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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. <As- 
tropolithon, a singular 
radiating marking of 
the Canadian Cambri- 
an,* seems to be some- 
thing organic, but of 
what nature is uncer- 
tain (Fig. 9). 

Ethabdichnites and 
Eophyton belong to im- 
pressions explicable by 
the trails of drifting 
sea-weeds, the tail-markings of Crustacea, and the ruts 
ploughed by bivalve mollusks, and occurring in the Silu- 
rian, Erian, and Carboniferous rocks.+ Among these are 
the singular bilobate forms described as Rusophycus by 
Hall, and which are probably burrows or resting-places 
of crustaceans. The tracks of such animals, when walk- 
ing, are the jointed impressions known as Arthrophycus 
and Orusiana. I have shown by the mode of occurrence 


* Supplement to “ Acadian Geology.” 
+ “Canadian Naturalist,” 1864, 


LAURENTIAN AND EARLY PALAZOZOIC. 81 


of these, and Nathorst has confirmed this conclusion by 
elaborate experiments on living animals, that these forms 
are really trails impressed on soft 
sediments by animals and mostly 
by crustaceans. 

I agree with Dr. Williamson * 
in believing that all or nearly all 
the forms referred to Crossochorda 
of Schimper are really animal im- 
pressions allied to Nereites, and due 
either to worms or, as Nathorst has 
shown to be possible, to small crus- 
taceans. Many impressions of this 
kind occur in the Silurian beds of 
the Clinton series in Canada and 
New York, and are undoubtedly 
mere markings. 

It is worthy of note that these 
markings strikingly resemble the so- 
called Hophyton, described by Torell 
from the Primordial of Sweden, and 
by Billings from that of Newfound- 
land; and which also occur abun- 
dantly in the Primordial of New ala 9. — Astropolithon 

: ce , 2 organism 
Brunswick. After examining ase- of the’ Lower Ca- 
ries of these markings from Sweden ay roe 
shown to me by Mr. Carruthers in 
London, and also specimens from Newfoundland and 
a large number in situ at St. John, I am convinced 
that they cannot be plants, but must be markings of 
the nature of Rhabdichnites. This conclusion is based 
on the absence of carbonaceous matter, the intimate 
union of the markings with the surface of the stone, 


* “Tracks from Yoredale Rocks,” “Manchester Literary and Philo- 
sophical Society,” 1885. 


82 THE GEOLOGICAL HISTORY OF PLANTS. 


their indefinite forms, their want of nodes or append- 
ages, and their markings being always of such a na- 
ture as could be produced by scratches of a sharp 
instrument. Since, however, fishes are yet unknown in 
beds of this age, they may possibly be referred to the 
feet or spinous tails of swimming crustaceans. Salter 
has already suggested this origin for some scratches of 
somewhat different form found in the Primordial of 
Great Britain. He supposed them to have been the 
work of species of Hymenocaris. These marks may, 
however, indicate the existence of some free-swim- 
ming animals of the Primordial seas as yet unknown 
to us. 

Three other suggestions merit consideration in this 
connection. One is that Alge and also land-plants, drift- 
ing with tides or currents, often make the most remark- 
able and fantastic trails. A marking of this kind has 
been observed by Dr. G. M. Dawson to be produced by 
a drifted Laminaria, and in complexity it resembled the 
extraordinary nigmichnus multiformis of Hitchcock 
from the Connecticut sandstones. Much more simple 
markings of this kind would suffice to give species of 
Eophyton. Another is furnished by a fact stated to the 
author by Prof. Morse, namely, that Lingule, when dis- 
lodged from their burrows, trail themselves over the 
bottom like worms, by means of their cirri. Colonies of 
these creatures, so abundant in the Primordial, may, 
when obliged to remove, have covered the surfaces of 
beds of mud with vermicular markings. The third is 
that the Rhabdichnite-markings resemble some of the 
grooves in Silurian rocks which have been referred to 
trails of Gasteropods, as, for instance, those from the 
Clinton group, described by Hall. 

Another kind of markings not even organic, but alto- 
gether depending on physical canses, are the beautiful 
branching rill-marks produced by the oozing of water 


LAURENTIAN AND EARLY PALZOZOIC. 33 


out of mud and sand-banks left by the tide, and which 
sometimes cover great surfaces with the most elaborate 
tracery, on the modern tidal shores as well as in some of 
the most ancient rocks. Dendrophycus* of Lesquereux 
seems to be an example of rill-mark, as well as Aristophy- 
cus, Clephycus, and Zygophycus, of Miller and Dyer, 
from the Lower Silurian. 

Rill-marks occur in very old rocks,+ but are perhaps 
most beautifully preserved in the Carboniferous shales 
and argillaceous sandstones, and 
even more elaborately ou the mod- 
ern mud-banks of the Bay of 
Fundy.{ Some of these simulate 
ferns and fronds of Laminaris, 
and others resemble roots, fucoids 
allied to Buthotrephis, or the ra- 
diating worm-burrows already re- 
ferred to (Fig. 10). 

Shrinkage-cracks are also abun- 
dant in some of the Carboniferous 
beds, and are sometimes accom- 
panied with impressions of rain- 
drops. When finely reticulated 
they might be mistaken for the 
venation of leaves, and, when 
complicated with little rill-marks 
tributary to their sides, they pre- : 

3 . . Fre. 10. whet weet 
cisely resemble the Dictyolites of ~ mark (Nova Scotia), re- 
Hall from the Medina sandstone duced, tai Ba 
(Fig. 11). 

An entirely different kind of shrinkage-crack is that 
which occurs in certain carbonised and flattened plants, 


* “Coal Flora of Pennsylvania,” vol. iii., Plate 88. 
+ “Journal of the Geological Society,” vol. xii, p. 251. 
¢ “Acadian Geology,” 2d ed., p. 26. 

5 


34 THE GEOLOGICAL HISTORY OF PLANTS. 


and which sometimes communicates to them a marvellous 
resemblance to the netted under surface of an exogenous 
leaf. Flattened stems of plants and Jayers of cortical 
matter, when carbonised, shrink in such a manner as to 
produce minute reticulated cracks. These become filled 
with mineral matter before the coaly substance has been 
completely consolidated. A further compression occurs, 
causing the coaly substance to collapse, leaving the little 
veins of harder mineral matter projecting. These im- 
press their form upon the clay or shale above and below, 
and thus when the mass is broken open we have a car- 
bonaceous film or thin layer covered with a network of 
raised lines, and 
corresponding mi- 
nute depressed 
lines on the shale 
in contact with it, 
The reticulations 
are generally ir- 
regular, but some- 
times they very 
closely resemble 
the veins of a re- 
ticulately veined 
leaf. One of the 
‘ most curious speci- 
ESN 2 Zo mens in my pos- 
Fie. 11.—Cast of shrinkage-cracks (Carbon- Session was collect- 

iferous, Nova Scotia), illustrating pre- ed by Mr. Elder 


tended Alga. 

: in the Lower Car- 
boniferous of Horton Bluff. The little veins which form 
the projecting network are in this case white calcite ; but 
at the surface their projecting edges are blackened with 
a carbonaceous film. 

Slickensided bodies, resembling the fossil fruits de- 
scribed by Geinitz as Gulielmites, and the objects believed: 


LAURENTIAN AND EARLY PALAOZOIC. 85 


by Fleming and Carruthers * to be casts of cavities filled 
with fluid, abound in the shales of the Carboniferous and 
Devonian. They are, no doubt, in most cases the results 
of the pressure and consolidation of the clay around small 
solid bodies, whether organic, fragmentary, or concre- 
tionary. They are, in short, local slickensides precisely 
similar to those found so plentifully in the cowl under- 
clays, and which, as I have elsewhere + shown, resulted 
from the internal giving way and slipping of the mass as 
the roots of Stigmaria decayed within it. Most collectors 
of fossil plants in the older formations must, I presume, 
be familiar with appearances of this kind in connection 
with small stems, petioles, fragments of wood, and car- 
polites. I have in my collection petioles of ferns and 
fruits of the genus Trigonocarpum partially slickensided 
in this way, and which if wholly covered by this kind of 
marking could scarcely have been recognised. I have 
figured bodies of this kind in my report on the Devonian 
and Upper Silurian plants of Canada, believing them, 
owing to their carbonaceous covering, to be probably 
slickensided fruits, though of uncertain nature. In every 
case I think these bodies must have had a solid nucleus of 
some sort, as the severe pressure implied in slickensiding 
is quite incompatible with a mere “ fluid-cavity,” even 
supposing this to have existed. 

Prof. Marsh has well explained another phase of the 
infinence of hard bodies in producing partial slickensides, 
in his paper on Stylolites, read before the American As- 
sociation in 1867, and the application of the combined 
forces of concretionary action and slickensiding to the 
production of the cone-in-cone coneretions, which occur 
in the coal-formation and as low as the Primordial. I 
have figured .a very perfect and beautiful form of this 


* “Journal of the Geological Society,” June, 1871. 
t Ibid., vol. x., p. 14. 


36 THE GEOLOGICAL HISTORY OF PLANTS. 


kind from the coal-formation of Nova Scotia, which is 
described in “‘ Acadian Geology” * (Fig. 12). 

I have referred to these facts here because they are 
relatively more important in that older period, which may 
be named the age of Alge, and because their settlement 
now will enable us to dispense with discussions of this 
kind further on. The able memoirs of Nathorst and 
Williamson should be studied by those who desire further 
information. 

But it may be asked, ‘‘ Are there no real examples of 
fossil Algze?” I believe there are many such, but the diffi- 
culty is to distinguish 
them. Confining our- 
selves to the older 
rocks, the following 
may be noted : 

The genus Bu- 
thotrephis of Hall, 
which is characterised 
as having stems, sub- 
cylindric or com- 


= Sa pressed, with numer- 


Fic. 12.—Cone-in-cone concretion (Carbon- gyg branches, which 
iferous, Nova Scotia), illustrating pre- pppoe 
tended Alge. are divaricating and 
sometimes leaf - like, 
contains some true Alge. MHall’s B. gracilis, from the 
Siluro-Cambrian, is one of these. Similar plants, referred 
to the same species, occur in the Clinton and Niagara 
formations, and a beautiful species, collected by Col. 
Grant, of Hamilton, and now in the McGill College col- 
lection, represents a broader and more frondose type of 
distinctly carbonaceous character. It may be described 
as follows : 
Buthotrephis Grantit, 8. N. (Fig. 13).—Stems and 


* Appendix, p. 676, edition of 1878. 


a 


referred to differ- 


‘of these plants 


LAURENTIAN AND EARLY PALAOZOIC. 37 


fronds smooth and slightly striate longitudinally, with 
curved and interrupted stria. Stem thick, bifurcating, 
the divisions terminating in irregularly pinnate fronds, 
apparently truncate at the extremities. The quan- 
tity of carbona- 
ceous matter pres- 
ent would indicate 
thick, though per- 
haps flattened, 
stems and dense 
fleshy fronds. 
The | species 
Buthotrephis sub- 
nodosa and B. 
flezuosa,, from 
the Utica shale, 
are also certain- |. 
ly plants, though 
it. is possible,. if 
their structures 
and fruit were 
known, some of 
these might -be 


ok 


SSeS 


ent genera. All 


have either car-. 
bonaceous matier 
or produce organ- \— 
ic stains on the 
matrix. 

’ ., The organism 
with diverging 
wedge-shaped fronds, described by Hall as Sphenothallus 
anguystifolius, is also a plant. Fine specimens, in the 
collection of the Geological Survey of Canada, show dis- 


Fie. 18.—Buthotrephis Grantii, a genuine Alga 
; from the Silurian, Canada, 


388 THE GEOLOGICAL HISTORY OF PLANTS. 


tinct evidence of the organic character of the wedge- 
shaped fronds. It is from the Utica shale, and elsewhere 
in the Siluro-Cambrian. It is just possible, as suggested 
by Hall, that this plant may be of higher rank than the 
Alge. 

The genus Paleophycus of Hall includes a great va- 
riety of uncertain objects, of which only a few are prob- 
ably true Alge. I have specimens of fragments similar 
to his P. virgatus, which show distinct carbonaceous 
films, and others from the Quebec group, which seem to 
be cylindrical tubes now flattened, and which have con- 
tained spindle-shaped sporangia of large size. Tortuous 
and curved flattened stems, or fronds, from the Upper 
Silurian limestone of Gaspé, also show organic matter. 

Respecting the forms referred to Licrophycus by 
Billings, containing stems or semi-cylindrical markings 
springing from a common base, I have been in great 
doubt. I have not seen any specimens containing une- 
quivocal organic matter, and am inclined to think that 
most of them, if not the whole, are casts of worm-bur- 
rows, with trails radiating from them. 

Though I have confined myself in this notice to plants, 
or supposed plants, of the Lower Paleozoic, it may be 
well to mention the remarkable Cauda-Galli fucoids, re- 
ferred by Hall to the genus Spirophyton, and which are 
characteristic of the oldest Erian beds. The specimens 
which I have seen from New York, from Gaspé, and 
from Brazil, leave no doubt in my mind that these were 
really marine plants, and that the form of a spiral frond, 
assigned to them by Hall, is perfectly correct. They 
must have been very abundant and very graceful plants 
of the early Erian, immediately after the close of the 
Silurian period. 

We come now to notice certain organisms referred to 
Algs, and which are either of animal origin, or are of 
higher grade than the sea-weeds. We have already dis- - 


LAURENTIAN AND EARLY PALZOZOIC. 89 


cussed the questions relating to Prototaxites. Drepano- 
phycus, of Goeppert,* I suspect, is only a badly preserved 
branch or stem of the Erian land-plant known as Arthro- 
stigma. In like manner, Haliserites Dechenianus,t of 
Goeppert, is evidently the land-plant known as Pstlophy- 
ton. Spherococcites dentatus and S. serra—the Fucoides 
dentatus and serra of Brongniart, from Quebec—are 
graptolites of two species quite common there.{ Dic- 
tyophyton and Uphanientia, as described by Hall and the 
author, are now known to be sponges. They have be- 
come Dictyospongie. The curious and very ancient fos- 
sils referred by Forbes to the genus Oldhamia are perhaps 
still subject to doubt, but are usually regarded as Zo- 
ophytes, though it is quite possible they may be plants. 
Though I have not seen the specimens, I have no doubt 
whatever that the plants, or the greater part of them, 
from the Silurian of Bohemia, described by Stur as Alge 
and Characew,* are really land-plants, some of them of 
the genus Pstlophyton. I may say in this connection 
that specimens of flattened Psilophyton and Arthrostig- 
ma, in the Upper. Silurian and Erian of Gaspé, would 
probably have been referred to Algx, but for the fact that 
in some of them the axis of barred vessels is preserved. 

It is not surprising that great difficulties have occurred 
in the determination of fossil Alge. Enough, however, 
remains certain to prove that the old Cambrian and Silu- 
rian seas were tenanted with sea-weeds not very dissimilar 
from those of the present time. It is further probable 
that some of the graphitic, carbonaceous, and bituminous 


* “Fossile Flora,” 1852, p. 92, Table xli. 

+ Ibid., p. 88, Table ii. 

+ Brongniart, ““Vegeteaux Fossiles,” Plate vi., Figs. 7 to 12. 

* “ Proceedings of the Vienna Academy,” 1881. Hostinella, of this 
author, is almost certainly Psilophyton, and his Barrandiana seems to in- 
clude Arthrostigma, and perhaps leafy branches of Berwynia. These 
curious plants should be re-examined. 


40 THE GEOLOGICAL HISTORY OF PLANTS. 


| shales and limestones of the Silurian owe their-carbona- 
ceous matters to the decomposition of Algs, though pos- 
sibly some of it may have been derived from Graptolites 
and other corneous Zodphytes. In aiiy case, such micro- 


~~ 


oan 


Fic. 14,—Silurian vegetation restored. Protannularia, Berwynia, Nema- 
tophyton, Spheioghysion, Arthrostigma, Psvlophyton. 


scopic examinations of these shales as I have made, have 
not produced any evidence of the existence of plants of 
higher grade, while those of the Erian and Carboniferous 
periods, similar to the naked eye, abound in such evi- 
dence. It is also to be observed that, on the surfaces of « 


LAURENTIAN AND EARLY PALAOZOIC. 41 


beds of sandstone in the Upper Cambrian, carbonaceous 
débris, which seems to be the remains of either aquatic 
or land plants, is locally not infrequent. 

Referring to the land vegetation of the older rocks, it 
is difficult to picture its. nature and appearance. We 
may imagine the shallow waters filled with aquatic or am- 
phibious Rhizocarpean plants, vast meadows or brakes of 
the delicate Psilophyton and the starry Protannularia 
and some tall trees, perhaps looking like gigantic club-' 
mosses, or possibly with broad, flabby leaves, mostly cellu- 
lar in texture, and resembling Algz transferred to the air. 
Imagination can, however, scarcely realise this strange 
and grotesque vegetation, which, though possibly copious | 
and luxuriant, must have been simple and monotonous in 
aspect, and, though it must have produced spores and 
seeds and even fruits, these were probably all of the types 
seen in the modern acrogens and gymnosperms. 


“Tn garments green, indistinct in the twilight, 
They stand like Druids of old, with voices sad and prophetic.” 


Prophetic they truly were, as we shall find, of the 
more varied forests of succeeding times, and they may 
also help us to realise the aspect of that still older vege- 
tation, which is fossilised in the Laurentian graphite ; 
though it is not impossible that this last may have been of 
higher and more varied types, and that the Cambrian and 
Silurian may have been times of depression in the vegeta- 
ble world, as they certainly were in the submergence of 
much of the land. 

These primeval woods served at least to clothe the 
nakedness of the new-born land, and they may have shel- 
tered and nourished forms of land-life still unknown to 
us, as.we find as yet only a few insects and scorpions in 
the Silurian. They possibly also served to abstract from 
the atmosphere some portion of its superabundant car- 
bonic acid harmful to animal life, and they stored up, 


42 THE GEOLOGICAL HISTORY OF PLANTS. 
, supplies of graphite, of petroleum, and of illuminating 
| gas, useful to man at the present day. We may write 
of them and draw their forms with the carbon which 
they themselves supplied. 


NOTE TO CHAPTER IL 


Examination or Protoraxires (Vematophyton), By Prov, PEn- 
HALLOW, OF McGitL University. 


Prof. Penhallow, having kindly consented to re-examine my 
specimens, has furnished me with elaborate notes of his facts and 
conclusions, of which the following is a summary, but which it is 
hoped will be published in full : 

“1. Concentric Layers,—The inner face of each of these is com- 
posed of relatively large tubes, having diameters from 13°6 to 346 
micro-millimetres. The outer face has tubes ranging from 13°8 to 
276mm. The average diameter in the lower surface approaches to 34, 
that in the outer to 18°8. There is, however, no abrupt termination 
to the surface of the layers, though in some specimens they separate 
easily, with shining surfaces, 

“2. Minute Structure—In longitudinal sections the principal 
part of the structure consists of longitudinal tubes of indeterminate 
length, and round in cross-section. They are approximately parallel, 
but in some cases may be seen to bend sinuously, and are not in 
direct contact. Finer myceloid tubes, 5°33 mm. in diameter, trav- 
erse the structure in all directions, and are believed to branch off 
from the larger tubes. In a small specimen supposed to be a branch 
or small stem, and in which the vertical tubes are somewhat distant 
from one another, this horizontal system is very largely developed ; 
but is less manifest in the older stems. The tubes themselves show 
no structure. The ray-like openings in the substance of the tissue 
are evidently original parts of the structure, but not of the nature of 
medullary rays. They are radiating spaces running outward in an 
interrupted manner or so tortuously that they appear to be inter- 
rupted in their course from the centre towards the surface. They 
show tubes turning into them, branching into them, and approxi- 
mately horizontal, but tortuous. On the external surface of some 
specimens these radial spaces are represented by minute pits irregu-: 


LAURENTIAN AND EARLY PALAOZOIC. 43 


larly or spirally arranged. The transverse swellings of the stem 
show no difference of structure, except that the tubes or cells may be 
a little more tortuous, and a transverse film of coaly matter extends 
from the outer coaly envelope inwardly. This may perhaps be 
caused by some accident of preservation. The outer coaly layer 
shows tubes similar to those of thestem.* The horizontal or oblique 
flexures of the large tubes seem to be mainly in the vicinity of the 
radial openings, and it is in entering these that they have been seen 
- to branch.” 

The conclusions arrived at by Prof. Penhallow are as follows : 

“1, The plant was not truly exogenous, and the appearance of 
rings is independent of the causes which determine the layers of 
growth in exogenous plants. 

“2, The plant was possessed of no true bark. Whatever cortical 
layer was present was in all probability a modification of the general 
structure.t 

“3, An intimate relation exists between the large tubular cells 
and the myceloid filaments, the latter being a system of small 
branches from the former; the branching being determined chiefly in 
certain special openings which simulate medullary rays, 

“4, The specimens examined exhibit no evidence of special de- 
cay, and the structure throughout is of a normal character. 

“5. The primary structure consists of large tubular cells without 
apparent terminations, and devoid of structural markings, with 
which is associated a secondary structure of myceloid filaments aris- 
ing from the former. 

“6, The structure of Nematophyton as a whole is unique; at least 
there is no plant of modern type with which it is comparable. 
Nevertheless, the loose character of the entire structure; the inter- 
minable cells; their interlacing; and, finally, their branching into a 
secondary series of smaller filaments, point with considerable force to 
the true relationship of the stem as being with Algs or other Thallo- 
" phytes rather than with Gymnosperms. A more recent examination 


* It is possible that these tubes may be merely part of the stem at- 
tached to the bark, which seems to me to indicate the same dense cellular 
structure seen in the bark of Lepidodendra, etc. 

+ On these points I would reserve the considerations: 1. That there 
must have been some relation between the mode of growth of these great 
stems and their concentric rings; and, 2. That the evidence of a bark is 
as strong as in the case of any Paleozoic tree in which the bark is, as 
usual, carbonised. 


44 THE GEOLOGICAL HISTORY OF PLANTS. 


of a laminated resinous substance found associated with the plant 
shows that it is wholly amorphous, and, as indicated by distinct lines 
of flow, that it must have been in a plastic state at a former period, 
The only evidence of structure was found in certain well-defined 
mycelia, which may have been derived from associated vegetable 
matter upon which they were growing, and over which the plastic 
matrix flowed.” 

I have only to add to this description that when we consider that 
Nematophyton Logani was a large tree, sometimes attaining a diam- 
eter of more than two feet, and a stature of at least twenty before 
branching; that it had great roots, and gave off large branches: that 
it was an aérial plant, probably flourishing in the same swampy flats 
with Pstlophyton, Arthrostigma, and Leptophlewm ; that the peculiar 
bodies known as Pachytheca were not unlikely its fruit—we have 
evidence that there were, in the early Paleozoic period, plants 
scarcely dreamt of by modern botany. Only when the appendages 
of these plants are more fully known can we hope to understand 
them. In the mean time, I may state that there were probably differ- 
ent species of these trees, indicated more particularly by the stems I 
have described as Nematoxylon and Celluloxylon.* There were, I 
think, some indications that the plants described by Carruthers as 
Berwynia, may also be found to have been generically the same. 
The resinous matter mentioned by Prof. Penhallow is found in great 
abundance in the beds containing Nematophyton, and must, I think, 
have been an exudation from its bark. 


* “Journal Geol. Society of London,” 1868, 1881. 


CHAPTER II. 


THE ERIAN OR DEVONIAN FORESTS—ORIGIN OF PETRO- 
LEUM—THE AGE OF ACROGENS AND GYMNOSPERMS. 


In the last chapter we were occupied with the com- 
paratively ‘few and obscure remains of plants entombed 
in the oldest geological formations: We now ascend to a 
higher plane, that of the Erian or Devonian period, in 
which, for the first time, we find varied and widely dis- 
tributed forests. 

The growth of knowledge with respect to this flora 
has been somewhat rapid, and it may be interesting to 
note its principal stages, as an encouragement to the hope 
that we may yet learn something more satisfactory re- 
specting the older floras we have just discussed. — 

In Goeppert’s memoir on the flora of the Silurian, 
Devonian, and Lower Carboniferous rocks, published in 
1860,* he enumerates twenty species as Silurian, but these 
are all admitted to be Algew, and several of them are re- 
mains which may be fairly claimed by the zodlogists as 
zoophytes, or trails of worms and mollusks. In the Lower 
Devonian he knows but six species, five of which are 
Algs, and the remaining one a Sigillaria, but this is of 
very doubtful nature. In the Middle Devonian he gives 
but one species, a land-plant of the genus Lepidodendron. 
In the Upper Devonian the number rises to fifty-seven, 
of which all but seven are terrestrial plants, representing 


* Jena, 1860. 


as 


46 THE GEOLOGICAL HISTORY OF PLANTS. 


a large number of the genera occurring in the succeeding 
Carboniferous system. 

Goeppert does not include in his enumeration the 
plants from the Devonian of Gaspé, described by the 
author in 1859,* having seen only an abstract of the 
paper at the time of writing his memoir, nor does he 
appear to have any knowledge of the plants of this age 
described by Lesquereux in Rogers’s ‘‘ Pennsylvania.” 
These might have added ten or twelve species to his list, 
some of them probably from the Lower Devonian. It is 
further to be observed that a few additional species had 
also been recognised by Peach in the Old Red Sandstone 
of Scotland. 

But from 1860 to the present time a rich harvest of 
specimens has been gathered from the Gaspé sandstones, 
from the shales of southern New Brunswick, from the 
sandstones of Perry in Maine, and from the wide-spread 
Erian areas of New York,. Pennsylvania, and Ohio. 
Nearly all these specimens have passed through my 
hands, and I am now able to catalogue about a hun- 
dred species, representing more than thirty genera, and 
including all the great types of vascular Cryptogams, the 
Gymnosperms, and even one (still doubtful) Angiosperm. 
Many new forms have also been described from the De- 
vonian of Scotland and of the Continent of Europe. 

Before describing these plants in detail, we may refer 
to North America for illustration of the physical condi- 
tions of the time. In a physical point of view the north- 
ern hemisphere presented a great change in the Erian 
period. There were vast foldings of the crust of the 
earth, and great emissions of volcanic rock on both sides 
of the Atlantic. In North America, while at one time 
the whole interior area of the continent, as far north as 


* “Journal of the Geological Society of London,” also ‘“ Canadian 
Naturalist.” 


\ 


THE ERIAN OR DEVONIAN FORESTS, 47 


the Great Lakes, was occupied by a vast inland sea, studded 
with coral islands, the long Appalachian ridge had begun 
to assume, along with the old Laurentian land, something 
of the form of our present continent, and on the margins 
of this Appalachian belt there were wide, swampy flats and 
shallow-water areas, which, under the mild climate that 
seems to have characterised this period, were admirably 
suited to nourish a luxuriant vegetation. Under this 
mild climate, also, it would seein that new forms of plants 
were first introduced in the far north, where the long 
continuance of summer sunlight, along with great warmth, 
seems to have aided in their introduction and early ex- 
tension, and thence made their way to the southward, a 
process which, as Gray and others have shown, has also 
occurred in later geological times. 

The America of this Erian age consisted during the 
greater part of the period of a more or less extensive belt 
of land in the north with two long tongues descending 
from it, one along the Appalachian line in the east, the 
other in the region west of the Rocky Mountains. On 
the seaward sides of these there were low lands covered 
with vegetation, while on the inland side the great in- 
terior sea, with its verdant and wooded islands, realised, 
though probably with shallower water, the conditions of 
the modern archipelagoes of the Pacific. 

