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By Jonn Mriyz, Professor of Mining and Geology in the Imperial College of Engineering, Tokio, Japan. With 88 Fieures. $1.75. . MICROBES, FERMENTS, AND MOULDS. By E. L. TrovessartT. With 10% Illustrations. $1.50. . THE GEOGRAPHICAL AND GEOLOGICAL DISTRIBUTION OF ANI- MALS. By AnaEto Hzprin. $2.00. WEATHER. A Popular Exposition of the Natare of Weather Changes from Day to Day. By Hon. Ratpo ABERcRoMBY. $1.75. ANIMAL MAGNETISM. By Atrrep Brnct and CoaRLes Féré, Assistant Physician at the Salpétriére. (aavM OW aalavay) ‘HWIL IVOIDOTOUD NI SLNVId JO AYOLSIH FHL JO WVADVIA 5% ‘NVLLNIGNYT DOZOF WvITENYSD "NYIENTIS "MYINOAIA *SNOYISINOT £4V9-OWYIS IIOZOIT¥S “SWIHL~ VEAP "SNOFIVLIYD *INIIOT * INII0OS7d = ON “NEFTOM? INTIOLSIT Id QIOZONFDI | W/0Z0SIN SHOCTTALONIG SWOUITALOIONOW) WUISINGD | HIIVOVIAI BWINITOSOIAT SINLLISINGZT SNIFS j99d v0 ZI "SNYFASOIONY “SWNTYIASSONWAD YVINISVA WFLANAOLYWIM "“SNVIONITVHA SHVPIOOLAAYDS “SNOILVAIIOS 7¥019070398 GEOLOGICAL HISTORY OF PLANTS BY SIR J. WILLIAM DAWSON C.M.G, LL.D., F.R.S., &. WITH ILLUSTRATIONS NEW YORK D. APPLETON AND COMPANY 1888 Corrrtcut, 1888, By D, APPLETON AND COMPANY. VA 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 conveni- ent manual of information. It is hoped that its treat- ment in the present volume will also be found sufii- ciently simple and popular to be attractive to the general reader. In a work of so limited dimensions, detailed descrip- tions 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. CHAPTER I. PAGE PRELIMINARY IpEas oF GEOLOGICAL CHRONOLOGY AND OF THE CLassI- FICATION OF PLANTS . : " r F " ‘ CUAPTER II. VEGETATION OF THE LAURENTIAN AND Earty PaL£ozo1c—QueEstions as TO ALGE . ‘ a CHAPTER II. Tae Ertan or Devonran Forests—Origin or PrrroneumM—THE Aas or ACROGENS AND GYMNOSPERMS CHAPTER IV. Tae Carponirerous FLora-—CULMINATION OF THE ACROGENS—For- MATION OF COAL CHAPTER V. Tue Frora or tHE Earty Mrsozorc—Reian or Pines anp Cycaps . CHAPTER VI. Tue Reian oF ANGIOSPERMS IN THE LATER CRETACEOUS 4ND EARLY TERTIARY OR Karnozoic . 2 45 . 110 175 . 191 viii CONTENTS. CHAPTER VII. PAGE Puants From THE TERTIARY To THE MODERN PERIOD . P . 219 CHAPTER VIII. General Laws or Origin anD Migrations or PLANTS—RELATIONS or Recent anp Fossit Fioras ‘ ei , : . 2387 APPENDIX. I, Comparative View or Patzozorc Froras. 5 248 TI, Herr’s Latest StaTEMENTS ON THE GREENLAND Fiona . 281 III. Mrnerarisation oF Fossis Piants . . 3 . 284 IV. Genera Works on PaLzoportany . ‘ ‘ ‘ . 286 LIST OF ILLUSTRATIONS. PAGE TaBLE or CuronoLoGy or PLants . 3 s . (Frontispicee.) Protannularia Harknessii - . 2 ‘ ‘ ‘ . 21 Nematophyton Logani (three Figures) 7 F a Fi . —:22, 28 Trail of King-Crab . 5 5 é : 2 : 3 ‘ . 28 Trail of Carboniferous Crustaccan . 2 r % 5 ‘ . 28 Rusichnites =. < . 2 * ‘ 3 . ‘i . 29 Paleophycus . . . : 7 : 7 5 ; . 80 Astropolithon . . : . - . : . : . . 81 Carboniferous Rill-mark . : . 2 - é : ‘ . 83 Cast of Shrinkage Cracks F , ‘ : j : . 84 Cone-in-cone . : - a . ‘ é ; ‘ is . 86 Buthotrephis . , i 3 ‘ : ¢ 3 . . 87 Silurian Vegetation . 5 ‘ . 3 3 ‘ ‘ : . 40 Erian Plants . - é . z 4 3 3 . 49 Protosalvinia . , : : . : : ‘ é . 54 Ptilophyton (two Figures) : . : . ee Gi . 62, 68 Psilophyton (two Figures) , ‘ : 4 é : . 64, 66 Sphenophyllum 3 ‘ . : 2 . : . - 65 Lepidodendron : . . F : : “ : . 66 Various Ferns . 3 x 5 - ‘ 2 : ‘ . 72, 78 Archeopteris . . ‘ . . : ‘ 5 , ‘ . 74 Caulopteris ; ‘ 5 3 4 < ‘ ‘ . 75 Megalopteris ; . F : : : : ‘ . r . 76 Calamites - 3 ‘ r . : . ‘ : é 2 oO Asterophyllites . ° ° . : . : i . 18 Dadoxylon sg ‘ - . . . . : . é . 79 x LIST OF ILLUSTRATIONS. PAGE Cordaites 3 2 < ‘ é . 3 : . 81 Erian Fruits . ‘ P , : . a , F . 82 Foliage from the Coal-formation . ‘ . : # . 111 Sigillarie (five Figures) . : . a c . . 112-114 Stigmariz (two Figures) . : - 3 : 5 F ‘ . 115 Vegetable Tissues . : : i : e 117 Coals and Erect Trees (two Figures) : ; 4 : - 118, 119 Lepidodendron F 3 z 2 . . 120 Lepidophloios . . é : : : . 121 Asterophyllites, &c. . : . . : ‘ : e » 122 Calamites (five Figures) . 4 . i : F : . 128-125 Ferns of the Coal-formation (six Figures) : : . 126-129 Noeggerathia dispar ‘ ‘ . . : : : . 180 Cordaites . s a . 3 5 ‘ , . 131 Fruits of Cordaites, &. . : ‘ ‘ 3 ‘ ‘ - 1382 Conifers of the Coal-formation (four Species) . ‘ ‘ . . 185 Trigonocarpum é e : : z F . F : . 136 Sternbergia , : 5 : é - a . 137 Walchia imbricatula . ; , F é ‘ : . 138 Foliage of the Jurassic Period . 7 . 4 , ‘ ~177 Podozamites . 5 . : : . . : 3 . 178 Salisburia ‘ : : = “ : . 180 Sequoia . é ‘ ‘ ‘ : 2 ; 3 s . 18) Populus primeva . : i * 5 : . 191 Stercalia and Laurophyllum . : ‘ 2 ‘ r é . 194 Vegetation of the Cretaceous Period ‘ : : . ; . 195 Platanus . i . 7 . j : ‘ . 198 Protophyllum . 3 ‘ : ‘ i : 5 . 199 Magnolia : ‘ : . : . . A és . 200 Liriodendron (two Figures) . ‘ A i : ‘ “ . 201 Brasenia . , : : 3 ‘ : , ‘ z - 207 Gaylussaccia resinosa x. is ° c ‘ ‘ s ‘ . 228 Populus balsamifera . z - . ; ‘ . 2 - 229 Fucus. 5 ‘ . ‘i . 5 : ° - . 280 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 frag- mentary 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 intelligi- ble 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 2 THE GEOLOGICAL HISTORY OF PLANTS. 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 pre- supposing some knowledge of the geological history of the earth, and of the classification and structures of mod- ern 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 de- voted toa 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 obser- vation, consists of many beds of rock superimposed on each other, and which must have been deposited succes- sively, 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 prima- rily 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- GEOLOGICAL CHRONOLOGY. 3 basins, ridges of elevated land, and broad plateaus inter- vening between the ridges, and which were at some times under water, and at other times land, with many inter- mediate 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 sub- merged, and deep ocean-basins, never except in some o their shallower portions elevated into land. By the study of the successive beds, more especially of those deposited in the times of continental submer- gence, 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 ex- posures 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 cafions 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. 4 THE GEOLOGICAL HISTORY OF PLANTS. The evidence is similar to that obtained by Schlie- mann on the site of Troy, where, in digging through suc- cessive 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. 3 ¢ Modern, Age of Man and 8 } eae! t Angiosperms and i a : ? i Mammalia. = | Miocene, Palms dominant. Ft | Eocene. g Cretaceous 4 * g ’ i Age of Reptiles. 8 | Jurassic, s wrens qnd Pines 2 Triassic. ; Permian, ahs ; | Carboniferous, f A 2 i ’ Age sa eae 8 | Erian, 1% | Acrogens and Gym- Age of Taverte- 8) Silurian, nosperms domi- brates. ‘a | Ordovician, nant. : Ai | Cambrian, . Huronian (Upper). g { Huronian (Lower), % ‘S | Upper Laurentian Protogens and ° ? Hee. of Bugiaeoa, 8 | Middle Laurentian, Alga. = | Lower Laurentian. It will be observed, since only the latest of the sys- tems 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 re- quire 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 GEOLOGICAL CHRONOLOGY. 5 of them in the older systems, that they must have re- quired 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 Paleozoic, with as much for the Eozoic as for the Palzozoic. This is Dana’s estimate. Another, by Hull and Houghton, gives the following ratios: Azoic, 34:3 per cent. ; Paleozoic, 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 our- selves 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 con- tinents as yet unformed, it will be evident that the con- ditions 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.* We know by -the evidence of * Croll, “ Climate and Time.” 6 THE GEOLOGICAL HISTORY OF PLANTS. 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 evidont nlso that in those periods when the continental areas wero largely submerged, there might be an excessive amount of moist- ure in the atmosphere, greatly modifying the climate, in so far as plants are concerned. Let us now consider the history of the vegotable king- dom 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 thoso which have no mani- fest flowers, and produce minute spores instead of seeds; and Phenogams, or those which possess flowers and pro- duce seeds containing an embryo of the future plant. The Cryptogams may be subdivided into tho following three groups : 1, Thaillogens, cellular plants not distinctly distin- guishable into stem and leaf. These are the Fungi, the Lichens, and the Algm, or sea-weeds, 2. Anogens, having stem and foliago, but wholly cel- lular. These are the Mosses and Liverworts. 3. Acrogens, which have long tubular fibros as woll as cells in their composition, and thus have tho capacity of attaining a more considerable magnitude. These aro the Ferns (/'lices), the Mavre’s-tails (Zgutsetacew), and the Olub-mosses (Lycopodiacee), and a curious little group of aquatic plants called Rhizocarps (Rhizocarpee), The Phanogams are all vascular, but thoy dilfer mach in the simplicity or complexity of their flowors or seeds. On this ground they admit of a twofold division : 1. Gymnosperms, or those which bear nakod seeds not enclosed in fruits. Thoy are the Pines and their allies, and the Oycads. CLASSIFICATION OF PLANTS. v6 2. Angiosperms, which produce true fruits enclosing the seeds. In this group there are two well-marked sub- divisions differing in the structure of the seed and stem. They are the Hndogens, or inside growers, with seeds hav- ing one seed-leaf only, as the grasses and the palms; and the Hzogens, 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 Algx, 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 Gym- nosperms, and in the later formations we find the higher Phenogams 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 occu- pied 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 PALZO- ZOIC—QUESTIONS AS TO ALG A. O.psst 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, crys- talline, 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, in- deed, are the exposures of these rocks, that we have good reason to believe that they underlie all the other forma- tions 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 por- tion 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 or- ganic—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 ani- mals obtain directly from their food, and indirectly from the calcareous matter dissolved in the sea-water. In like LAURENTIAN AND EARLY PALAOZOIO. 9 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 Hozoon Canadense have been recognised in the Laurentian lime- stones, 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 ani- mal. But we are not left merely to this inference. Great quantities of carbon or charcoal in the form of the sub- stance 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 Lau- rentian thick beds of graphite and beds of limestone charged with detached grains and crystals of this sub- stance, and graphitic gneisses and schists and veins of, graphite traversing the beds, we recognise the same} phenomena that are apparent in later formations con- | taining vegetable débris. The carbon thus occurring in the Laurentian is not to be regarded as exceptional or rare, but is widely dis- tributed 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 3 10 THE GEOLOGICAL HISTORY OF PLANTS. those of the containing rock. Sir William Logan states * that “the deposits of plumbago generally occur m 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 lime- stone, 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 lime- stones ; large crystalline scales of it are occasionally dis- seminated 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 cal- cite, quartz, orthoclase, or pyroxene, and either in dis- seminated 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 men- tions 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 count- less 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 char- acter 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 * “Geology of Canada,” 1863. LAURENTIAN AND EARLY PALAOZOIC. 11 of bitumen found in the bituminous shales of the Car- boniferous and Silurian rocks. Nor can there be any doubt that the graphite found in the beds has been de- posited along with the calcareous matter or muddy and sandy sediment of which these beds were originally com- posed. * 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 crys- tals 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 dis- trict 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 * Paper by the author on Laurentian Graphite, “‘ Journal of London Geological Society,” 1876. 12 THE GEOLOGICAL HISTORY OF PLANTS. 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 Hozoon limestones, and that rich graphitic deposits exist in the continuation of this sys- tem 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.* It may fairly be assumed that in the present world, and in those geological periods with whose organic re- mains we are more familiar than with those of the Lau- rentian, 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 in- stance, 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 else- where 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. * Matthew in “Quarterly Journal of the Geological Society,” vol. xxi., p. 423, “ Acadian Geology,” p. 662. LAURENTIAN AND EARLY PALZOZOIC. 18 We may compare the disseminated graphite to that which we find in those districts of Canada in which Silu- rian 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.