenum"><a name="Page_286" id="Page_286">« 286 »</a></span> -now made for the use of amateurs. In the case of exogenous woods, -three sections are necessary to exhibit the whole of the structures. -One of these should be transverse and two longitudinal, the latter in -radial and tangential planes.</p> - - - -<hr class="chap" /> -<p class="caption2"><a name="APPENDIX_IV" id="APPENDIX_IV"></a>IV.—GENERAL WORKS ON PALÆOBOTANY.</p> - - -<p>In the text frequent reference has been made to special memoirs -and reports on the fossil plants of particular regions or formations. -There are, however, some general books, useful to students, which -may be mentioned here. Perhaps the most important is Schimper’s -“Traité de Paléontologie Végétale.” Very useful information is -also contained in Renault’s “Cours de Botanique Fossile,” and in -Balfour’s “Introduction to Palæontological Botany,” and Nicholson’s -“Palæontology.” Unger’s “Genera et Species,” Brongniart’s -“Histoire des Végétaux Fossiles,” and Lindley and Button’s “Fossil -Flora,” are older though very valuable works. Williamson’s “Memoirs,” -in the “Philosophical Transactions,” have greatly advanced -our knowledge of the structures of Palæozoic plants. Lastly, the -“Palæophytology” of Schenk, now in course of publication in German -and French, in connection with Zittel’s “Palæontology,” is an -important addition to manuals of the subject.</p> - -<hr class="chap" /> - -<p><span class="pagenum"><a name="Page_287" id="Page_287">« 287 »</a></span></p> - - - - -<p class="caption2"><a name="INDEX" id="INDEX">INDEX.</a></p> - -<p class="p0"> -Acer, <a href="#Page_228">228</a>.<br /> -Acrogens, <a href="#Page_6">6</a>.<br /> -Agassiz, Prof., <a href="#Page_16">16</a>.<br /> -Alaska, Flora of, <a href="#Page_245">245</a>.<br /> -Algæ, real and spurious, <a href="#Page_26">26</a>, <a href="#Page_230">230</a>.<br /> -Amboy clays, Flora of, <a href="#Page_203">203</a>.<br /> -America, Cretaceous of, <a href="#Page_190">190</a>.<br /> -Angiosperms, <a href="#Page_6">6</a>.<br /> -Annularia, <a href="#Page_122">122</a>.<br /> -Anogens, <a href="#Page_6">6</a>.<br /> -Antholithes, <a href="#Page_132">132</a>.<br /> -Aporoxylon, <a href="#Page_25">25</a>.<br /> -Araucarioxylon, <a href="#Page_148">148</a>.<br /> -Araucarites, <a href="#Page_134">134</a>.<br /> -Archæocalamites, <a href="#Page_170">170</a>.<br /> -Archæopteris, <a href="#Page_77">77</a>, <a href="#Page_85">85</a>.<br /> -Arctic origin of plants, <a href="#Page_221">221</a>, <a href="#Page_238">238</a>.<br /> -Arthrophycus, <a href="#Page_30">30</a>.<br /> -Arthrostigma, <a href="#Page_67">67</a>.<br /> -Asterophyllites, <a href="#Page_78">78</a>, <a href="#Page_122">122</a>, <a href="#Page_170">170</a>.<br /> -Asteropteris, <a href="#Page_77">77</a>, <a href="#Page_85">85</a>.<br /> -Astropolithon, <a href="#Page_30">30</a>.<br /> -Atané, Plants of, <a href="#Page_242">242</a>, <a href="#Page_281">281</a>.<br /> -Atanekerdluk, Plants of, <a href="#Page_283">283</a>.<br /> -Australia, Palæozoic flora of, <a href="#Page_147">147</a>.