Europe presented conditions somewhat similar, having 
in the earlier and middle portions of the period great sea 
areas with insular patches of land, and later wide tracts 
of shallow and in part enclosed water areas, swarming 
with fishes, and having an abundant vegetation on their 
shores. These were the conditions of the Eifel and 
Devonshire limestones, and of the Old Red Sandstone of 
Scotland, and the Kiltorcan beds of Ireland. In Europe 
also, as in America, there were in the Erian age great 
ejections of igneous rock. On both sides of the Atlantic 
there were somewhat varied and changing conditions of 


48 THE GEOLOGICAL HISTORY OF PLANTS. 


land and water, and a mild and equable climate, permit- 
ting the existence of a rich vegetation in high northern 
latitudes. Of this latter fact a remarkable example is 
afforded by the beds holding plants of this age in Spitz- 
bergen and Bear Island, in its vicinity. Here there seem 
to be two series of plant-bearing strata, one with the 
vegetation of the Upper Erian, the other with that of 
the Lower Carboniferous, though both have been united 
by Heer under his so-called ‘‘ Ursa Stage,” in which he 
has grouped the characteristic plants of two distinct 
periods. This has recently been fully established by the 
researches of Nathorst, though the author had already 
suggested it as the probable explanation of the strange 
union of species in the Ursa group of Heer. 

In studying the vegetation of this remarkable period, 
we must take merely some of the more important forms 
as examples, since it would be impossible to notice all 
the species, and some of them may be better treated in 
the Carboniferous, where they have their headquarters. 
(Fig. 15.) 

I may first refer to a family which seems to have cul- 
minated in the Erian age, and ever since to have occupied 
a less important place. It is that of the curious aquatic 
plants known as Rhizocarps,* and referred to in the last 
chapter. 

My attention was first directed to these organisms by 
the late Sir W. E. Logan in 1869. He had obtained from 
the Upper Erian shale of Kettle Point, Lake Huron, 
specimens filled with minute circular discs, to which he 
referred, in his report of 1863, as “‘ microscopic orbicular 
bodies.” Recognising them to be macrospores, or spore- 
cases, I introduced them into the report on the Erian 


* Or, as they have recently been named by some botanists, “ Hete- 
rosporous Filices,” though they are certainly not ferns in any ordinary 
sense of that term. 


“THE ERIAN OR DEVONIAN FORESTS. 49 


flora, which I was then preparing, and which was pub- 

lished in 1871, under the name Sporangites Huronensis. 
In 1871, having occasion to write a communication to 

the ‘‘ American Journal of Science” on the question then 


Fia. 16.—Vegetation of the Devonian period, restored. Calamites, Psilo- 
plyton, Leptophieum, Lepidodendron, Cordaites, Sigillaria, Dadoxy- 
nm, Asterophyllites, Platyphylium. 


raised as to the share of spores and spore-cases in the ac- 
cumulation of coal, a question to be discussed in a sub- 


50 THE GEOLOGICAL HISTORY OF PLANTS. 


sequent chapter, these curious little bodies were again 
reviewed, and were described in substance as follows : 

“The oldest bed of spore-cases known to me is that 
at Kettle Point, Lake Huron. It is a bed of brown 
bituminous shale, burning with much flame, and under 
a lens is seen to be studded with flattened disc-like bodies, 
scarcely more than a hundredth of an inch in diameter, 
which under the microscope are found to be spore-cases 
(or macrospores) slightly papillate externally (or more 
properly marked with dark pores), and sometimes show- 
ing a point of attachment on one side and a slit more or 
less elongated and gaping on the other. When slices of 
the rock are made, its substance is seen to be filled with 
these bodies, which, viewed as transparent objects, appear 
yellow like amber, and show little structure, except that 
the walls can be distinguished from the internal cavity, 
which may sometimes be seen to enclose patches of granu- 
lar matter. In the shale containing them are also vast 
numbers of rounded, translucent granules, which may be 
escaped spores (microspores).” The bed containing these 
spores at Kettle Point was stated, in the reports of the 
“Geological Survey of Canada,” to be twelve or fourteen 
feet in thickness, and besides these specimens it contained 
fossil plants referable to the species Calamites inornatus 
and Lepidodendron primevum, and I not unnaturally 
supposed that the Sporangites might be the fruit of the 
latter plant. I also noticed their resemblance to the 
spore-cases of LZ. corrugatum of the Lower Carboniferous 
(a Lepidodendron allied to L. primevum), and to those 
from Brazil described by Carruthers under the name 
Flemingites, as well as to those described by Huxley 
from certain English coals, and to those of the Tasmanite 
or white coal of Australia. The bed at Kettle Point is 
shown to be marine by its holding the sea-weed known 
as Spirophyton, and shells of Lingula. 

The subject did not again come under my notice till 


THE ERIAN OR DEVONIAN FORESTS, 5t 


1882, when Prof. Orton, of Columbus, Ohio, sent me 
some specimens from the Erian shales of that State, 
which on comparison seemed undistinguishable from 
Sporangites Huronensis.* Prof. Orton read an interest- 
ing paper on these bodies, at the meeting-of the American 
Association in Montreal, in which were some new and 
striking facts. One of these was the occurrence of such 
bodies throughout the black shales of Ohio, extending 
**from the Huron River, on the shore of Lake Erie, to 
the mouth of the Scioto, in the Ohio Valley, with an 
extent varying from ten to twenty miles in breadth,” and 
estimated to be three hundred and fifty feet in thickness. 
I have since been informed by my friend Mr. Thomas, of 
Chicago, that its thickness, in some places at least, must 
be three times that amount. About the same time, Prof. 
Williams, of Cornell, and Prof. Clarke, of Northampton, 
announced similar discoveries in the State of New York, 
so that it would appear that beds of vast area and of great 
thickness are replete with these little vegetable discs, usu- 
ally converted into a highly bituminous, amber-like sub- 
stance, giving a more or less inflammable character to the 
containing rock. 

Another fact insisted on by Prof. Orton was the ab- 
sence of Lepidodendroid cones, and the occurrence of 
filamentous vegetable matter, to which the Sporangites 
seemed to be in some cases attached in groups. Prof. 
Orton also noticed the absence of the trigonal form, which 
belongs to the spores of many Lepidodendra, though this 
is not a constant character. In the discussion on Prof. 
Orton’s paper, I admitted that the facts detailed by him 
shook my previous belief of the lycopodiaceous character 


_ * These shales have been described, as to their chemical and geological 
relations, by Dr. T. Sterry Hunt, “ American Journal of Science,” 1863, 
and by Dr, Newberry, in the “‘ Reports of the Geological Survey of Ohio,” 
vol, i., 1868, and vol. iii., 1878. 


52 THE GEOLOGICAL HISTORY OF PLANTS. 


of these bodies, and induced me to suspect, with Prof. 
Orton, that they might have belonged to some group of 
aquatic plants lower than the Lycopods. 

Since the publication of my paper on Rhizocarps in 
the Paleozoic period above referred to, I have received 
two papers from Mr. Edward Wethered, F. G.8., in one 
of which he describes spores of plants found in the lower 
limestone shales of the Forest of Dean, and in the other 
discusses more generally the structure and origin of Car- 
boniferous coal-beds.* In both papers he refers to the 
occurrence in these coals and shales of organisms essen- 
tially similar to the Erian spores. 

In the “‘Bulletin of the Chicago Academy of Science,” 
January, 1884, Dr. Johnson and Mr. Thomas, in their 
paper on the “ Microscopic Organisms of the Boulder Clay 
of Chicago and Vicinity,” notice Sporangites Huronensis 
as among these organisms, and have discovered them also 
in large numbers in the precipitate from Chicago city 
water-supply. They refer them to the decomposition of 
the Erian shales, of which boulders filled with these or- 
ganisms are of frequent occurrence in the Chicago clays. 
The Sporangites and their accompaniments in the boulder 
clay are noticed in a paper by Dr. G. M. Dawson, in the 
“ Bulletin of the Chicago Academy,” June, 1885. 

Prof. Clarke has also described, in the “ American 
Journal of Science” for April, 1885, the forms already 
alluded to, and which he finds to consist of macrospores 
enclosed in sporocarps. He compares these with my 
Sporangites Huronensts and Protosalvinia bilobata, but 
I think it is likely that one of them at least is a distinct 
species. 

I may add that in the ‘‘Geological Magazine” for 
1875, Mr. Newton, F. G.8., of the Geological Survey of 


* “Cotteswold Naturalists’ Field Club,” 1884; “Journal of the 
Royal Microscopical Society,” 1885, 


THE ERIAN OR DEVONIAN FORESTS. 53 


England, published a description of the Tasmanite and 
Australian white coal, in which he shows that the or- 
ganisms in these deposits are similar to my Sporangites 
Huronensis, and to the macrospores previously described. 
by Prof. Huxley, from the Better-bed coal. Mr. Newton 
does not seem to have been_aware of my previous descrip- 
tion of Sporangites, and proposes the name Zasmanites 
punctatus for the Australian form. 

Here we have the remarkable fact that the waste 
macrospores, or larger spores of a species of Cryptoga- 
mous plant, occur dispersed in countless millions of tons 
through the shales of the Erian in Canada and the United 
States. 

No certain clue seemed to be afforded by all these 
observations as to the precise affinities of these widely 
distributed bodies ; but this was furnished shortly after 
from an unexpected quarter. In March, 1883, Mr. Or- 
ville Derby, of the Geological Survey of Brazil, sent me 
specimens found in the. Erian of that country, which 
seemed to throw a new light on the whole subject. These 
I described and pointed out their connection with Sporan- 
gites at the meeting of the American Association at Min- 
neapolis, in 1883, and subsequently published my notes 
respecting them in its proceedings, and in the “Canadian 
Record of Science.” 

Mr. Derby’s specimens contained the curious spiral 
sea-weed known as Spirophyton, and also minute rounded 
Sporangites like those obtained in the Erian of Ohio, and 
of which specimens had been sent to me some years be- 
fore by the late Prof. Hartt. But they differed in show- 
ing the remarkable fact that these rounded bodies are 
enclosed in considerable numbers in spherical and oval 
sacs, the walls of which are composed of a tissue of 
hexagonal cells, and which resemble in every respect the 
involucres or spore-sacs of the little group of modern 
acrogens known as Rhizocarps, and living in shallow 


54 THE GEOLOGICAL HISTORY OF PLANTS, 


water. More especially they resemble the sporocarps of 
the genus Salvinia. This fact opened up an entirely 
new field of investigation, and I at once proceeded to 
compare the specimens with the fructification of modern 
Rhizocarps, and found that substantially these multitu- 
dinous spores embedded in the Erie shales may be re- 
garded as perfectly analogous to the larger spores of the 
modern Salvinia natans of Europe, as may be seen by 
the representation of them in Fig. 16. 


Fie. 16.—Sporangites (Protosalvinia). a, Sporangites Braziliensis, natural 
size. ax, Same, magnified. 3, Sp. dcloba, natural size. 0, Detached 
maacrospores. wD, Spore-cases of Salvinia natans. px, Same, magnified. 
£, Shale with sporangites, vertical section, highly magnified. 


The typical macrospores from the Erian shales are 
perfectly circular in outline, and in the flattened state ap- 
pear as discs with rounded edges, their ordinary diameter 
being from one seventy-fifth to one one hundredth of an 
inch, though they vary considerably in size. This, how- 
ever, I do not regard as an essential character. The 
edges, as seen in profile, are smooth, but the flat surface 
often presents minute dark spots, which at first I mis-- 


THE ERIAN OR DEVONIAN FORESTS, 55 


took for papille, but now agree with Mr. Thomas in rec- 
ognising them as minute pores traversing the wall of the 
disc, and similar to those which Mr. Newton has described 
in Tasmanite, and which Mr. Wethered has also recog- 
nised in the similar spores of the Forest of Dean shales. 
The walls also sometimes show faint indications of con- 
centric lamination, as if they had been thickened by suc- 
cessive deposits. 

As seen by transmitted light, and either in front or in 
profile, the discs are of a rich amber colour, translucent 
and structureless, except the pores above referred to. 
The walls are somewhat thick, or from one-tenth to one- 
twentieth the diameter of the disc in thickness, They 
never exhibit the triradiate marking seen in spores of Ly- 
copods, nor any definite point of attachment, though 
they sometimes show a minute elongated spot which may 
be of this nature, and they are occasionally seen to have 
opened by slits on the edge or front, where there would 
seem to have been a natural line of dehiscence. The in- 
terior is usually quite vacant or structureless, but in some 
cases there are curved internal markings which may indi- 
cate a shrunken lining membrane, or the remains of a 
prothallus or embryo. Occasionally a fine granular sub- 
stance appears in the interior, possibly remains of mi- 
crospores. 

The discs are usually detached and destitute of any 
envelope, but fragments of flocculent cellular matter are 
associated with them, and in one specimen from the cor- 
niferous limestone of Ohio, in Mr. Thomas’s collection, I 
have found a group of eight or more discs partly enclosed 
in a cellular gac-like membrane of similar character to 
that endlosing the Brazilian specimens already referred to. 

The characters of all the specimens are essentially 
similar, and there is a remarkable absence of other organ- 
isms in the shale. In one instance only, I have observed 
a somewhat smaller round body with a dark centre or 


56 THE GEOLOGICAL HISTORY OF PLANTS. 


nucleus, and a wide translucent margin, marked by a 
slight granulation. Even this, however, may indicate 
nothing more than a different state of preservation. 

It is proper to observe here that the wall or enclosing 
sac of these macrospores must have been of very dense 
consistency, and now appears as a highly bituminous sub- 
stance, in this agreeing with that of the spores of Lyco- 
pods, and, like them, having been when recent of a highly 
carbonaceous and hydrogenous quality, very combustible 
and readily admitting of change into bituminous matter. 
In the paper already referred to, on spore-cases in coals, 
I have noticed that the relative composition of lyco- 
podium and cellulose is as follows : 

Cellulose, C,,H, ,Oo,- 

Lycopodium, C,,H,,,NO,,. 

Thus, such spores are admirably suited for the pro- 
duction of highly carbonaceous or bituminons coals, ete. 

Nothing is more remarkable in connection with these 
bodies than their uniformity of structure and form over 
so great areas and throughout so great thickness of rock, 
and the absence of any other kind of spore-case. This 
is more especially noteworthy in contrast with the coarse 
coals and bituminous shales of the Carboniferous, which 
usually contain a great variety of spores and sporangia, 
indicating the presence of many species of acrogenous 
plants, while the Erian shales, on the contrary, indicate the 
almost exclusive predominance of one form. This con- 
trast is well seen in the Bedford shales overlying these 
beds, and I believe Lower Carboniferous.* Specimens of 
these have been kindly communicated to me by Prof. 
Orton, and have been prepared by Mr. Thomas. In these 
we see the familiar Carboniferous spores with triradiate 
markings called Triletes by Reinsch, and which are simi- 
lar to those of Lycopodiaceous plants. Still more abun- 


* According to Newberry, lower part of Waverly group. 


THE ERIAN OR DEVONIAN FORESTS. 57 


dant are those spinous and hooked spores or sporangia, 
to which the names Sporocarpon, Zygosporites, and Tra- 
quaria have been given, and some of which Williamson 
has shown to be spores of Lycopodiaceous plants.* 

The true ‘‘Sporangites,” on the contrary, are round 
and smooth, with thick bituminous walls, which are 
punctured with minute transverse pores. In these re- 
spects, as already stated, they closely resemble the bodies 
found in the Australian white coal and Tasmanite. The 
precise geological age of this last material is not known 
with certainty, but it is believed to be Paleozoic. 

With reference to the mode of occurrence of these 
bodies, we may note first their great abundance and wide - 
distribution. The horizontal range of the bed at Kettle 
Point is not certainly known, but it is merely a northern 
outlier of the great belt of Erian shales referred to by 
Prof. Orton, and which extends, with a breadth of ten to 
twenty miles, and of great thickness, across the State of 
Ohio, for nearly two hundred miles. This Ohio black 
shale, which lies at the top of the Erian or the base of 
the Carboniferous, though probably mainly of Erian age, 
appears to abound throughout in these organisms, and in 
some beds to be replete with them. In like manner, in 
Brazil, according to Mr. Derby, these organisms are dis- 
tributed over a wide area and throughout a great thick- 
ness of shale holding Spirophyton, and apparently belong- 
ing to the Upper Erian. The recurrence of similar forms 
in the Tasmanite and white coal of Tasmania and Aus- 
tralia is another important fact of distribution. To this 


* Traquaria is to be distinguished from the calcareous bodies found 
in the corniferous limestone of Kelly’s Island, which I have described in 
the “ Canadian Naturalist ” as Saccamina Hriana, and believe to be Fo- 
raminiferal tests. They have since been described by Ulrich under a 
different name (Mellerina: contribution to “ American Paleontology,” 
1886). See Dr. Williamson’s papers in “ Transactions of Royal Society 
of London.” 


7 


58 THE GEOLOGICAL HISTORY OF PLANTS. 


we may add the appearance of these macrospores in coals 
and shales of the Carboniferous period, though there in 
association with other forms. 

It is also to be observed that the Erian shales, and the 
Forest of Dean beds described by Wethered, are marine, 
as shown by their contained fossils ; and, though I have 
no certain information as to the Tasmanite and Austra- 
lian white coal, they would seem, from the description of 
Milligan, to occur in distinctly aqueous, possibly estua- 
rine, deposits. Wethered has shown that the discs de- 
scribed by Huxley and Newton in the Better-bed coal 
occur in the earthy or fragmentary layers, as distin- 
guished from the pure coal. Those occurring in cannel 
coal are in the same case, so that the general mode of 
occurrence implies water-driftage, since, in the case of 
bodies so large and dense, wind-driftage to great distances 
would be impossible. 

These facts, taken in connection with the differences 
between these macrospores and those of any known land- 
plant of the Palwozoic, would lead to the inference that 
they belonged to aquatic plants, and these vastly abundant 
in the waters of the Erian and Carboniferous periods. 

It is still further to be observed that they are not, in 
the Erian beds, accompanied with any remains of woody 
or scalariform tissues, such as might be expected in con- 
nection with the débris of terrestrial acrogens, and that, 
on the other hand, we find them enclosed in cellular 
sporocarps, though in the majority of cases these have 
been removed by dehiscence or decay. 

These considerations, I think, all point to the prob- 
ability which I have suggested in my papers on this sub- 
ject referred to above, that we have in these objects the 
organs of fructification of plants belonging to the order 
Rhizocarpee, or akin to it. The comparisons which I 
have instituted with the sporocarps and macrospores of 
these plants confirm this suggestion. Of the modern 


THE ERIAN OR DEVONIAN FORESTS. 59 


species which I have had an opportunity to examine, 
Salvinia natans of Europe perhaps presents the closest 
resemblance. In this plant groups of round cellular 
sporocarps appear at the bases of the floating fronds. 
They are about a line in diameter when mature, and are 
of two kinds, one containing macrospores, the other mi- 
crospores or antheridia. The first, when mature, hold a 
number of closely packed globular or oval sporangia of 
loose cellular tissue, attached to a central placenta. Each 
of these sporangia contains a single macrospore, perfectly 
globular and smooth, with a dense outer membrane (ex- 
hibiting traces of lamination, and showing within an 
irregularly vacuolated or cellular structure, probably a 
prothallus). I cannot detect in it the peculiar pores 
which appear in the fossil specimens. Each macrospore 
is about one-seventieth of an inch in diameter when ma- 
ture. The sporocarps of the microspores contain a vastly 
greater number of minute sporangia, about one two-hun- 
dredths of an inch in diameter. These contain disc-like 
antheridia, or microspores of very minute size. 

The discs from Kettle Point and from the Ohio black 
shale, and from the shale boulders of the Chicago clays, 
are similar to the macrospores of Salvinia, except that 
they have a thicker wall and are a little less in diameter, 
being about one-eightieth of an inch. The Brazilian 
sporocarps are considerably larger than those of the mod- 
ern Salvinia, and the macrospores approach in size to 
those of the modern species, being one seventy-fifth of an 
inch in diameter. They also seem, like the modern spe- 
cies, to have thinner walls than those from Canada, Ohio, 
and Chicago. No distinct indication has been observed 
in the fossil species of the inner Sporangium of Salvinia. 
Possibly it was altogether absent, but more probably it is 
not preserved as a distinct structure. 

With reference to the microspores of Salvinia, it is to 
be observed that the sporocarps, and the contained spores 


60 THE GEOLOGICAL HISTORY OF PLANTS. 


or antheridia, are very delicate and destitute of the dense 
outer wall of the macrospores. Hence such parts are 
little likely to have been preserved in a fossil state; and 
in the Erian shales, if present, they probably appear 
merely as flocculent carbonaceous matter not distinctly 
marked, or as minute granules not well defined, of which 
there are great quantities in some of the shales. 

The vegetation appertaining to the Sporangites has 
not been distinctly recognised. I have, however, found 
in one of the Brazilian specimens two sporocarps attached 
to what seems a fragment of a cellular frond, and numer- 
ous specimens of the supposed Algx, named Spirophyton, 
are found in the shales, but there is no evidence of any 
connection of this plant with the Protosalvinia. 

Modern Rhizocarps present considerable differences as 
to their vegetative parts. Some, like Pilularia, have 
simple linear leaves ; others, like Marsilea, have leaves in 
whorls, and cuneate in form; while others, like Azolla 
and Salvinia, have frondose leaves, more or less pinnate 
in their arrangement. If we inquire as to fossils repre- 
senting these forms of vegetation, we shall find that some 
of the plants to be noticed in the immediate sequel may 
have been nearly allied to the Rhizocarps. In the mean 
time I may state that I have proposed the generic name 
Protosalvinia for these curious macrospores and their 
coverings, and have described in the paper in the “ Bul- 
letin of the Chicago Academy of Sciences,” already 
quoted, five species which may be referred to this genus. 

These facts lead to inquiries as to the origin of the 
bituminous matter which naturally escapes from the 
rocks of the earth as petroleum and inflammable gas, or 
which may be obtained from certain shales in these forms 
by distillation. These products are compounds of carbon 
and hydrogen, and may be procured from recent vegetable 
substances by destructive distillation. Some vegetable 
matters, also, are much richer in carbon and hydrogen 


THE ERIAN OR DEVONIAN FORESTS. 61 


than others, and it is a remarkable fact that the spores of 
certain cryptogamous plants are of this kind, as we see in 
the inflammable character of the dry spores of Lycopo- 
dium ; and we know that the slow putrefaction of such 
material underground effects chemical changes by which 
bituminous matter can be produced. ‘There is, there- 
fore, nothing unreasonable in the supposition advanced 
by Prof. Orton, that the spores so abundantly contained 
in the Ohio black shales are important or principal sources 
of the bituminous matter which they contain. Micro- 
scopic sections of this shale show that much of its mate- 
rial consists of the rich bituminous matter of these spores 
(Fig. 16). At the same time, while we may trace the 
bitumen of these shales, and of some beds of coal, to this 
cause, we must bear in mind that there are other kinds of 
bituminous rocks which show no such structures, and may 
have derived their combustible material from other kinds 
of vegetable matter, whether of marine or of land plants. 
We shall better understand this when we have considered 
the origin of coal. 

The macrospores above referred to may have belonged 
to humble aquatic plants mantling the surfaces of water 
or growing up from the bottom, and presenting little 
aérial vegetation. But there are other Erian plants, as 
already mentioned, which, while of higher structure, may 
be of Rhizocarpean affinities. 

One of these is the beautiful plant with whorls of 
wedge-shaped leaves, to which the name Sphenophyllum 
(see Fig. 20) has been given. Plants referred to this 
genus have been described by Lesquereux from the upper 
part of the Siluro-Cambrian,* and a beautiful little spe- 
cies occurs in the Erian shales of St. John, New Bruns- 
wick.t The genus is also continued, and is still more 


* “ American Journal of Science.” 
+ Dawson, “ Report on Devonian Plants,” 1870. 


62 THE GEOLOGICAL HISTORY OF PLANTS. 


abundant, in the Carboniferous. Many years ago I ob- 
served, in a beautiful specimen collected by Sir W. E. 
Logan, in New Brunswick, that the stem of this plant 
had an axis of reticulated and scalariform vessels, and an 
outer bark.* Renault and Williamson have more recently 
obtained more perfect specimens, and the former has 
figured a remarkably complex triangular axis, containing 
punctate and barred vessels, and larger punctate vessels 
filling in its angles. Outside of this there is a cellular 
inner bark, and this is surrounded by a thick fibrous en- 
velope. That a structure so complex should belong to 
a plant so humble in its affinities is one of the strange 
anomalies presented by the old world, and of which we 
shall find many similar instances. The fruit of Spheno- , 
phyllum was borne in spikes, with little whorls of bracts 
or rudimentary leaves bearing round sporocarps. 


Fie. 17.—Ptilophyton da pti (Lower Carboniferous, Nova Scotia). 
atural size and magnified. 


A second type of plant, which may have been Rhizo- 
carpean in its affinities, is that to which I have given the 
name Ptilophyton.t It consists of beautiful feathery 


* “Journal of the Geological Society,” 1865. 
+ Plumalina of Hall. 


“THE ERIAN OR DEVONIAN FORESTS. 63 


fronds, apparently bearing on parts of the main stem or 
petiole small rounded sporocarps. They are found abun- 
dantly in the Middle Erian of the State of New York, 
and also occur in Scotland, while one species appears to 
occur in Nova Scotia, as high as the Lower Carboniferous 
(Figs. 1%, 18). 

These organisms have been variously referred to Lyco- 
pods, to Algx, or to Zodphytes, but an extended compari- 


Fie. 18.—Ptilophyton Thomsoni (Scotland). a, Impression of plant in 
vernation. 6, Branches eompaarnally restored. c, Branches of Lyco- 


son of American and Scottish specimens has led me to 
the belief that they were aquatic plants, more likely to 
have been allied to Rhizocarps than to any other group. 
Some evidence of this will be given in a note appended 
to this chapter. 


64 THE GEOLOGICAL HISTORY OF PLANTS. 


Fic. 19.— Psilophyton princeps, restored 
(Lower Erian, Gaspé). @, Fruit, natural 
size. 6, Stem, natural size. c, Scalari- 
form tissue of the axis, highly magni- 
fied. In the restoration, one side is repre- 
sented in vernation and the other in fruit. 


Another genus, 
which I have named 
Psilophyton* (Figs. 
19, 21), may be re- 
garded as a connect- 
ing link between the 
Rhizocarps and the 
Lycopods. It is so 
named from its resem- 
blance, in some re- 
spects, to the curi- 
ous parasitic Lycopods 
placed in the modern 
genus Psilotum. Sev- 
eral species have been 
described, and they are 
eminently characteris- 
tic of the Lower Eri- 
an, in which they 
were first discovered 
in Gaspé. The typ- 
ical species, Psilophy- 
ton princeps, which 
fills many beds of shale 
and sandstone in Gas- 
pé Bay and the head 
of the neighbouring 
Bay des Chaleurs with 
its slender stems and 
creeping, cord-like rhi- 
zomes, may be thus de- 
scribed : 

Stems branching 


* “ Journal of the Geological Society,” vols. xv., xviii, and xix., “Re- 


port on Devonian Plants of Canada,” 1871. 


a 


THE ERIAN OR DEVONIAN FORESTS. 65 


dichotomously, and covered with interrupted ridges. 
Leaves rudimentary, or short, rigid, and pointed; in 
barren stems, numerous and spirally arranged ; in fertile 
stems and branchlets, sparsely scattered or absent; in 
decorticated specimens, represented by a 
minute punctate scars. Young branch- 
. Ves circinate ; rhizomata cylindrical, cov- 
ered with hairs or ramenta, and having 
circular areoles irregularly disposed, giv- 
ing origin to slender cylindrical rootlets. 
Internal structure—an axis of scalari- 
form vessels, surrounded by a cylinder of 


parenchymatous cells, and by an outer ae 
cylinder of elongated woody cells. Fruc- ¥ te aah = ee 
tification consisting of naked oval spore- %qguwm (Erian, 


. é B ick). 
cases, borne usually in pairs on slender, —_ gee pp. 61, 67. ) 


curved pedicels, either lateral or terminal. 