* 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 Que- bec 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 palexozoic analo- gies would lead us to infer that the larger part of the Laurentian graphite falls under the second class of de- posits above mentioned, and that, if of vegetable origin, the organic matter must have been thoroughly disin- tegrated 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. Dr. Hunt has, however, observed an indication of ter- restrial vegetation, or at least of subaérial 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 sub- stances produced in the decay of plants. In this case such great ore-beds as that of Hull, on the Ottawa, seventy * Granby, Melbourne, Owl’s Head, &c., “Geology of Canada,” 1863, p- 599. ‘ 14 THE GEOLOGICAL HISTORY OF PLANTS. feet thick, or that near Newborough, two hundred feet thick,* must represent a corresponding quantity of vege- table 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. It would be very desirable to confirm such conclusions as those above deduced by the evidence of actual micro- scopic structure. It is to be observed, however, that when, in more modern sediments, Alge have been con- verted into bituminous matter, we cannot ordinarily ob- tain 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 Mount- ains in Canada, the pores of brachiopodous shells and the cells of corals have been penetrated by black bitu- minous 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 Hozoon penetrated by matter once bituminous, but now in the state of graphite. * “ Geology of Canada,” 1863. LAURENTIAN AND EARLY . PALZOZOIC. 15 When paleozoic 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 com- paratively unaltered specimens from the coal-formation.* 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 laminz, 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 Lau- rentian of Canada, though they certainly underlie the Primordial series of the Acadian group, and are sepa- rated from it by beds having the character of the Hu- ~ ronian. 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 * “ Acadian Geology,” p.585. In calcified specimens the structures remain in the graphite after decalcification by an acid. 16 THE GEOLOGICAL HISTORY OF PLANTS. 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 compara- tively 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 Alge. , 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 Lauren- ‘tian 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 lime- ' stone, 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 devel- { oped, and that it equalled, perhaps surpassed, in its re- me in the way of geological accumulation, that of any “subsequent period. Many years ago, at the meeting of the American As- sociation 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 re- mains of a Devonian tree contemporaneous with his LAURENTIAN AND EARLY PALAOZOIC. 17 fishes of that age. ‘How I wislr I could sit under its shade !” was the smiling reply of the great zodlogist ; 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 di- oxide 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 con- stitutes the largest ingredient in vegetable tissues. Under these circumstances the whole world must have resembled a damp, warm greenhouse, and plants loving such an at- mosphere could have grown luxuriantly. In these cir- cumstances 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 Paleozoic 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 struc- ture not known in modern times. In the previous Lau rentian age something similar may have happened to Algez, to Fungi, to Lichens, to Liverworts, and Mosses. The Algz may have attained to gigantic dimensions, and 18 THE GEOLOGICAL HISTORY OF PLANTS. ral 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 con- ’ stitute 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 his- ory 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 otber 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 pleni- tude 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-ani- mals. The fact that there have existed, even in modern times, eceanic islands rich in vegetation, yet untenanted by the higher forms of animal life, prepares us to believe LAURENTIAN AND EARLY PALAOZOIC, 19 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 astate to enable it to be used as min- eral 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 ig remarkable that, in ascending from the Lauren- tian, 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 Alge, or sea-weeds. An eminent Swedish geologist, Linnarsson, has de- 20 THE GEOLOGICAL HISTORY OF PLANTS.. scribed, under the name of Zophyton, 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 Alge, are specimens kindly presented to me by Dr. Alleyne Nicholson, of Aberdeen, and which he had named Buthotrephis Harknessii* and B. radiata. They are from the Skiddaw rocks of Cum- berland. On examining these specimens, and others subsequently collected in the same locality by Dr. G. M. Dawson, while convinced by their form and carbonaceous character that they are really plants, I am inclined to re- fer them not to Alge, 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,+t 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.t{ Ifa plant, this may * “ Geological Magazine,” 1869. + See figure in next chapter. x Dyntocts, Py gma sigillarioides, Lesqucreux. LAURENTIAN AND EARLY PALAOZOIC. a1 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 Rhizo- carps and of Lyco- pods. If we ascend into the Upper Si- lurian, or Siluri- an proper, the evi- dences of land veg- etation somewhat increase. In 18591 described, in “The Journal of the Geo- logical Society,” of London, a remark- able tree from the Lower Erian of ~ Gaspé, under the ~~ name Prototazites, init r but for which I : now prefer the Fre. 1.—Protannularia Harknessié (Nichol- name Nematophy- ae nC ee fon. When in Lon- don, in 1870, I obtained permission to examine cer- tain 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 Silu- rian of Cape Bon Ami, New Brunswick. Lastly, Dr. Hicks has discovered similar wood, and also similar 4 iN it \ qh ill fi e i, =. fo —- = “= 92 THE GEOLOGICAL HISTORY OF PLANTS. fruits, in the Denbighshire grits, at the base of the Si- lurian.* | f Fie. 2.—Wematophyton Logami (magnified), Vertical section. From comparison of this singular wood, the structure of which is represented in Figs. 2, 3, 4, with the dédris OM GO BUG 19.2 O9000, 6 ty Q ra Fic. 8.—WNematophyton Logani (magnified). Horizontal section, showing part of one of the radial spaces, with tubes passing into it. of fossil taxine woods, mineralised after long maceration in water, I was inclined to regard Prototazites, or, as I * “Journal of the Geological Society,” August, 1881. LAURENTIAN AND EARLY PALZOZOIC, 93 have more recently named it, Nematophyton, as a prime- val gymnosperm allied to those trees which Unger had described from the Erian of Thuringia, under the name Aporoxylon.* Later examples of more lax tissues from branches or young stems, and the elaborate examinations kindly undertaken for me by Professor Penhallow and ( mare Fie. 4.—Nematophyton Logani (magnified). Restoration.t+ 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 be- * “ Palaeontologie des Thuringer Waldes,” 1856. + Figs. 2, 3, and 4 are drawn from nature by Prof. Penhallow, of McGill College. 94 THE GEOLOGICAL HISTORY OF PLANTS. | ginning of the Silurian age and to have finally disap- pad 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, cylin- drical tubes, traversed by a complex network of horizontal tubes thinner walled and of smaller size. The tubes are arranged in concentric zones, which, if annualrings, 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 con- tained 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 Alge, and has even proposed to change the name to Nematophycus, or ‘thread-sea-weed”; but the resem- blance is by no means clear, and it would be quite as rea- sonable to compare the tissue to that of some Fungi or Li- chens, or even to suppose that a plant composed of cylin- drical 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 dura- ble and resisting character is shown by its state of preser- vation ; and the structure of the seeds called Pachytheca, with their constant association with these trees, give coun- tenance to the belief that they are the fruit of Nema- tophyton. Of the foliage or fronds of these strange plants we unfortunately know nothing. They seem, how- LAURENTIAN AND EARLY PALAOZOIC. 95 ever, to realise the idea of arboreal plants having struct- ures 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 Nematodendrew may be given, and of which Nematophyton will constitute one genus and Aporoxylon of Unger another.* Another question arises as to the possible relation of these plants to other trees known by their external forms. The Profostigma 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.t 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 Ber- wynia. It is just possible that these plants may have belonged to the Nematodendrew. 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 Mematophy- ton, and the spirally arranged punctures which it shows on its surface. In this case I should be disposed to re- * See report by the author on “ Erian Flora of Canada,” 1871 and 1882, for full description of these fossils, + “ American Journal of Science,” 1878. 26 THE GEOLOGICAL HISTORY OF PLANTS. gard the supposed stigmaria-like roots as really stems, and the supposed rootlets as short, spine-like rudiment- ary leaves. All such comparisons must, however, in the mean time be regarded as conjectural. We seem, how- ever, to have here a type of tree very dissimilar to any even of the later Palzozoic age, which existed through- out 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 ? Multitudes of markings occurring on the surfaces of the older rocks have been referred to the Alge or sea- weeds, and indeed this group has been a sort of refuge for the destitute to which paleontologists have been accus- tomed to refer any anomalous or inexplicable form which, while probably organic, could not be definitely referred to he 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 Algz 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 di- vergence 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 LAURENTIAN AND EARLY PALAOZOIC, ye vegetable kingdom so many of them as some of his con- temporaries.* The considerations which seem most im- portant in making such distinctions are the following : 1. The presence or absence of carbonaceous matter. True Alge 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 indi- cate 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 Algsx, 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 im- pressions. 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 Algz, but may be shallow burrows arched upward on top, or castings of worms thrown up upon the surface. Some- times, howeyer, 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 consoli- dated by pressure being better able to resist the denuding agency. The footprints from the Potsdam sandstone in Can- ada, for which the name Protichnites was proposed by * “Tmpressions and Footprints of Aquatic Animals,” “American Journal of Science,” 1873, a 98 THE GEOLOGICAL HISTORY OF PLANTS. Owen, and which were by him referred to crustaceans probably resembling Limulus, were shown by the writer, in 1862,* to correspond precisely with those of the American Limulus (Poly- phemus Occidentalis) (Fig. 5). I proved by experi- ment with the modern ani- WALL, Y Lene MMA Hf! I ml Uphill N SES ; == mal that the recurring se- eS ng HI ries of groups of markings were produced by the toes SS > of the large posterior tho- Wo. ab, willugrete fataone et © Tacic feet, the irregular Plants sometimes named Bilo- scratches seen in Protich- nites lineatus by the ordi- nary 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 iy Hh f y . LLY ih ti Y / a se au if} porerersiy os AN YE Fie. 6.—Trail of Carboniferous crustacean (Rusichnites Acadicus), Nova Scotia, to illustrate supposed Alge. * “Canadian Naturalist,” vol, vii. LAURENTIAN AND EARLY PALZOZOIC. 99 Climactichnites, from the same beds which afford Pro- tichnites. The principal difference between Protichnites and their modern representatives is that the latter have two lateral furrows produced by the sides of the cara- pace, which are wanting in the for- mer. I subsequently applied the same explanation to sev- eral other ancient forms now known under the gener- al name Bilobites (Figs. 6 and 7).* The tubercu-. lated impressions known as Phyma- toderma and. Caul- erpttes may, as Zeil- ig. 7. Rusophyous (Rusichnites) Grenvillen- ler has shown, be sis, an animal burrow of the Siluro-Cam- brian, probably of a crustacean. a, Track made by the bur- connected with it. : rowing of the mole- cricket, and fine examples occurring in the Clinton forma- tion of Canada are probably the work of Crustacea. It is probable, however, that some of the later forms referred to these genera are really Alge 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 setw, and some of the X Sy * The name Bilobites was originally proposed by De Kay for a bivalve shell (Conocardium). Its application to supposed Alge was an error, but this is of the less consequence, as these are not true plants but only animal trails. 30 THE GEOLOGICAL HISTORY OF PLANTS. markings referred to Paleochorda, Palwophycus, 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 As- terophycus, are ex- plained by the branch- ing burrows of worms illustrated by Nathorst and the author. Creek beds. Lemna and Pistia beds of bad lands Lower Laramie or St. on egal arallel, Red Deer River, Upper Mary River. fh ii ignites. Report 49th Crean ae Parallel atl Memoir of 1885, A Fox Hill series. ......... oe @anian and | Port Pierre series. ........ Senonian). "Sequoia and Brasenia beds of S: Belly River................ katchewan, Belly River, &c., with lignites. Memoir of 1885. Coal measures of Nanai- eee of 1883. Many dicotyle- mo, B.C., probably here. dons, palms, &c. Middle Creta- | DPunvegan series of Peace | | vomoir of 1883. Man dicotyle- ceous (Tu- ee Detors group, dons, cycads, ! ronian and| U- §. mboy clays, - : sd Se nomani- ‘icotyledonous leaves, similar to an). At creek’ Deals of Rocky Dakota group of the U.S. Me- moir of 1885, pushes ever beds. and ueen Charlotte Islan Lower Creta-| coal series. Intermedi- | | C¥c@4s, pines, a few dicotyledons. ceous (Ne- ate beds of Rocky Report Geol. Survey. Memoir ocomian, Mountains. | Potomac &e.). series of Virginia. J} Kootanie series of Rocky {1° erly ag eines, and ferns, Memoir Mountains. CHAPTER VI. THE REIGN OF ANGIOSPERMS IN THE LATER CRETACEOUS AND KAINOZOIC, Ir 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 be- ginning of the Eocene Tertiary. The dicotyledonous Angiosperms, which correspond to them in the vegetable king- dom, occur far earlier—in the beginning of the Upper Cre- taceous or close of the Lower Cretaceous. The reign of cy- cads and pines holds through- out the Lower Cretaceous, but at the close of that age there is a sudden incoming of the high- er plants, and a proportionate decrease, more especially of the cycads. I have already referred to the F16,88—Populueprimava, . Leer. ‘retaceo! angiospermous wood supposed Greenland. One of the to be Devonian, but I fear to oe “ rest any conclusion on this iso- lated fact. Beyond this, the earliest indications of plants of this class have been found in the Lower Cretaceous. Many years ago Heer described and fig- ured the leaves of a poplar (Populus primeva) from 192 THE GEOLOGICAL HISTORY OF PLANTS. the supposed Lower Cretaceous of Komé, in Greenland (Fig. 68). Two species, a Sterculia and a Laurus or Saliz, 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 angio- spermous species (Sassafras, Menispermites, Sapindus, Aralia, Populus, &c.) mixed with a rich flora of cycads and pines. These are the early forerunners of the mod- ern 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. J may add that the new discoveries made since 1884 would probably tend to increase the proportionate number of dicotyledons in the newer groups. DicoryLeponots TREES IN THE CRETACEOTS. Upper Senonian... 1... .ceceeereeee esp muptghd 179 species. (Fox Hill group of America.) Lower Senonian.. 0. c cece cence nee ee enees 81 species. Upper white chalk of Europe; Fort Pierre group of America; coal-measures of Na- naimo ? TUPONN s 6 a5 hase 8 ds eas Gb eosin sheen 20 species. Lower white chalk; New Jersey marls; Belly R. group. CENOMANIAN.. 6. cence ence creer nnn eennaee 357 species. (Chalk-marl, greensand, and Gault, Niobrara and Dakota groups of America); Dun- vegan group of Canada; Amboy clays of New Jersey. LATER CRETACEOUS AND KAINOZOIC, 193 1 20 species.* (Lower greensand and Speeton clay, Wealden and Hastings sands, Kootanie and Queen Charlotte groups of Canada.) 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 phenome- non of the sudden appearance of so many forms, and some of them the most highly differentiated of dicotyle- donous 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 dis- puted.” + The leaves described by Heer, from the Middle Cre- taceous of Greenland, are those of a poplar (P. primeva). Those which I have described from a corresponding hori- zon in the Rocky Mountains are a Sterculites (S. vetus- tula), 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 * Including an estimate of Fontaine’s undescribed species. + “Monde des Plantes,” p. 197. 194 THE GEOLOGICAL HISTORY OF PLANTS. of the United States and the corresponding formations in Canada. On the eastern side of the American conti- nent, in Virginia, the Potomac series is supposed to be of Lower Cretaceous age, i and here Fontaine, as already stated, has found an abundant flora of cy- cads, conifers, and ferns, with a few angiosperm- ous leaves, which have not yet been described. In the Canadian Rocky Mountains, a few hun- dreds of feet above the beds holding the before- mentioned species, are the Fre. 69.—Stercalia and Laurophyllum shales of the Mill Creek Pete he csotaccous mada, series, rich in many spe- cies 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-sandstone of Ger- many as types of the plant-bearing Cenomanian, and may notice the forms occurring in them. Tn the first place, we recognise here the successors of our old friends, the ferns and the pines, the latter repre- sented by such genera as Tazxites, 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 Sabdal, which is the characteristic American type of fan-palm, and there is one genus which Saporta regards as intermediatc between the fan-palms and the pinnately leaved species. There are also many fragments of stems Se —— = See == = == LATER CRETACEOUS AND KAINOZOIC. 195 and leaves of carices and grasses, so that these plants, now so important to the nourishment of man and his com- panion animals, were already represented. Fic. 70.—Vegetation of Later Cretaceous. Exogens and palms. (After Saporta. ) But the great feature of the time was its dicotyle- donous 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 196 THE GEOLOGICAL HISTORY OF PLANTS. 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, un- doubtedly 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 approxi- mate certainty.* 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 Jrapa 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 in- ferred 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. In the matter of names of fossil leaves, J sympathise very strongly with Dr. Nathorst, of Stockholm, in his * 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. H LATER CRETACEOUS AND KAINOZOIC. 197 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 ‘‘ttes” 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 inex- pedient 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 follow- ing: Liguidambar, 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.* Populus (poplar), as already stated, appears very early in Green- land, and continues with increasing number of species throughout the Cretaceous and Tertiary. Salix (willow) appears only a little later and continues. Of the family Cupulifere 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 * 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 en- tire leaves, quite unlike except in venation those of the parent tree, and having an aspect very similar to that of the Cretaceous poplars. 198 THE GEOLOGICAL HISTORY OF PLANTS. (birch) is represented by a few species, and specimens of its peculiar bark are also common. Alnus (alder) ap- pears in one species at least. The genus Platanus (Fig. 71), that of the plane-trees, represented at present by one \ ae a ane Re eae 1 me ss, v Fic. 71.—Platanus nobilis, Newberry, variety basilobata. Much reduced. Laramie. European and one American species, has several species in the Cretaceous, though the plane-trees seem to culmi- nate in the early part of the succeeding Eocene, where there are several species with immense leaves. The large LATER CRETACEOUS AND KAINOZOIC. 199 leaves, known as Crednerta, 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. Dios- pyros, the persimmon-tree, was also a Cretaceous genus. Fia. 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 repre- sented in the American flora, were equally plentiful in the Cretaceous (Fig. 73). The walnut family were well repre- sented by species of Juglans (butternut) and Carya, or hickory. In all, no Jess than forty-eight genera are pres- ent belonging to at least twenty-five families, ranning through the whole range of the dicotyledonous exogens. This ig a remarkable result, indicating a sudden profusion 200 THE GEOLOGICAL HISTORY OF PLANTS. 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 Ore- taceous and dwindle to- ward the modern. In others the reverse is the case—they have expand- ed in modern times. In a number there seems to have been little change. Dr. Newberry ‘has given, in the ‘ Bulletin of the Torrey Botanical Club,” an interesting résumé of the history of the beautiful Lirio- dendron, 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 Lirio- dendron, as all botan- ists know, is represent- ed in the present flora by a single species, ‘ the tulip-tree,’ which is con- fined to eastern Amer- ica, but grows over all the area lying between the Lakes and the Gulf, the Mississippi and the Fie. 78.—Magnolia magnifica, Dawson, Atlantic. It is a mag- reduced. Upper Cretaceous, Canada. nificent tree, on the LATER CRETACEOUS AND KAINOZOIC. 901 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 sur- passed by the flowers and _ ~ foliage of its first cous- in, Magnolia grandiflora. That a plant so splendid yy Fie. 74.—Liriodendron Meekii, ie. 15.—Ltriodendron primavum, Heer. (After Lesquereux.) Newberry. (After Newberry.) 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.) “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 rep- 19 202 THE GEOLOGICAL HISTORY OF PLANTS. resented 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 distin- guished 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 procaccinit. The genus has also been noticed in Hurope 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 ZLiriodendron 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 iden- tical with a Greenland form referred by Heer to L. Meeki of the Dakota group. Thus, if all Lesque- reux’s species are to be accepted, the genus begins LATER CRETACEOUS AND KAINOZOIC. 203 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 pre- liminary notice in the “ Bulletin of the Torrey Botanical Club” :* “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 Cre- taceous clays of Greenland and Aachen (Aix Ja Chapelle), which not only indicates a chronological parallelism, but shows aremarkable and unexpected similarity in the vege- tation of these widely separated countries in the middle and last half of the Cretaceous age. The botanical char- acter of the flora of the Amboy clays will be seen from the following brief synopsis : ‘* Alg@.—A small and delicate form, allied to Chon- drites. “« 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. * March, 1886. 904 THE GEOLOGICAL HISTORY OF PLANTS. ‘* Conifers. —Fourteen species, belonging to the genera Moriconia, Brachyphyllum, Cunninghamites, Pinus, Se- quota, and others referred by Heer to Juniperus, Libo- cedrus, Frenelopsis, Thuya, and Dammara. Of these, the most abundant and most interesting are Mortconia cyclotozon—the most beautiful of conifers—and Cunning- hamites elegans, both of which occur in the Cretaceous clays of Aachen, Prussia, and Patoot, Greenland. The Brachyphyllum was a large and strong species, with im- bricated 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 ap- parently identical with those described by Heer as belong- ing to Andromeda, Cissites, Cornus, Dewalquea, Dios- pyros, Eucalyptus, Ficus, Ilex, Juglans, Laurus, Meni- spermites, 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 lcaves resem- bled those of the recent tulip-tree, but were larger. Both had the peculiar emargination and the nervation of Lirio- dendron. “‘Among the most interesting plants of the collection are fine species of Bauhinia and Hymenea, 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. Bauhi- nia is a leguminous genus allied to Cercis, and now in- LATER CRETACEOUS AND KAINOZOIC. 205 habits tropical and warm temperate climates in both hemispheres. Only one species occurs in the United States, Bauhinia lunarioides, Gray, found by Dr. Bige- low on the Rio Grande. “« Hymenea is another of the leguminosm, and inhab- its tropical America. A species of this genus has been found in the Upper Cretaceous of France, but quite dif- ‘ferent 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 Paleanthus. 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 composite, 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 Cre- taceous rocks of Greenland, and named by Heer William- sonia cretacea, but he questions the reference of the genus to the Cycades, 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 Composite, like the Leguminosae, Magnoliacee, Ce- lastracew, and other highly organised plants, formed part 206 THE GEOLOGICAL HISTORY OF PLANTS. of the Cretaceous flora. No composite flowers have be- fore 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 form- ative changes.” The above presents some interesting new types not heretofore found in the Middle Cretaceous. More espe- cially the occurrence of large flowers of the composite type presents a startling illustration of the early appear- ance 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 occur- ring 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 Creta- ceous coal-field of Vancouver Island, where there is a very rich Upper Cretaceous flora, which I have noticed in de- tail m the ‘‘ Transactions of the Royal Society of Cana- da.” * In these Upper Cretaceous beds there are fan- palms as far north at least as the latitude of 49°, indicat- ing 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. The dicotyledonous plants above referred to aro 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 * Vol. ii, 1884. LATER CRETACEOUS AND KAINOZOIC 207 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. 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 pres- ent, 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 Cre- taceous, 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.