<br /> -<span style="margin-left: 1em;">Tertiary flora of, <a href="#Page_217">217</a>.</span><br /> -<br /> -Bauhinia, <a href="#Page_204">204</a>.<br /> -Bear Island, <a href="#Page_241">241</a>.<br /> -Betula, <a href="#Page_198">198</a>.<br /> -Bilobites, <a href="#Page_28">28</a>.<br /> -Bovey Tracey, Plants of, <a href="#Page_226">226</a>.<br /> -Brasenia, <a href="#Page_207">207</a>.<br /> -Buckland, Dr., <a href="#Page_179">179</a>.<br /> -Buthotrephis, <a href="#Page_37">37</a>.<br /> -<br /> -Calamites, <a href="#Page_77">77</a>, <a href="#Page_123">123</a>, <a href="#Page_166">166</a>.<br /> -Calamodendron, <a href="#Page_125">125</a>.<br /> -Cambrian flora, <a href="#Page_20">20</a>.<br /> -Canada, Erian of, <a href="#Page_103">103</a>.<br /> -Carboniferous of, <a href="#Page_110">110</a>.<br /> -<span style="margin-left: 1em;">Laramie of, <a href="#Page_209">209</a>.</span><br /> -<span style="margin-left: 1em;">Pleistocene of, <a href="#Page_227">227</a>.</span><br /> -Carbon in Laurentian, <a href="#Page_9">9</a>.<br /> -Carboniferous flora, <a href="#Page_110">110</a>.<br /> -Carboniferous, Climate of, <a href="#Page_138">138</a>.<br /> -<span style="margin-left: 1em;">of Southern Hemisphere, <a href="#Page_147">147</a>.</span><br /> -Cardiocarpum, <a href="#Page_82">82</a>, <a href="#Page_153">153</a>.<br /> -Carruthers, Mr., <a href="#Page_24">24</a>, <a href="#Page_98">98</a>, <a href="#Page_180">180</a>.<br /> -<span style="margin-left: 1em;">On modifications of modern plants, <a href="#Page_225">225</a>, <a href="#Page_269">269</a>.</span><br /> -Carya, <a href="#Page_196">196</a>.<br /> -Cauda-galli fucoid, <a href="#Page_105">105</a>.<br /> -Caulerpites, <a href="#Page_29">29</a>.<br /> -Caulopteris, <a href="#Page_75">75</a>, <a href="#Page_94">94</a>.<br /> -Clarke, Prof., <a href="#Page_51">51</a>.<br /> -Climate, Causes of, <a href="#Page_247">247</a>.<br /> -Climate and plants, <a href="#Page_216">216</a>, <a href="#Page_220">220</a>, <a href="#Page_232">232</a>.<br /> -<span style="margin-left: 1em;">of Carboniferous, <a href="#Page_138">138</a>.</span><br /> -<span style="margin-left: 1em;">of Cretaceous and Eocene, <a href="#Page_216">216</a>.</span><br /> -<span style="margin-left: 1em;">of Devonian, <a href="#Page_47">47</a>.</span><br /> -<span class="pagenum"><a name="Page_288" id="Page_288">« 288 »</a></span> -<span style="margin-left: 1em;">of Early Mesozoic, <a href="#Page_178">178</a>.</span><br /> -Climate and plants of Laurentian, <a href="#Page_17">17</a>.<br /> -<span style="margin-left: 1em;">of Pleistocene, <a href="#Page_227">227</a>, <a href="#Page_230">230</a>.</span><br /> -<span style="margin-left: 1em;">of Pliocene, <a href="#Page_223">223</a>.</span><br /> -Coal, origin of, <a href="#Page_117">117</a>, <a href="#Page_139">139</a>.<br /> -Comparison of floras, <a href="#Page_272">272</a>.<br /> -Composite, <a href="#Page_266">266</a>.<br /> -Cone-in-cone, <a href="#Page_36">36</a>.<br /> -Coniferæ, Erian, <a href="#Page_78">78</a>, <a href="#Page_96">96</a>.