This species was fully described by me in the papers 
referred to above, from specimens obtained from the rich 
exposures at Gaspé Bay, and which enabled me to illus- 
trate its parts more fully, perhaps, than those of any 
other species of so great antiquity. In the specimens I 
had obtained I was able to recognise the forms of the 
rhizomata, stems, branches, and rudimentary leaves, and 
also the internal structure of the stems and rhizomata, 
and to illustrate the remarkable resemblance of the forms 
and structures to those of the modern Psilotwm. The 
fructification was, however, altogether peculiar, consist- 
ing of narrowly ovate sporangia, borne usually in pairs, 
on curved and apparently rigid petioles. Under the 
microscope these sporangia show indications of cellular 
structure, and appear to have been membranous in char- 
acter. In some specimens dehiscence appears to have 
taken place by a slit in one side, and, clay having entered 
into the interior, both walls of the spore-case can be seen. 
In other instances, being flattened, they might be mis- 


66 THE GEOLOGICAL HISTORY OF PLANTS. 


taken for scales. No spores could be observed in any of 
the specimens, though in some the surface was marked 
by slight, rounded prominences, possibly the impressions 
of the spores within. This peculiar and very simple style 


Fic. 21.—Lepidodendron and Pyilophyton (Erian, New Brunswick). 
A, Lepidodendron Gaspianum. , 0, Prilophyton elegans. 


of spore-case is also characteristic of other species, and 
gives to Psilophyton a very distinct generic character. 
These naked spore-cases may be compared to those of 
such lycopodiaceous plants as Psilotum, in which the 


THE ERIAN OR DEVONIAN FORESTS. 67 


scales are rudimentary. They also bear some resemblance, 
though on a much larger scale, to the spore-cases of some 
Erian ferns (Archq@opteris), to be mentioned in the 
sequel. On the whole, however, they seem most nearly 
related to the sporocarps of the Rhizocarpezx. 

Arthrostigma, which is found in the same beds with 
Psilophyton, was a plant of more robust growth, with 
better-developed, narrow, and pointed leaves, borne ina 
verticillate or spiral manner, and bearing at the ends of 
its branches spikes of naked sporocarps, apparently simi- 
lar to those of Psilophyton but more rounded in form. 
The two genera must have been nearly related, and the 
slender branchlets of Arthrostigma are, unless well pre- 
served, scarcely distinguishable from the stems of Psilo- 
phyton.* 

If, now, we compare the vegetation of these and simi- 
lar ancient plants with that of modern Rhizocarps, we 
shall find that the latter still present, though in a de- 
pauperated and diminished form, some of the character- 
istics of their. predecessors. Some, like Pilularia, have 
simple linear leaves ; others, like Marstlea, have leaves in 
verticils and cuneate in form; while others, like Azolla 
and Salvinia, have frondose leaves, more or less pinnate 
in their arrangement. The first type presents little that 
is characteristic, but there are in the Erian sandstones 
and shales great quantities of filamentous and linear ob- 
jects which it has been impossible to refer to any genus, 
and which might have belonged to plants of the type of 
Pilularia. It is quite possible, also, that such plants as 
Psilophyton glabrum and Cordaites angustifolia, of which 
the fructification is quite unknown, may have been allied 
to Rhizocarps. With regard to the verticillate type, we 
are at once reminded of Sphenophyllum (Fig. 20), which 


* Reports of the auther on “ Devonian Plants,” “ Geological Survey of 
Canada,” which see for details as to Erian Flora of northeastern America. 


68 THE GEOLOGICAL HISTORY OF PLANTS. 


many palxo-botanists have referred to the Marsiliace, 
though, like other Paleozoic Acrogens, it presents com- 
plexities not seen in its modern representatives. S. pri- 
mevum of Lesquereux is found in the Hudson River 
group, and my 8. antiguwm in the Middle Hrian. Be- 
sides these, there are in the Silurian and Erian beds 
plants with verticillate leaves which have been placed 
with the Annularie, but which may have differed from 
them in fructification. Annularia laxa, of the Erian, 
and Protannularia Harknessti, of the Siluro-Cambrian, 
may be given as examples, and must have been aquatic 
plants, probably allied to Rhizocarps. It is deserving of 
notice, also, that the two best-known species of Pstlophy- 
ton (P. princeps and P. robustius), while allied to Ly- 
copods by the structure of the stem and such rudimentary 
foliage as they possess, are also allied, by the form of 
their fructification, to the Rhizocarps, and not to ferns, 
as some paleo-botanists have incorrectly supposed. A 
similar remark applies to Arthrostigma ; and the beautiful 
pinnately leaved Pitlophyton may be taken to represent 
that type of foliage as seen in modern Rhizocarps, while 
the allied forms of the Carboniferous which Lesquereux 
has named Trochophyllum, seem to have had sporocarps 
attached to the stem in the manner of Azolla. 

The whole of this evidence, I think, goes to show that 
in the Erian period there were vast quantities of aquatic 
plants, allied to the modern Rhizocarps, and that the so- 
called Sporangites referred to in this paper were probably 
the drifted sporocarps and macrospores of some of these 
plants, or of plants allied to them in structure and habit, 
of which the vegetative organs have perished. I have 
shown that in the Erian period there were vast swampy 
flats covered with Psilophyton, and in similar submerged 
tracts near to the sea the Protosalvinia may have filled 
the waters and have given off the vast multitudes of 
macrospores which, drifted by currents, have settled in the 


THE ERIAN OR DEVONIAN FORESTS. 69 


mud of the black shales. We have thus a remarkable 
example of a group of plants reduced in modern times to 
a few insignificant forms, but which played a great réle in 
the ancient Paleozoic world. 

Leaving the Rhizocarps, we may now turn to certain 
other families of Erian plants. The first to attract our 
attention in this age would naturally be the Lycopods, 
the club-mosses or ground-pines, which in Canada and 
the Eastern States carpet the ground in many parts of 
our woods, and are so available for the winter decoration 
of our houses and public buildings. If we fancy one of 
these humble but graceful plants enlarged to the dimen- 
sions of a tree, we shall have an idea of a Lepidodendron, 
or of any of its allies (Figs. 15, 21). These large lycopo- 
diaceous trees, which in different specific and generic 
forms were probably dominant in the Erian woods, re- 
sembled in general those of modern times in their fruit 
and foliage, except that their cones were large, and prob- 
ably in most cases with two kinds of spores, and their 
leaves were also often very long, thus bearing a due pro- 
portion to the trees which they clothed. Their thick 
stems required, however, more strength than is necessary 
in their diminutive successors, and to meet this want 
some remarkable structures were introduced similar to 
those now found only in the stems of plants of higher 
rank. ‘The cells and vessels of all plants consist of thin 
walls of woody matter, enclosing the sap and other con- 
tents of these sacs and tubes, and when strength is re- 
quired it is obtained by lining their interior with suc- 
cessive coats of the hardest form of woody matter, usually 
known as lignin. But while the walls remain thin, they 
afford free passage to the sap to nourish every part. If 
thickened all over, they would become impervious to sap, 
and therefore unsuited to one of their most important 
functions. These two ends of strength and permeability 
are secured by partial linings of lignin, leaving portions of 

8 


70 THE GEOLOGICAL HISTORY OF PLANTS. 


the original wall uncovered. But this may be done ina 
great variety of ways. 

The most ancient of these contrivances, and one still 
continued in the world of plants, is that of the barred 
or scalariform vessel. This may be either square or hex- 
agonal, so as to admit of being packed without leaving 
vacancies. It is strengthened by a thick bar of ligneous 
matter up each angle, and these are connected by cross- 
bars so as to form a framework resembling several ladders 
fastened together. Hence the name scalariform, or lad- 
der-like. Now, in a modern Lycopod there is a central 
axis of such barred vessels associated with simpler fibres 
or elongated cells. Even in Sphenophyllum and Psitlo- 
phyton, already referred to as allied to Rhizocarps,* there 
is such a central axis, and in the former rigidity is given 
to this by the vascular and woody elements being ar- 
ranged in the form of a three-sided prism or three-rayed 
star. But such arrangements would not suffice for a tree, 
and hence in the arboreal Lycopods of the Hrian age a 
more complex structure is introduced. The barred ves- 
sels were expanded in the first instance into a hollow 
cylinder filled in with pith or cellular tissue, and the 
outer rind was strengthened with greatly thickened cells. 
But even this was not sufficient, and in the older stems 
wedge-shaped bundles of barred tissue were run out from 
the interior, forming an external woody cylinder, and in- 
side of the rind were placed bundles of tough bast fibres. 
Thus, a stem was constructed having pith, wood, and 
bark, and capable of additions to the exterior of the 
woody wedges by a true exogenous growth. The plan is, 
in short, the same with that of the stems of the exogenous 
trees of modern times, except that the tissues employed 
are less complicated. The structures of these remarkable 


* First noticed by the author, “ Journal of Geological Society,” 1865; 
but more completely by Renault, “ Comptes Rendus,” 1870, 


THE ERIAN OR DEVONIAN FORESTS. "1 


trees, and the manner in which they anticipate those of 
the true exogens of modern times, have been admirably 
illustrated by Dr. Williamson, of Manchester. His 
papers, it is true, refer to these plants as existing in the 
Carboniferous age, but there is every reason to believe 
that they were of the same character in the Erian. The 
plan isthe same with that now seen in the stems of exoge- 
nous phenogams, and which has long ceased to be used 
in those of the Lycopods. In this way, however, large 
and graceful lycopodiaceous trees were constructed in the 
Erian period, and constituted the staple of its forests. 
The roots of these trees were equally remarkable with 
their stems, and so dissimilar to any now existing that 
botanists were long disposed to regard them as inde- 
pendent plants rather than roots. They were similar in 
general structure to the stems to which they belonged, 
but are remarkable for branching in a very regular man- 
ner by bifurcation like the stems above, and for the fact 
that their long, cylindrical rootlets were arranged in a 
spiral manner and distinctly articulated to the root after 
the manner of leaves rather than of rootlets, and fitting 
them for growing in homogeneous mud or vegetable 
muck. They are the so-called Stigmaria roots, which, 
though found in the Erian and belonging to its lycopo- 
diaceous plants, attamed to far greater importance in the 
Carboniferous period, where we shall meet with them again. 
There were different types of lycopodiaceous plants 
in the Erian. In addition to humble Lycopods like those 
of our modern woods and great Lepidodendra, which were 
exaggerated Lycopods, there were thick-stemmed and less 
graceful species with broad rhombic scars (Leptophleum), 
and others with the leaf-scars in vertical rows (Sigillaria), 
and others, again, with rounded leaf-scars, looking like 
the marks on Stigmaria, and belonging to the genus 
Cyclostigma. Thus some variety was given to the arbo- 
real club-mosses of these early forests. (See Fig. 15.) 


"2 THE GEOLOGICAL HISTORY OF PLANTS. 


Another group of plants which 
attained to great development in 
the Hrian age is that of the Ferns 
or Brackens. The oldest of these 
yet known are found in the Mid- 
dle Erian. The Hopteris of Sa- 
porta, from the Silurian, at one 
time supposed to carry this type 
much further back, has unfortu- 
nately been found to be a mere 
imitative form, consisting of 
films of pyrites of leaf-like shapes, 
and produced by crystallisation. 
In the Middle Erian, however, 
more especially in North Ameri- 
ca, many species have been found 
(Figs. 22 to 24).* I have myself 
recorded more than thirty spe- 
cies from the Middle Erian of 
Canada, and these belong to sev- 
eral of the genera found in the 
Carboniferous, though some are 
peculiar to the Erian. Of the 
latter, the best known are per- 
haps those of the genus Arche- 
opteris (Fig. 24), so abundant 
in the plant-beds of Kiltorcan 
in Ireland, as well as in North 
America. In this genus the 
fronds are large and luxuriant, 
with broad obovate pinnules de- 
Fic, 22.—Erian ferns (New current on the leaf-stalk, and 

Brunswick). a, Aneimites : ‘ “ 

obtusa. 0, Neuropteris poly- With simple sac-like spore-cases 

ee Fyn opt tiies borne on modified pinne. An- 

subfurcatus, other very beautiful fern found 


* For descriptions of these ferns, see reports cited above. 


THE ERIAN OR DEVONIAN FORESTS. 73 


Fic. 23.—Erian ferns (New ame y ie B, Cyclopteris valida, and 
gay enlarged. p, Spheno, rginata, an sige enlarged. 
Hartii. 6, yy llites curtilo 


zl Vcogieres opti egaieaiay 1, Ale, Darin hee ane. 
serrulata. eters mrccoan M, “Nahopterts Parleyi. 


44. THE GEOLOGICAL HISTORY OF PLANTS. 


with Archeopteris is that which I have named Platyphyl- 
lum, and which grew on a creeping stem or parasitically 
on stems of other plants, and had marginal fructification.* 


ey gs 


Fie. 24.—Archeopteris Jacksoni, Dawson (Maine). An Upper Erian 
fern, a, 6, Pinnules showing venation. 


* “Reports on Fossil Plants of the Devonian and Upper Silurian of 
Canada,” 1871, &c. : 


THE ERIAN OR DEVONIAN FORESTS. v6) 


Another very remarkable fern, which some botanists have 
supposed may belong to a higher group than the ferns, is 
Megalopteris (Fig. 26). 

Some of the Erian ferns attained to the dimensions of 
tree-ferns. Large stems of these, which must have floated 
out far from land, have been found by Newberry in the 
marine limestone of Ohio (Caulopteris antigua and C. 
peregrina, Newberry),* and Prof. Hall has found in the 


Fie. 25.—An Erian tree-fern. Canilopteris Lockwoods Dawson, 
reduced. (From a specimen from Gilboa, New .York.) 


Upper Devonian of Gilboa, New York, the remains of a 
forest of tree-ferns standing im situ with their great 
masses of aérial roots attached to the soil in which they 
grew (Caulopteris Lockwoodt, Dn.).t 

' These aérial roots introduce us to a new contrivance 
for strengthening the stems of plants by sending out into 
the soil multitudes of cord-like cylindrical roots from 


* “ Journal of the Geological Society,” 1871. + Ibid. 


"6 THE GEOLOGICAL HISTORY OF PLANTS. 


various heights on the stem, and which form a series of 
stays like the cordage of a ship. This method of support 


{ 


Vy 


Fic. 26.—Megalopteris Dawsoni, Hartt (Erian, New Brunswick). a, Frag- 
ment of pinna. 6, Point of pinnule. c, Venation, (The midrib is not 
accurately given in this figure.) 


still continues in the modern tree-ferns of the tropics 
and the southern hemisphere. In one kind of tree-fern 


THE ERIAN OR DEVONIAN FORESTS. 


17 


stem from the Erian of New York, there is also a special 
arrangement for support, consisting of a series of pecul- 
iarly arranged radiating plates of scalariform vessels, not 
exactly like those of an exogenous stem, but doing duty 


for it (A steropterts).* 
Similar plants have 
been described from 
the Erian of Falken- 
berg, in Germany, 
and of Saalfeld, in 
Thuringia, by Goep- 
pert and Unger, and 
are referred to ferns 
by the former, but 
treated as doubtful 
by the latter. This 


peculiar type of tree-. 


fern is apparently a 
precursor of the more 
exogenous type of 
Heterangium, recent- 
ly described and re- 
ferred to ferns by 
Williamson. Here, 
again, we have a me- 
chanical contrivance 
now restricted to 
higher plants appro- 
priated by these old 
cryptogams. 


| ne 


Ss ( 
“ee bli 
se iY 


Fig. 27.—Calaméites radiatus (Erian, New 


Brunswick). 


The history of the ferns in geological time is remark- 
ably different from that of the Lycopods ; for while the 


* “Journal of the Geological Society,” London, 1881. 


+ “Sphenopteris Refracta,” Goeppert; 


“Flora des Uebergangsge- 


birges.” “Cladoxylon Mirabile,” Unger ; s PelesueOlae des There 


Waldes.” 


78 THE GEOLOGICAL HISTORY OF PLANTS. 


latter have long ago descended from their pristine emi- 
nence to a very humble place in nature, the former still, 
in the southern hemisphere at least, retain their arboreal 
dimensions and an- 
cient dominance. 

The family of 
the Hquisetacew, or 
mare’s-tails, was also 
represented. by large 
species of Calamites 
and by Asterophyl- 
lites in the Erian ; 
but, as its headquar- 
ters are in the Car- 
boniferous, we may 
defer its considera- 
tion till the next 
chapter. (Figs. 2%, 
28.) 

Passing over these 
for the present, we 
find that the flower- 
ing plants are repre- 
J sented in the Erian 
Fic, 28.—Asterophyllites (Evian, New Bruns- forests by at least 

per of stom (fait, 0 oF A. soutigere’ two types of Gym- 
pv, A. latifola, larger whorl of leaves. nosperms, that of 


D:, Leaf. : 

Taxinee or yews, 
and an extinct family, that of the Cordattes (Figs. 30, 31). 
The yew-trees are closely allied to the pines and spruces, 
and are often included with them in the family of Conifere. 
They differ, however, in the habit of producing berries or 
drupe-like fruits instead of cones, and there is some 
reason to believe that this was the habit of the Erian 
trees of this group, though their wood in some in- 
stances resembles rather that of the Araucaria, or Nor- 


THE ERIAN OR DEVONIAN FORESTS. 79 


folk Island pine, than that of the modern yews. These 
trees are chiefly known to us by their mineralised trunks, 
which are often found like drift-wood on modern sand- 
banks embedded in the Erian sandstones or limestones. 
It often shows its structure in the most perfect man- 
ner in specimens penetrated by calcite or silica, or by 
pyrite, and in which the original woody matter has 


= 
~ 
~ 
« 
s 
- 
s 
a 
“ 


0G D 
= eae 
a 
} gae 
L 
| L 
bad 
5 b 

7] “| 


Fie. 29.—Dadorylon Ouangondianum, an Erian conifer. 4 Fragment 
showing Sternbergia pith and wood; a, medullary sheath ; 6, pith; 
ec, wood; d, section of pith. x, Wood-cell ; a, hexagonal areole ; 
3, pore. 0, ‘Longitudinal section of wood, showing, a, areolation, an 
6, medullary rays. p, Transverse section, showing, a, wood-cells, and 
6, limit of layer of growth. (xs, 0, p, highly magnified. ) 


been resolved into anthracite or even into graphite. 
These trees have true woody tissues presenting that beau- 
tiful arrangement of .pores or thin parts enclosed in cup- 
like discs, which is characteristic of the coniferous trees, 
and which is a great improvement on the barred tissue 
already referred to, affording a far more strong, tough, 


80 THE GEOLOGICAL HISTORY OF PLANTS. 


and durable wood, such as we have in our modern pineg 
and yews (Fig. 29). 

These primitive pines make their appearance in the 
Middle Erian, in various parts of America, as well as in 
Scotland and Germany, and they are represented by wood 
indicating the presence of several species. I have myself 
indicated and described five species from the Erian of 
Canada and the United States. From the fact that these 
trees are represented by drifted trunks embedded in sand- 
stones and marine limestones, we may, perhaps, infer that 
they grew on the rising grounds of the Erian land, and 
that their trunks were carried by river-floods into the sea, 
No instance has yet certainly occurred of the discovery of 
their foliage or fruit, though there are some fan-shaped 
leaves usually regarded as ferns which may have belonged 
to such trees. These in that case would have resembled. 
the modern Gingko of China, and some of the fruits re- 
ferred to the genus Cardiocarpwm may have been pro- 
duced by them. Various names have been given to these 
trees. I have preferred that given by Unger, Dadozylon, 
as being more non-committal as to affinities than the 
others.* Many of these trees had very long internal 
pith-cylinders, with curious transverse tubule, and which, 
when preserved separately,-have been named Sternbergia. 

Allied to these trees, and perhaps intermediate between 
them and the Cycads, were those known as Cordaites 
(Fig. 30), which had trunks resembling those of Dadoxy- 
lon, but with still larger Sternbergia piths and an internal 
axis of scalariform vessels, surrounded by a comparatively 
thin woody cylinder. Some of them have leaves over a 
foot in length, reminding one of the leaves of broad-leaved 
grasses or iridaceous plants. Yet their flowers and fruit 
seem to have been more nearly allied to the yews than to 
any other plants (Fig. 31). Their stems were less woody 


* Araucarites, Goeppert ; Araucariorylon, Kraus. 


THE ERIAN OR DEVONIAN FORESTS. 81 


and their piths larger than in the ‘true pines, and some 
of the larger-leaved species must have had thick, stiff 
branches. They are regarded as constituting a separate 
family, intermediate between pines and cycads, and, be- 


ginning in the Middle Devonian, they terminate in the 
Permian, where, however, some of the most gigantic spe- 
cies occur. In so far as the form and structure of the 
leaves, stems, and fruit are concerned, there is marvel- 


lously little difference between the species found in the 
9 


82 THE GEOLOGICAL HISTORY OF PLANTS. 


Erian and the Permian. They culminated, however, in 
the Carboniferous period, and the coal-fields of southern 
France have proved so far the richest in their remains, 
Lastly, a single specimen, collected by Prof. James 
Hall, of Albany, at Highteen-mile Creek, Lake Erie, hag 
the structure of an ordinary angiospermous exogen, and 
has been described by me as Syringoxylon mirabile.* 


ih 


Fie. 31,—Erian fruits, &c., some gymnospermous, and probably of Cordaites 
and Taxine trees (St. John, New Brunswick). a, Cardiocarpum cor- 
nutum. 8, Cardiocarpum acutum. 0, Cardiocarpum OCrampii. Dp, Car- 


diocarpum Baileyt. x", Trig pum 1 Bl, 52, Fruits en- 
larged. 3, Antholithes Devonicus. @, Annularia acuminata. 2B, As- 
terophyllites acicularis. %, Fruit of the same. x, Cardiocarpum 
(? young of A.). 1, Pinnutaria dispalans (probably a root). : 


This unique example is sufficient to establish the fact of 
the existence of such plants at this early date, unless some 
accident may have carried a specimen from a later forma- 


* “ Journal of the Geological Society,” vol. xviii. 


THE ERIAN OR DEVONIAN FORESTS. 83 


tion to be mixed with Erian fossils. It is to be observed, 
however, that the non-occurrence of any similar wood in 
all the formations between the Upper Erian and the Mid- 
dle Cretaceous suggests very grave doubt as to the authen- 
ticity of the specimen. I record the fact, waiting further 
discoveries to confirm it. Of the character of the speci- 
men which I have described I entertain no doubt. 

We shall be better able to realise the significance and 
relations of this ancient flora when we have studied that 
of the succeeding Carboniferous. We may merely remark 
here on the fact that, in these forests of the Devonian 
and in the marshes on their margins, we find a wonder- 
ful expansion of the now modest groups of Rhizocarps 
and Lycopods, and that the flora as a whole belongs to 
the highest group of Cryptogams and the lowest of Ph- 
nogams, so that it has about it a remarkable aspect of 
mediocrity. Further, while there is evidence of some 
variety of station, there is also evidence of much equality 
of climate, and of a condition of things more resembling 
that of the insular climates of the temperate portions of 
the southern hemisphere than that of North America or 
Hurope at present. 

The only animal inhabitants of these Devonian woods, 
so far as known, were a few species of insects, discovered 
by Hartt in New Brunswick, and described by Dr. Scud- 
der. Since, however, we now know that scorpions as 
well as insects existed in the Silurian, it is probable that 
these also occurred in the Erian, though their remains 
have not yet been discovered. All the known insects of 
the Erian woods are allies of the shad-flies and grasshop- 
pers (Newroptera and Orthoptera), or intermediate be- 
tween the two. It is probable that the larve of most of 
them lived in water and fed upon the abundant vegetable 
matter there, or on the numerous minute crustaceans and 
worms. There were no land vertebrates, so far as known, 
but there were fishes (Dipterus, etc.), allied to the mod- 


84 THE GEOLOGICAL HISTORY OF PLANTS. 


ern Barramunda or Ceratodus of Australia, and with 
teeth suited for grinding vegetable food. It is also possi- 
ble that some of the smaller plate-covered fishes (Placo- 
ganoids, like Pterichthys) might have fed on vegetable 
matter, and, in any case, if they fed on lower animals, the 
latter must have subsisted on plants. I mention these 
facts to show that the superabundant vegetation of this 
age, whether aquatic or terrestrial, was not wholly useless 
to animals. It is quite likely, also, that we have yet 
much to learn of the animal life of the Erian swamps and 
woods. 


NOTES TO CHAPTER III. 


I—CLASSIFICATION OF SPORANGITES. 


Ir is, of course, very unsatisfactory to give names to mere frag- 
ments of plants, yet it seems very desirable to have some means of 
arranging them. With respect to the organisms described above, 
which were originally called by me Sporangites, under the sup- 
position that they were Sporangia rather than spores, this name 
has so far been vindicated by the discovery of the spore-cases belong- 
ing to them, so that I think it may still be retained as a provisional 
name; but [ would designate the whole as Protosalvinie, meaning 
thereby plants with rhizocarpean affinities, though possibly when 
better understood belonging to different genera. We may under 
these names speak of their detached discs as macrospores and of 
their cellular envelopes as sporocarps. The following may be recog- 
nized as distinct forms: 

1. Protosalvinia Huronensis, Dawson, Syn., Sporangites Huron- 
ensis, “ Report on Erian Flora of Canada,” 1871.—Macrospores, in 
the form of discs or globes, smooth and thick-walled, the walls pene- 
trated by minute radiating pores. Diameter about one one-hun- 
dredth of an inch, ora little more, When 7m situ several macro- 
spores are contained in a thin cellular sporocarp, probably globular 
in form. From the Upper Erian, and perhaps Lower Carboniferous 
shales of Kettle Point, Lake Huron, of various places in the State of 
Ohio, and in the shale boulders of the boulder clay of Chicago and 
vicinity. First collected at Kettle Point by Sir W. E. Logan, and 


THE ERIAN OR DEVONIAN FORESTS. 85 


in Ohio by Prof. Edward Orton, and at Chicago by Dr, H. A. John- 
son and Mr. B. W. Thomas, also in New York by Prof. J. M. Clarke. 

The macrospores collected ‘by Mr. Thomas from the Chicago 
clays and shales conform closely to those of Kettle Point, and prob- 
ably belong to the same species. Some of them are thicker in the 
outer wall, and show the pores much more distinctly. These have 
been called by Mr. Thomas S. Chicagoensis, and may be regarded as 
a varietal form. Specimens isolated from the shale and mounted 
dry, show what seems to have been the hilum or scar of attachment 
better than those in balsam. 