* To this interval also would seem to belong the Belly River series of western Canada, which contains important beds S of coal, but is closely as- pyg. 7g. Brasnia antigua. Upper Cre- sociated with the marine Seo, pote paki ett Fort Pierre series. A tion, slightly enlarged. very curious herbaceous plant of this group, which I have named Brasenta anr- fiqua, 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 * See paper by the author in the “ Transactions of the Royal Society of Canada,” 1882. 208 THE GEOLOGICAL HISTORY OF PLANTS. 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 go 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 —Paleocene, Eocene, Oligocene, Miocene, and Pliocene. Throughout these a flora, similar to that of the Creta- ceous 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 com- mitted by paleobotanists, 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 Ter- tiary, 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 LATER CRETACEOUS AND KAINOZOIC. 209 studied both in the United States* and Canada; and, though their flora was originally referred by mistake to the Miocene, it is now known to be Eocene or Paleocene, or even in part a transition group between the latter and the Cretaceous. The following remarks, taken. chiefly from recent papers by the author, + will serve to illustrate this: On the geological map of Canada the Laramie series, formerly known as the lignitic or lignite Tertiary, oc- curs, 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 denuda- tion 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.{ The age of the Laramie beds is thus stratigraphically determined to be between the Fox Hill Cretaceous and the Lower * See more especially the elaborate and valuable reports by Lesque- reux and Newberry, and a recent memoir by Ward on “Types of the Laramie Flora,” “ Bulletins of the United States Geological Survey,” 1887. + “Transactions of the Royal Society of Canada,” 1886-’87. t “Report of the Geological Survey of Canada,” 1885. 210 THE GEOLOGICAL HISTORY OF PLANTS. 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.* Neither division has as yet afforded mammalian remains. The western area is of still larger dimensions, and ex- tends 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 recog- nised 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 recog- nised 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 appen- dix 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 * Cope, in Dr. G. M. Dawson’s “‘ Report on the 49th Parallel.” LATER CRETACEOUS AND KAINOZOIC. 911 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 re- ferred 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, how- ever, 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 stratigraphica] 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 paleobotanists to refer the plants of the Upper Laramie to the Miocene age, although in the re- ports 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 in- - clined 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* Dr. Newberry gives a comparative table, in which he correlates the Lower . * Newberry, “Transactions of the New York Academy,” February, 1886. 212 THE GEOLOGICAL HISTORY OF PLANTS. 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 *—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, how- ever, 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 ob- serve 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. t Two ferns occurring in these beds are remarkable as evidence of the persistence of species, and of the pecul- jarities 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 asso- * “Transactions of the Royal Society of Canada,” vol. ii. + 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. LATER CRETACEOUS AND KAINOZOIC. 918 ciated with this species another and more delicate fern, the modern Davallia (Stenloma) tenuifolia, but this, un- like its companion, no longer occurs in America, but is found in the mountains of Asia. This is a curious illus- tration 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 vite (the so-called ‘‘cedar” of Canada). ‘The Laramie species has been named 7. interrupta by Newberry, but it approaches very closely in its foliage to J. occidentalis, of eastern Canada, while its fruit resembles that of the western species, Z. 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 abun- dance 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 Glypto- strobus, Taxodium, and Taxus ; and the genus Salisburia or gingko—so characteristic of the Jurassic and Creta- ceous—is still represented in America as well as in Hurope in the early Eocene. We have no palms in the Canadian or Scottish Palexo- cene, 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 gi- gantic size of a foot or more in diameter of its blade. The hazels are represented by a large-leaved species, C. 20 914 THE GEOLOGICAL HISTORY OF PLANTS, Macquarii, 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. repre- sented 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 Ca- talpa and Sapindus, and some curious leaves which seem to indicate the presence of the modern genus Symphoro- carpus, 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 Mio- cene 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 Bel- gium, 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 iden- tical or closely allied, and so are many of the dicotyledo- nous leaves. For example, Platanoides Hebridicus is very near to P. nobilis, and Corylus Macquarrii is com- mon to both formations, as well as Populus Arctica and P. Richardsonit. YI may add that ever since 1875-76, when I first studied the Laramie plants, I have main- tained their identity with those of the Fort Union group LATER CRETACEOUS AND KAINOZOIC. 915, 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 dis- covery of true Lower Miocene beds in the Canadian north- west, overlying the Laramie or lignite series. In a bulletin of the United States Geological Sur- vey (1886), Dr. White has established in the West the continuous stratigraphical succession of the Laramie and the Wahsatch Eocene, thus placing the Laramie con- formably 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 Wah- satch 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 depre- cate the remark, which I see occasionally made, that fossil plants are of little value in determining geological hori- zons in the Oretaceous 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 differ- ences and general similarity are not of a nature to in- validate inferences as to age. No doubt, so long as palzobotanists seemed obliged, in deference to authority, and to the results of investigations limited to a few Eu- ropean localities, to group together, without distinction, all the floras of the later Cretaceous and earlier Tertiary, ” 916 THE GEOLOGICAL HISTORY OF PLANTS. 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 im- perfection in our knowledge of the Cretaceous and Ter- tiary 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 Cre- taceous, and the latter from the Tertiary ; and, with the aid of the work already done by Lesquereux and New- berry 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 admit- ting of discussion whether the Eocene flora of latitudes so different as those of Greenland, Mackenzie River, north- west Canada, and the United States, were strictly con- temporaneous, or successive within a long geological period in which climatal changes were gradually pro- ceeding. 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 contem- poraneity. 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 LATER CRETACEOUS AND KAINOZOIC. O17 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 be- tween 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 paleobotanists 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 Cre- taceous up to the close of the Eocene; and to deter- mine, for America at least, the manner and conditions under which the angiospermous flora of the later Creta- ceous succeeded to the pines and cycads which charac- terised the beginning of the Cretaceous period. In so far as Hurope 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,* Ettingshausen holds that the flora of * “ Geological Magazine,” August, 1887. 218 THE GEOLOGICAL HISTORY OF PLANTS. the Tertiary, as a whole, was of a generalised character ; forms now confined to the southern and northern hemi- spheres respectively being then common to both. It would thus seem that the present geographical diversities must have largely arisen from the great changes in cli- mate and distribution of land and water in the later Tertiary. The length of our discussion of the early angiosperm- ous flora does not permit us to trace it in detail through the Miocene and Pliocene, but we may notice the con- nection 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 respect- ively. 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 pe- riod which was characterised by the advent and culmina- tion 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 gym- nospermous 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 Oretaceous 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 sub- mergence of land is indicated by the prevalence of chalk and marine limestones over the surface of both conti- nents; but a cireumpolar belt seems to have been main- tained, protecting the Atlantic and Pacific basins from 920 THE GEOLOGICAL HISTORY OF PLANTS. 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 Oretaceous. As time advanced the quantity of land gradually in- creased, 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 pe- culiar flora, which indicates a mild climate and consider- able 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 thé vegetation became still more modern in aspect. In that period of the Hocene, 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 Eu- rope, was not equally great in America, which also by the north and south extension of its mountain-chains per- mitted 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, perma- nently 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 dif- THE TERTIARY TO THE MODERN PERIOD. 221 ferent latitudes. However equable the climate, there must have been some appreciable difference in proceed- ing from north to south. If, therefore, as seems in every way probable, the new species of plants origi- nated on the Arctic land and spread themselves south- ward, 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 ex- tension 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 Cre- taceous 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 tempera- ture 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 929 THE GEOLOGICAL HISTORY OF PLANTS. allowing of the growth of a temperate flora in Greenland. As Dr. Brown has shown,* 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 con- stant continuance of light in the summer is, on the con- trary, a very great stimulus and advantage. It is a remarkable phenomenon in the history of gen- era 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 mod- ern; 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, Lirio- dendron, Magnolia, and many other genera, affords re- markable 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 Kocene ; and, if I mistake not, this will be found to ac- cord 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 * “ Florula Discoana,” THE TERTIARY TO THE MODERN PERIOD. 993 tefuge 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 ex- ceptions 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 vege- tation 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 ac- companied 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 ticher 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 294 THE GEOLOGICAL HISTORY OF PLANTS. 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 sum- mary 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 new- er 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 some- what 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 (Zrapa natans, Willd.) has disap- peared 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., Gnanthe Tichenalit, Sm., Potamogeton pterophyllus, Sch., and Pinus abies, L.) are found at present only in Europe, and a fifth (Pota- mogeton trichoides, Cham.) extends also to North Ameri- ca; two species (Peucedanum palustre, Moench, and Pinus sylvestris, L.) are found also in Siberia, while six more (Sanguisorba officinalis, L., Rubus fruticosus, L., Cornus sanguinea, L., Huphorbia amygdaloides, L., Quercus robur, L., and Potamogeton crispus, L.) extend into western Asia, and two (Fugus 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 THE TERTIARY TO THE MODERN PERIOD. 995 are Thalictrum minus, L., Thalictrum flavum, L., Ra- nunculus 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 cespitosa, Schultz, Sueda maritima, Dum., Ceratophyl- lum demersum, L., Sparganium ramosum, Huds., Pota- mogeton pectinatus, L., Carex paludosa, Good., and Os- munda regalis, L.) are found also in North America. Of the remainder, ten species (Nuphar luteum, Sm., Meny- anthes trifoliata, L., Stachys palustris, L., Rumex mari- timus, L., Rumex acetosella, L., Betula alba, L., Scirpus paucifiorus, Lightf., Tarus baccata, L., and Isoetes la- custris, L.) extend round the north temperate zone, while three (Lycopus europeus, L., Alisma plantago, L., and Phragmites communis, Trin.), having the same distribu- tion 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., dis- tributed 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 begin- ning 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 21 2296 THE GEOLOGICAL HISTORY OF PLANTS. 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 &. polaris, Wahl.; and Betula nana, L., has re- treated to the mountains of Scotland. Three others (Dryas octopetala, L., Arctostaphylos uva-ursi, L., and Saliz herbacea, L.) have withdrawn to the mountains of northern England, Wales, and Scotland, while the re- mainder are still found scattered over the country. Not- withstanding 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 hold- ing 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. THE TERTIARY TO THE MODERN PERIOD. 