<br /> -<span style="margin-left: 1em;">Carboniferous, <a href="#Page_134">134</a>, <a href="#Page_148">148</a>.</span><br /> -<span style="margin-left: 1em;">Mesozoic, etc., <a href="#Page_181">181</a>.</span><br /> -Cope, Mr., <a href="#Page_215">215</a>.<br /> -Cordaites, <a href="#Page_78">78</a>, <a href="#Page_130">130</a>, <a href="#Page_151">151</a>.<br /> -Corylus, <a href="#Page_213">213</a>.<br /> -Crepin, M., <a href="#Page_99">99</a>.<br /> -Cretaceous, Flora of, <a href="#Page_190">190</a>.<br /> -<span style="margin-left: 1em;">Climate of, <a href="#Page_216">216</a>.</span><br /> -Croll on climate, <a href="#Page_252">252</a>.<br /> -Cromer, Plants of, <a href="#Page_224">224</a>.<br /> -Cycads, Mesozoic, <a href="#Page_178">178</a>.<br /> -Cyclostigma, <a href="#Page_157">157</a>.<br /> -<br /> -Dadoxylon, <a href="#Page_96">96</a>, <a href="#Page_134">134</a>, <a href="#Page_148">148</a>.<br /> -Dawson, Dr. G. M., <a href="#Page_52">52</a>, <a href="#Page_210">210</a>.<br /> -Delgado, Prof., <a href="#Page_26">26</a>.<br /> -Dendrophycus, <a href="#Page_33">33</a>.<br /> -Derby, Orville, <a href="#Page_53">53</a>.<br /> -Devonian flora, <a href="#Page_45">45</a>.<br /> -Devonian or Erian, <a href="#Page_107">107</a>, <a href="#Page_279">279</a>.<br /> -<span style="margin-left: 1em;">Climate of, <a href="#Page_47">47</a>.</span><br /> -Dicotyledons, Cretaceous, <a href="#Page_192">192</a>.<br /> -<span style="margin-left: 1em;">Table of, <a href="#Page_192">192</a>.</span><br /> -Dictyolites, <a href="#Page_33">33</a>.<br /> -Dictyospongia, <a href="#Page_39">39</a>.<br /> -Disco, Exotic plants at, <a href="#Page_256">256</a>.<br /> -<span style="margin-left: 1em;">Flora of, <a href="#Page_245">245</a>, <a href="#Page_282">282</a>.</span><br /> -Drepanophycus, <a href="#Page_39">39</a>.<br /> -Drosera, <a href="#Page_228">228</a>.<br /> -Dunvegan beds, <a href="#Page_244">244</a>.<br /> -<br /> -Eocene, Flora of, <a href="#Page_208">208</a>, <a href="#Page_214">214</a>.<br /> -<span style="margin-left: 1em;">Climate of, <a href="#Page_216">216</a>.</span><br /> -Eophyton, <a href="#Page_31">31</a>.<br /> -Eopteris, <a href="#Page_72">72</a>.<br /> -Eozoon of Laurentian, <a href="#Page_9">9</a>.<br /> -Equisetum, <a href="#Page_176">176</a>, <a href="#Page_230">230</a>.<br /> -Erian flora, <a href="#Page_45">45</a>, <a href="#Page_279">279</a>.<br /> -<span style="margin-left: 1em;">Climate of, <a href="#Page_47">47</a>.</span><br /> -Erian or Devonian, <a href="#Page_107">107</a>.<br /> -Ettingshausen, Dr., <a href="#Page_187">187</a>, <a href="#Page_215">215</a>.<br /> -Exogens, Cretaceous, <a href="#Page_192">192</a>.<br /> -<span style="margin-left: 1em;">Tertiary, <a href="#Page_213">213</a>, <a href="#Page_224">224</a>.</span><br /> -<br /> -Fagus, <a href="#Page_196">196</a>, <a href="#Page_197">197</a>.<br /> -Ferns, Erian, <a href="#Page_72">72</a>.<br /> -<span style="margin-left: 1em;">Carboniferous, <a href="#Page_126">126</a>, <a href="#Page_171">171</a>.