Sections of the Kettle Point shale show, in addition to the ma- 
crospores, wider and thinner shreds of vegetable matter, which I am 
inclined to suppose to be remains of the sporocarps. 

2. Protosalvinia (Sporangites) Braziliensis, Dawson, “ Canadian 
Record of Science,” 1888.—Macrospores, round, smooth, a little 
longer than those of the last species, or about one seventy-fifth of 
an inch in diameter, enclosed in round, oval, or slightly reniform 
sporocarps, each containing from four to twenty-four macrospores. 
Longest diameter of sporocarps three to six millimetres. Structure 
of wall of sporocarps hexagonal cellular. Some sporocarps show no 
macrospores, and may possibly contain microspores. The specimens 
are from the Erian of Brazil. Discovered by Mr. Orville Derby. 
The formation, according to Mr. Derby, consists of black shales be- 
low, about three hundred feet thick, and containing the fucoid known 
as Sptrophyton, and probably decomposed vegetable matter. Above 
this is chocolate and reddish shale, in which the well-preserved speci- 
mens of Protosalinia occur. These beds are very widely distributed, 
and abound in Protosalvinia and Spirophyton. 

3. Protosaluinia (Sporangites) bilobata, Dawson, “Canadian 
Record of Science,” 1883.—Sporocarps, oval or reniform, three 
to six millimetres in diameter, each showing two rounded 
prominences at the ends, with a depression in the middle, and 
sometimes a raised neck or isthmus at one side connecting the 
prominences, Structure of sporocarp cellular. Some of the speci- 
mens indicate that each prominence or tubercle contained several 
macrospores. At: first sight it would be easy to mistake these bodies 
for valves of Beyrichia. , 

Found in the same formations with the last species, though, in so 
far as the specimens indicate, not precisely in the same beds, Col- 
lected by Mr. Derby. 

4, Protosalvinia Clarket, Dawson, P. bilobata, Clarke, “ American 
Journal of Science.”—Macrospores two-thirds to one millimetre in 


86 THE GEOLOGICAL HISTORY OF PLANTS. 


diameter. One, two, or three contained in each sporocarp, which is 
cellular, The macrospores have very thick walls with radiating tor- 
tuous tubes, Unlessthis structure is a result of mineral crystallisa- 
tion, these macrospores must have had very thick walls and must have 
resembled in structure the thickened cells of stone fruits and of the 
core of the pear, or the tests of the Silurian and Erian seeds known 
as Pachytheea, though on a smaller scale. 

It is to be observed that bodies similar to these occur in the Bog- 
head earthy bitumen, and have been described by Credner. 

1 have found similar bodies in the so-called“ Stellar coal” of the 
coal district of Pictou, Nova Scotia, some layers of which are filled 
with them. They occur in groups or patches, which seem to be en- 
closed in a smooth and thin membrane or sporocarp. It is quite 
likely that these bodies are generically distinct from Protosalvinia. 

5. Protosalvinia punctata, Newton, “ Geological Magazine,” New 
Series, December 2d, vol. ii—Mr. Newton has named the discs 
found in the white coal and Tasmanite, Tasmanites, the species be- 
ing Tasmanites punctatus, but as my name Sporangites had priority, 
I do not think it necessary to adopt this term, though there can be 
little doubt that these organisms are of similar character. The same 
remark may be made with reference to the bodies described by Hux- 
ley and Newton as occurring in the Better-bed coal. 

In Witham’s “Internal Structure of Fossil Vegetables,” 1833, 
Plate XI, are figures of Lancashire cannel which shows Sporangites of 
the type of those in the Erian shales. Quekett, in his “ Report on the 
Torbane Hill Mineral,” 1854, has very well figured similar structures 
from the Methel coal] and the Lesmahagow cannel coal. These are 
the earliest publications on the subject known to me; and Quekett, 
though not understanding the nature of the bodies he observed, 
holds that they are a usual ingredient in cannel coals. 


IL—Tue Nature anp AFFINITIES oF PrILOPpHYToN,. 


(Lycopodites Vanuxemit of “Report on Devonian and Upper 
Silurian Plants,” Part L., page 35. L. plumula of “ Report on Lower 
Carboniferous Plants,” page 24, Plate I, Figs. 7, 8,9.) In the re- 
ports above referred to, these remarkable pinnate, frond-like objects 
were referred to the genus Lycopodites, as had been done by Goep- 
pert in his description of the European species Lycopodites penne- 
formis, which is very near to the American Erian form. Since 1871, 
however, there have been many new specimens obtained, and very 
various opinions expressed as to their affinities. While Hall has 
named some of them Plumalina, and has regarded them as animal 


THE ERIAN OR DEVONIAN FORESTS. 87 


structures, allied to hydroids, Lesquereux has described some of the 
Carboniferous forms under the generic name Zrochophyllum, which 
is, however, more appropriate to plants with verticillate leaves which 
are included in this genus. Before I had seen the publications of 
Hall and Lesquereux on the subject, I had in a paper on “Scottish 
Devonian Plants ” * separated this group from the genus Lycopodites, 
and formed for it the genus Ptilophyton, in allusion to the feather- 
like aspect of the species. My reasons for this, and my present in- 
formation as to the nature of: these plants, may be stated as follows: 

Schimper, in his “ Palontologie Vegetale” (possibly from inat- 
tention to thedescriptions or want of access to specimens), doubts the 
lycopodiaceous character of species of Lycopodites described in my 
published papers on plants of the Devonian of America and in my 
Report of 1871. Of these, Z. Richardsoni and L. Matthewi are un- 
doubtedly very near to the modern genus Lycopodium. L. Vanuz- 
emii is,I admit, more problematical; but Schimper could scarcely 
have supposed it to be a fern or a fucoid allied to Caulerpa had he 
observed that both in my species and the allied L. penneformis of 
Goeppert, which he does not appear to notice, the pinnules are ar- 
ticulated upon the stem, and leave scars where they have fallen off. 
When in Belfast in 1870, my attention was again directed to the 
affinities of these plants by finding in Prof. Thomson’s collection a 
specimen from Caithness, which shows a plant apparently of this 
kind, with the same long narrow pinnz or leaflets, attached, how- 
ever, to thicker stems, and rolled upin acircinate manner. It seems 
to be a plant in vernation, and the parts are too much crowded and 
pressed together to admit of being accurately figured or described ; 
but 1 think I can scarcely be deceived as to its true nature. The 
circinate arrangement in this case would favour a relationship to 
ferns; but some lycopodiaceous plants also roll themselves in this 
way, and so do the branches of the plants of the genus Psilophyton. 
(Fig. 17, supra.) 

The specimen consists of a short, erect stem, on which are placed 
somewhat stout alternate branches, extending obliquely outward and 
then curving inward in a circinate manner. The lower ones appear 
to produce on their inner sides short lateral branchlets, and upon 
these, and also upon the curved extremities of the branches, are long, 
narrow, linear leaves placed in a crowded manner. The specimen is 
thus not a spike of fructification, but a young stem or branch in ver- 
nation, and which when unrolled would be of the form of those 


* “Canadian Naturalist,” 1878. 


88 THE GEOLOGICAL HISTORY OF PLANTS. 


peculiar pinnate Lycopodites of which L. Vanuxemii of the Ameri- 
can Devonian and L. penneformis of the European Lower Carbon- 
iferous are the types, and it shows, what might have been anticipated 
from other specimens, that they were low, tufted plants, circinate in 
vernation. The short stem of this plant is simply furrowed, and 
bears no resemblance to a detached branch of Lycopodites Millert 
which lies at right angles to it on the same slab. As to the affinities 
of the singular type of plants to which this specimen belongs, I may 
quote from my “Report on the Lower Carboniferous Plants of 
Canada.” in which | have described an allied species, L. plumula: 

“The botanical relations of these plants must remain subject to 
doubt, until either their internal structure or their fructification can 
be discovered. In the mean time I follow Goeppert in placing them 
in what we must regard as the provisional genus Lycopodites. On 
the one hand, they are not unlike the slender twigs of Tazodium 
and similar Conifers, and the highly carbonaceous character of the 
stems gives some colour to the supposition that they may have been 
woody plants. On the other hand, they might, so far as form is con- 
cerned, be placed with Alge of the type of Brongniart’s Chondrites 
obtusus, or the modern Caulerpa plumaria, Again, in a plant of 
this type from the Devonian of Caithness to which I have referred in 
a former memoir, the vernation seems to have been circinate, and 
Schimper has conjectured that these plants may be ferns, which 
seems also to have been the view of Shumard.” 

On the whole, these plants are allied to Lycopods rather than to 
ferns; and as they constitute a small but distinct group, known only, 
so far as I am aware, in the Lower Carboniferous and Erian or De- 
vonian, they deserve a generic name, and I proposed for them in my 
“Paper on Scottish Devonian Plants,” 1878, that of Ptilophyton, a 
name sufficiently distinct in sound from Psilophyton, and expressing 
very well their peculiar feather-like habit of growth. The genus was 
defined as follows: 

“Branching plants, the branches bearing long, slender leaves in 
two or more ranks, giving them a feathered appearance; vernation 
circinate. Fruit unknown, but analogy would indicate that it was 
borne on the bases of the leaves or on modified branches with shorter 
leaves,” 

The Scottish specimen above referred to was named Fi. Thom- 
sont, and was characterised by its densely tufted form and thick 
branches. The other species known are: Pt. penneformis, Goep- 
pert, L. Carboniferous; Pt. Vanuxemii, Dawson, Devonian; Pt. 
plumula, Dawson, L. Carboniferous. 


THE ERIAN OR DEVONIAN FORESTS. 89 


Shumard’s Filtcites gracilis, from the Devonian of Ohio, and 
Stur’s Pinttes antecedens, from the Lower Carboniferous of Silesia, 
may possibly belong to the same genus. The Scottish specimen re- 
ferred to is apparently the first appearance of this form in the 
Devonian of Europe. 

I have at a still later date had opportunities of studying con- 
siderable series of these plants collected by Prof. Williams, of Cornell 
University, and prepared a note in reference to them for the Ameri- 
can Association, of which, however, only an abstract has been pub- 
lished. I have also been favoured by Prof. Lesquereux and Mr. 
Lacoe, of Pittston, with the opportunity of studying the specimens 
referred to Trochophyllum. 

Prof. Williams’s specimens occur in a dark shale associated with 
remains of land-plants of the genera Psilophyton, Rhodea, &., and 
also marine shells, of which a small species of Rhynchonella is often 
attached to the stems of the Pilophyton. Thus these organisms 
have evidently been deposited in marine beds, but in association 
with land-plants. 

The study of the specimens collected by Prof. Williams develops 
the following facts: (1) The plants are not continuous fronds, but 
slender stems or petioles, with narrow, linear leaflets attached in a 
pinnate manner. (2) The pinnules are so articulated that they break 
off, leaving delicate transverse sears, and the lower parts of the stems 
are often thus denuded of pinnz for the length of one or more 
inches, (8) The stems curve in such a manner as to indicate a cir- 
cinate vernation. (4) In a few instances the fronds were observed 
to divide dichotomously toward the top; but this is rare. (5) There 
are no indications of cells in the pinnules; but, on the other hand, 
there is no appearance of fructification unless the minute granules 
which roughen some of the stems are of this nature. (6) The stems 
seem to have been lax and flexuous, and in some instances they 
seem to have grown on the petioles of ferns preserved with them in 
the same beds. (7) The frequency of the attachment of small brachio- 
pods to the specimens of Pitlophyton would seem to indicate that 
the plant stood erect in the water. (8) Some of the specimens show 
so much carbonaceous matter as to indicate that the pinnules were 
of considerable consistency. All these characters are those rather 
of an aquatic plant than of an animal organism or of a land-plant. 

The specimens communicated by Prof. Lesquereux and Mr. 
Lacoe are from the Lower Carboniferous, and evidently represent a 
different species with similar slender pitted stems, often partially 
denuded of pinnules below; but the pinnules are much broader and 


90 THE GEOLOGICAL HISTORY OF PLANTS. 


more distant. They are. attached by very narrow bases, and ap- 
parently tend to lie on a plane, though they may possibly have been 
spirally arranged. On the same slabs are rounded sporangia or 
macrospores like those of Lepidodendron, but there is no evidence 
that these belonged to Trochophyllum. On the stems of this plant, 
however, there are small, rounded bodies apparently taking the places 
of some of the pinnules, These may possibly be spore-cases; but 
they may be merely imperfectly developed pinnules. Still the fact 
that similar small granules appear on the stems of the Devonian 
species, favours the idea that they may be organs of fructification, 

The most interesting discovery, however, which results from the 
study of Mr. Lacoe’s specimens, is that the pinnules were cylindrical 
and hollow, and probably served to float the plant. This would 
account for many of the peculiarities in the appearance and mode 
of occurrence of the Devonian Ptilophyton, which are readily ex- 
plained if it is supposed to be an aquatic plant, attaching itself to 
the stems of submerged vegetable remains and standing erect in the 
water by virtue of its hollow leaves. It may well, however, have 
been a plant of higher organisation than the Algw, though no doubt 
eryptogamous, 

The species of Ptilophyton will thus constitute a peculiar group 
of aquatic plants, belonging to the Devonian and Lower Carbonif- 
erous periods, and perhaps allied to Lycopods and Pillworts in their 
organisation and fruit, but specially distinguished by their linear 
leaves serving as floats and arranged pinnately on slender stems, 
The only species yet found within the limits of Canada is Pt. plu- 
mula, found by Dr. Honeyman in the Lower Carboniferous of Nova 
Scotia; but as Pt. Vanuxemii abounds in the Erian of New York, 
it will no doubt be found in Canada also. 


IIL—Tree-Ferns or THE Ertan PERtoD. 


As the fact of the occurrence of true tree-ferns in rocks so old 
as the Middle Erian or Devonian has been doubted in some quar- 
ters, the following summary is given from descriptions published in 
the “Journal of the Geological Society of London” (1871 and 1881), 
where figures of the species will be found: 

Of the numerous ferns now known in the Middle and Upper 
Devonian of North America, a great number are small and delicate 
species, which were probably herbaceous; but there are other species 
which may have been tree-ferns, Little definite information, how- 
ever, has, until recently, been obtained with regard to their habit of 
growth. 


THE ERIAN OR DEVONIAN FORESTS, 91 


The only species known to me in the Devonian of Europe is the 
Caulopteris Peachti of Salter, figured in the * Quarterly Journal of 
the Geological Society” for 1858. ‘The original specimen of this I 
had an opportunity of seeing in London, through the kindness of 
Mr. Etheridge, and have no doubt that it is the stem of a small 
arborescent fern, allied to the genus Caulopteris, of the coal forma- 
tion. 

In my paper on the Devonian of Eastern America (“ Quarterly 
Journal of the Geological Society,” 1862), I mentioned a plant found 
by Mr. Richardson at Perry, as possibly a species of Megaphyton, 
using that term to denote those stems of tree-ferns which have the 
leaf-scars in two vertical series; but the specimen was obscure, and 
I have not yet obtained any other. 

More recently, in 1869, Prof. Hall placed in my hands an inter- 
esting collection from Gilboa, New York, and Madison County, New 
York, including two trunks surrounded by aérial roots, which I have 
described as Psaronius fextilis and P. Erianus, in my “ Revision of 
the Devonian Flora,” read before the Royal Society.* In the same 
collection were two very large petioles, Rhachiopteris gigantea and 
R. palmata, which I have suggested may have belonged to tree-ferns, 

My determination of the species of Psaronius, above mentioned, 
has recently been completely confirmed by the discovery on the part 
of Mr. Lockwood, of Gilboa, of the upper part of one of these stems, 
with its leaf-scars preserved and petioles attached, and also by some 
remarkable specimens obtained by Prof. Newberry, of New York, 
from the Corniferous limestone of Ohio, which indicate the exist- 
ence there of three species of tree-ferns, one of them with aérial 
roots similar to those of the Gilboa specimens. The whole of these 
specimens Dr. Newberry has kindly allowed me to examine, and has 
permitted me to describe the Gilboa specimen, as connected with 
those which I formerly studied in Prof. Hall’s collections. The 
specimens from Ohio he has himself named, but allows me to notice 
them here by way of comparison with the others. I shall add some 
notes on specimens found with the Gilboa ferns. 

It may be further observed that the Gilboa specimens are from 
a bed containing erect stumps of tree-ferns, in the Chemung group 
of the Upper Devonian, while those from Ohio are from a marine 
limestone, belonging to the lower part of the Middle Devonian. 

1. Caulopterts Lockwoodi, Dawson—Trunk from two to three 


* Abstract in “Proceedings of the Royal Society,” May, 1870; also 
“Report on Erian Plants of Canada,” 1871. 


92 THE GEOLOGICAL HISTORY OF PLANTS. 


inches in diameter, rugose longitudinally. Leaf-scars broad, rounded 
above, and radiatingly rugose, with an irregular scar below, arranged 
spirally in about five ranks; vascular bundles not distinctly pre- 
served. Petioles slender, much expanded at the base, dividing at 
first in a pinnate manner, and afterwards dichotomously. Ultimate 
pinne with remains of numerous, apparently narrow pinnules. 

This stem is probably the upper part of one or other of the 
species of Psaronius found in the same bed (P. Erianus, Dawson, 
and P. teatilis, Dawson).* It appears to have been an erect stem 
embedded in situ in sandstone, and preserved asacast. The stem 
is small, being only two inches, or a little more, in diameter. It 
is coarsely wrinkled longitudinally, and covered with large leaf- 
scars, each an inch in diameter, of a horseshoe-shape. The peti- 
oles, five of which remain, separate from these scars with a distinct 
articulation, except at one point near the base, where probably a 
bundle or bundles of vessels passed into the petiole. They retain 
their form at the attachment to the stem, but a little distance 
from it they are flattened. They are inflated at the base, and some- 
what rapidly diminish in size. The leaf-scars vary in form, and are 
not very distinct, but they appear to present a semicircular row of 
pits above, largest in the middle. From these there proceed down- 
ward a series of irregular furrows, converging to a second and more 
obscure semicircle of pits, within or below which is the irregular scar 
or break above referred to. The attitude and form of the petioles 
will be seen from Fig. 24, supra. 

The petioles are broken off within a few inches of the stem; 
but other fragments found in the same beds appear to show their 
continuation, and some remains of their foliage. One specimen 
shows a series of processes at the sides, which seem to be the re- 
mains of small pinnx, or possibly of spines on the margin of the 
petiole. Other fragments show the division of the frond, at first in 
# pinnate manner, and subsequently by bifurcation; and some frag- 
ments show remains of pinnules, possibly of fertile pinnules. These 
are very indistinct, but would seem to show that the plant ap- 
proached, in the form of its fronds and the arrangement of its 
fructification, to the Cyclopterids of the subgenus Anevmites, one of 
which (Aneimites Acadica), from the Lower Carboniferous of Nova 
Scotia, I have elsewhere described as probably a tree-fern.t The 


* Memoir on Devonian Flora, “ Proceedings of the Royal Society,” 
May, 1870. 
+ “Quarterly Journal of the Gcological Society,” 1860, 


THE ERIAN OR DEVONIAN FORESTS. 93 


fronds were evidently different from those of Arch@opteris,* a genus 
characteristic of the same beds, but of very different habit of growth. 
This accords with the fact that there is in Prof. Hall’s collection a 
mass of fronds of Cyclopteris (Archwopterts) Jacksont, so arranged 
as to make it probable that the plant was an herbaceous fern, pro- 
ducing tufts of fronds on short stems in the ordinary way. The 
obscurity of the leaf-scars may render it doubtful whether the plant 
above described should be placed in the genus Caelopteris or in Stem- 
matopteris; but it appears most nearly allied to the former. The 
genus is at present, of course, a provisional one; but I have thought 
it only justice to the diligent labours of Mr. Lockwood to name 
this curious and interesting fossil Caulopteris Lockwoodt. 

J have elsewhere remarked on the fact that trunks, antl petioles, 
and pinnules of ferns are curiously dissociated in the Devonian beds 
—an effect of water-sorting, characteristic of a period in which the 
conditions of deposition were so varied. Another example of this 
is, that: in the sandstones of Gaspé Bay, which have not as yet af- 
forded any example of fronds of ferns, there are compressed trunks, 
which Mr. Lockwood’s specimens allow me at least to conjecture 
may have belonged to tree-ferns, although none of them are suffi- 
ciently perfect for description. 

Mr. Lockwood’s collection includes specimens of Psaronius tex- 
filis ; and in addition to these there are remains of erect stems some- 
what different in character, yet possibly belonging to the higher parts 
of the same species of tree-fern. One of these is a stem crushed in 
such a manner that it does not exhibit its form with any distinctness, 
but surrounded by smooth, cylindrical roots, radiating from it in 
bundles, proceeding at first horizontally, and then curving down- 
ward, and sometimes terminating in rounded ends. They resemble 
in form and size the aérial roots of Psaronius Erianus ; and I believe 
them to be similar roots from a higher part of the stem, and some 
of them young and not prolonged sufficiently far to reach the ground. 
This specimen would thus represent the stem of P. Erianus at a 
higher level than those previously found. We can thus in imagina- 
tion restore the trunk and crown of this once graceful tree-fern, 
though we have not the detail of its fronds. Mr. Lockwood’s 
collections also contain a specimen of the large fern-petiole which 
I have named Rhachiopteris punctata. My original specimen 
was obtained by Prof. Hall from the same horizon in New York, 


* The genus to which the well-known Cyclopteris (Adiantites) Hiber- 
nicus of the Devonian of Ireland belongs. 
10 


94 THE GEOLOGICAL HISTORY OF PLANTS, 


That of Mr. Lockwood is of larger size, but retains no remains of the 
frond. It must have belonged to a species quite distinct from Cau- 
lopteris Lockwoodt, but which may, like it, have been a tree-fern, 

2. Caulopteris antigua, Newberry.—This is a flattened stem, on 
a slab of limestone, containing Brachiopods, Trilobites, &c., of the 
Corniferous limestone. It is about eighteen inches in length, and 
three and a half inches in average breadth. The exposed side shows 
about twenty-two large leaf-scars arranged spirally. Tach leaf, 
where broken off, has left a rough fracture; and above this is a 
semicircular impression of the petiole against the stem, which, as 
well as the surface of the bases of the petioles, is longitudinally 
striated or tuberculated. The structures are not preserved, but 
merely the outer epidermis, as a coaly film. The stem altogether 
much resembles Caulopteris Peachii, but is of larger size. It differs 
from C. Lockwoodi in the more elongated leaf-bases, and in the 
leaves being more remotely placed; but it is evidently of the same 
general character with that species. 

8. Caulopteris (Protopteris) peregrina, Newberry.— This is a 
much more interesting species than the last, as belonging to a ge- 
neric or subgeneric form not hitherto recognised below the Carbonif- 
erous, and having its minute structure in part preserved. 

The specimens are, like the last, on slabs of marine limestone of 
the Corniferous formation, and flattened. One represents an upper 
portion of the stem with leaf-scars and remains of petioles; another 
a lower portion, with aérial roots. The upper part is three inches 
in diameter, and about a foot in length, and shows thirty leaf-scars 
which are about three-fourths of an inch wide, and rather less in 
depth. The upper part presents a distinct. rounded and sometimes 
double marginal line, sometimes with a slight depression in the mid- 
dle. The lower part is irregular, and when most perfect shows seven 
slender vascular bundles, passing obliquely downward into the stem. 
The more perfect leaf-bases have the structure preserved, and show 
a delicate, thin-walled, oval parenchyma, while the vascular bundles 
show scalariform vessels with short bars in several rows, in the man- 
ner of many modern ferns, Some of the scars show traces of the 
hippocrepian mark characteristic of Protopteris; and the arrange- 
ment of the vascular bundles at the base of the scars is the same as 
in that genus, as are also the general form and arrangement of the 
scars. On careful examination, the species is indeed very near to the 
typical P. Sternbergvi, as figured by Corda and Schimper.* 


* Corda, “ Beitraige,” Pl. 48, copied by Schimper, Pl. 52. 


THE ERIAN OR DEVONIAN FORESTS. 95 


The genus Protopteris of Sternberg, though the original species 
¢P. punctata) appears as a Lepidodendron in his earlier plate (Plate 
4), and as a Sigillaria (S. punctata) in Brongniart’s great work, is a 
true tree-fern; and the structure of one species (P. Cottat) has been 
beautifully figuered by Corda. The species hitherto described are 
from the Carboniferous and Permian. 

The second specimen of this species represents lower part of 
the stem. It is thirteen inches long and about four inches in diam- 
eter, and is covered with a mass of flattened aérial roots lying paral- 
lel to each other, in the manner of the Psaronites of the coal-forma- 
tion and of P. Erianus of the Upper Erian or Devonian. 

4, Asteropteris noveboracensis, gen. and sp..u.—The genus As- 
teropteris is established for stems of ferns having the axial portion 
composed of vertical radiating plates of scalariform tissue embedded 
in parenchyma, and having the outer cylinder composed of elongated 
cells traversed by leaf-bundles of the type of those of Zygopteris. 

The only species known to me is represented by a stem 2°5 cen- 
timetres in diameter, slightly wrinkled and pitted externally, per- 
haps by traces of aérial roots which have perished. The transverse 
section shows in the centre four vertical plates of scalariform or im- 
perfectly reticulated tissue, placed at right angles to each other, and 
united in the middle of the stem. At a short distance from the 
centre, each of these plates divides into two or three, so as to form 
an axis of from ten to twelve radiating plates, with remains of cellu- 
lar tissue filling the angular interspaces. The greatest diameter of 
this axis is about 1°5 centimetre. Exterior to the axis the stem con- 
sists of elongated cells, with somewhat thick walls, and more dense 
toward the circumference. The walls of these cells present a curious 
reticulated appearance, apparently caused by the cracking of the 
ligneous lining in consequence of contraction in the process of car- 
bonization. Embedded in this outer cylinder are about twelve vas- 
cular bundles, each with a dumb-bell-shaped group of scalariform 
vessels enclosed in a sheath of thick-walled fibres, Each bundle is 
opposite to one of the rays of the central axis. The specimen shows 
about two inches of the length of the stem, and is somewhat bent, 
apparently by pressure, at one end. 

This stem is evidently that of a small tree-fern of a type, so 
far as known to me, not before described,* and constituting a very 
complex and symmetrical form of the group of Paleozoic ferns allied 


* Prof. Williamson, to whom I have sent a tracing of the structure, 
agrees with me that it is new. 


96 THE GEOLOGICAL HISTORY OF PLANTS. 


to the genus Zygopteris of Schimper. The central axis alone has a 
curious resemblance to the peculiar stem described by Unger (“ De- 
vonian Flora of Thuringia”) under the name of Cladoxylon mira- 
bile; and it is just possible that this latter stem may be the axis 
of some allied plant. The large aérial roots of some modern tree- 
ferns of the genus Angiopteris have, however, an analogous radiating 
structure. 

The specimen is from the collection of Berlin H. Wright, Esq., 
of Penn Yan, New York, and was found in the Portage group (Upper 
Erian) of Milo, New York, where it was associated with large petioles 
of ferns and trunks of Lepidodendra, probably L. Chemungense and 
LD. primevun. 

The occurrence of this and other stems of tree-ferns in marine 
beds has recently been illustrated by the observation of Prof. A. 
Agassiz that considerable quantities of vegetable matter can be 
dredged from great depths in the sea on the leeward side of the 
Caribbean Islands. The occurrence of these trunks further connects 
itself with the great abundance of large petioles (Rhachiopteris) in 
the same beds, while the rarity of well-preserved fronds is explained 
by the coarseness of the beds, and also by the probably long macera- 
tion of the plant-remains in the sea-water. 