227 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* the following facts, with a few additional notes : 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 num- ber, 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, con- tained apparently in a layer somewhat lower than that holding the ichthyolites, remains of land-plants are some- what 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 * “Canadian Naturalist,” 1866. 928 THE GEOLOGICAL HISTORY OF PLANTS. 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: New- foundland, and thence, according to Hooker, to the Arctic circle. It is also European. 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 va- riety. It occurs in Canada and New England, but I have no in- formation as to its range north- ward. 4 4, Gaylussacera resinosa, Tor- Fie. 77.—G@aylussaceia reee- vey and Gray. Leaf in nodule rosa. Pleistocene, Can- 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 Eng- land and Canada. It extends to the Arctic circle, and is THE TERTIARY TO THE MODERN PERIOD. 929 abundant on the shores of the Great Slave Lake and on the McKenzie River, and according to Richardson con- stitutes much of the drift timber of the Arctic coast (Fig. 78). 6. Thuja occidentalis, Linn. Trunks and branches in the Leda clay at Montreal. This tree occurs in New England and Canada, and extends northward into the Fic. 78.—Populus balsamifera. Pleistocene, Canada. 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 Richard- son 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 230 THE GEOLOGICAL HISTORY OF PLANTS: the river Ottawa, where it flows over the beds containing these fossils. 9. Caricee and Graminee. Fragments in nodules from Green’s Creek appear to belong to plants of these groups, but I cannot venture to determine their species. 10. Hquisetum scirpoides, Michx. Fragments in nod- ules, Green’s Creek. This is a widely distributed spe- cies, occurring in the Northern States and Canada. 11. Fontinalis. In nodules at Green’s Creek there occur, somewhat plentifully, branches of a moss appar- ently of the genus Fon- tinalis. 12. Alge. With the plants above mentioned, both at Green’s Oreek 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 nod- ules would seem to indi- . cate a large Laminaria. Fig. 79.—Frond of Mucus. Pleisto- With the above there are cene, Canada. e 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 character- ised 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 THE TERTIARY TO THE MODERN PERIOD. 931 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 oc- curs plentifully on the Ottawa, would not be so pre- dominant. But such an assemblage of drift-plants might be furnished by any American stream flowing in the lati- tude 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 as- sume 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 Lab- rador 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 con- ditions 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 Eng- land, must have given for the Ottawa coast of that period a summer temperature very similar to that at present ex- perienced on the Labrador coast, and with this conclusion the marine remains of the Leda clay, as well as the few 232 THE GEOLOGICAL HISTORY OF PLANTS. land molluscs whose shells have been found in the beds containing the plants, and which are species still occur- ring 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 re- frigeration may be assumed to correspond with the re- quirements 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 diminu- tion 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 ascend- ing order: (1) The boulder clay; (2) a deep-water de- posit, 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 THE TERTIARY TO THE MODERN PERIOD. 933 glacialis, the most exclusively arctic shell of these de- posits. In other words, I regard the plants above men- tioned as probably belonging to the period of greatest re- frigeration 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.* 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 diminu- tion 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 in- teresting to observe that at Green’s Creek, at Pakenham Mills, at Montreal, and at Olarenceville on Lake Cham- plain, 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 du- ration, though its length has been much exaggerated by certain schools of geologists.t It passed away, and a re- turning cosmic spring gladdened the earth, and was ush- ered in by a time of great rainfall and consequent denu- dation and deposit, which has been styled the ‘‘ Pluvial Period.” The remains of the Pliocene forests then re- turned—with somewhat diminished numbers of species— * Notes on Post-Pliocene of Canada, “ Canadian Naturalist,” 1872. + This I have long maintained on grounds connected with Pleistocene fossils, amount of denudation and deposit, &., and I am glad to see that Prestwich, the best English authority on such subjects, bas recently an- nounced similar conclusions, based on independent reasons. 234 THE GEOLOGICAL HISTORY OF PLANTS. from the south and again occupied the land, though they have not been able, in their decimated condition, to re- store 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 al- ready stated, the return was more abundant than in Europe. Simultaneously with the return of the old temperate flora, the arctic plants that had overspread the land re- treated to mountain-tops, now bared of ice and snow, and back to the polar lands whence they came ; and so it hap- pens 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 migra- tory 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 Scandi- navian plants, perhaps survivors of the Glacial age, or carried by migratory birds; and still another element consists of Spanish plants, brought north by spring mi- grants, and establishing themselves in warm and sheltered spots, just as-the arctic plants do on the bleak hill-tops. THE TERTIARY TO THE MODERN PERIOD. 935 The Bermudas, altogether recent islands, have one hun- dred and fifty species of native plants, all of which are West Indian and American, and must have been intro- duced 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 revo- lution 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 reinains 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 struct- ure, 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 be- comes apparent. The relations in these respects between the living cell and the soil, the atmosphere and the sun- shine, were apparently as perfect in the early Paleozoic 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 rudi- mentary, 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 fructifi- cation there has been more progress, for, so far as we - know, the highest and most complex forms of flowers, 236 THE GEOLOGICAL HISTORY OF PLANTS. 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 struct- ures of bisexual reproduction were perfected in the early Paleozoic, and the improvements introduced in the gym- nosperm and the angiosperm of later periods have con- sisted mainly in additions of accessory parts, and in modi- fications 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 Grin- nell Land, under circumstances which show that these were their primal homes. The fact bristles with physical difficulties, yet is fertile of the most interesting theoreti- cal 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. * 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 re- * 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.” 22 938 THE GEOLOGICAL HISTORY OF PLANTS. turned to the subject in 1872, and more fully developed this conclusion with reference to the Tertiary floras,* and he has recently still further discussed these questions in an able lecture on ‘‘ Forest Geography and Archeol- ogy.” t In this he puts the case so well and tersely that we may quote the following sentences as a text for what follows : “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 differ- ence), and especially Seguoias, not only the two which obviously answer to the two big-trees now peculiar to California, but several others; that they equally com- prise 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 sur- vives ; that we have evidence, not merely of pines and maples, poplars, birches, lindens, and whatevér else char- acterise 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 an- cestors 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 tem- perate region as well as in Europe.” * Address to American Association. + “ American Journal of Science,” xvi., 1878, GENBRAL LAWS OF ORIGIN AND MIGRATION. 939 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 cveads and pines. Ln 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 progvss 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 subsi- denee, 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 Roral Society of London, in the Bakerian lecture of that year. and in a memoir illustrat- ing no less than one hundred and twenty-five species of plants alder than the crear Carboniferous system, these deductions were stated in connection with the conclusions of Hall, Logan, and Dana, as to the distribution of sedi- ment along the northeast side of the American continent. and the anticipation was hazarded that the oldest Paleo- zoie floras would be discovered to the north of Newfound- Yand. Mention was also made of the apparent carler and more copions birth of the Devonian flora in America than in Europe. a fact which is itself connected with the greater northward extension of this continent. 240 THE GEOLOGICAL HISTORY OF PLANTS. 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 Sur- vey of Canada.” The part of the memoir relating to Cana- dian fossil plants, with a portion of the theoretical deduc- tions, was published in a report issued in 1871.* In this report the following language was used : “Tn eastern America, from the Carboniferous period onward, the centre of plant distribution has been the Ap- palachian 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 non- existent 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 distribu- tion from the Appalachians, and links of connection in the Atlantic bed between the floras of Europe and Ameri- ca. 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 Hrian ¢ flora in eastern America, especially in the St. John beds, it might be a * “Fossil Plants of the Devonian and Upper Silurian Formations of Canada,” pp. 92, twenty plates, Montreal, 1871. + See pages 107 and 108. GENERAL LAWS OF ORIGIN AND MIGRATION. 941 fair inference that the northeastern end of the Appala- chian ridge was the original birthplace or centre of crea- tion of what we may call the later Paleozoic flora, or of a large part of that flora.” When my paper was written I had not seen the ac- -count published by the able Swiss palwobotanist Heer, of the remarkable Devonian flora of Bear Island, near Spitz- bergen.* 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 char- acterised 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 hori- zons may have been intermixed in the collections sub- mitted to Heer. * “Transactions of the Swedish Academy,” 1871; “Journal of the London Geological Society,” vol. xxviii. 942 THE GEOLOGICAL HISTORY OF PLANTS. Between 1870 and 1873 my attention was turned to the two subfloras intermediate between those of the Devo- nian and the coal-formation, the floras of the Lower Carboniferous (Subcarboniferous of some American geol- ogists) and the Millstone Grit, and in a report. upon these * 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 Car- boniferous system. The same fact is observed in the coal-beds of Scotland, as compared with those of Eng- land, 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. 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, accord- ing to Heer, by the supposed Jurassic flora of Siberia, we find, especially at Komé and Atané in Greenland, an in- teresting occurrence of those earliest precursors of the truly modern forms of plants which appear in the Creta- ceous, 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 en- tirely 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 tem- perate genera, as Populus, Myrica, Ficus, Sassafras, and Magnolia. This is regarded as Upper Cretaceous. Rest- ing upon these Upper Cretaceous beds, without the inter- * “Fossil Plants of Lower Carboniferous and Millstone Grit Forma- tions of Canada,’ pp. 47, ten plates, Montreal, 1873. GENERAL LAWS OF ORIGIN AND MIGRATION. 943 vention of any other formation,* 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 Eu- rope 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. + If now we turn to the Cretaceous and Tertiary floras of western America, as described by Lesquereux, New- berry, 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 t 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 over- lying 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,* 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 suc- ceeded by thick Upper Cretaceous deposits of clay and sandstone, with marine remains, though very sparsely * Nordenskiéld, “ Expedition to Greenland,” “ Geological Magazine,” 1872, + Yet even here the bald cypress (Zaxodium distichum), or a tree nearly allied to it, is found, though this species is now limited to the Southern States. Fielden and De Rance, “Journal of the Geological So- ciety,” 1878. + Lesquereux, “ Report on Cretaceous Flora.” # G. M. Dawson, “ Report on Forty-ninth Parallel.” 244 THE GEOLOGICAL HISTORY OF PLANTS. 