</span><br /> -<span style="margin-left: 1em;">Fructification of, <a href="#Page_128">128</a>.</span><br /> -<span style="margin-left: 1em;">Stems of, <a href="#Page_90">90</a>, <a href="#Page_129">129</a>.</span><br /> -<span style="margin-left: 1em;">Tertiary, <a href="#Page_212">212</a>.</span><br /> -Filices, <a href="#Page_72">72</a>, <a href="#Page_126">126</a>, <a href="#Page_171">171</a>.<br /> -Flora of Cambrian, <a href="#Page_26">26</a>.<br /> -<span style="margin-left: 1em;">of Carboniferous, <a href="#Page_110">110</a>, <a href="#Page_274">274</a>.</span><br /> -<span style="margin-left: 1em;">of Cretaceous, <a href="#Page_190">190</a>.</span><br /> -<span style="margin-left: 1em;">of Early Mesozoic, <a href="#Page_175">175</a>.</span><br /> -<span style="margin-left: 1em;">of Erian, <a href="#Page_45">45</a>, <a href="#Page_279">279</a>.</span><br /> -<span style="margin-left: 1em;">of Jurassic, <a href="#Page_177">177</a>, <a href="#Page_186">186</a>.</span><br /> -<span style="margin-left: 1em;">of Laramie, <a href="#Page_209">209</a>.</span><br /> -<span style="margin-left: 1em;">of Laurentian, <a href="#Page_8">8</a>.</span><br /> -<span style="margin-left: 1em;">of Miocene, <a href="#Page_220">220</a>, <a href="#Page_223">223</a>.</span><br /> -<span style="margin-left: 1em;">of Modern, <a href="#Page_219">219</a>.</span><br /> -<span style="margin-left: 1em;">of Permian, <a href="#Page_274">274</a>.</span><br /> -<span style="margin-left: 1em;">of Pleistocene, <a href="#Page_223">223</a>, <a href="#Page_227">227</a>.</span><br /> -<span style="margin-left: 1em;">of Tertiary, <a href="#Page_191">191</a>, <a href="#Page_208">208</a>, <a href="#Page_214">214</a>, <a href="#Page_219">219</a>.</span><br /> -Fontaine, Prof., <a href="#Page_130">130</a>, <a href="#Page_176">176</a>.<br /> -Fontinalis, <a href="#Page_230">230</a>.<br /> -Fort Union beds, <a href="#Page_210">210</a>.<br /> -Fucoids, <a href="#Page_27">27</a>.<br /> -<br /> -Gardner, Mr. Starkie, <a href="#Page_212">212</a>.<br /> -Geinitz, Dr., <a href="#Page_174">174</a>.<br /> -Geological formations, Table of, <a href="#Page_4">4</a>.<br /> -Glossopteris, <a href="#Page_147">147</a>.<br /> -Glyptodendron, <a href="#Page_25">25</a>.<br /> -Glyptostrobus, <a href="#Page_194">194</a>.<br /> -Goeppert, Dr., <a href="#Page_99">99</a>.<br /> -Grant, Col., <a href="#Page_36">36</a>.<br /> -<span class="pagenum"><a name="Page_289" id="Page_289">« 289 »</a></span> -Graphite from plants, <a href="#Page_8">8</a>.<br /> -Gray, Dr., Origin of floras, <a href="#Page_223">223</a>, <a href="#Page_237">237</a>.<br /> -Greenland, Climate of, <a href="#Page_216">216</a>.<br /> -<span style="margin-left: 1em;">Fossil flora of, <a href="#Page_247">247</a>.</span><br /> -Gulielmites, <a href="#Page_35">35</a>.<br /> -Gymnosperms, <a href="#Page_6">6</a>.<br /> -<br /> -Haliserites, <a href="#Page_39">39</a>.<br /> -Hartt, Prof., <a href="#Page_53">53</a>.<br /> -Heer, Dr., <a href="#Page_108">108</a>, <a href="#Page_181">181</a>.<br /> -Helderberg period, Sea of, <a href="#Page_250">250</a>.