In connection with this I may refer to the remarkable facts re- 
cently stated by Williamson* respecting the stems known as Hete- 
rangium and Lyginodendron. It would seem that these, while having 
strong exogenous peculiarities, are really stems of tree-ferns, thus 
placing this family in the same position of advancement with the 
Lycopods and Hquisetacee of the Coal period. 


IV.—On Enian TREES OF THE Genus Dapoxyton, UNGER. 
(Araucarites or GoEPPERT, Araucartoxylon or KRavs.) 


Large woody trunks, carbonised or silicified, and showing wood- 
cells with hexagonal areoles having oval pores inscribed in them, 
occur abundantly in some beds of the Middle Erian of America, and 
constitute the most common kind of fossil wood all the way to the 
Trias. They have in the older formations, generally, several rows 
of pores on each fibre, and medullary rays composed of two or more 
series of cells, but become more simple in these respects in the Per- 
mian and Triassic series. The names Araucarites and Araucartoxy- 
ion are perhaps objectionable, inasmuch as they suppose affinities to 
Araucaria which may not exist. Unger’s name, which is non- 


* “Proceedings of the Royal Society,” January 6, 1887. 


THE ERIAN OR DEVONIAN FORESTS. Qo 


committal, is therefore, I think, to be preferred. In my “ Acadian 
Geology,” and in my “Report on the Geology of Prince Edward 
Island,’ I have given reasons for believing that the foliage of some 
at least of these trees was that known as Wailchia, and that they may 
have borne nutlets in the manner of Taxine trees (Trigonocarpum, 
&c.). Grand d’Eury has recently suggested that some of them may 
have belonged to Cordaites, or to plants included in that somewhat 
varied and probably artificial group. 

The earliest discovery of trees of this kind in the Erian of 
America was that of Matthew and Hartt, who found large trunks, 
which I afterwards described as Dadoxylon Ouangondianum, in the 
Erian sandstone of St. John, New Brunswick, hence named by those 
geologists the “Dadoxylon sandstone.” A little later, similar wood 
was found by Prof. Hall and Prof. Newberry in the Hamilton group 
of New York and Ohio, and the allied wood of the genus Ormoxylon 
was obtained by Prof. Hall in the Portage group of the former 
State. These woods proved to be specifically distinct from that of 
St. John, and were named by me D. Halli, D, Newberry, and Or- 
moaylon Erianum. The three species of Dadozylon agreed in hay- 
ing composite medullary rays, and would thus belong to the group 

— Paleozylon of Brongniart. In the case of Ormoxylon this character 
could not be very distinctly ascertained, but the medullary rays 
appeared to be simple. 

I am indebted to Prof. J. M. Clarke, of Amherst College, Massa- 
chusetts, for some well-preserved specimens of another species from 
the Genesee shale of Canandaigua, New York. They show small 
stems or branches, with a cellular pith surrounded with wood of 
coniferous type, showing two to three rows of slit-formed, bordered 
pores in hexagonal borders. The medullary sheath consists of 
pseudo-scalariform and reticulated fibres; but the most remarkable 
feature of this wood is the structure of the medullary rays, which 
are very frequent, but short and simple, sometimes having as few 
as four cells superimposed. This is a character not before observed 
in coniferous trees of so great age, and allies this Middle Erian . 
form with some Carboniferous woods which have been supposed to 
belong to Cordaites or Sigillaria. In any case this structure is new, 
and I have named the species Dadozylon Clark, after its discoverer. 
The specimens occur, according to Prof. Clarke, in a calcareous layer 
which is filled with the minute shells of Styliola jfissurella of Hall, 
believed to be a Pteropod; and containing-also shells of Goniatites 
and Gyroceras. The stems found are only a few inches in diameter, 
but may be branches of larger trees. 


eee 


98 THE GEOLOGICAL HISTORY OF PLANTS. 


It thus appears that we already know five species of Coniferous 
trees of the genus Dadoxylon in the Middle Erian of America, an 
interesting confirmation of the facts otherwise known as to the 
great richness and variety of this ancient flora. The late Prof. 
Goeppert informed me that he had recognised similar wood in the 
Devonian of Germany, and there can be no doubt that the fossil 
wood discovered by Hugh Miller in the Old Red Sandstone of Scot- 
land, and described by Salter and McNab, is of similar character, and 
probably belongs to the genus Dadoxylon. Thus this type of Conif- 


; erous tree seems to have been as well established and differentiated 


into species in the Middle Devonian as in the succeeding Carbonif- 
erous. 

I may here refer to the fact that the lower limit of the trees of 
this group coincides, in America, with the upper limit of those prob- 
lematical trees which in the previous chapter I have named Proto- 
gens (Vematophyton, Celluloalyon,* Nematoxylon +), though Apo- 
roxylon of Unger extends, in Thuringia, up to the Upper Devonian 
(Cypridina schists), 


V.—Scortish Drevontan Puants or Hues MILLER AND OTHERS, 
(Edinburgh Geological Society, 1877.) 


Previously to the appearance of my descriptions of Devonian 
plants from North America, Hugh Miller had described forms from 
the Devonian of Scotland, similar to those for which I proposed the 
generic name Psilophyton ; and I referred to these in this connection 
in my earliest description of that genus.t He had also recognised 
what seemed to be plants allied to Lycopods and Conifers. Mr. 
Peach and Mr. Duncan had made additional discoveries of this kind, 
and Sir J. Hooker and Mr. Salter had described some of these re- 
mains. More recently Messrs. Peach, Carruthers, and McNab have 
worked in this field, and still later* Messrs. Jack and Etheridge 
have summed up the facts and have added some that are new. 

The first point to which I shall refer, and which will lead to the 
other matters to be discussed, is the relation of the characteristic 
Lepidodendron of the Devonian of eastern America, L. Gaspianum, 
to L. nothum of Unger and of Salter. At the time when I described 
this species I had not access to Scottish specimens of Lepidodendron 


* “ Journal of the Geological Society,” May, 1881. 

+ Ibid., vol. xix, 1863. 

t ‘Journal of the Geological Society,” London, 1859. 
#* Tbid., 1877, 


THE ERIAN OR DEVONIAN FORESTS. 99 


from the Devonian, but these had been well figured and described 
by Salter, and had been identified with L. nothum of Unger, a species 
evidently distinct from mine, as was also that figured and described 
by Salter, whether identical or not with Unger’s species. In 1870 
I had for the first time an opportunity to study Scottish specimens 
in the collection of Mr. Peach; and on the evidence thus afforded I 
stated confidently that these specimens represented a species distinct 
from L. Gaspianum, perhaps even generically so.* It differs from 
L. Gaspianum in its habit of growth by developing small lateral 
branches instead of bifurcating, and in its foliage by the absence or 
obsolete character of the leaf-bases and the closely placed and some- 
what appressed leaves. If an appearance of swelling at the end of a 
lateral branch in one specimen indicates @ strobile of fructification, 
then its fruit was not dissimilar from that of the Canadian species 
in its position and general form, though it may have differed in 
details. On these grounds I declined to identify the Scottish species 
with L. Gaspianum. The Lepidodendron from the Devonian of 
Belgium described and figured by Crepin,} has a better claim to such 
identification, and would seem to prove that this species existed in 
Europe as well as in America. I also saw in Mr. Peach’s collection 
in 1870 some fragments which seemed to me distinct from Salter’s 
species, and possibly belonging to L. Gaspianum.t 

In the earliest description of Psilophyton I recognised its prob- 
able generic affinity with Miller’s “ dichotomous plants,” with Salter’s 
“rootlets,” and with Goeppert’s Haliserites Dechenianus, and stated 
that I had “little doubt that materials exist in the Old Red Sand- 
stone of Scotland for the reconstruction of at least one species of 
this genus.” Since, however, Miller’s plants had been referred to 
coniferous roots, and to fucoids, and Goeppert’s Haliserites was a 
name applicable only to fucoids, and since the structure and fruit 
of my plants placed them near to Lycopods, I was under the neces- 
sity of giving them a special generic name, nor could I with cer- 
tainty affirm their specific identity with any European species. The 
comparison of the Scottish specimens with woody rootlets, though 
incorrect, is in one respect creditable to the acumen of Salter, as in 
almost any state of preservation an experienced eye can readily per- 
ceive that branchlets of Psilophyton must have been woody rather 


* “Report on Devonian Plants of Canada,” 1871. 


+ “Observations sur quelques Plantes Fossiles des dépéts Devoni- 
ens.” 


t “Proceedings of the Geological Society of London,” March, 1871. 


100 THE GEOLOGICAL HISTORY OF PLANTS. 


than herbaceous, and their appearance is quite different from that 
of any true Alga. 

The type of Psilophyton is my P. princeps, of which the whole 
of the parts and structures are well known, the entire plant being 
furnished in abundance and ¢n sifu in the rich plant-beds of Gaspé. 
A second species, P. robustius, has also afforded well-characterised 
fructification. P, elegans, whose fruit appears as “oval scales,” no 
doubt bore sac-like spore-cases resembling those of the other species, 
but in a different position, and perfectly flattened in the specimens 
procured. The only other Canadian species, P. glabrum, being some- 
what different in appearance from the others, and not having af- 
forded any fructification, must be regarded as uncertain. 

The generic characters of the first three species may be stated as 
follows: 

Stems dichotomous, with rudimentary subulate leaves, sometimes 
obsolete in terminal branchlets and fertile branches; and in decor- 
ticated specimens represented only by punctiform scars. Young 
branches circinate. Rhizomata cylindrical, with circular root- 
areoles, Internal structure of stem, an axis of scalariform vessels 
enclosed in a sheath of imperfect woody tissue and covered with a 
cellular bark more dense externally. Fruit, naked sac-like spore- 
cases, in pairs or clusters, terminal or lateral. 

The Scottish specimens conform to these characters in so far as 
they are known, but not having as yet afforded fruit or internal 
structure, they cannot be specifically determined with certainty. 
More complete specimens should be carefully searched for, and will 
no doubt be found. : 

In Belgium, M. Crepin has described a new species from the 
Upper Devonian of Condroz under the name P. Condrusianum 
(1875). It wants, however, some of the more important characters of 
the genus, and differs in having a pinnate ramification, giving it the 
aspect of afern. In a later paper (1876) the author considers this 
species distinct from Pstlophyton, and proposes for it a new generic 
name Rhacophyton. 

The characters given by Mr. Carruthers, in his paper of 1878, for 
the species P. Dechenitanwm, are very few and general: “Lower 
branches short and frequently branching, giving the plant an oblong 
circumscription.” Yet even these characters do not apply, so far as 
known, to Miller’s fucoids or Salter’s rootlets or Goeppert’s Halise- 
rites, They merely express the peculiar mode of branching already 
referred to in Salter’s Lepidodendron nothum. The identification of 
the former plants with the Lepidodendron and Lycopodttes, indeed, 


THE ERIAN OR DEVONIAN FORESTS. 101 


rests only on mere juxtaposition of fragments, and on the slight resem- 
blance of the decorticated ends of the branches of the latter plants 
to Psilophyton. It is contradicted by the obtuse ends of the 
branches of the Lepidodendron and Lycopodites, and by the appar- 
ently strobilaceous termination of some of them. 

Salter’s description of his Lepidodendron nothum is quite defi- 
nite, and accords with specimens placed in my hands by Mr. Peach: 
“Stems half an inch broad, tapering little, branches short ; set on at 
an acute angle, blunt at their terminations. Leaves in seven to ten 
rows, very short, not a line long, and rather spreading than closely 
imbricate.” These characters, however, in so far as they go, are 
rather those of the genus Lycopodites than of Lepidodendron, from 
which this plant differs in wanting any distinct leaf-bases, and in its 
short, crowded leaves. It is to be observed that they apply also to 
Salter’s Lycopodiies Millert, and that the difference of the foliage 
of that species may be a result merely of different state of preser- 
vation. For these reasons I am disposed to place these two sup- 
posed species together,and to retain for the species the name 
Lycopodites Millert,. It may be characterised by the description 
above given, with merely the modification that the leaves are some- 
times nearly one-third of an inch long and secund (Fig. 17, supra, 
lower figure). 

Decorticated branches of the above species may no doubt be mis- 
taken for Psilophyton, but are nevertheless quite distinct from it, and 
the slender branching dichotomous stems, with terminations which, 
as Miller graphically states, are “ like the tendrils of a pea,” are too 
characteristic to be easily mistaken, even when neither fruit nor 
leaves appear. With reference to fructification, the form of L. 
Millert renders it certain that it must have borne strobiles at the 
ends of its branchlets, or some substitute for these, and not naked 
spore-cases like those of Pstlophyton. 

The remarkable fragment communicated by Sir Philip Egerton 
to Mr. Carruthers,* belongs to a third group, and has, I think, been 
quite misunderstood. I am enabled to make this statement with 
some confidence, from the fact that the reverse or counterpart of Sir 
Philip’s specimen was in the collection of Sir Wyville Thomson, and 
was placed by him in my hands in 1870. It was noticed in my 
paper on “ New Devonian Plants,” in the “Journal of the Geologi- 
cal Society of London,” and referred to my genus Ptilophyton, as 
stated above under Section II., page 86 ef seq. 


* “ Journal of Botany,” 1873. 


102 THE GEOLOGICAL HISTORY OF PLANTS. 


Mr. Salter described, in 1857,* fragments of fossil wood from the 
' Scottish Devonian, having the structure of Dadoxylon, though very 
imperfectly preserved ; and Prof. McNab has proposed + the generic 
name Paleopitys for another specimen of coniferous wood collected 
by Hugh Miller, and referred.to by him in the “ Testimony of the 
Rocks.” From Prof. McNab’s description, I should infer that this 
wood may, after all, be generically identical with the woods usually 
referred to Dadozylon of Unger (Araucariorylon of Kraus). The 
description, however, does not mention the number and disposition 
of the rows of pores, nor the structure of the medullary rays, and I 
have not been able to obtain access to the specimens themselves. I 
have described five species of Dadoxylon from the Middle and Up- 
per Erian of America, all quite distinct from the Lower Carbonifer- 
ous species. There is also one species of an allied genus, Ormoxylon. 
A)l these have been carefully figured, and it is much to be desired 
that the Scottish specimens should be re-examined and compared 
with them. 

Messrs. Jack and Etheridge have given an excellent summary 
of our present knowledge of the Devonian flora of Scotland, in the 
Journal of the London Geological Society (1877). From this it 
would appear that species referable to the genera Calamites, Lept- 
dodendron, Lycopodites, Psilophyton, Arthrostigma, Archwopteris, 
Caulopteris, Paleopitys, Araucartoxylon, and Stigmaria have been 

L_recognised. 

The plants described by these gentlemen from the Old Red 
Sandstone of Callender, I should suppose, from their figures and 
descriptions, to belong to the genus Arthrostigma, rather than to 
Psilophyton. Ido not attach any importance to the suggestions re- 
ferred to by them, that the apparent leaves may be leaf-bases, Long 
leaf-bases, like those characteristic of Lepidofioyos, do not occur in 
these humbler plants of the Devonian. The stems with delicate 
“horizontal processes” to which they refer may belong to Plilophy- 
ton or to Pinnularia. 

In conclusion, I need scarcely say that I do not share in the 
doubts expressed by some British paleontologists as to the distinct- 
ness of the Devonian and Carboniferous floras. In eastern’ America, 
where these formations are mutually unconformable, there is, of 
course, less room for doubt than in Ireland and in western Ameri- 
ca, where they are stratigraphically continuous. Still, in passing 


* “ Journal of the London Geological Society.” | & ps 
+ “Transactions of the Edinburgh Botanical Society,” 1870. 


THE ERIAN OR DEVONIAN FORESTS, 108 


from the one to the other, the species are for the most part differ- 
ent, and new generic forms are met with, and, as I have elsewhere 
shown, the physical conditions of the two periods were essentially 
different.* 

It is, however, to be observed that since—as Stur and others have 
shown—Calamites radiatus, and other forms distinctively Devonian 
in America, occur in Europe in the Lower Carboniferous, it is not 
unlikely that the Devonian flora, like that of the Tertiary, appeared 
earlier in America. It is also probable, as I have shown in the “ Re- 
ports” already referred to, that it appeared earlier in the Arctic than 
in the temperate zone. Hence an Arctic or American flora, really 
Devonian, may readily be mistaken for Lower Carboniferous by a 
botanist basing his calculations on the fossils of temperate Hurope. 
Even in America itself, it would appear, from recent discoveries in 
Virginia and Ohio, that certain Devonian forms lingered longer in 
those regions than farther to the northeast ;+ and it would not be 
surprising if similar plants occurred in later beds in Devonshire or 
in the south of Europe than in Scotland. Still, these facts, properly 
understood, do not invalidate the evidence of fossil plants as to 
geological age, though errors arising from the neglect of them are 
still current. : 


VI—GEoLogicaL RELATIONS OF SOME PLANT-BEARING BEDS oF 
Eastern Canapa. (“Report on Erian Plants,” 1871.) 


The Gaspé sandstones have been fully described by Sir W. E. 
Logan, in his “ Report on the Geology of Canada,” 1863. He there 
assigns to them a thickness of seven thousand and thirty-six feet, 
and shows that they rest conformably on the Upper Silurian lime- 
stones of the Lower Helderberg group (Ludlow), and are in their 
turn overlaid unconformably by the conglomerates which form the 
base of the Carboniferous rocks of New Brunswick. I shall add 
here merely a few remarks on points in their physical character 
connected with the occurrence of plants in them. 

Prototaxites (Nematophyton) Logani and other characteristic 
Lower Erian plants occur in the base of the sandstones at Little 
Gaspé. This fact, along with the occurrence, as stated in my paper 
of 1863, of rhizomes of Psilophyton preserving their scalariform 


*“ Reports on Devonian Plants and Lower Carboniferous Plants of 
Canada.” 

+ Andrews, “Palwontology of Ohio,” vol. ii.; Meek, “Fossil Plants 
from Western Virginia,” Philosophical Society, Washington, 1875. 


104 THE GEOLOGICAL HISTORY OF PLANTS. 


structure, in the upper part of the marine Upper Silurian lime- 
stones,* proves the flora of the Devonian rocks to have had its 
beginning at least in the previous geological period, and to charac- 
terise the lower as well as the upper beds of the Devonian series. In 
this connection I may state that, from their marine fossils, as well 
as their stratigraphical arrangement, Sir W. E. Logan and Mr. 
Billings regard the lower portions of the Gaspé sandstones as the 
equivalents of the Oriskany sandstone of New York. On the other 
hand, the great thickness of this formation, the absence of Lower 
Devonian fossils from its upper part, and the resemblance of the 
upper beds to those of the newer members of the Devonian else- 
where, render it probable that the Gaspé sandstones, though defi- 
cient in the calcareous members of the system, seen farther to the 
westward, represent the whole of the Devonian period. 

The Gaspé sandstones, as their name imports, are predominantly 
arenaceous, and often coarsely so, the sandstones being frequently 
composed of large grains and studded with quartz-pebbles. Grey 
and buff are prevalent colours, but red beds also occur, more espe- 
cially in the upper portion, There are also interstratified shaly 
beds, sometimes occurring in groups of considerable thickness, and 
associated with fine-grained and laminated argillaceous sandstone, 
the whole having in many places the lithological aspect of the coal- 
measures. At one place, near the middle of the series, there is a 
bed of coal from one inch to three inches in thickness, associated 
with highly bituminous shales abounding in remains of plants, and 
also containing fragments of crustaceans and fishes (Pterygotus, 
Ctenacanthus ? &c.). The beds connected with this coal are grey 
sandstones and grey and dark shales, much resembling those of the 
ordinary coal formation. The coal is shining and laminated, and 
both its roof and floor consist of laminated bituminous shale with 
fragments of Pstlophyton. It has no true under-clay, and has been, 
I believe, a peaty mass of rhizomes of. Psilophyton. It occurs near 
Tar Point, on the south side of Gaspé Bay, a place so named from 
the occurrence of a thick dyke of trap holding petroleum in its 
cavities. The coal is of considerable horizontal extent, as in its line 
of strike a similar bed has been discovered on the Douglas River, 
about four miles distant. It has not been recognised on the north 


* The marine fossils of these beds have been determined by Mr. 
Billings. They are Upper Silurian, with an intermixture of Lower Devo- 
nian in the upper part. Fragments of Nematophyton occur in beds of 
the same age in the Bay des Chaleurs, at Cape Bon Ami, 


THE ERIAN OR DEVONIAN FORESTS, - 105 


side of the bay, though we find there beds, probably on very nearly 
the same horizon, holding Pstlophyton in situ. 

As an illustration of one of the groups of shaly beds, and of the 
occurrence of roots of Pstlophyton, 1 may give the following sec- 
tional list of beds seen near “ Watering Brook,” on the north shore 
of the bay. The order is descending: 


. IN, 

1. Grey sandstones and reddish pebbly sandstone of great = 

thickness ....... eee eee ween Wig vsieceuenl teete 
2, Bright-red shale... ... 0c. ee cece eee eee e eens 8 0 
8. Grey shales with stems of ees very abundant 

but badly preserved... ate 0 65 
4, Grey incoherent clay, wfickensided, antl with mitaiy 

rhizomes and roots of Psilophyton........ s+. 0 3 
5. Hard grey clay or shale, with fragments and roots of 

PSUOPhYlOn, 00 issn ccieies ciwaniensisa* dae tena 5 4 0 
G; Red: SHAG. siicsisc:sss 6 sees vies Haisnsieisio temas eee s 8 0 
4, Grey and reddish crumbling sandstone............. 


Groups of beds similar to the above, but frequently much more 
rich in fossils, occur in many parts of the section, and evidently in- 
clude fossil soils of the nature of under-clays, on which little else 
appears to have grown than a dense herbage of Psilophyton, along 
with plants of the genus Arthrosiigma, 

In addition to these shaly groups, there are numerous examples 
of beds of shale of small thickness included in coarse sandstones, 
and these beds often occur in detached fragments, as if the rem- 
nants of more continuous layers partially removed by currents of 
water. It is deserving of notice that nearly all these patches of 
shale are interlaced with roots or stems of Psilophyton, which some- 
times project beyond their limits into the sandstone, as if the vege- 
table fibres had preserved the clay from removal.’ In short, these 
lines of patches of shale seem to be remnants of soils on which 
Psilophyton has flourished abundantly, and which have been par- 
tially swept away by the currents which deposited the sand. Some 
of the smaller patches may even be fragments of tough swamp soils 
interwoven with roots, drifted by the agency of the waves or possibly 
by ice; such masses are often moved in this way on the borders of 
modern swamps on the sea-coast. 

The only remaining point connected with local geology to which 
T shall allude is the admirable facilities afforded by the Gaspé coast 
both for ascertaining the true geological relations of the beds, and 
for studying the Devonian plants, as distinctly exposed on large sur 

il 


106 THE GEOLOGICAL HISTORY OF PLANTS. 


faces of rock. On the coast of the river St. Lawrence, at Cape 
Rozier and ‘its vicinity, the Lower Silurian rocks of the Quebec 
group are well exposed, and are overlaid unconformably by the mas- 
sive Upper Silurian limestones of Cape Gaspé, which rise into cliffs 
six hundred feet in height, and can be seen filled with their char- 
acteristic fossils on both sides of the cape. Resting upon these, and 
dipping at high angles toward Gaspé Bay, are the Devonian sand- 
stones, which are exposed in rugged cliffs slightly oblique to their 
line of strike, along a co&$t-line of ten miles in length, to the head 
of the bay. On the opposite side of the bay they reappear; and, 
‘thrown into slight undulations by three anticlinal curves, occupy 
a line of coast fifteen miles in length. The perfect manner in which 
the plant-bearing beds are exposed in these fine natural sections may 
serve to account for the completeness with which the forms and 
habits of growth of the more abundant species can be described. 

In the Bay des Chaleurs, similar rocks exist with some local 
variations. In the vicinity of Campbellton are calcareous and mag- 
nesian breccia or agglomerate, hard shales, conglomerates and sand- 
stones of Lower Devonian age. The agglomerate and lower shales 
contain abundant remains of fishes of the genera Cephalaspis, Coc- 
costeus, Clenacanthus, and Homacanthus, and also fragments of 
Plerygotus. The shales and sandstones abound in remains of Psilo- 
_phyton, with which are Nematophyton, Arthrostigma, and Lepto- 
phleum of the same species found in the Lower Devonian of Gaspé 
Bay. These beds near Campbellton dip to the northward, and the 
Restigouche River here occupies a synclinal, for on the opposite side, 
at Bordeaux Quarry, there are thick beds of grey sandstone dipping 
to the southward, and containing large silicified trunks of Proto- 
taxites, in addition to Pselophyton. These beds are all undoubtedly 
Lower Erian, but farther to the eastward, on the north side of the 
river, there are newer and overlying strata. These are best seen at 
Scaumenac Bay, opposite Dalhousie, between Cape Florissant and 
Maguacha Point, where they consist of laminated and fine-grained 
sandstone, with shales of grey colours, but holding some reddish beds 
at top, and overlaid unconformably by a great thickness of Lower 
Carboniferous red conglomerate and sandstone. In these beds nu- 
merous fossil fishes have been found, among which Mr, Whiteaves 
recognises species of Pterichthys, Glyptolepis, Cheirolepis, &c. With 
these are found somewhat plentifully four species of fossil ferns, all 
of Upper Erian types, of which one is peculiar to this locality; but 
the others are found in the Upper Erian of Perry, in Maine, or in 
the Catskill group of New York. 


THE ERIAN OR DEVONIAN FORESTS, 107 

In order that distinct notions may be conveyed as to the geo- 
logical horizons of the species, I may state that the typical Devonian 
or Erian series of Canada and New York may be divided in descend- 
ing order into—1. The Chemung group, including the Chemung and 
Portage sandstones and shales. 2. The Hamilton group, including 
the Geriesee, Hamilton, and Marcellus shales. 3. The Corniferous 
limestone and its associated beds. 4, The Oriskany sandstone. As 
the Corniferous limestone, which is the equivalent of the Lower 
Carboniferous limestone in the Carbonifefous period, is marine, and 
affords scarcely any plants, we may, as is usually done for like pur- 
poses in the Carboniferous, group it with the Oriskany under the 
name Lower Erian. The Hamilton rocks will then be Middle Erian, 
and the Chemung group Upper Erian. In the present state of our 
knowledge, the series, may be co-ordinated with the rocks of Gaspé, 
New Brunswick, and Maine, as in the following table: 


New York Gaspé - Southern Coast 
Subdivisions. and and Bay des ew of 
Western Canada.) Chaleurs. Brunswick, Maine. 
Upper Chemung Upper MispecGroup. | Perry Sand- 
Devonian or Group. Sandstones. | Shale, Sand- stones. 
Erian. Long Cove, &.| stone, and 
Scauminae | Conglomer- 
Beds. ate. 
Middle Hamilton Middle | LittleR.Group 
Devonian or Group. Sandstones. | (including 
Erian. Bois Brulé, Cordaite 
Cape Oiseau, | Shales and 
&e, Dadoxylon 
Sandstone). 
Lower | Corniferous Lower Lower Con- 
Devonian or and Sandstones. | glomerates, 
Erian. Oriskany | Gaspé Basin, &e. 
groups. Little Gaspé, 
&e. 
Campbellton 
Beds. 