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 Nio- brara group, and filling 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 dis- trict, on the northern shore of the great Cretaceous Medi- terranean ;* 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 Pa- cific 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 Lig- nitic. 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 Hocene, though farther south extending up- ward toward the Miocene age.+ 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 * “ Reports of Dr. G. M. Dawson, Geological Survey of Canada.” Also, “Transactions of the Royal Society of Canada,” vol. i. + Lesquereux’s “Tertiary Flora”; “ White on the Laramie Group”; Stevenson, “ Geological Relations of Lignitic Groups,” American Philo- sophical Society, June, 1875; Dawson, ‘“‘ Transactions of the Royal So- ciety of Canada,” vol. iv.; Ward, “ Bulletin of United States Geological Survey.” GENERAL LAWS OF ORIGIN AND MIGRATION. 945 McKenzie River valley, described by Heer as Miocene, and probably also with those of Alaska, referred to the same age.* Now this truly Hocene 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. + In looking at this question, we may fairly assume that no climate, however equable, could permit the vegeta- tion 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. Hither 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 temper- ate Europe to those of Greenland. If Greenland required a temperature of about 50°, as Heer calculates, to main- tain 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 * 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. + “Nature,” December 12, 1878, 946 THE GEOLOGICAL HISTORY OF PLANTS. Charlotte Islands,* and still earlier in Virginia.t 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.{ 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 begin- ning 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 cli- mate, 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 * “Reports of the Geological Survey of Canada.” + Fontaine has well described the Mesozoic flora of Virginia, “ Ameri- ean Journal of Science,” January, 1879, and ‘‘ Report on Early Mesozoic Floras.” : ¢ 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 north- ern hemisphere. GENERAL LAWS OF ORIGIN AND MIGRATION. 947 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 be- tween the so-called Upper Cretaceous (really Middle Cre- taceous) and the so-called Miocene (really Lower Eocene) floras of Greenland. This latter established itself in Greenland, and prob- ably 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 conti- nents 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 de- tails; 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 cli- mates in the north, apparently demanded by the vicissi- tudes 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 Eng- land will not live in Canada, though species to all appear- ance 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 948 THE GEOLOGICAL HISTORY OF PLANTS. 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 sub- ject, 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 evi- dence 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 s0 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 fol- lowed 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 astro- nomical evidence, prevent us from assuming any consid- erable change in the obliquity of the axis of the earth during geological time. 3. That the earth and the sun have diminished ip heat during geological time seems probable ; but physical and geological facts alike render it certain that this influ- ence could have produced no appreciable effect, even in the times of the earliest floras, and certainly not in the case of Tertiary vegetation. GENERAL LAWS OF ORIGIN AND MIGRATION. 949 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 ex- istence. 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, pro- vided that we fail to find known causes sufficient to ac- count 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 Tyn- dail 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, re- garding 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 af- fecting 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 distri- bution 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 23 250 THE GEOLOGICAL HISTORY OF PLANTS. 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 Silu- rian period (the Lower Helderberg age), vast areas of the American continent* were covered with an ocean in which were deposited organic limestones whose fossils show that this great interior sea was pervaded by equa- torial waters bringing food and warmth, while the in- cipient 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 incur- sions of the arctic ice-laden currents, bearing loads of fine sediment !+ 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 * See a memoir and map by Prof. Hall, “ Reports of the Regents of New York,” 187475, + It seems certain that the faune of the old limestones, like the Tren- ton, Niagara, Lower Helderberg, and Corniferous, belong to warm and sheltered sea areas, and that those rich in graptolites and trilobites, en- closed in muddy sediments, belong to the colder arctic waters. Such arctic faune are those of the Quebec group and of the Utica shale, and to some extent that of the Hamilton group. GENERAL LAWS OF ORIGIN AND MIGRATION. 951 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 Car- boniferous limestone preceded the advent of the great and rich flora of the coal-formation. Lyell’s theory on this subject has, I think, in some re- cent publications, been somewhat misapprehended. It is true that he stated hypothetically two contrasted con- ditions 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 dis- cussions as to ocean currents, he was always careful to at- tach due value to these in connection with subsidences and elevations.* 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. 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.t It is evident, therefore, that only excep- tionally unfavourable circumstances prevent the Greenland area from still possessing a temperate flora, and these un- favourable circumstances possibly tell even on the locali- ties with which we have compared it. Further, the mouth of the McKenzie River isin the same latitude with * See “ Principles of Geology,” edition of 1840, chapter vii. + See ‘‘ Macoun’s Report,” “ Geological Survey of Canada,” and Rich- ardson’s “ Boat Voyage.” 952 THE GEOLOGICAL HISTORY OF PLANTS. Disco, near which are some of the most celebrated locali- ties of fossil Cretaceous and Tertiary plants. Yet the mouth of the McKenzie River enjoys a much more favour- able 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 re- quirements of its extinct floras is 50°,* which is probably above rather than below the actual temperature required. Since, then, geological facts assure us of mutations of the continents much greater than those apparently re- quired 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.¢ If, however, there are other true causes which might either aid or counteract those above referred to, it may be well to consider them. Mr. Croll has, in his valuable work ‘‘ Climate and Time,” and in various memoirs, brought forward an in- genious astronomical theory to account for changes of climate. This theory, as stated by himself in a recent paper, { 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 north- east, and compel them to blow over upon the northern * Heer. See, also, papers by Prof. Haughton and by Gardner in “Nature” for 1878. + Sir William Thomson, “Transactions of the Geological Society of Glasgow,” February 22, 1878. t “ Cataclysmic Theories of Geological Climate,” ‘‘ Geological Maga- zine,” May, 1878. GENERAL LAWS OF ORIGIN AND MIGRATION. 953 hemisphere as far as the Tropic of Cancer. The result is that all the great equatorial currents of the ocean are im- pelled into the northern hemisphere, which thus, in con- sequence 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 be- comes clad in ice, and the southern has its temperature raised. 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 al- ways been the case, but that in many cases submergence was accompanied with the influx of warm equatorial waters and a raised temperature, this apparently depend- ing 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 occa- sioned by contraction, by equatorial subsidences resulting from the retardation of the earth’s rotation, and by the ex- cess 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 de- nudation caused by atmospheric action at the equator, and must have tended to increase the disposition to equa- torial collapse occasioned by retardation of rotation.* While such considerations as those above referred to * 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 débria toward the south and southwest. 954 THE GEOLOGICAL HISTORY OF PLANTS. 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 abund- dance 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 distribu- tion of plants. This may help us to deal with the peculiarities of the great Glacial age, which may have been rendered excep- tionally severe by the combination of several of the causes of refrigeration. We must not suppose, however, that GENERAL LAWS OF ORIGIN AND MIGRATION. 955 the views of those extreme glacialists who suppose conti- nental 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. Simi- lar 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 re- newal of warmth. If, however, our modern flora is thus one that has re- turned 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 256 THE GHOLOGICAL HISTORY OF PLANTS. winter snow not only protects evergreen plants from those sudden alternations of temperature which are more de- structive 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.* 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 subtropical 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 in- troduction, or at least for the rapid growth and multipli- cation, of new and more varied types of plants. 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 re- gions, 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 * “Florula Discoana,” Botanical Society of Edinburgh, 1868. GENERAL LAWS OF ORIGIN AND MIGRATION. 957 in Europe, and in the modern epoch forms that would be regarded in Europe as Miocene still exist. Much confu- sion 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 his- tory has served strangely to change some of our precon- ceived 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 arc- tic 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 pos- sibilities which lie hidden under some of the most com- mon 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 thé 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 in- voke the action of an Almighty mind, operating through long ages, and correlating with boundless power and wis- dom all the energies inherent in inorganic and organic 258 THE GEOLOGICAL HISTORY OF PLANTS. nature. Even then we shall perhaps be able to compre- hend 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 spontane- ously 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 succes- sive 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 vegétable life may be recognised, and I propose to state these in connection with the Paleozoic 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 paleontology. This results prin- cipally 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 per- GENERAL LAWS OF ORIGIN AND MIGRATION. 959 fect 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 advan- tages ; 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 sub- ject, 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 in- quiries 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 gen- eral 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 er- roneous 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 960 THE GEOLOGICAL HISTORY OF PLANTS. of preservation, it is still more hkely to occur. Every revision of any group of fossils detects numerous syn- onyms, 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 pe- riod 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 com- parison of so-called species which may, in many cases, be mere varictal 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 be- long to distinct forms which cannot pass into each other, at least within the mits of one geological period. 4. When we compare the specific types of one period with those of another immediately precedent or subse- quent, 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 spe- cies, we may account for the appearance of new types in the latter by the deficiency of information as to the for- mer; 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 un- GENERAL LAWS OF ORIGIN AND MIGRATION. 961 likely that we should have failed to discover their con- tinuance, we may fairly assume that they have become extinct, at least locally ; and where the field of observa- tion is very extensive, as in the great coal-fields of Europe and America, we may esteem such extinction as practi- eally 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 zoologist 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 positicn 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 fos- sils may be of more difficult detection. Our business at present, in the prosecution of paleobotany, is to discover, if possible, what are elementary or original types, and, hav- ing found these, to enquire as to the law of their creation. 7. In prosecuting such questions geographical rela- tions must be carefully considered. When the floras of 24 962 THE GEOLOGICAL HISTORY OF PLANTS. 