<br /> -Heterangium, <a href="#Page_77">77</a>.<br /> -Hicks, Dr., <a href="#Page_21">21</a>.<br /> -Hunt, Dr. Sterry, <a href="#Page_13">13</a>, <a href="#Page_143">143</a>.<br /> -Huxley, Prof., <a href="#Page_53">53</a>.<br /> -Hymenæa, <a href="#Page_204">204</a>.<br /> -<br /> -Insects, Erian, <a href="#Page_83">83</a>.<br /> -<br /> -Juglans, <a href="#Page_196">196</a>.<br /> -Jurassic flora, <a href="#Page_177">177</a>.<br /> -<br /> -Kainozoic flora, <a href="#Page_191">191</a>, <a href="#Page_208">208</a>, <a href="#Page_214">214</a>, <a href="#Page_219">219</a>.<br /> -Kidston, Mr. R., <a href="#Page_128">128</a>, <a href="#Page_273">273</a>.<br /> -King, Mr. Clarence, <a href="#Page_211">211</a>.<br /> -Komé, Plants of, <a href="#Page_242">242</a>, <a href="#Page_281">281</a>.<br /> -<br /> -Laramie flora, <a href="#Page_209">209</a>, <a href="#Page_215">215</a>.<br /> -Laurentian plants, <a href="#Page_8">8</a>.<br /> -Laurentian, Climate of, <a href="#Page_17">17</a>.<br /> -Laurophyllum, <a href="#Page_193">193</a>.<br /> -Laws of introduction of plants, <a href="#Page_237">237</a>, <a href="#Page_266">266</a>.<br /> -<br /> -Leda clay, Flora of, <a href="#Page_232">232</a>.<br /> -Lepidodendron, <a href="#Page_120">120</a>, <a href="#Page_156">156</a>, <a href="#Page_162">162</a>.<br /> -Lepidophloios, <a href="#Page_121">121</a>, <a href="#Page_157">157</a>, <a href="#Page_165">165</a>.<br /> -Leptophleum, <a href="#Page_157">157</a>.<br /> -Lesquereux, Mr. L., <a href="#Page_169">169</a>, <a href="#Page_214">214</a>.<br /> -Licrophycus, <a href="#Page_30">30</a>.<br /> -Lignitic series of America, <a href="#Page_208">208</a>.<br /> -Liquidambar, <a href="#Page_197">197</a>.<br /> -Liriodendron, <a href="#Page_199">199</a>.<br /> -Lower Carboniferous flora, <a href="#Page_277">277</a>.<br /> -Logan, Sir W., <a href="#Page_48">48</a>.<br /> -Lyell on climate, <a href="#Page_249">249</a>.<br /> -<br /> -Magnolia, <a href="#Page_200">200</a>.<br /> -McConnell, Mr., <a href="#Page_209">209</a>.<br /> -McNab, Prof., <a href="#Page_169">169</a>.<br /> -Megalopteris, <a href="#Page_76">76</a>.<br /> -Megaphyton, <a href="#Page_129">129</a>.<br /> -Mesozoic flora, <a href="#Page_175">175</a>.<br /> -<span style="margin-left: 1em;">Climate of, <a href="#Page_178">178</a>.</span><br /> -Migrations of plants, <a href="#Page_240">240</a>, <a href="#Page_245">245</a>.<br /> -Miller, Hugh, <a href="#Page_98">98</a>.<br /> -Miocene flora, <a href="#Page_220">220</a>.<br /> -Miocene, Supposed, <a href="#Page_242">242</a>.<br /> -Modern flora, <a href="#Page_219">219</a>.<br /> -Modern plants, how modified, <a href="#Page_269">269</a>.<br /> -Modifications of plants, <a href="#Page_266">266</a>.<br /> -<br /> -Nathorst, Dr., <a href="#Page_26">26</a>, <a href="#Page_196">196</a>.<br /> -Nematodendreæ, <a href="#Page_25">25</a>.<br /> -Nematophycus, <a href="#Page_23">23</a>.<br /> -Nematophyton, <a href="#Page_21">21</a>, <a href="#Page_22">22</a>, <a href="#Page_42">42</a>.