It may be proper, before closing this note, to state the reasons 


which have induced me to suggest in the following pages the use of 
the term “Eran,” as equivalent to “ Devonian,” for the great sys- 
tem of formations intervening between the Upper Silurian and the 
Lower Carboniferous‘in America. 1 have been induced to adopt 
this course by the following considerations: 1. The great area of 


108 THE GEOLOGICAL HISTORY OF PLANTS. 


undisturbed and unaltered rocks of this age, including a thickness 
in some places of eighteen thousand feet, and extending from east 
to west through the Northern ‘States of the Union and western 
Canada for nearly seven hundred miles, while it spreads from north 
to south from the northern part of Michigan far into the Middle 
States, is undoubtedly the most important Devonian area now known 
to geologists. 2. This area has been taken by all American geolo- 
gists as their typical Devonian region. It is rich in fossils, and 
these have been thoroughly studied and admirably illustrated by 
the New York and Canadian Surveys. 3. The rocks of this area 
surround the basin of Lake Erie, and were named, in the original’ 
reports of the New York Survey, the “ Hrie Division.” 4. Great 
difficulties have been experienced in the classification of the Euro- 
pean Devonian, and the uncertainties thus arising have tended to 
throw doubt on the results obtained in America in circumstances in 
which such difficulties do not occur. 

These reasons are, I think, sufficient to warrant me in holding 
the great Hrie Division of the New York geologists as the typical 
representative of the rocks deposited between the close of the Upper 
Silurian and the beginning of the Carboniferous period, and to use 
the term Erian as the designation of this great series of deposits as 
developed in America, in so far at least as their flora is concerned. 
In doing so, I do not wish to introduce a new name merely for the 
sake of novelty ; but I hope to keep before the minds of geologists 
the caution that they should not measure the Erian formations of 
America, or the fossils which they contain, by the comparatively 
depauperated representatives of this portion of the geological scale 
in the Devonian of western Europe. 


VII.—On THE RELATIONS OF THE SO-CALLED “Ursa STaGE” oF 
Bear JIsnanp wirH THE Patmozoic Fiora or NortH 
AMERICA, 


The following note is a verbatim copy of that published by me 
in 1873, and the accuracy of which has now been vindicated by the 
recent observations of Nathorst : 

The plants catalogued by Dr. Heer, and characterising what he 
calls the “ Ursa Stage,” are in part representatives of those of the 
American flora which I have described as the “ Lower Carboniferous 
Coal-Measures ” (Subcarboniferous of Dana), and whose characteristic 
species, as developed in Nova Scotia, I noticed in the “ Journal of 
the Geological Society ” in 1858 (vol. xv.). Dr. Heer’s list, however, 
includes some Upper Devonian forms; and I would suggest that 


THE ERIAN OR DEVONIAN FORESTS. 109 


either the plants of two distinct beds, one Lower Carboniferous and 
the other Upper Devonian, have been near to or in contact with each 
other and have been intermixed, or else that in this high northern 
latitude, in which (for reasons stated in my “ Report on the Devo- 
nian Flora” *) I believe the Devonian plants to have originated, there 
was an actual intermixture of the two floras, In America, at the 
base of the Carboniferous of Ohio, a transition of this kind seems 
to occur; but elsewhere in northeastern America the Lower Car- 
boniferous plants are usually unmixed with the Devonian. 

Dr. Heer, however, proceeds to identify these plants with those 
of the American Chemung, and even with those of the Middle De- 
vonian of New Brunswick, as described by me—a conclusion from 
which I must altogether dissent, inasmuch as the latter belong to 
beds which were disturbed and partially metamorphosed before the 
deposition of the lowest Carboniferous or “Subcarboniferous ” beds. 

Dr. Heer’s error seems to have arisen from want of acquaintance 
with the rich flora of the Middle Devonian, which, while differing in 
species, has much resemblance in its general facies, and especially in 
its richness in ferns, to that of the coal-formation. 

To geologists acquainted with the stratigraphy and the accom- 
panying animal fossils, Dr. Heer’s conclusions will of course appear 
untenable ; but they may regard them as invalidating the evidence 
of fossil plants; and for this reason it is, I think, desirable to give 
publicity to the above statements. 

’ Teonsider the British equivalent of the lower coal-measures of 
eastern’ America to be the lower limestone shales, the Tweedian 
group of Mr. Tate (1858), but which have sometimes been called the 
“ Calciferous Sandstone ” (a name preoccupied for a,Cambrian group 
in America). This group does not constitute “beds of passage” to 
the Devonian, more especially in eastern America, where the lower 
coal-formation rests unconformably on the Devonian, and is broadly 
distinguished by its fossils. 

The above notes would not have been extended to so great 
length, but for the importance of the Erian flora as the precursor 
of that of the Carboniferous, and the small amount of attention 
hitherto given to it by geologists and botanists, 


* “ Geological Survey of Canada,” 1871. ra 


CHAPTER IV. 


THE CARBONIFEROUS FLORA—CULMINATION OF THE 
ACROGENS—FORMATION OF COAL, 


ASCENDING from the Erian to the Carboniferous sys- 
tem, so called because it contains the greatest deposits of 
anthracite and bituminous coal, we are still within the 
limits of the Paleozoic period. We are still within the 
reign of the gigantic club-mosses, cordaites, and taxine 
pines. At the close of the Erian there had been over 
the whole northern hemisphere great changes of level, 
accompanied by active voleanic phenomena, and under 
these influences the land flora seems to have much dimin- 
ished. At length all the old Erian species had become 
extinct, and their place was supplied by a meagre group 
of lycopods, ferns, and pines of different species from 
those of the preceding Erian. This is the flora of the 
Lower Carboniferous series, the Tweedian of England, 
the Horton series of Nova Scotia, the lower coal-meas- 
ures of Virginia, the culm of Germany. But the land 
again subsided, and the period of the marine limestone 
of the Lower Carboniferous was introduced. In this the 
older flora disappeared, and when the land emerged we 
find it covered with the rich flora of the coal-formation 
proper, in which the great tribes of the lycopods and 
cordaites attained their maxima, and the ferns were con- 
tinued as before, though under new generic and specific 
forms. 


e 


THE CARBONIFEROUS FLORA. 111 


There is something very striking in this succession of 
a uew plant world without any material advance. It is 
like passing in the modern world from one district to 
another, in which we see the same forms of life, only 
represented by distinct though allied species. Thus, when 
the voyager. crosses the Atlantic from Europe to Amer- 
ica, he meets with pines, 
oaks, birches, poplars, 
and beeches of the same 
genera with those he 
had left behind ; but 
the species are distinct. 
Ti is something like this 
that meets us in our as- 
cent into the Carbonif- 
erous world of plants, 
Yet we know that this 
is a succession in time, 
that all our old Erian 
friends are dead and 
buried long ago, and 


that these are new forms abedefg 
lately introduced ig. Fra. 82.—Foliage from the coal-for- 
32) y ced (Fig mation, a, dlethopteris tonchitios 


; fm Nee rage 3, Sphenoplgt- 
Conveying ourselves, cogucdron poneron HATED) “2 “ee 
then, in imagination for- ee jplons (#) (Sydney). 
ward to the time when _— amis mre ta Fete, 
our greatest accumula- ae saounecray, TEx. 
tions of coal were formed, 
and fancying that we are introduced to the Ameri- 
can or European continent of that period, we find our- 
selves in a new and strange world. In the Devonian 
age, and even in the succeeding Lower Carboniferous, 
there was in the interior of America a wide inland sea, 
with forest belts clinging to its sides or clothing its isl- 


ands. But in the coal period this inland sea had given 


112 THE GEOLOGICAL HISTORY OF PLANTS. 


place to vast swampy flats, and which, instead of the oil- 
bearing shales of the Hrian, were destined to produce 
those immense and wide-spread accumulations of vege- 
table matter which constitute our present beds of bitu- 
minous and anthracite coal. The 
atmosphere of these great swamps 
is moist and warm. Their vege- 
tation is most exuberant,. but of 
forms unfamiliar to modern eyes, 
and they swarm with insects, 
millepedes, and scorpions, and 
with batrachian reptiles large 
and small, among which we look 
in vain for representatives of the 
birds and beasts of the present 
day. 
Prominent among the more 
gigantic trees of these swampy 
forests are those known to us as 
Sigillarie (Fig. 33). They have 
tall, pillar-like trunks, often sev- 
eral feet in diameter, ribbed like 
fluted columns, but in the re- 
verse way, and spreading at the 
top into a few thick branches, 
which are clothed with long, 
grass-like leaves. They resem- 
= ble in some respects the Lepi- 
mr" =" dodendra of the Erian age, but 
Fic. 83.—Sigillaria, restored. are more massive, with ribbed in- 
4, Sigiliaria Brownti. 
B, Sigillaria elegans. stead of scaly trunks, and longer 
leaves. If we approach one of 
them more closely, we are struck with the regular ribs of. 
its trunk, dotted with rows of scars of fallen leaves, from 
which it receives its name Sigillaria, or seal-tree (Figs. 
34-37). If we cut into its stem, we find that, instead of 


THE CARBONIFEROUS FLORA. 113 


the thin bark and firm wood with which we are familiar 
in our modern trees, it has a hard external rind, then a 
great thickness of cellular matter with rope-like bands of 
fibres, constituting an inner bark, while in the centre is 
a firm, woody axis of comparatively small diameter, and 


Wht 
} <a 
iis aH 

j S 
A 


c 


Fic. 34.—Sigillaria Lorwa ‘ana, Dawson. a, Zones of fruit-scare, b, Leaf- 
sear enlarged. ¢, Tuit-scar enlarged. See appended note. 


somewhat intermediate in its structures between that of 
the Lepidodendra and those of the cycads and the taxine 
conifers. Thus a great stem, five feet in diameter, may 
consist principally of cellular and bast fibres with very 
little true woody matter. The roots of this tree are 


114 TUE GEOLOGICAL HISTORY OF PLANTS. 


perhaps its most singular feature. They usually start 
from the stem in four main branches, then regularly 
bifurcate several times, and then run out into great 


Fie. 35.—Stem of Sigillaria Fie. 86.—Two ribs of Sigillaria Brownti. 
Brownii, reduced. Natural size. 


cylindrical cables, running for a long distance, and evi- 
dently intended to anchor the plant firmly in a soft and 
oozy soil. They were furnished 
with long, cylindrical rootlets 
placed regularly in a spiral man- 
ner, and go articulated that when 
they dropped off they left regu- 
lar rounded scars. They are, 
in short, the Stigmarie, which 
we have already met with in 
the Erian (Figs. 38, 39). In 
Fig. 33 I have endeavoured to 
restore these strange trees. It is 
not wonderful that such plants 

oe have caused much botanical con- 
Fic. 37—Portion of lower troversy. It was long before bot- 


art of stem of 8. Brownii. i . 
atural size, anists could be convinced that 


THE CARBONIFEROUS FLORA. 115 


their roots are properly roots at all, and not stems 
of some aquatic plant. Then the structure of their 


Fie. 88.—Stigmaria root, seen from above, showing its regular divisions. 
From “ Acadian Geology.” eu 


stems is most puzzling, and their fruit is an enigma, 
for while some have found connected with them cones 


supposed to resemble those of 
lycopods, others attribute to 
them fruits like those of yew- 
trees. For years I have been 
myself gathering materials from 
the rich coal-formation deposits 
of Nova Scotia in aid of the 
solution of these questions, and 
in the mean time Dr. William- 
son, of Manchester, and Renault 
and other botanists in France, 
have been amassing and study- 
ing stores of specimens, and it 
is still uncertain who may final- 
ly be the fortunate discoverer 


to set all controversies at rest. 


saga palate of bark of 
igmaria, showing scars 
of attachment of rootlets. 


My present belief is, 


that the true solution consists in the fact that there are 
many kinds of Sigillarie. While in the modern forests 


116 THE GEOLOGICAL HISTORY OF PLANTS. 


of America and Europe the species of any of our ordinary 
trees, as oaks, birches, or maples, may almost be counted 
on one’s fingers, Schimper in his vegetable paleontology 
enumerates about eighty species of Carboniferous Sigil- 
larie@ ; and while on the one hand many of these are so 
imperfectly known that they may be regarded as uncer- 
tain, on the other hand many species must yet remain to 
be discovered.* Now, in so vast a number of species 
there must be a great range of organisation, and, indeed, 
it has already been attempted to subdivide them into 
several generic groups. The present state of the question 
appears to me to be this, that in these Sigillarie we have 
a group divisible into several forms, some of which will 
eventually be classed with the Lepidodendra as lycopods, 
while others will be found to be naked-seeded pheno- 
gams, allied to the pines and cycads, and to a remarkable 
group of trees known as Cordattes, which we must shortly 
notice. 

Before considering other forms of Carboniferous vege- 
tation, let us glance at the accumulation of coal, and the 
agency of the forests of Stgillart@ therein. Let us im- 
agine, in the first instance, such trees as those represented 
in the figures, growing thickly together over vast swampy 
flats, with quantities of undergrowth of ferns and other 
plants beneath their shade, and accumulating from age to 
age in a moist soil and climate a vast thickness of vege- 
table mould and trunks of trees, and spores and spore- 
cases, and we have the conditions necessary for the growth 
of coal. Many years ago it was observed by Sir William 
Logan that in the coal-field of South Wales it was the 
rule with rare exceptions that, under every bed of coal, 
there is a bed of clay filled with roots of the Stigmaria, 
already referred to as the root of Sigillaria. This dis- 


*In a recent memoir (Berlin, 1887) Stur has raised the number of 
species in one subdivision of the Sigillarie (the Favularie) to forty- 
seven ! 


THE CARBONIFEROUS FLORA. 117 


covery has since been extended to all the coal-fields of 
Europe and America, and it is a perfectly conclusive fact 
as regards the origin of coal. Each of these ‘‘under- 
clays,” as they are called, must, in fact, have been a soil 
on which grew, in the first instance, Sigillaris and other 
trees having stigmaria-roots. Thus, the growth of a 
forest of Sigillaria was the first step toward the accumu- 
lation of a bed of coal. More than this, in some of the 
coarser and more impure coals, where there has been 
sufficient earthy matter to separate and preserve impres- 
sions of vegetable forms, we can see that the mass of the 
coal is made up of flattened Sigillariw, mixed with vege- 


te B 


Fie. 40.—Vegetable neue am coal. a, Sigillaria = Cordaites. 
b, Calamodendron. 


itn Vinay 


table débris of all kinds, including sometimes vast quan- 
tities of lepidodendroid spores, and the microscopic study 
of the coal gives similar results (Fig. 40). Further, on 
the surfaces of many coals, and penetrating the shales or 
sandstones which form their roofs, we find erect stumps 
of sigillaria and other trees, showing that the accumula- 
tion of the coal terminated as it had begun, by a forest- 
growth. I introduce here a section of a few of the nu- 
merous beds of coal exposed in the cliffs of the South 
Joggins,’ in Nova Scotia, in illustration of these facts. 
We can thus see how in the slowly subsiding areas of the 
coal-swamps successive beds of coal were accumulated, 
alternating with beds of sandstone and shale (Figs. 41, 
42). For other details of this kind I must refer to 


papers mentioned in the sequel. 
12 


118 THE GEOLOGICAL HISTORY OF PLANTS. 


Returning to the more special subject of this work, I 
may remark that the lepidodendroid trees and the ferns, 
both the arborescent and herbaceous kinds, are even more 
richly represented in the Carboniferous than in the pre- 
ceding Erian. I must, however, content myself with 
merely introducing a few representatives of some of 

: the more common 

S kinds, in an ap- 

2 pended note, and 


SS 


aT 
oreo TT 


here give a figure 

of a well-known 

8 Lower Carbonifer- 

ous lepidodendron, 

with its various 

forms of leaf-bases, 

2 and its foliage and 

fruit (Fig. 43), and 

a similar ilustra- 

—— 4 tion of an allied 

we / generic form, that 

; , 6 known as Lepido- 

* a 7 aaa phloios* (Fig. 44). 
a. 41.—Beds associated with the main coal 

(8. Joggins, Nova Scotia). 1, Shale and sand- Another group 

stone—plants with Spirorbis attached; rain- which claims our 

marks (4). (2, Sandstone and shale, eight : : 

feet—erect Calamites; 8, Gray sandstone, attention is that 
seven feet; 4, Gray shale, four teet—an erect 
coniferous (?) tree, rooted on the shale, passes 
up through fifteen feet of the sandstones and 
shale.) 5, Gray sandstone, fourfeet. 6, Gray 
shale, six inches—prostrate and erect trees, 
with rootlets, leaves, Vazadites, and Spiror- 
éés on the plants. , Main _coal-seam, five 

feet of coal in two seams. 8, Underclay, with 

rootlets. 


of the Calamites. 
These are tall, cy- 
lindrical, branch- 
less stems, with 
whorls of branch- 
lets, bearing needle- 


like leaves and spreading in stools from the base, so as to 
form dense thickets, like Southern cane-brakes (Fig. 46). 
They bear, in habit of growth and fructification, a close 


* For full descriptions of these, see ‘‘ Acadian Geology.” 


THE CARBONIFEROUS FLORA. 119 


relation to our modern equisetums, or mare’s-tails, but, 
as in other cases we have met with, are of gigantic size 
and comparatively complex structure. Their stems, in 
cross-section, show radi- 
ating bundles of fibres, 
like those of exogenous 
woods, yet the whole plan 
of structure presents some 
curious resemblances to 
the stems of their hum- 
ble successors, the mod- 
ern mare’s-tails. It would 
seem, from the manner 
in which dense brakes of 
these Calamites have been 
preserved in the coal-for- 
mation of Nova Scotia, 
that they spread over low 
and occasionally inun- 
dated flats, and formed 
fringes on the seaward ' 
sides of the great Sigilla- Fro, 42,Erect Sigillaria, standing 
ria forests. In this way oot S08 (S Joagins, Nova 
they no doubt contrib- 
uted to prevent the invasion of the areas of coal ac- 
cumulation ‘by the muddy waters of inundations, and 
thus, though they may not have furnished much of the 
material of coal, they no doubt contributed to its purity. 
Many beautiful plants of the genera Asterophyllites and 
Annularia are supposed to have been allied to the Cala- 
mites,.or to have connected them with the Rhizocarps. 
The stems and fruit of these plants have strong points of 
resemblance to those of Sphenophyllum, and the leaves 
are broad, and not narrow and angular like those of the 
true Oalamites (Fig. 45). 

No one has done more than my friend Dr. William- 


120 THE GEOLOGICAL HISTORY OF PLANTS. 


) 
tt 
VAS Pol: 
a \, We 


h 
"i 
‘ 


\ if 4 
—_ Wi 
" WA 


i 
Fic. 48.—Lepidodendron corrugatum, Dawson. 
Lower Carboniferous. a, Restoration. 3 
and branch. p, Branch and leaves. 5, v 
¥, Sporangium. 1, L, M, Bark, with leaf-scars. n, Bark, with leaf- 
scars of old stem. 0, Decorticated stem (norria). 


THE CARBONIFEROUS FLORA. 121 


Fie. 44.—Lepidophloios Acadianus, Dawson, a lepidodendroid tree of the 
coal-formation. , Restoration. 8, Portion of bark (two thirds natural 
size). 0, Ligneous surtace of the same. ¥, Cone (twothirds natural size), 
c, Leaf (natural Bue K, Portion of woody cylinder, showing outer and 
inner series of vessels magnified. 1, Scalariform vessels (highly magni- 
fied). m, Various forms of leaf-scara and leaf-bases (natural size). 


122 THE GEOLOGICAL IISTORY OF PLANTS. 


son, of Manchester, to illustrate the structure of Cala- 
mites, and he hus shown that these plants, like other 
cryptogams of the Carboniferous, had mostly stems with 
regular fibrous wedges, like those of exogens. The 
structure of the stem is, indeed, so complex, and differs 
so much in different stages of growth, and different states 
of preservation, that we are in danger of falling into the 
greatest confusion in classifying these plants. Sometimes 
what we call a Calamite is a mere cast of its pith showing 
longitudinal stria and constrictions at the nodes. Some- 


Fie. 45.—Asterophyllites, Sphenophyllum, and Annularia, a, Astero- 
phyllites trinerne. 1, Leaf enlarged. 3, Annularia henophylloides, 
B!, Loaf enlarged. 0, Sphenophyllum erosum. o', Leaflet enlarged. 
c?, Sculariform vessel of Sphenophyllum. pv, Pinnularia ramosissima, 
probably a root. 

times we have the form of the outer surface of the woody 

cylinder, showing longitudinal ribs, nodes, and marks of 

the emission of the branchlets. Sometimes we have the 
outer surface of the plant covered with a smooth bark 
showing flat ribs, or almost smooth, and having at the 
nodes regular articulations with the bases of the verticil- 


THE CARBONIFEROCS FLORA. 133 


late branchlets, or on the lower part of the stem the 
marks of the attachment of the roots) The Calamites 
grew in dense clumps, budding off from one another, 
sometimes at different levels, as the mud or sand accumu- 
lated about their stems, and in some 
species there were creeping rhizomata 
or root-stocks (Figs. 46 to 49). 

But all Calamites were not alike 
in structure. In a recent paper * 


y 


ty 


Fic. 46. — Calamites. 
cee Se es Se 
re Lit) 
* Acadian Geolo- (Nova Sco- leaves (Nova Sco- 
gy.”) tia). tia). 
Dr. Williamson describes three distinct structural types. 
What he regards as typical Calamites has in its woody 
zone wedges of barred vessels, with thick bands of cel- 
lular tissue separating them. A second type, which 


* “Memoirs of the Philosophical Society,” Manchester, 1836-87. 


194 THE GEOLOGICAL HISTORY OF PLANTS. 


he refers to Calumopitus, has woody bundles com- 
posed of reticulated or multiporous fibres, with their 
porous sides parallel to the medullary rays, which are 
better developed than in the previous form. Tho inter- 
vening cellular masses are composed of elongated cells. 
This is a decided advance in structure, and is of the type 
of those forms having the most wocdy and largost stems, 


e) in 


WMA 


Fig. 49.—Eroct Calamites (C. Suckovit), showing the mode of growth of 
now stems (2), and different forms of the ribs (a, ¢). (Pictou, Nova 
Scotia.) Half natural size, 


which Brongniart named Calamodendron (Fig. 50). A 
third form, to which Dr. Williamson scems to profer to 
assign this last name, has the tissue of the woody wedges 
barred, as in the first, but the medullary rays are botter 
developed than in the second. In this third form the 
intermediate tissue, or primary medullary rays, is truly 
fibrous, and with secondary medullary rays traversing it. 
My own observations lead mo to infer that there was a 
fourth type of calamitean stem, loss endowed with woody 
matter, and having a larger fistulous or cellular cavity 
than any of those described by Dr. Williamson. 

There is every reason to belicve that all these various 


THE CARBONIFEROUS FLORA, 125 


and complicated stems belonged to higher and nobler 
types of mare’s-tails than those of the modern world, and 
that their fructification was equisetaceous and of the 
form known as Calamostachys. 

We have already seen that noble tree-ferns existed in 
the Erian period, and these were continued, and their 
number and variety greatly extended, in the Carbonifer- 
ous. In regard to the structure of their stems, and the 
method of supporting these by a&rial roots, the tree-ferns 
of all ages have been nearly alike, and the form and 
structure of the leaves, except in some comparatively rare 
and exceptional types, has also been much the same. 
Any ordinary observer examining a collection of coal- 
formation ferns recognises at once their kinship to the 
familiar brackens of our own time. Their fructification 
is, unfortunately, rarely preserved, so that we are not 
able, in the case of many species, to speak confidently of 


es Oo O 
= wie 
P| L 2Iks 
WANES d BysaD 

5 

Ss ep 

= 

3 OM 

rc 


Fre. 50.—Stems of Cilrmodeadron re Big magnified (Nova Scotia). 
a, & Case oF ati in ah 


ry on Woody tissue (highly nar aa 


their affinities with modern forms ; but the knowledge of 
this sabject has been constantly extending, and a suffi- 
cient amount of information has been obtained to enable 
us to say something as to their probable relationships. 
(Figs. 51 to 55.) 

The families into which modern ferns are divided are, 
it must be confessed, somewhat artificial, and im the case 


126 THE GEOLOGICAL HISTORY OF PLANTS. 


of fossil ferns, in which the fructification is for the most 
part wanting, it is still more so, depending in great part 
on the form and venation of the divisions of the fronds. 


Fie. 51.—Group of coal-formation ferns. a, Odontopteris subcuneata (Bun- 
bury). 3, Neuropteris cordatu (Brongniart). 0, age lonehitica 
(Brongniart). pv, Dictyopteris obliqua (Bunbury). =, Phyllopteris an- 
tigua (Dawson), magnified; e!, Natural size. ¥, Neuropteris cyclopte- 
roides (Dawson). 


Of about eight families into which modern ferns are 
divided, seven are found in a fossil state, and of these, 
four at least, the Cyathacew, the Ophioglossee, the Hy- 


Fra. 58.—Cyclopteris (Anetmites) Acadica (Dawson), a tree-fern of the 
Lower Carboniferous. a, Pinnules. 6, Fragment of petiole. ¢, Re- 
mains of fertile pinnules. 


128 THE GEOLOGICAL HISTORY OF PLANTS. 


menophyllacee, and the Marattiacee, go back to the coal- 
formation.* 

Some of these ferns have the more complex kind of 
spore-case, with a jointed, elastic ring. It is to be ob- 


Fie, 54.—Sphenopteris latior, Dawson. Coal-formation. a, Pinnule 
magnified, with traces of fructification. 


served, however, that those forms which have a simple 
spore-case, either netted or membranous, and without 
annulus, are most common in the Devonian and lowest: 


Fic, 55.—Fructification of Paleozoic ferns. a, Thece of Archeopteris 
(Erian). 5, Theca otf Senftenbergia (Carboniferous). c, Thece of 
Asterotheca (Carboniferous). 


Carboniferous. Some of the forms in these old rocks are 
somewhat difficult to place in the system. Of these, the 


* Mr. R, Kidston has recently described very interesting forms of 
fern fructification from the coal-formation of Great Britain, and much 
has been done by European paleobotanists, and also by Lesquereux and 
Fontaine in America, 


THE CARBONIFEROUS FLORA. 129 


eI | 


Fie. 58.—Tree-ferns of the Carboniferous. a, Megaphyton magnificum, 
Dawson, restored. 8, Leaf-scar of the same, two thirds natural size, 
B1, Row of leat-scars, reduced. c, Paleoptervs Harti, scars half natu- 
ral size. pv, Paleopteris Acadica, scars half natural size. 


13 


130 THE GEOLOGICAL HISTORY OF PLANTS. 


species of Archwopéeris, of the Upper and Middle Hrian, 
are eminent as examples. This type, however, scarcely 
extends as high as the coal-formation.* Some of the 
tree-ferns of the Carboniferous present very remarkable 
features. One of these, of the genus Megaphyton, seems 
to have two rows of great leaves, one at each side of the 
stem, which was probably sustained by large bundles of 
aérial roots (Fig. 56). 

In the Carboniferous, as in the Erian, there are leaves 
which have been referred to ferns, but are subject to 
doubt, as possibly belonging to broad-leaved taxine trees 
allied to the gingko-tree of China. One of these, repre- 
sented in Fig. 5%, has been 
found in the coal-formation of 
Nova Scotia, and referred to the 
doubtful genus Noeggerathia. 
Fontaine has proposed for simi- 
lar leaves found in Virginia the 
new generic name Saportea. 