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 Carbonifer- ous 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 un- broken continuity of specific types. I desire, however, under this head, to affirm my con- viction that, with reference to the Erian and Carbonifer- ous 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 Palzo- zoic period evidences a similar series of physical phenom- ena on the grandest scale throughout the northern hemi- sphere. The succession of marine animals implies the continuity of the sea-bottoms on which they lived. The headquarters of the Hrian 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 fre- quently 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 feat- ures 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, impor- GENERAL LAWS OF ORIGIN AND MIGRATION. 963 tant climatal changes must also occur. On the re-emer- gence of the land such of these species as remained would again extend themselves over their former areas of distri- bution, 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 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 varie- ties 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 cer- tain, 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 con- nection is one of cause and effect; there are, indeed, in- dications 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 Paleozoic 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 fa- vourable to the introduction of new forms of land-plants. Hence, there has been throughout geological time a gen- eral movement of new floras from the Palearctic 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 conclu-. 964 THE GEOLOGICAL HISTORY OF PLANTS. sions. The Erian flora is comparatively poor, and its types are in the main similar to those of the Carbonifer- ous. Of these types a few only reappear in the middle coal-formation under identical forms ; a great number ap- pear 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 Car- boniferous 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 Car- boniferous, 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 lime- stone 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 Car- boniferous 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 sub- sidences and marine conditions were almost at a maxi- mum. GENERAL LAWS OF ORIGIN AND MIGRATION. 965. Bearing in mind these peculiarities of the area in question, we may now group in a tabular form the dis- tinct specific types recognised in the Erian system, indi- cating, 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 canneformis extends as a species into the Carboniferous; Asterophyl- lites 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. . 3 aia Pet Blab a ‘Exian types.’ Represented in |'3 & 3 \| Brian types. Represented in |S & 3 I arboniferous— BeTRS boniferous— - —s [= ist Peleg ; esas 1. Syringoxylon mirabile ? 27. Cordaites Robbii..... * 2. Nematoxylon ........ ; 28. C. angustifolia... ... 3. Nematophyton........ 29. Archeopteris Jacksoni 4, Aporoxylon........ ea 30. Aneimites obtusa..... Ls 5. Ormoxylon .......... 31. Platyphyllum Brownii. 6. Dadoxylon......... ne * || 32. Cyclopteris varia ..... = 7. Sigillaria Vanuxemii .. * || 88. C. obtusa............ 8. S. palpebra.......... * || 34, Neuropteris 9. Didymophyllum pha...... 3 * 10. Calamodendron * || 85. N. serrulata......... * 11. Calamites transitionis..| * 36, N. retorquata........ = 12. C. canneformis ...... * 37. N. resecta 13. Asterophyllites scutige- 38. Megalopteris Dawsoni. Psa csvapers eee pa oe 89. Sphenopteris Heening- 14, A. latifolia,.......... * hausi............. * 15, Annularia laxa 40, S. Harttii........... * 16. Sphenophyllum 41. Hymenophyllites curti- quum........ * lobus.........+06. 17. Cyclostigma ... 42. H. obtusilobus...... $ a 18. Arthrostigma 43. Alethopteris discrepans * 19. Lepidodendron Gaspia- 44, Pecopteris serrulata.. . * MUM eis: aye: 5 0 Bae 0s * || 45. P. preciosa.........- 20. L. corrugatum........ ba 46. Trichomanites........ * 21. Lycopodites Matthewi . * 1/47. Callipteris .......... bes 22. L. Richardsoni....... 48, Cardiocarpum ....... = 23. Ptilophyton Vanuxemii 49. C. Crampii.........- 24. Lepidophloios antiquus. * |50, Antholithes ......... * 25. Psilophyton princeps. . | 51. Trigonocarpum ...... * 26. P. robustius ......... : 266 THE GEOLOGICAL HISTORY OF PLANTS. 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 Carbon- iferous, while there remain a very large number of Car- boniferous 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 De- vonian 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 embry- onic retardation or acceleration,* 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 con- * In the manner illustrated by Hyatt and Cope. GENERAL LAWS OF ORIGIN AND MIGRATION. 267 fines of the groups of Acrogens and Gymnosperms may be supposed favourable to such exchanges. (3) The con- traction 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 es- pecially of improved, varieties. 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 ascer- tain the external conditions favourable to their produc- tion. In order to attain even to this it will be necessary to inquire critically, with reference to every acknowl- edged 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 condi- tions 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 compres- sion or expansion, or to what extent the appearance of new types may be independent of any external condi- tions, 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 com- prehension of the laws of the creation, as distinguished from those of the continued existence of species. 8. In the present state of our knowledge we have no good ground either to limit the number of specific types 268 THE GEOLOGICAL HISTORY OF PLANTS. 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 subse- quent 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 pre- viously 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 an- ticipating by unwarranted assertions conclusions which may perhaps suddenly dawn upon us through the inspira- tion of some great intellect, or may for generations to come baffle the united exertions of all the earnest pro- moters 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 distribu- tion 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 Zea- land. There is, however, no reason to believe that any specific change has occurred to any plant within the Pleis- tocene or modern period. GENERAL LAWS OF ORIGIN AND MIGRATION. 969 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 Egypt- ian tombs present no appearance of change. This fact appears also in the leaves and other organs of plants pre- served in the nodules in the Pleistocene clays of the Ot- tawa, and in specimens of similar age found in various places in Britain and the continent of Europe.* 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 de- serves careful study. One of his illustrations is that ancient willow, Saliz 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 varia- ble 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 1s easy to construct a theoretical phylogeny of the deri- vation of the willows from a supposed ancestral source, but when we take our little 8. polaris we find that this one twig of cur ancestral tree takes us back without change to the Glacial period. The six species would take us still farther, and the sections, subgenera, and genus at the same rate would require an incalculable amount of past time. He concludes the inquiry in the following terms : * “Proceedings British Association,” 1886, “Pleistocene Plants of Canada,” Canadian Naturalist, 1866. 270 THE GEOLOGICAL HISTORY OF PLANTS. “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, Salicines. 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 repre- sented by six and the poplars by nine species. The or- dinal 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 Saliciness 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 amen- tiferous type, and thereafter the various groups of apetal- ous 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 interme- diate 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 Saliz 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 prin- ciple of slow and gradual evolution, and we are driven GENERAL LAWS OF ORIGIN AND MIGRATION. 971 back on the theory of periods of rapid origin, as we have already seen suggested by Saporta in the case of the Cre- taceous dicotyledons. Such abrupt and plentiful intro- duction of species over large areas at the same time, by whatever cause effected—and we are at present quite igno- rant of any secondary causes—becomes in effect something not unlike the old and familiar idea of creation. Science must indeed always be baffied 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 con- sist.” APPENDIX. I—COMPARATIVE VIEW OF THE SUCCESSIVE PALA0- ZOIC 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,* to summarise the various Palsozoic 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,G.S. For lists referring to the west- ern and southern portions of America, I may refer to the reports of Lesquereux and Fontaine and White.+ In this connection I am reminded, by an excellent little paper of M. Zeiller, | 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 south- ern hemisphere. Of eleven species brought from the Zambesi by M. Lapierre and examined by M. Zeiller, all were identical with Euro- * “ Acadian Geology,” “Reports on Fossil Plants of Canada,” Geo- logical Survey of Canada. + “Geological Surveys of Pennsylvania, Ohio, and Illinois,” ¢ Paris, 1883. 25 274 APPENDIX. pean species of the uppor conl-formation, and tho snmne facet. has been observed in the coal flora of the Capo Colony. These facts bear testimony to tho remarkablo uniformity of climate and vegetation in tho coal period, and IJ perfectly agreo with Zeiller that thoy show, when taken in connection with other parallelisnis in fossils, an actual contemporancousness of tho coul flora over the wholo world. 1. Carpontrerous ILora. (1) Permo-Carboniferous Sub- Flora: This occurs in the upper member of the Carboniferous system of Nova Scotia and Prince Kdward Island, originally named by the writer the Nowor Coal-formation, and moro 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 thore is a predominance of red sandstones and shales, and il contains no productive beds of coal, Ils fossil plants are for the most part of species found in the Middle or Productive Coal-formation, but aro loss 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: Dadorylon materiarium, Dawson. * Walchia (Araucarites) robusta, Dn. * W. (A,) gracilis, Dn. * W. imbricatula, Dn. Calamites Suckatii, Brongt. CL Cistit, Brongt. * (. gigas, Brongt. Neuropteria rartnervis, Bunbury. Alethopleris nervosa, Brongt, Pecopterts arboreseens, Brougt. * P. rigida, Dn, P, orvapteroides, Brongt. * Cordaites aimpler, 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 bo found describod, and several of them figured, in my “Report on the Geology of Princo Kdward Island.” + Tho others are * Grey, “Journal of the Goologicnl Socicty,” vol. xxvii. + 1871. APPENDIX. O75 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, It is worthy of remark here that the association in the Permo- Carboniferous of numerous trunks of Dadozylon with the branches of Walehia 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,* and the reasons which these authors adduce for considering the latter equiv- alent 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. (2) Coat-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 head- quarters of the Carboniferous flora. From this formation I have catalogued + 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 Sigillartw, 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 Sigillarie, Lepidodendra, and ferns are characteristic of this sub-flora; and among the ferns certain species of europteris, Pecopterts, Alethopteris, and Sphenopteris greatly preponderate. These beds are the equivalents of the Middle Coal-measures, or Productive Coal-measures of Pennsylvania, Ohio, &c., and of the eoal-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 di- minish, * “Report on the Permian Flora of Western Virginia and South Pennsylvania,” 1880. + “Acadian Geology,” and “Report on Flora of Lower Carbonifer- ous,” 1873. 276 APPENDIX. (8) The Millstone Grit Sub-Flora: In this formation the abundance of plants and the number of species are greatly diminished.* 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 charac- teristic. Calamites undulatum is abundant and seems to replace C. Suckovit, though C. canneformis and C. cistit continue. Sigillarie 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 Ameri- ca, 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. The following would appear to be the equivalents of this forma- tion, 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). 8. 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 Mill- stone Grit of the north of Ireland. 7 The Jiingste 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 * “Report on Fossil Plants of the Lower Carboniferous and Millstone Grit of Canada,” 1878. APPENDIX. 277 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 Archeocalamites radiatus—which in Amer- ica are Krian—appear in this formation. (8) 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 follow- ing: Dadoxylon (Paleoxylon) antiquius, Dn.—A species with large medullary rays of three or more series of cells. Lepidodendron corrugatum, Dn.—A species closely allied to L. Velthetmianum 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-character- ised stigmaria roots, and constitutes the oldest erect forest known in Nova Scotia. Lepidodendron tetragonum, Sternberg. LZ. obovatum, Sternb. : LL 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 fructifi- cation, however, is nearer to that of Aneimia than to that of Ad?- antum. Ferns of the genera Cardiopteris and Hymenophyliites also occur, though rarely. Ptilophyton plumula, Dn.