<br /> -Newberry, Dr., <a href="#Page_200">200</a>, <a href="#Page_203">203</a>, <a href="#Page_214">214</a>.<br /> -Newfoundland, Fossil plants of, <a href="#Page_242">242</a>.<br /> -Newton, Mr., <a href="#Page_52">52</a>.<br /> -Nicholson, Dr. A., <a href="#Page_20">20</a>.<br /> -Niobrara series, <a href="#Page_243">243</a>, <a href="#Page_246">246</a>.<br /> -Noeggerathia, <a href="#Page_130">130</a>.<br /> -Northern origin of plants, <a href="#Page_238">238</a>.<br /> -<br /> -Origin of plants, <a href="#Page_237">237</a>.<br /> -Orton, Prof., <a href="#Page_51">51</a>.<br /> -<br /> -Pachytheca, <a href="#Page_21">21</a>.<br /> -Palæanthus, <a href="#Page_205">205</a>.<br /> -Palæochorda, <a href="#Page_30">30</a>.<br /> -Palæophycus, <a href="#Page_30">30</a>, <a href="#Page_38">38</a>.<br /> -Palæozoic floras compared, <a href="#Page_273">273</a>.<br /> -Palms, <a href="#Page_188">188</a>, <a href="#Page_194">194</a>.<br /> -Pandanus, <a href="#Page_188">188</a>.<br /> -Patoot beds, <a href="#Page_282">282</a>.<br /> -Peach, Mr., <a href="#Page_98">98</a>.<br /> -Petroleum, Origin of, <a href="#Page_56">56</a>.<br /> -Phymatoderma, <a href="#Page_29">29</a>.<br /> -Plants, Classification of, <a href="#Page_6">6</a>.<br /> -Platanus, <a href="#Page_198">198</a>.<br /> -Platyphyllum, <a href="#Page_74">74</a>.<br /> -<span class="pagenum"><a name="Page_290" id="Page_290">« 290 »</a></span> -Pleistocene climate, <a href="#Page_227">227</a>, <a href="#Page_230">230</a>.<br /> -Pleistocene flora, <a href="#Page_223">223</a>, <a href="#Page_227">227</a>.<br /> -Pliocene climate, <a href="#Page_223">223</a>.<br /> -Podozamites, <a href="#Page_178">178</a>.<br /> -Poles, Supposed change of, <a href="#Page_248">248</a>.<br /> -Populus, <a href="#Page_191">191</a>, <a href="#Page_228">228</a>.<br /> -Potamogeton, <a href="#Page_229">229</a>.<br /> -Potentilla, <a href="#Page_228">228</a>.<br /> -Protannularia, <a href="#Page_21">21</a>.<br /> -Protichnites, <a href="#Page_27">27</a>.<br /> -Protophyllum, <a href="#Page_199">199</a>.<br /> -Protosalvinia, <a href="#Page_52">52</a>.<br /> -Protostigma, <a href="#Page_20">20</a>.<br /> -Prototaxites, <a href="#Page_21">21</a>.<br /> -Psaronius, <a href="#Page_93">93</a>.<br /> -Psilophyton, <a href="#Page_64">64</a>.<br /> -Ptilophyton, <a href="#Page_62">62</a>, <a href="#Page_86">86</a>.<br /> -<br /> -Quercus, <a href="#Page_197">197</a>.<br /> -<br /> -Rhizocarps, <a href="#Page_48">48</a>.<br /> -Rill-marks, <a href="#Page_33">33</a>.<br /> -Rusichnites, <a href="#Page_28">28</a>.<br /> -<br /> -Saccamina, <a href="#Page_57">57</a>.<br /> -Salisburia, <a href="#Page_180">180</a>.<br /> -Salter, Mr., <a href="#Page_98">98</a>.<br /> -Salvinia, <a href="#Page_54">54</a>.<br /> -<br /> -Saporta, Count de, <a href="#Page_26">26</a>, <a href="#Page_193">193</a>.<br /> -Saportea, <a href="#Page_57">57</a>.<br /> -Sassafras, <a href="#Page_199">199</a>.<br /> -Scalariform tissue, <a href="#Page_70">70</a>.<br /> -Schimper, Dr., <a href="#Page_116">116</a>, <a href="#Page_169">169</a>, <a href="#Page_208">208</a>.