Ferns, as might be inferred 
from their great age, are at the 
present time dispersed over the 

aan whole world; but their head- 

Tie, Car eet 5 quarters, and the regions to 

which tree-ferns are confined, 

are the more moist climates of the tropics and of the 

southern hemisphere. The coal-swamps of the northern 

hemisphere seem to have excelled even these favoured 
regions of the present world as a paradise for ferns. 

I have already stated that the Carboniferous consti- 
tutes the headquarters of the Cordattes (Fig. 58), of which 
a large number of species have been described, both in 


* The pretty little ferns of the genus Botrychium (moonwort), so 
common in American and European woods, seem to be their nearest mod- 
ern allies, 


THE CARBONIFEROUS FLORA. 1381 


Europe and America. We sometimes, though rarely, 
find their stems showing structure. In this case we have 
a large cellular pith, often divided by horizontal parti- 
tions into flat chambers, and constituting the objects 
which, when detached, are called Sternbergie (Fig. 62). 
These Sternbergia piths, however, occur in true coni- 
fers as well, as they do 
in the modern world 
in some trees, like our 
common butternut, of 
higher type; and I 
showed many years ago 
that the Sternbergia 
type may be detected 
in the young twigs of 
the balsam-fir (Adves 
balsamifera). The pith 
was surrounded by a 
ring of scalariform or 
barred tissue, often of 
considerable thickness, 
and in young stems so 
important as to have 
suggested lycopodia- 
ceous affinities. But as 
the stem grew in size, 
a regular ring of woody 
wedges, with tissue hav- 
ing rounded or hex- Fie. "Gut hee 
agonal pores or discs, 

like those of pines, was developed. Outside this was a 
bark, often apparently of some thickness. This struct- 
ure in many important points resembles that of cycads, 
and also approaches to the structure of Sigillaria, while 
in its more highly developed forms it approximates to 
that of the conifers. 


182 THE GEOLOGICAL HISTORY OF PLANTS. 


On the stems so constructed were placed long and 
often broad many-nerved leaves, with rows of stomata or 
breathing-pores, and attached by somewhat broad bases 
to the stem and branches. The fruit consisted of racemes, 
or clusters of nutlets, which seem to have been provided 


Fie, 59.—Fruits of Cordaites and Taxine Conifers (coal-formation, Nova 
Scotia.) a, Antholithes squamosus (two thirds). 3B, .A. rhabdocarpt 
(two thirds). 3, Carpel restored. c, A. spinogus (natural size). 
D, Trigonocarpum intermedium. &, 7 Neggerathit, w, T. avella- 
num. G, Rhabdocarpus insignis, reduced. u, Antholithes_pygmaus. 
1, Cardiocarpum fluitans. «x, Cardiocarpum bisectum. 1, Sporangites 
papitlata, lycopodiaceous macrospores (natural size and magnified). » 


THE CARBONIFEROUS FLORA. 133 


with broad lateral wings for flotation in the air, or in 
some cases with a pulpy envelope, which flattens into a 
film. There seem to have been structures of both these 
kinds, though in the state of preservation of these curious 
seeds it is extremely difficult to distinguish them. In the 
first case they must have been intended for dissemination 
by the wind, like the seeds of spruces. In‘the latter case 
they may have been disseminated like the fruits of taxine 
trees by the agency of animals, though what these were 
it would be difficult to guess. These trees had very great 
reproductive power, since they produced numerous seeds, 
not singly or a few together, as in modern yews, but in 
long spikes or catkins bearing many seeds (Fig. 59). 

It is to be observed that the Cordaites, or the Cor- 
daiting, as they have been called, as a family,* constitute 
another of those intermediate groups with which we have 
already become familiar. On the one hand they approach 
closely to the broader-leaved yews like Gingko, Phyllo- 
cladus, and Podocarpus, and, on the other hand, they 
have affinities with Cycadacer, and even with Sigillariz. 
They were beautiful and symmetrical trees, adding some- 
thing to the variety of the rather monotonous Paleo- 
zoic forests. They contributed also somewhat to the ac- 
cumulation of coal. I have found that some thin beds are 
almost entirely composed of their leaves, and the tissues 
of their wood are not infrequent in the mineral charcoal 
of the larger coal-seams. There is no evidence that their 
roots were of the stigmaroid type, though they evidently 
grew in the same swampy flats with the Sigillarie and 
Calamites. 

It may, perhaps, be well to say here that I believe 
there was a considerably.wide range of organisation in the 
Cordaitinz as well as in the Calamites and Sigillarie, and 
that it will eventually be found that there were three lines 


* Engler; Cordaitées of Renault. 


184 THE GEOLOGICAL HISTORY OF PLANTS. 


of connection between the higher cryptogams and the 
phenogams, one leading from the lycopods by the Sigil- 
larie, another leading by the Cordaites, and the third 
leading from the Equisetums by the Calamites. Still 
further back the characters afterward separated in the 
club-mosses, mare’s-tails, and ferns, were united in the 
Rhizocarps, ‘or, as some now, but I think somewhat un- 
reasonably, prefer to call them, the “‘heterosporous Fili- 
cine.” In the more modern world, all the connecting 
links have become extinct and the phenogams stand 
widely separated from the higher cryptogams. I do not 
make these remarks in a Darwinian sense, but merely to 
state what appear to be the lines of natural affinity and 
the links wanting to give unity to the system of nature. 
Of all the trees of the modern world, none are perhaps 
so widely distributed as the pines and their allies. On 
mountain-tops and within the Arctic zone, the last trees 
that can struggle against the unfavourable conditions of 
existence are the spruces and firs, and in the warm and 
moist islands of the tropics they seem equally at home 
with the tree-ferns and the palms. We have already seen 
that they are a very ancient family, and in the sandstones 
of the coal-formation their great trunks are frequently 
found, infiltrated with calcareous or silicious matter, and 
still retaining their structure in the greatest perfection 
(Fig. 60). So far as we know, the foliage of some of them 
which constitutes the genera Walchia and Araucarites of 
some authors (Figs. 60, 63) was not dissimilar from that 
of modern yews and spruces, though there is reason to 
believe that some others had broad, fern-like leaves like 
those of the gingko. None of them, so far as yet cer- 
tainly known, were cone-bearing trees, their fruit having 
probably been similar to that of the yews (Fig. 61). 
The minute structures of their stems are nearer to those 
of the conifers of the islands of the southern hemisphere 
than to that of those in our northern climes—a cor- 


THE CARBONIFEROUS FLORA. 185 


o 
eer 
anes 
ane 
FE awaal 
ch | rey 
nN 1 Bs | 
a y3 
My ap 
nn ah 
ry aa 
aa ag 
me Re 
Ly ea 
an oa 
aa an 
as ry 
nd fa 
a 
am 


Fie. 60.—Coniferous wood and foliage (Carboniferous). a, Araucarites 
gracilis, reduced. 3B, Dadoxylon Acadianum (radial), 90 diams. ; 
Bi (engental), 90 diams.; 8?, cell showing areolation, 250 diams. 
0, Dadoxylon materiarium (radial), 90 diams.; c! (tangential), 90 
diams.; 0, cell showing areolation, 250 diams. vp, Dadoxylon anti- 
quius (radial), 90 diams.; p' (tangential), 90 diams.; p?, cell showing 
areolation, 250° diams. 


136 THE GEOLOGICAL HISTORY OF PLANTS. 


relation, no doubt, to the equable climate of the period. 
There is not much evidence that they grew with the Si- 
gillarie in the true coal-swamps, though some specimens 
have been found in this association. It is more likely 
that they were in the main inland and upland trees, and 


13 eC 


Pal os 
4 lai; 


Wd i 


ih 


Pig. 61.—Trigonocarpum Tlookeri, Daw- 
son, from the coal-measures of Cape 
Breton. Probably the fruit of a Tax- Wel Vi 
ine tree, A, Broken speermen magni 
fied twice natural size. on, Section maenified: a, the testa: b, the tog 
men; ¢, the nucleus; d, the embryo. c, Portion of the surfaee of the 
inner coat more highly magnitied. 


that in consequence they are mostly known to us by 
drifted trunks borne by river inundations into the seas 
and estuaries. 

A remarkable fact in connection with them, and show- 
ing also the manner in which the most durable vegetable 
structures may perish by decay, is that, like the Cordaites, 
they had large piths with transverse partitions, a struct- 


THE CARBONIFEROUS FLORA, 137 


ure which, as I have already mentioned, appears on a 
minute scale in the twigs of the fir-tree, and that some- 
times casts of these piths in sandstone appear in a separate 
form, constituting what have been named Sfernbergie or 
Artisie. As Renault well remarks with reference to 
Cordaites, the existence of this chambered form of pith 
implies rapid elongation of the stem, so that the Cordaites 
and conifers of the coal-formation were probably quickly 
growing trees (Fig. 62). 

The same general statements may be made as to the 
coal-vegetation as in relation to that of the Erian. In 


Uy Wir —— 
ay, ne meat ART 


yg ern. 


Mt "TATA 
a 2 a 


Fie. 62.—Sternbergia pith of Dadovylon. a, Specimen (natural size), 
showing remains of wood at a, a. 8B, Junction of wood and pith, mag- 
nited. o, Cells of the wood of do., a, a; 6, medullary ray; ¢, areo- 
ation. 


the coal period we have found none of the higher ex- 
ogens, and there are only obscure and uncertain indica- 
tions of the presence of endogens, which we may reserve 
for a future chapter ; but gymnosperms abound and are 
highly characteristic. On the other hand, we have no 
mosses or lichens, and very few Algw, but a great num- 
ber of ferns and Lycopodiacee or club-mosses (Fig. 63). 
Thus, the coal-formation period is botanically a meeting- 
place of the lower pheenogams and the higher cryptogams, 
and presents many forms which, when imperfectly known, 
have puzzled botanists in regard to their position in one 
or other series. In the present world, the flora most akin 


138 THE GEOLOGICAL HISTORY OF PLANTS, 


to that of the coal period is that of warm, temperate re- 
gions in the southern hemisphere. It is not properly a 
tropical flora, nor is it the flora of a cold region, but 
rather indicative of a moist and equable climate. Still, 


Fie. 63.— Walchia imbricatula, 8. N., Permian, Prince Edward Island, 


we must bear in mind that we may often be mistaken in 
reasoning as to the temperature required by extinct 
species of plants, differing-from those now in existence. 
Further, we must not assume that the climatal conditions 
of the northern hemisphere were in the coal period at all 
similar to those which now prevail. As Sir Charles Lyell 
has shown, a less amount of land in the higher latitudes 
would greatly modify climates, and there is every reason 
to believe that in the coal period there was less land than 
now. Further, it has been shown by Tyndall that a very 
small additional amount of carbonic acid in the atmos- 
phere would, by obstructing the radiation of heat from 
the earth, produce almost the effect of a glass roof or con- 
servatory, extending over the whole world. Again, there 
is much in the structure of the leaves of the coal-plants, 
as well as in the vast amount of carbon which they ac- 
cumulated in the form of coal, and the characteristics of 
the animal life of the period, to indicate, on independent 


THE CARBONIFEROUS FLORA. 139 


grounds, that the carboniferous atmosphere differed from 
that of the present world in this way, or in the presence 
of more carbonic acid—a substance now existing in the 
very minute proportion of one thousandth of the whole— 
a quantity adapted to the present requirements of vege- 
table and animal life, but probably not to those of the 
coal period. 

_ Thus, if we inquire as to any analogous distribution of 
plants in the modern world, we find this only in the warm- 
er insular climates of the southern hemisphere, where 
ferns, lycopods, and pines appear under forms some- 
what akin to those of the Carboniferous, but mixed with 
other types, some of which are modern, others allied to 
those of the next succeeding geological ages of the Meso- 
zoic and Tertiary; and under these periods it will be 
more convenient to make comparisons. 

The readers of recent English popular works on geol- 
ogy will have observed the statement reiterated that a 
large proportion of the material of the great beds of bi- 
tuminous coal is composed of the spore-cases of lycopo- 
diaceous plants—a statement quite contrary to that re- 
sulting from my microscopical examinations of the coal 
of more than eighty coal-beds in Nova Scotia and Cape 
Breton, as stated in ‘“‘ Acadian Geology” (page 463), and 
more fully in my memoir of 1858 on the ‘‘ Structures in 
Coal,” * and that of 1866, on the “Conditions of Ac- 
cumulation of Coal.” + The reason of this mistake is, 
that an eminent English naturalist, happening to find in 
certain specimens of English coal a great quantity of re- 
mains of spores and spore-cases, though even in his speci- 
mens they constitute only a small portion of the mass, 
and being apparently unacquainted with what others had 
done in this field, wrote a popular article for the ‘‘ Con- 
temporary Review,” in which he extended an isolated and 


* “ Journal of the Geological Society,” vol. xv. + Ibid., vol. xxii. 


140 THE GEOLOGICAL HISTORY OF PLANTS. 


exceptional fact to all coals, and placed this supposed 
origin of coal in a light so brilliant and attractive that he 
has been followed by many recent writers. The fact is, 
as stated in ‘‘ Acadian Geology,” that trunks of Sigillarie 
and similar trees constitute a great part of the denser 
portion of the coal, and that the cortical tissues of these 
rather than thé wood remain as coal. But cortical or 
epidermal tissues in general, whether those of spore-cases 
or other parts of plants, are those which from their re- 
sistance to water-soakage and to decay, and from their 
highly carbonaceous character, are best suited to the pro- 
duction of coal. In point of fact, spore-cases, though 
often abundantly present, constitute only an infinitesimal 
part of the matter of the great coal-beds. In an article 
in “ The American Journal of Science,” which appeared 
shortly after that above referred to, I endeavoured to cor- 
rect this error, though apparently without effect in so far 
as the majority of British geological writers are con- 
cerned. From this article I have taken with little change 
the following passages, as it is of importance in theoretical 
geology that such mistakes, involving as they do the 
whole theory of coal accumulation, should not continue 
to pass current. The early part of the paper is occupied 
with facts as to the occurrence of spores and spore-cases as 
partial ingredients in coal. Its conclusions are as follows : 

It is not improbable that sporangites, or bodies re- 
sembling them, may be found in most coals; but it 
is most likely that their occurrence is accidental rather 
than essential to coal accumulation, and that they are 
more likely to have been abundant in shales and cannel 
coals, deposited in ponds or in shallow waters in the vi- 
cinity of lycopodiaceous forests, than in the swampy 
or peaty deposits which constitute the ordinary coals. 
It is to be observed, however, that the conspicuous ap- 
pearance which these bodies, and also the strips and 
fragments of epidermal tissue, which resemble them in 


THE CARBONIFEROUS FLORA. 141 


texture, present in slices of coal, may incline an observer, 
not having large experience in the examination of coals, 
to overrate their importance ; and this I think has been 
done by most microscopists, especially those who have 
confined their attention to slices prepared by the lapidary. 
One must also bear in mind the danger arising from mis- 
taking concretionary accumulations of bituminous matter 
for sporangia. In sections of the bituminous shales ac- 
companying the Devonian coal above mentioned, there 
are many rounded yellow spots, which on examination 
prove to be the spaces in the epidermis of Psilophyton 
through which the vessels passing to the leaves were 
emitted. To these considerations I would add the fol- 
lowing, condensed from the paper above referred to 
(p. 139), in which the whole question of the origin of 
coal is fully discussed :* 

1. The mineral charcoal or ‘ mother coal’ is obviously 
woody tissue and fibres of bark, the structure of the va- 
rieties of which, and the plants to which it probably be- 
longs, I have discussed in the paper above mentioned. 

2. The coarser layers of coal show under the micro- 
scope a confused mass of fragments of vegetable matter 
belonging to various descriptions of plants, and includ- 
ing, but not usually in large quantities, sporangites. 

8. The more brilliant layers of the coal are seen, 
when separated by thin lamine of clay, to have on their 
surfaces the markings of Sigillari@ and other trees, of 
which they evidently represent flattened specimens, or 
rather the bark of such specimens. Under the micro- 
scope, when their structures are preserved, these layers 
show cortical tissues more abundantly than any others. 

4. Some thin layers of coal consist mainly of flat- 
tened layers of leaves of Cordaites or Pychnophyllum. 

5. The Stigmaria underclays and the stumps of 


* See also “ Acadian Geology,” 2d ed., pp. 188, 461, 493. 
14 


142 THE GEOLOGICAL HISTORY OF PLANTS. 


Sigillaria in the coal-roofs ‘equally testify to the accu- 
mulation of coal by the growth of successive forests, more 
especially of Sigillarie. There is, on the other hand, no 
necessary connection of sporangite-beds with Stigmarian 
soils. Such beds are more likely to be accumulated in 
water, and consequently to constitute bituminous shales 
and cannels. : 

6. Lepidodendron and its allies, to which the spore- 
cases in question appear to belong, are evidently much 
less important to coal accumulation than Sigillaria, which 
cannot be affirmed to have produced spore-cases similar 
to those in question, even though the observation of 
Goldenberg as to their fruit can be relied on ; the ac- 
curacy of which, however, I am inclined to doubt. 

On the whole, then, while giving due credit to those 
who have advocated the spore-theory of coal, for directing 
attention to this curious and no doubt important constit- 
uent of mineral fuel, and admitting that I may possibly 
have given too little attention to it, I must maintain that 
sporangite-beds are exceptional among coals, and that 
cortical and woody matters are the most abundant ingre- 
dients in all the ordinary kinds; and to this I cannot 
think that the coals of England constitute an exception. 

It is to be observed, in conclusion, that the spore- 
cases of plants, in their indestructibility and richly car- 
bonaceous character, only partake of qualities common to 
most suberous and epidermal matters, as I have explained 
in the publications already referred to. Such epidermal 
and cortical substances are extremely rich in carbon and 
hydrogen, in this resembling bituminous coal. They are 
also very little liable to decay, and they resist more than 
other vegetable matters aqueous infiltration—properties 
which have caused them to remain unchanged, and to 
continue free from mineral additions more than other 
vegetable tissues. These qualities are well seen in the 
bark of our American white birch. It is no wonder that 


THE CARBONIFEROUS FLORA. 143 


materials of this kind should constitute considerable 
portions of such vegetable accumulations as the beds of 
coal, and that when present in large proportion they 
should afford richly bituminous beds. All this agrees 
with the fact, apparent on examination of the common 
coal, that the greater number of its purest layers consist 
of the flattened bark of Stgillarie and similar trees, just 
as any single flattened trunk embedded in shale becomes 
a layer of pure coal. It also agrees with the fact that 
other layers of coal, and also the cannels and earthy 
bitumens, appear under the microscope to consist of 
finely comminuted particles, principally of epidermal tis- 
sues, not only from the fruits and spore-cases of plants, 
but also from their leaves and stems. These considera- 
tions impress us, just as much as the abundance of spore- 
cases, with the immense amount of the vegetable matter 
which has perished during the accumulation of coal, in 
comparison with that which has been preserved. 

I am indebted to Dr. T. Sterry Hunt for the fol- 
lowing very valuable information, which at once places 
in a clear and precise light the chemical relations of 
epidermal tissue and spores with coal. Dr. Hunt says: 
“The outer bark of the cork-tree, and the cuticle of 
many if not all other plants, consists of a highly car- 
bonaceous matter, to which the name of suberin has been 
given. The spores of Lycopodium also approach to this 
substance in composition, as will be seen by the follow- 
ing, one of two analyses by Duconi,* along with which 
I give the theoretical composition of pure cellulose or 
woody fibre, according to Payen and Mitscherlich, and 
an analysis of the suberin of cork, from Quercus suber, 
from which the ash and 2°5 per cent of cellulose have 
been deducted. ft 


* Liebig and Kopp, “ Jahresbuch,” 1847-48, 
+ Gmelin, “ Handbook,” xv., 145, 


144 THE GEOLOGICAL HISTORY OF PLANTS, 


Cellulose. Cork. Lycopodium, 
CORDON ast. ela tecunsns cevect dimen nereie 44°44 65°73 64°80 
Hydrogen oe 6°17 8°33 8°73 
INT ETO BOD tacscerin neers mi enaie doe ane. soe 1°50 6°18 
ORY OT ciescairccte stein wvelbaks tea seineas ve 49°39 24°44 20°29 
Gta ica csridasvevtinnn cation wow ce 100-00 100-00 100-00 


‘This difference is not less striking when we reduce 
the above centesimal analyses to correspond with the 
formula of cellulose, C.,H.0., and represent cork and 
Lycopodium as containing twenty-four equivalents of 
carbon. For comparison I give the composition of speci- 
mens of peat, brown coal, lignite, and bituminous coal :* 


CelltlOse yuan wercnewe dere wseeae ssa CosH 20020 
Cotliseckenese see oustsno es coms oe CosH re Oers 
Lycopodium Sie 64 Ted GS See ee ew eae Cogs pts N Osis 
Peat (Vaux iow snceccs ees a ..osuee ames CogH azo Or0 
Brown coal (Schréther).............. CoH asi ors 
Lignite (Vaux)......2.cccceeeceeece CosHirvsOor'g 
Bituminous coal (Regnault)........... CoH 00 si4y 


“Tt will be seen from this comparison that, in ulti- 
mate composition, cork and Lycopodium are nearer to 
lignite than to woody fibre, and may be converted into 
coal with far less loss of carbon and hydrogen than the 
latter. They in fact approach closer in composition to 
resins and fats than to wood, and, moreover, like those 
substances repel water, with which they are not easily 
moistened, and thus are able to resist those atmospheric 
influences which effect the decay of woody tissue.” 

I would add to this only one further consideration. 
The nitrogen present in the Lycopodium spores, no doubt, 
belongs to the protoplasm contained in them, a substance 
which would soon perish by decay ; and subtracting this, 
the cell-walls of the spores and the walls of the spore- 


* “Canadian Naturalist,” vi., 253. 


THE CARBONIFEROUS FLORA. 145 


cases would be most suitable material for the production 
of bituminous coal. But this suitableness they share with 
the epidermal tissue of the scales of strobiles, and of the 
stems and leaves of ferns and lycopods, and, above all, 
with the thick, corky envelope of the stems of Sigillaria 
and similar trees, which, as I have elsewhere shown,* 
from its condition in the prostrate and erect trunks con- 
tained in the beds associated with coal, must have been 
highly carbonaceous and extremely enduring and im- 
permeable to water. In short, if, instead of ‘‘ spore-cases,” 
we read “‘epidermal tissues in general, including spore- 
cases,” all that has been affirmed regarding the latter will 
be strictly and literally true, and in accordance with the 
chemical composition, microscopical characters, and mode 
of occurrence of coal. It will also be in accordance with 
the following statement, from my paper on the “ Struct- 
ures in Coal,” published in 1859: 

“A single trunk of Sigillaria in an erect forest pre- 
sents an epitome of a coal-seam. Its roots represent the 
Stigmaria underclay; its bark the compact coal; its 
woody axis the mineral charcoal ; its fallen leaves (and 
fruits), with remains of herbaceous plants growing in its 
shade, mixed with a little earthy matter, the layers of 
coarse coal. The condition of the durable outer bark of 
erect trees concurs with the chemical theory of coal, in 
showing the especial suitableness of this kind of tissue for 
the production of the purer compact coals, It is also 
probable that the comparative impermeability of the bark 
to mineral infiltration is of importance in this respect, 
enabling this material to remain unaffected by causes 
which have filled those layers, consisting of herbaceous 
materials and decayed wood, with pyrites and other min- 
eral substances.” 


* “Vegetable Structures in Coal,” “ Journal of Geological Society,” 
xv., 626. “Conditions of Accumulation of Coal,” idid., xxii., 95. “ Aca- 
dian Geology,” 197, 464. 


‘4 
146 THE GEOLOGICAL HISTORY OF PLANTS. 


We need not go far in search of the uses of the coal 
vegetation, when we consider the fact that the greatest 
civilised nations are dependent on it for their fuel. With- 
out the coal of the Carboniferous period and the iron-ore 
which is one of the secondary consequences of coal ac- 
cumulation, just as bog-ores of iron occur in the subsoils 
of modern peats, it would have been impossible either to 
sustain great nations in comfort in the colder climates of 
the northern hemisphere or to carry on our arts and 
manufactures. The coal-formation yields to Great Brit- 
ian alone about one hundred and sixty million tons of 
coal annually, and the miners of the United States ex- 
tract mainly from the same formation nearly a hundred 
million tons, while the British colonies and dependen- 
cies produce about five million tons; and it is a re- 
markable fact that it is to the English race that the 
greatest supply of this buried power and heat and light 
has been given. 

The great forests of the coal period, while purifying 
the atmosphere of its excess of unwholesome carbonic 
acid, were storing up the light and heat of Paleozoic 
summers in a form in which they could be recovered in our 
human age, so that, independently of their uses to the 
animals which were their contemporaries, they are indis- 
pensable to the existence of civilised man. 

Nor can we hope soon to be able to dispense with the 
services of this accumulated store of fuel. The forests 
of to-day are altogether insufficient for the supply of our 
wants, and though we are beginning to apply water-power 
to the production of electricity, and though some promis- 
ing plans have been devised for the utilisation of the 
direct heat and light of the sun, we are sti]l quite as de- 
pendent as any of our predecessors on what has been done 
for us in the Paleozoic age. 

In the previous pages I have said little respecting the 
physical geography of the Carboniferous age ; but, as may 


THE CARBONIFEROUS FLORA. 147 


be inferred from the vegetation, this in the northern 
hemisphere presented a greater expanse of swampy flats 
little elevated above the sea than we find in any other pe- 
riod. As to the southern hemisphere, less is known, but 
the conditions of vegetation would seem to have been es- 
sentially the same. 

Taking the southern hemisphere as a whole, I have 
not seen any evidence of a Lower Devonian or Upper Si- 
lurian flora; but in South Africa and Australia there are 
remains of Upper Devonian or Lower Carboniferous 
plants. These were succeeded by a remarkable Upper 
Carboniferous-or Permian group, which spread itself all 
over India, Australia, and South Africa,* and contains 
some forms (Vertebraria, Phyllotheca, Glossopteris, &c.) 
not found in rocks of similar age in the northern hemi- 
sphere, so that, if the age of these beds has been correctly 
determined, the southern hemisphere was in advance in 
relation to some genera of plants. This, however, is to 
be expected when we consider that the Triassic and Ju- 
rassic flora of the north contains or consists of intruders 
from more southern sites. These beds are succeeded in 
India by others holding cycads, &c., of Upper Jurassic 
or Lower Cretaceous types (Rajmahal and Jabalpur 
groups). 

Blanford has shown that there is a very great similar- 
ity in this series. all over the Australian and Indian re- 
gion.t Hartt and Darby have in like manner distin- 
guished Devonian dnd Carboniferous forms in Brazil akin 
to those of the northern hemisphere. Thus the southern 
hemisphere would seem to have kept pace with the north- 
ern, and according to Blanford there is evidence there of 
cold conditions in the Permian, separating the Paleozoic 


*® Wyley, “Journal Geol. Society,” vol. xxiii., p. 172; Daintree, ibid., 
vol. xxviii.; also Clarke and McCoy. 
+ “Journal Geol. Society,” vol. xxxi, 


148 THE GEOLOGICAL HISTORY OF PLANTS. 


flora from that of the Mesozoic, in the same manner that 
Ramsay has supposed a similar period of cold to have done 
north of the equator. This would imply a very great 
change of climate, since we have evidence of the exten- 
sion of the Lower Carboniferous flora at least as far 
north as Spitzbergen. The upper coal-formation we 
cannot, however, trace nearly so far north; so that a 
gradual refrigeration may have been going on before 
the Permian. Thus in both hemispheres there was a 
general similarity in the later Paleozoic flora, and per- 
haps similar conditions leading to its extinction and to 
its replacement by that to be described in the next 
chapter. , 


NOTES TO CHAPTER IV. 