—This is the latest appearance of this Erian genus, which also occurs in the Lower Carboniferous of Eu- rope 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 sepa- rated by the. great length of. time required for the deposition of the marine limestones and their associated beds, in which no land-plants 278 APPENDIX. have been found ; nor is this gap filled up by the conglomerates and coarse arenaceous beds which, as I have explained in * Acadian Ge- ology,” in some localities take the place of the limestones, as they do also in the Appalachian region farther south, The paleobotanical and strategraphical equivalents of this serics abroad would seem to bo the following: 1, The Vespertine group of Rogers in Pennsylvania. 2. The Kinderhook group of Worthen in Illinois. 8. 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 Carboniforous 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 de- scribed by Schimper. 10, The Older Coal-formation of the Ural, as described by Eich- wald. 11. The so-called “ Ursa Stage” of Heer includes this, but ho has united it with Devonian beds, so that the name cannot be used ox- cept for the local development of these beds at Bear Island, Spitz- bergen. The Carboniferous plants of arctic America, Melville Isl- and, &c., as well as those of Spitzbergen, appear all to bo Lower Carboniferous,* All of the above groups of rocks are charactorised by the prova- lence of Lepidodendra of the type of L. corrugatum, L. Veltheinia- num, and L, Glincanum ; pines of the sub-genus Pitus of Witham, Paleorylon of Brongniart, and peculiar ferns of the genera Cy- clopteris, Cardiopteris, Triphylopteris, 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 Archeopteris, which in the north aro Upper Erian, occur in this group. Unless there have been somo errors in fixing the lower limit of the Vespertine, this would indicate a longer continuance of old forms in the south, * “Notes on Geological Map of the Northern Portion of the Dominion of Canada,” by Dr. G. M. Dawson, 1887, APPENDIX. 279 2. Erian Fora. (1) Upper Brian 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 Archgopteris, along with species referred to the genus Cyclopteris, but which, in so far as their barren fronds are concerned, for the most part resemble Archwopteris. The characteristic American species are Archeopteris Jacksont, A. Rogersi, and A. Gaspiensis. Cyclopteris obtusa and C. (Platy- phyllum) Brownti are also very characteristic species. In Europe, Archeopteris Hibernica is a prevalent species. Leptophieum rhombicum and fragments of Pstlophyton are also found in the Upper Erian. There is evidence of the existence of vast numbers of Ahzzocarps 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 distin- guished, 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 Cornifer- ous series in the West, as well as trunks of Dadozylon. It is, how- ever, 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 Archwopteris and Megalopteris. 280 APPENDIX. In addition to ferns, it has small Lepidodendra, of which L. Gaspi- anum is the chief. Calamitee occur, Archeocalamites radiatus being the dominant species, This plant, which in Europe appears to reach _up into the Lower Carboniferous, is so far strictly Erian in north- east America. Sigillarde scarcely appear, but Cordattes is abun- dant, 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. (8) 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 ab- sence of true ferns, Calamites and Sigillarie, and by the presence of such forms as Psilophyton, Arthrostigma, Leptophleum, and Ne- matophyton. Lepidodendron Gaspianum and Leptophieum already occur, though not nearly so abundant as Pstlophyton. 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 De- vonian horizons respectively, occur in association with fossil plants of these horizons, and have been described by Mr. Whiteaves.* It is interesting to note that, as Fontaine and White have ob- served, certain forms which are Erian in the northeast are found in the Lower members of the Carboniferous in West Virginia, indicat- ing the southward march of species in these periods. 8. Tue Srmurian FLorA AND STILL Hariier INDICATIONS OF Pants, In the upper beds of the Silurian, those of the Helderberg series, we still find Pstlophyton 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 exist- ence of lycopodiaceous and annularian types as far back as the be- * “Transactions of the Royal Society of Canada.” APPENDIX. 981 ginning 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 Ber- wynia. In the Lower Silurian the Profannularia 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 impos- sible to decide at present. it would thus appear that our certain knowledge of land-vegeta- tion begins with the Upper Silurian or the Silurio-Cambrian, and that its earliest, forms were Acrogens allied to Lycopods, and proto- typal trees, forernnners 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 Car- boniferous, and including pines, tree-ferns, and arboreal forms of Lycopods and of equisetaceous plants, as well as numerous herba- ceous plants. At the elose of the Erian the flora again became meagre, and continued so in the Lower Carboniferous. It again be- came rich and varied in the Middle Carboniferous, to decay in the succeeding Permian. IL—HEER’S LATEST RESULTS IN THE GREENLAND FLORA. A very valuable report of Prof. Steenstrup, published in Copen- hagen 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 under- ne.* The plant-bearing beds of Greenland are as follows, in ascending order : i. CrETacrots. 1. The Komé series, of black shales resting on the Laurentian gneiss. These beds are found at various other localities, but the = Meddelelser om Gronland, Hefte V., Copenhagen, 1883. 282 APPENDIX. name above given is that by which they are generally known. Their flora is limited to ferns, cyeads, conifers, and a few endogens, with only Populus primeva 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, Sequota by five, and Salisburta by two, with three of the allied genus Batera. 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, Sapo- tacites, Fraxinus, Viburnum, Cornus, Acer, Celastrus, Paliurus, Ceanothus, Zizyphus, and Crategus as new genera of modern aspect. On the whole there have been found in all these beds 385 species, belonging to 60 families, of which 36 are dicotyledonous, and repre- sent all the leading types of arborescent dicotyledons of the temper- ate latitudes. The flora is a warm temperate one, with some re- markable mixtures of sub-tropical forms, among which perhaps the most remarkable are Kaidocarpum referred to the Pandanee, and such exogens as Ficus and Cinnamomum. 2. TERTIARY. 4, The Unartok series. This is believed to be Eocene. It con- sists of sandstone, which appears on the shores of Disco Island, and APPENDIX. 983 possibly at some other places on the coast. The beds rest directly and apparently conformably on the Upper Cretaceous, and have af- forded 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,* Viburnum, Juglans, Quercus, each by one species; the ubiquitous Sequoias by S. Langsdorffit. This is pretty clearly a Lower Laramie flora. 5. The Atanekerdluk series, consisting of shaly beds, with lime- stone 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, Taxodiwm distichum, Glyptostro- bus Huropeus, and Sequoia Langsdorfit, 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 spe- cies 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 al- together 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 dimi- nution 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° centi- grade. Such temperatures, ranging from 71° to 58° 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 Paleozoic as well as in the Mesozoic and early Ter- tiary, should perhaps lead us to conclude that, relatively to the whole of geological time, the present arctic climate is unusually severe, and * Viburnum marginatum of Lesquereux. 984 APPENDIX. that. a temperate climate in the arctic regions has throughout geo- logical time been the rule rather than the exception. II]—MINERALISATION OF FOSSIL PLANTS. Tue 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 de- posits 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 ar- ranged 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 dis- solve 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. (0) Organic matters may be entirely replaced by mineral sub- stances, In this case the cavities and pores have been first filled, t \ APPENDIX. 285 and then—the walls or solid parts being removed by decay or solu- tion—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 sub- stance. 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 di- oxide 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. (ec) The cavities left by fossils which have decayed may be filled with clay, sand, or other foreign matter, and this, becoming subse- quently 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 car- bonaceous coating on their surfaces. In connection with this state may be mentioned that in which, the wood having decayed, an entire trunk has been fiattened 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 (5), 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. (8) 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 trans- lucent. In most cities there are lapidaries who prepare slices of this kind; but the amateur can readily acquire the art by a little prac- tice, 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 26 286 APPENDIX. 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 PALAZOBOTANY. 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 Paleontological Botany,” and Nichol- son’s “ Paleontology.” Unger’s “ Genera et Species,” Brongniart’s “ Histoire des Végétaux Fossiles,” and Lindley and Hutton’s “ Fossil Flora,” are older though very valuable works. Williamson’s “ Me- moirs,” in the “ Philosophical Transactions,” have greatly advanced our knowledge of the structures of Paleozoic plants. Lastly, the “ Paleophytology ” of Schenk, now in course of publication in Ger- man and French, in connection with Zittel’s “ Palaontology,” is an important addition to manuals of the subject. INDEX. Acer, 228. Acrogens, 6. Agassiz, Prof., 16. Alaska, Flora of, 245. Algz, 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. Archzocalamites, 1/70. Archeopteris, 77, 85. Arctic origin of plants, 221, 238. Arthrophycus, 30. Arthrostigma, 67. Asterophyllites, 78, 122, 170. Asteroptcris, 77, 85. Astropolithon, 30. Atané, Plants of, 242, 281. Atanekerdluk, Plants of, 283. -Australia, Paleozoic 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 cf, 247. Climate and plants, 216, 220, 232. of Carboniferous, 138. of Cretaceous and Eocene, 216. of Devonian, 47. of Early Mesozoic, 178. 288 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. Conifere, Erian, 78, 96. Carboniferous, 134, 148. Mesozoic, ete., 181. Cope, Mr., 215. Cordaites, 78, 180, 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. INDEX, Eopteris, 72. Eozoon of Laurentian, 9. Equisetum, 176, 230. Erian flora, 45, 279. Climate of, 47. Erian or Devonian, 107. itingshausen, Dr., 187, 215. Exogens, Cretaceous, 192, Tertiary, 218, 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 Evian, 45, 279. of Jurassic, 177, 186. of Laramie, 209. of Laurentian, 8. of Miocene, 220, 228, of Modern, 219. of Permian, 274. of Pleistocene, 228, 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. INDEX. Graphite from plants, 8. Gray, Dr., Origin of floras, 228, 237, Grecnland, Climate of, 216. Fossil flora of, 247, Gulielmites, 35, Gyronosperms, 6, Haliserites, 39, Hartt, Prof., 53. Heer, Dr., 108, 181. Helderberg period, Sea of, 250. Heterangium, 77. Hicks, Dr., 21. Hunt, Dr. Sterry, 18, 148. Huxley, Prof., 53. Hymenza, 204, Insects, Erian, 88. Juglans, 196. Jurassic flora, 177. Kainozoic flora, 191, 208, 214, 219. Kidston, Mr. R., 128, 278. 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. 289 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. Nematodendrem, 25, Nematophycus, 28. Nematophyton, 21, 22, 42. Newberry, Dr., 200, 208, 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. Paleanthus, 205. Paleochorda, 30, Paleophycus, 30, 38. Paleozoic floras compared, 278, 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. 290 Pleistocene climate, 227, 230. Pleistocene flora, 223, 22/7. 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, 278. Carboniferous in, 147, THE INDEX. Southern Hemisphere, 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, 1386, 153. Tyndall, Prof., 138. Ulrich, Prof., 57. Unartok beds, 281. Ursa stage of Heer, 108, 241. Walchia, 134, 138. Ward, Mr. L. T., 192, 212, 215. Wethered, Mr. E., 52. White, Dr., 213. Williams, Prof., 51. Williamson, Dr., 26, 31, 71, 167. Williamsonia, 188. END. D, APPLETON & @0.’S8 PUBLICATIONS. CHARLES DARWIN’S WORKS. ORIGIN OF SPECIES BY MEANS OF NATURAL SELECTION, OR THE PRESERVATION OF FA- VORED RACES IN THE STRUGGLE FOR LIFE. Revised edition, with Additions. 12mo, Cloth, $2.00. DESCENT OF MAN, AND SELECTION IN RELATION TO SEX. With many Illustrations. A new edition. 12mo. 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D, APPLETON & C0,’8 PUBLICATIONS, Dr. H. ALLEYNE NICHOLSON’S WORKS. TEXT-BOOK OF ZOOLOGY, for Schools and Colleges.. 12mo. Half roan, $1.60. MANUAL OF ZOOLOGY, for the Use of Students, with 4 Gen- eral Introduction to the Principles of Zodlogy. Second edition. Revised and enlarged, with 243 Woodcuts. 12mo. Cloth, $250, TEXT-BOCK OF GEOLOGY, for Schools and Colleges. 12mo. Half roan, $1.25. INTRODUCTION TO THE STUDY OF BIOLOGY. Illustrated. 12mo. Cloth, 60 cents, THE ANCIENT LIFE-HISTORY OF THE EARTH. A Comprehensive Outline of the Principles and Leading Facts of Palzontological Science. 12mo. Cloth, $2.00. “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. 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