<br /> -Scolithus, <a href="#Page_30">30</a>.<br /> -Scottish Devonian, <a href="#Page_98">98</a>.<br /> -Sequoia, <a href="#Page_181">181</a>.<br /> -Shrinkage cracks, <a href="#Page_33">33</a>.<br /> -Sigillaria, <a href="#Page_71">71</a>, <a href="#Page_112">112</a>, <a href="#Page_154">154</a>.<br /> -Southern Hemisphere, <a href="#Page_217">217</a>, <a href="#Page_273">273</a>.<br /> -<span style="margin-left: 1em;">Carboniferous in, <a href="#Page_147">147</a>.</span><br /> -<span style="margin-left: 1em;">Tertiary in, <a href="#Page_217">217</a>.</span><br /> -Sphenophyllum, <a href="#Page_61">61</a>, <a href="#Page_122">122</a>, <a href="#Page_171">171</a>.<br /> -Spirophyton, <a href="#Page_38">38</a>.<br /> -Spitzbergen, <a href="#Page_241">241</a>.<br /> -Sterculites, <a href="#Page_193">193</a>.<br /> -Sternbergia, <a href="#Page_137">137</a>, <a href="#Page_152">152</a>.<br /> -Stigmaria, <a href="#Page_115">115</a>.<br /> -Stur, Dr., on Sigillaria, <a href="#Page_116">116</a>.<br /> -Symphorocarpus, <a href="#Page_214">214</a>.<br /> -Syringodendron, <a href="#Page_156">156</a>.<br /> -Syringoxylon, <a href="#Page_82">82</a>.<br /> -<br /> -Table of formations, <a href="#Page_4">4</a>.<br /> -Tasmania, Fossil plants of, <a href="#Page_217">217</a>, <a href="#Page_246">246</a>.<br /> -Tasmanite, <a href="#Page_57">57</a>.<br /> -Tertiary period, Flora of, <a href="#Page_191">191</a>, <a href="#Page_208">208</a>, <a href="#Page_214">214</a>, <a href="#Page_219">219</a>.<br /> -Tertiary of Australia, <a href="#Page_217">217</a>.<br /> -Thallogens, <a href="#Page_6">6</a>.<br /> -Thomas, Mr., <a href="#Page_51">51</a>.<br /> -Thuja, <a href="#Page_213">213</a>, <a href="#Page_229">229</a>.<br /> -Time, Geological, <a href="#Page_5">5</a>.<br /> -Trapa, <a href="#Page_196">196</a>.<br /> -Tree-ferns, <a href="#Page_90">90</a>, <a href="#Page_129">129</a>.<br /> -Triassic flora, <a href="#Page_176">176</a>.<br /> -Trigonocarpum, <a href="#Page_136">136</a>, <a href="#Page_153">153</a>.<br /> -Tyndall, Prof., <a href="#Page_138">138</a>.<br /> -<br /> -Ulrich, Prof., <a href="#Page_57">57</a>.<br /> -Unartok beds, <a href="#Page_281">281</a>.<br /> -Ursa stage of Heer, <a href="#Page_108">108</a>, <a href="#Page_241">241</a>.<br /> -<br /> -Walchia, <a href="#Page_134">134</a>, <a href="#Page_138">138</a>.<br /> -Ward, Mr. L. T., <a href="#Page_192">192</a>, <a href="#Page_212">212</a>, <a href="#Page_215">215</a>.<br /> -Wethered, Mr. E., <a href="#Page_52">52</a>.<br /> -White, Dr., <a href="#Page_215">215</a>.<br /> -Williams, Prof., <a href="#Page_51">51</a>.<br /> -Williamson, Dr., <a href="#Page_26">26</a>, <a href="#Page_31">31</a>, <a href="#Page_71">71</a>, <a href="#Page_167">167</a>.<br /> -Williamsonia, <a href="#Page_188">188</a>.<br /> -</p> - - -<p class="caption3 pmb4">THE END.</p> - -<p><span class="pagenum"><a name="Page_1a" id="Page_1a">« 1a »</a></span></p> - - -<p class="caption2nb"><i>D. APPLETON & CO.'S PUBLICATIONS.</i></p> - -<hr class="chap" /> - -<p class="caption3">CHARLES DARWIN’S WORKS.</p> - -<p class="hanging"><b>ORIGIN OF SPECIES BY MEANS OF NATURAL SELECTION, OR THE -PRESERVATION OF FAVORED RACES IN THE STRUGGLE FOR LIFE.</b> -Revised edition, with Additions. 12mo. 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As a -contribution to insect psychology, it will be long before this book finds a -parallel.”—<i>London Athenæum.</i></p> - -<hr class="r40" /> - -<p class="center pmb2">New York: D. APPLETON & CO., 1, 3, & 5 Bond Street.</p> - - -<p><span class="pagenum"><a name="Page_6a" id="Page_6a">« 6a »</a></span></p> - -<p class="caption2nb"><i>D. APPLETON & CO.'S PUBLICATIONS.</i></p> - -<hr class="chap" /> - - -<p class="caption3">Br. H. ALLEYNE NICHOLSON’S WORKS.</p> - - -<p class="hanging"><b>TEXT-BOOK OF ZOÖLOGY,</b> for Schools and Colleges. 12mo. -Half roan, $1.60.</p> - -<p class="hanging"><b>MANUAL OF ZOÖLOGY,</b> for the Use of Students, with a General -Introduction to the Principles of Zoölogy. Second edition. -Revised and enlarged, with 243 Woodcuts. 12mo. Cloth, $2 50.</p> - -<p class="hanging"><b>TEXT-BOOK OF GEOLOGY,</b> for Schools and Colleges. 12mo. -Half roan, $1.25.</p> - -<p class="hanging"><b>INTRODUCTION TO THE STUDY OF BIOLOGY,</b> -Illustrated. 12mo. Cloth, 60 cents.</p> - -<p class="hanging"><b>THE ANCIENT LIFE-HISTORY OF THE EARTH.</b> -A Comprehensive Outline of the Principles and Leading Facts of -Palæontological Science. 12mo. Cloth, $2.00.</p> - -<p>“A work by a master in the science who understands the significance -of every phenomenon which he records, and knows how to make it reveal -its lessons. As regards its value there can scarcely exist two opinions. As -a text-book of the historical phase of palæontology is will be indispensable -to students, whether specially pursuing geology or biology; and without -it no man who aspires even to an outline knowledge of natural science can -deem his library complete.”—<i>The Quarterly Journal of Science</i>.</p> - -<p>“The Professor of Natural History in the University of St. Andrews -has, by his previous works on zoology and paleontology, so fully established -his claim to be an exact thinker and a close reasoner, that scarcely -any recommendation of ours can add to the interest with which all students -in natural history will receive the present volume. It is, as its second title -expresses it; a comprehensive outline of the principles and leading facts of -palæontoiogical science. Numerous woodcut illustrations very delicately -executed, a copious glossary, and an admirable index, add much to the -value of this volume.”—<i>Athenæum</i>.</p> - -<hr class="r40" /> - -<p class="center pmb2">New York: D. APPLETON & CO., 1, 3, & 5 Bond Street.</p> - - -<hr class="full" /> - - -<div class="trans_notes"> - -<p class="caption2">Transcriber Notes</p> - -<p>All images were moved so as to not split paragraphs.</p> -</div> - - - - - - - - - -<pre> - - - - - -End of the Project Gutenberg EBook of The Geological History of Plants, by -Sir J. 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