J. CHARACTERS AND CLASSIFICATION oF PaLzozoic PLANTS, 


In the space available in this work it would be impossible to 
enter fully into the classification of Paleozoic plants; but it may be 
well to notice some important points for the guidance of those who 
may desire to collect specimens; more especially as much uncer- 
tainty exists as to affinities and very contradictory statements are 
made. The statements below may be regarded as the results of 
actual observation and of the study of specimens 7m st¢u in the rocks, 
as well as in the cabinet and under the microscope. 


GYMNOSPERMEA, 


Family ContrFerz; Genus Dapoxyton, Endlicher; ARAUCARITES, 
Goeppert ; ARsUCARIOXYLON, Kraus. 


The trunks of this genus occur from the Middle Devonian to the 
Permian inclusive, as drift-logs calcified, silicified, or pyritised. The 
only foliage associated with them is of the type of Walchia and 
Araucarites—viz., slender branches with numerous small spiral acicu- 
lar leaves. Two of the coal-formation species, D. materiarum and 
another, had foliage of this type. That of the others is unknown. 
They are all distinct from the wood of Cordattes, for which see under 
that genus. 


THE CARBONIFEROUS FLORA. 149 


The following are North American species: 


Trunks. 
Dadoxylon Ouangondianum, Dn ..M. Erian..... ... Report, 1871.* 
Dy Halla, Dre... cece eee eee ec eees He © | shaveriisitreibte “ 
D, Newberryt, Di... cs ce eeee cues CS acidueleuatere 
D. Clarkit, Dn. (Cordeoxylon f)... i geemeuiaee Report, 1882. 
D. Acadianum, Dn.........0.00 Coal-formation Acadian Geol- 
and millstone ogy. 
prit. 
D. Materiarwm, Dn ......--..0+- Do. and Permo- ee 
Carb. 
D. (Paleoxylon) antiquius, Dn ...L, Carboniferous. ie 
D. annulatum, Dn ... 2... .. 0000 Coal-formation. es 
Ormoxylon Erianum, Dn ........ Brigny; ese esas se Report, 1871. 
Foliage. 
Araucarites gracilis, Dn.......... N. Coal-formation be 
and Permian, 
Walchia robusta, Dn...,.... ... Permian. vas oe 4 
W. imbricatula, Dn.........2006. Bs sacar 
ward Island. 


All of the above can be vouched for as good species based upon 
microscopic examination of a very large number of trunks from dif- 
ferent parts of North America. The three Erian species of Dadoxylon 
and D. antiqutus from the Lower Carboniferous have two or more 
tows of cells in the medullary rays. The last named has several 
rows, and is a true Palwoxylon allied to D. Withami of Great 
Britain. .D. materiarium is specially characteristic of the upper 
coal-formation and Permian, and to it must belong one or both of 
the species of foliage indicated above. D. Clarkii has very short, 
simple medullary rays of only a few cells superimposed, and has an 
inner cylinder of scalariform vessels, approaching in these points to 
Cordaites. Ormoxylon has a very peculiar articulated pith and 
simple medullary rays. 

Witham in 1833 described several Carboniferous species of pine- 

~ wood, under the generic name Pinites, separating under the name 
Pitus species which appeared to have-the discs-on the eell-walls 


* “Geological Survey of Canada: Fossil Plants of Erian and Upper 
Silurian Formations,” by J. W. Dawson. 


150 THE GEOLOGICAL HISTORY OF PLANTS. 


separate and in transverse lines, Witham’s name was changed by 
Goeppert to Araucarites, to indicate the similarity of these woods to 
Araucaria, Pinites being reserved for trees more closely allied to the 
ordinary pines. Endlicher, restricting Araucarites to foliage, etc., 
of Araucaria-like trees, gave the name Dadoxylon to the wood; and 
this, through Unger’s “Genera and Species,” has gained somewhat 
general acceptance. Endlicher also gave the name Pissadendron to 
the species which Witham had called Pitus; but Brongniart pro- 
posed the name Paleozxylon to include all the species with thick 
and complex medullary rays, whatever the arrangement of the discs. 
In Schimper’s new work Kraus substitutes Araucarioxylon for End- 
licher’s Dadoxylon, and includes under Pissadendrgn all the species 
placed by Brongniart in Paleoxylon. 

To understand all this confusion, it may be observed that the 
characters available in the determination of Paleozoic coniferous 
wood are chiefly the form and arrangement of the wood-cells, the 
character of the bordered pores or discs of their walls, and the form 
and composition of the medullary rays. 

The character on which Witham separated his genus Pitus from 
Pinites is, as I have ascertained by examination of slices of one of 
his original specimens kindly presented to me by Mr. Sanderson, of 
Edinburgh, dependent on state of preservation, the imperfectly pre- 
served discs or areolations of the walls of the fibre presenting the 
appearance of separate and distinct circles, while in other parts of 
the same specimens these discs are seen to be contiguous and to as- 
sume hexagonal forms, so that in this respect they do not really 
differ from the ordinary species of Dadoxylon. The true character 
for subdividing those species which are especially characteristic of 
the Carboniferous, is the composite structure of the medullary rays, 
which are thick and composed of several radial piles of cells placed 
side by side. This was the character employed by Brongniart in 
separating the genus Palwoxylon, though he might with convenience 
have retained Witham’s name, merely transferring to the genus the 
species of Witham’s Pinttes which have complex medullary rays. 
The Erian rocks present the greatest variety of types, and Palewoxylon 
is especially characteristic of the Lower Carboniferous, while species 
of Dadozylon with two rows of bordered pores and simple medullary 
rays are especially plentiful in the upper coal-formation and Permo- 
Carboniferous. 

The following table will clearly show the distinctive characters 
and relations of the genera in question, as held by the several authors 
above referred to: 


THE CARBONIFEROUS FLORA. 151 


Wood of Palaozoic Conifers. 


‘Woody fibres, Medullary raya and pith, Generic names. Geological age. 
No discs. One or two series | Aporoxylon, Unger. Devonian 
of cells. (Erian). 


Pitua, W; Middle and 
Sas Palaebaylon, B Brongni- Lower Car- 
cells, Piessdendron, End- end Derot 
Pith Sternbergian. licher. + nian. 


‘ ‘Araucarites, Goeppert| 
Discs in one se- | Simple, or of one Upper Carbo- 
ries contigu-|_ row of ce Dadoxylon, igndlie er.) “niferous and 


os or in sev- Pith Sternbergian. ae Permian, 

need. ar- Eb ty Seren Ormoxylon,* Dn. Devonian. 
eset ae shea Dadozylon (cibetaiiee: Devonian. 
Medullary ra lon),+ D 


sequent, , Simple, 


* Type O. Erianum, Dn., “ Report on Canadian Plants,” 1871. 
+ Type D. Clarkii, Dn., ‘“‘ Report on Canadian Plants,’ 1882. This may be 
wood of Cordaites, to which it approaches very closely. 


Family Corpaites, Genus Corparres, Brongniart. 


Trunks marked by transverse scars of attachment of bases of 
leaves; leaves broad, with many parallel veins, and attached by a 
broad base; pistillate and staminate catkins of the nature of An- 
tholithes. Fruit winged or pulpy, of the kind known as Cardio- 
carpum. Stem with a Sternbergia pith, usually large, surrounded by 
a ring of pseudo-scalariform vessels, and with a cylinder usually 
narrow, of woody wedges, with bordered pores in one or more series, 
and with simple medullary rays. 

From specimens kindly presented to me by Prof. Renault, I 
have been able to ascertain that the stems of some at least of these 
plants (Hucordaites) are distinct in structure from all the species of 
Dadoxylon, above mentioned, except D. Clarkit, of the Erian. They 
may be regarded as intermediate between those of conifers and 
cycads, which is indeed the probable position of these remarkable 
plants, 

Grand Eury has divided the Cordaites into sub-genera, as fol- 
lows: 

1. Hucordaites—Leaves spatulate, obovate, elliptical, or lan- 


152 THE GEOLOGICAL HISTORY OF PLANTS. 


ceolate, sessile, entire, with rounded apices and of leathery con- 
sistency. The leaves are from twenty to ninety centimetres in 
length. The nerves are either equally or unequally strong. 

2. Dorycordaites.—Leaves lanceolate, with sharp points; nerves 
numerous, fine, and equal in strength. The leaves attain a length 
of from forty to fifty centimetres. 

3. Poacordattes.—Leaves narrow, linear, entire, blunt at the 
point, with nerves nearly equally strong. The leaves are as much 
as forty centimetres in length. 

To these Renault and Zeiller have added a fourth group, Scuto- 
cordaites, 

Genus STERNBERGLA. 

This is merely a provisional genus intended to receive casts of 
the pith cylinders of various fossil trees. Their special peculiarity 
is that, as in the modern Cecropia peltata, and some species of Ficus, 
the pith consists of transverse dense partitions which, on the elonga- 
tion of the internodes, become separated from each other, so as to 
produce a chambered pith cavity, the cast of which shows transverse 
furrows. The young twigs of the modern Adies balsamifera pre- 
sent a similar structure on a minute scale. I have ascertained and 
described such pith-cylinders in large stems of Dadoxylon Ouangon- 
dianum, and D. materiartum. ‘They occur also in the stems of 
Cordattes and probably of Sigillarie. I have discussed these curi- 
ous fossils at length in “ Acadian Geology” and in the “Journal of 
the Geological Society of London,” 1860. The following summary 
is from the last-mentioned paper: 

a. As Prof. Williamson and the writer have shown, many of 
the Sternbergia piths belong to coniferous trees of the genus Da- 
doxylon. 

6, A few specimens present multiporous tissue, of the type of 
Dictyoxylon, a plant of unknown affinities, and which, according to 
Williamson, has a Sternbergia pith. 

ce. Other examples show w true scalariform tissue, comparable 
with that of Lepidodendron or Sigillaria, but of finer texture. Corda 
has shown that plants of the type of the former genus (his Loma- 
tophlotos) had Sternbergia piths. Some plants of this group are by 
external characters loosely reckoned by botanists as ribless Sigularie 
(Clathraria); but I believe that they are not related even ordinally 
to that genus. 

d, Many Carboniferous Sternbergie show structures identical 
with those described above as occurring in Cordattes, and also in 
some of the trees ordinarily reckoned as Sigiilaria., 


THE CARBONIFEROUS FLORA. 153 


Genus CaRDIOCARPUM. 


I have found at least eight species of these fruits in the Erian 
and Carboniferous of New Brunswick and Nova Scotia, all of which 
are evidently fruits of gymnospermous trees. They agree in hav- 
ing a dense coaly nucleus of appreciable thickness, even in the 
flattened specimens, and surrounded by a thin and veinless wing or 
margin. They have thus precisely the appearance of samaras of 
many existing forest-trees, some of which they also resemble in the 
outline of the margin, except that the wings of samaras are usually 
veiny. The character of the nucleus, and the occasional appearance 
in it of marks possibly representing cotyledons or embryos, forbids 
the supposition that they are spore-cases. They must have been 
fruits of phenogams. Whether they were winged fruits or seeds, 
or fruits with a pulpy envelope like those of cyecads and some 
conifers,-may be considered less certain. The riot infrequent dis- 
tortion of the margin is an argument in favour of the latter view, 
though this may also be supposed to have occurred in samaras par- 
tially decayed. On the other hand, their being always apparently 
flattened in one plane, and the nucleus being seldom, if ever, found ° 
denuded of its margin, are arguments in favour of their having been 
winged nutlets or seeds; Until recently I had regarded the latter 
view as more probable, and so stated the matter in the second edi- 
tion of “ Acadian Geology.” I have, however, lately arrived at the 
conclusion that the Cardiocarpa of the type of C. cornutum were 
gymnospermous seeds, having two cotyledons embedded in an albu- 
men and covered with a strong membranous or woody tegmen sur- 
rounded by a fleshy outer coat, and that the notch at the apex rep- 
resents the foramen or micropyle of the ovule. The structure was 
indeed very similar to that of the seeds of Taxus and of Salisburia, 
With respect to some of the other species, however, especially those 
with very broad margins, it still appears likely that they were winged. 

The Cardiocarpa were borne in racemes or groups, and it seems 
certain that some of them at least are the seeds of Cordaites. The 
association of some of them and of those of the next genus with 
Sigillarie is so constant that I cannot doubt that some of them 
belong to plants of that genus, or possibly to taxine conifers. The 
great number of distinct species of these seeds, as compared with 
that of known trees which could have produced them, is very re- 
markable. 

Genus TRIGONOCARPUM. 

These are large angled nuts contained in a thick envelope, and 

showing internal structures resembling those of the seeds of modern 
15 


154 THE GEOLOGICAL HISTORY OF PLANTS. 


Taxinew, There are numerous species, as well as allied seeds re- 
ferred to the provisional genera Rhabdocarpus and Carpolithes. 
In Trigonocarpwm Hookert I have described the internal structure 
of one of those seeds, and many fine examples from the coal-field of 
St. Etienne, in France, have been described by Brongniart, so that 
their internal structure is very well known. 


Genus ANTHOLITHES. 


This is also a provisional genus, to include spikes of floral 
organs, some of which are known to have belonged to Cordaittes, 
others probably to Sigillaric. 


Or Uncertain AFFINITIES. 
Family SiguuaRacez, 


Under this name paleobotanists have included a great’ number 
of trees of the Carboniferous system, all of which are characterised 
by broad leaf-sears, with three vascular scars, and usually arranged 
in vertical rows, and by elongated three-nerved leaves, and roots of 
the stigmaria type—that is, with rounded pits, marking the attach- 
ment of rootlets spirally arranged. These trees, however, collected 
in the genus Stgillaria by arbitrary characters, which pass into 
those of the Lepidodendroid trees, have been involved in almost inex- 
tricable confusion, to disentangle which it will be necessary to con- 
sider: 1. The external characters of Sigillaria, and trees confounded 
with them. 2. Subdivision of Stgillarie by external markings, 3. 
The microscopic character of their stems. 4, What is known of 
their foliage and fruit. 


1. Characters of Sigillaroid and Lepidedendroid Trunks, 


It may be premised that the modes of determination in fossil 
botany are necessarily different from those employed in recent bot- 
any. The paleobotanist must have recourse to characters derived 
from the leaves, the scars left by their fall, and the internal struct- 
ures of the stem. These parts, held in little esteem by botanists in 
describing modern plants, and much neglected by them, must hold 
the first place in the regard of the fossil botanist, whereas the fructi- 
fication, seldom preserved, and generally obscure, is of compara- 
tively little service. It is to be remarked also that in such general- 
ised plants as those of the Paleozoic, remarkable rather for the de- 
velopment of the vegetative than of the reproductive organs, the 
former rise in importance as compared with their value in the study 
of modern plants. 


THE CARBONIFEROUS FLORA, 155 


In Sigillarie, Lepidodendra, &c., the following surfaces of the 
stem may be presented to our inspection : 

1, The outer surface of the epidermis without its leaves, but 
with the leaf-bases and leaf-scars more or less perfectly preserved. 
On this surface we may recognise: (1) Cellular swellings or pro- 
jections of the bark to which the leaves are attached. These may be 
called leaf-bases, and they are sometimes very prominent. (2) The 
actual mark of the attachment of the leaf situated in the most 
prominent part of the leaf-base. This is the leaf-scar. (8) In the 
leaf-scar when well preserved we can see one or more minute punct- 
ures or prominences which are the points where the vascular bundles 
passing to the leaf found exit. These are the vascular scars. 

When the leaves are attached, the leaf-scars and vascular scars 
cannot be seen, but the leaf-bases can be made out. Hence it is 
important, if possible, to secure specimens with and without the 
leaves. In flattened specimens the leaf-bases are often distorted by 
pressure and marked with furrows which must not be mistaken for 
true structural characters. The leaf-bases, which are in relief on the 
outer surface of the stem, of course appear as depressions on the 
mould in the containing rock, in which the markings often appear 
much more distinctly than on the plant itself. 

2. The outer surface of the epidermis may have been removed or 
may be destroyed by the coarseness of the containing rock. In this 
case the leaf-bases are usually preserved on the surface of the outer 
or corky bark, but the leaf-scars and vascular scars have disappeared. 
This gives that condition of Lepidodendroid trees to which the name 
Knorria has been applied. When plants are in this state careful in- 
spection may sometimes discover traces of the leaf-scars on portions 
of the stem, and thus enable the Knorria to be connected with the 
species to which it belongs. 

8. The outer or corky bark may be removed, exposing the sur- 
face of the inner or fibrous and cellular bark, which in the plants in 
question is usually of great thickness, In this case neither the leaf- 
bases nor the scars are seen, but punctures or little furrows or ridges 
appear where the vascular bundles entered the inner bark. Speci- 
mens in this state are usually said to be decorticated, though only 
the outer bark is removed. It is often difficult to determine plants 
in this condition, unless some portion of the stem can be found still 
retaining the bark; but when care is taken in collecting, it will not 
infrequently be found that the true outer surface can be recovered 
from the containing rock, especially if a coaly layer representing the 
outer bark intervenes between this and the inner impression. Speci- 


156 TIE GEOLOGICAL HISTORY OF PLANTS. 


mens of this kind, taken alone, have been referred to the genera 
Knorria, Bothrodendron, and Halonia. 

4, In some cases, though not frequently, the outer surface of the 
ligneous cylinder is preserved. It almost invariably presents a 
regularly striated or irregularly wrinkled appearance, depending 
upon the vertical woody wedges, or the positions of the medullary 
rays or vascular bundles. Specimens of this kind constituted some 
of the Endogenites of the older botanists, and the genus Schizoden- 
dron of Hichwald appears to include some of them, Many of them 
have also been incorrectly referred to Calamites. 

5. In some cases the cast of the medullary cylinder or pith may 
alone be preserved. This may be nearly smooth or slightly marked 
by vertical striew, but more usually presents a transverse striation, 
and not infrequently the transverse constrictions and septa charac- 
teristic of the genus Sternbergia. Loose Sternbergie afford little 
means of connecting them with the species to which they belong, 
except by the microscopic examination of the shreds of the ligneous 
cylinder which often cling to them.* 

These facts being premised, the following general statements 
may be made respecting some of the more common Paleozoic genera, 
referring, however, principally to the perfect markings as seen on 
the epidermis: : 

Sigillaria.—Leaf-bases hexagonal or elongated, or confluent on 
a vertical ridge. Leaf-scars hexagonal or shield-shaped. Vascular 
scars three, the two lateral larger than the central. This last char- 
acter is constant, depending on the fact that the leaves of Sigillaria 
have two or more vascular bundles. All so-called Sigillart@ having 
the central vascular scar largest, or only one vascular bundle, should 
be rejected from this genus. In young branches of branching Sigdl- 
larie the leaf-scars sometimes appear to be spiral, but in the older 
stems they form vertical rows; interrupted, however, by transverse 
rows or bands of fruzt-scars, each with a single large central vascular 
scar, and which have borne the organs of fructification. Arthro- 
eaulis of McCoy is founded on this peculiarity. 

Syringodendron.—Differs from Sigillaria in the leaf-scars, which 
are circular and with w single vascular bundle. It isa matter of 
doubt whether these plants were of higher rank than Sigillaria 
tending toward the pines, or of lower rank tending toward Cyclo- 
stigma. Their leaf-bases form vertical ridges. : 

Lepidodendron.—Leaf-bases rhombic, oval, or lanceolate, moder- 


* See my paper, “Journal of Geological Society,” vol. xxvii. 


THE CARBONIFEROUS FLORA. 157 


ately prominent. Leaf-scars rhombic or sometimes shield-shaped or 
heart-shaped, in the middle or upper part of the leaf-base. Vascular 
scars three—the middle one always largest and corresponding to the 
single nerve of the leaf; the lateral ones sometimes obsolete, 

In older stems three modes of growth are observed. In some 
species the expansion of the bark obliterates the leaf-bases and 
causes the leaf-scars to appear separated by wide spaces of more or 
less wrinkled bark, which at length becomes longitudinally furrowed 
and simulates the ribbed character of Sigillaria. In others the leaf- 
bases grow in size as the trunk expands, so that.even in large trunks 
they are contiguous though much larger than those on the branches, 
In others the outer bark, hardening at an early age, is incapable of 
either of the above changes, and merely becomes cleft into deep fur- 
rows in the old trunks, 

Lepidophioios.—Leaf-bases transverse and prominent — often 
very much so. Leaf-scars transversely rhombic or oval with three 
vascular scars, the central largest. Leaves very long and one- 
nerved. Large strobiles or branchlets borne in two ranks or spirally 
on the sides of the stem, and leaving large, round scars (cone-scars), 
often with radiating impressions of the basal row of scales. 

_Species with long or drooping leaf-bases have been included in 
Lepidophioios and Lomatophioios. Species with short leaf-bases and, 
cone-scars in two rows have been called Ulodendron, and some of 
them have been included in Sigillaria (sub-genus Clathraria). De- 
corticated stems are Bothrodendron and Halonia. Some of the 
species approach near to the last genus, especially to the Lepidoden- 
dra with rhombic leaf-bases like Z. tetragonum. 

Cyclostigma. — Leaf-bases undeveloped. Leaf-scars circular or 
horseshoe-shaped,.small, with a central vascular scar. In old trunks 
of Cyclostigma the leaf-scars become widely separated, and some- 
times appear in vertical rows. Young branches of Lepidodendron 
sometimes have the leaf-scars similar to those of Cyclostigma. 

Leptophleum. — Leaf-bases flat, rhombic; leaf-scars obsolete; 
vascular scar single, central. The last two genera are character- 
istically Devonian. 

In contradistinction from the trees above mentioned, the follow- 
ing general statements may be made respecting other groups: 

In conifers the leaf-bases are usually elongated vertically, often 
scaly.in appearance, and with the leaf-scar terminal and round, oval, 
or rhombic, and with a single well-marked vascular scar. 

In Calamites, Calamodendron, and Asterophyllites the scars of 
the branchlets or leaves are circular or oval, with only a single vas- 


158 THE GEOLOGICAL HISTORY OF PLANTS. 


cular scar, and situated in verticils at the top of well-marked nodes 
of the stem. 

In tree-ferns the leaf-bases are large and usually without a dis- 
tinct articulating surface. The vascular bundles are numerous, 
.Protopteris has rounded leaf-scars with a large horseshoe-shaped 
bundle of vessels above and small bundles below. Caulopteris has 
large elliptic or oval leaf-scars with vascular scars disposed con- 
centrically. Paleopteris,* of Geinitz, has the leaf-scars transversely 
oval and the vascular bundles confluent in a transverse band with an 
appendage or outlying bundle below. Stemmatopteris has leaf- 
scars similar to those of Caulopteris, but the vascular bundles united 
into a horseshoe-shaped band. 


2. Subdivision of Sigillarie in Accordance with their Markings, 


The following groups may be defined in this way; but, being 
based on one character only, they are of course in all probability far 
from natural: 

1. Sigillaria, Brongniart. Type, Sigillaria reniformis, Bron- 
. gniart, or S. Brounit, Dawson.—Stem with broad ribs, usually much 
broader than the usually oval or elliptical tripunctate areoles, but 
disappearing at base, owing to expansion of the stem. Leaves nar- 
row, long, three-nerved. . 

2. Rhytidolepis, Sternberg. Type, S. scutellata, Brongniart.— 
Ribs narrow, and often transversely striate. Areoles large, hexag- 
onal or shield-shaped, tripunctate. Leaves as in last group. Rings 
of rounded scars on the stems and branches mark attachment of 
fruit. It is possible that some of the smaller stems of this group 
may be branches of trees of group first. 

3. Syringodendron, Sternberg. Type, S. organum, L. and H., 
S. oculata, Brongniart.—Stems ribbed; areoles small and round, 
and apparently with a single scar, or three closely approximated. 
These are rare, and liable to be confounded with decorticated ex- 
amples of other groups; but I have some specimens which unques- 
tionably represent the external surface. 

4, Favularia, Sternberg. Type, Sigillaria elegans of Brongni- 
art.—Leaf-bases hexagonal, or in young branches elliptical, in vertical 
rows, but without distinct ribs, except in old or decorticated stems. 
Fruit borne in verticils on the branches bearing transverse rows of 
rounded scars. Leaves somewhat broad and longitudinally striate. 


* This name, preoccupied by Geinitz, has been inadvertently misap- 
plied to the Devonian ferns of the genus Archwopieris. 


THE CARBONIFEROUS FLORA. 159 


5. Letoderma, Goldenberg. Type, S. Sydnensis, Dawson. — 
Ribs obsolete. Cortical and ligneous surfaces striate. Vascular 
sears double, elongate longitudinally, and alike on cortical and inner 
surfaces, Areoles in rows and distinct; stigmaria-roots striate, with 
sinall and distinct areoles. 

6. Clathraria, Brongniart. Type, S. Menardi, Brongniart.— 
Areoles hexagonal, not in distinct rows, but having a spiral appear- 
ance. Some of the plants usually referred to this group are probably 
branches of Favularia. Others are evidently fragments of plants 
of the genus Lepidophloios. 


3. Internal Structures of Sigillaria-Stems. 


I long ago pointed out, on the evidence of the external markings 
and mode of growth, that the stems of Sigillari# must have been 
exogenous, and this conclusion has now been fully confirmed by the 
microscopic-researches of Williamson, not only in the case of Sigil- 
larie, but of Lepidodendra and Calamodendra as well. Coufining 
myself to my own observations, three types of Sigillaria are known 
to me by their internal structures, though I cannot certainly corre- 
late all of these with the external markings referred to above. 

1. Diploxylon, in which the stem consists of a small internal 
axis surrounded by a very thick inner bark and a dense outer cortex. 
A fine example from the South Joggins is thus described : * 

“The axis of the stem is about six centimetres in its greatest 
diameter, and consists of a central pith-cylinder and two concen- 
tric. coats of scalariform tissue. The pith-cylinder is replaced 
by sandstone, and is about one centimetre in diameter. The inner 
cylinder of scalariform tissue is perfectly continuous, not radiated, 
and about one millimetre in thickness. Its vessels are somewhat 
crushed, but have been of large diameter. Its outer surface, which 
readily separates from that of the outer cylinder, is striated longi- 
tudinally. The outer cylinder, which constitutes by much the 
largest part of the whole, is also composed of scalariform tissue; 
but this is radially arranged, with the individual cells quadrangular 
in cross-section, The cross-bars are similar on all the sides and 
usually simple and straight, but sometimes branching or slightly 
reticulated. The wall intervening between the bars has extremely 
delicate longitudinal waving lines of ligneous lining, in the manner 
first described by Williamson as occurring in the scalariform tissue 
of certain Lepidodendra. A few small radiating spaces, partially 


* “ Journal of the Geological Society of London,” November, 1877. 


160 THE GEOLOGICAL HISTORY OF PLANTS. 


occupied with pyrites, obscurely represent the medullary rays, which 
must have been very feebly developed. The radiating bundles 
passing to the leaves run nearly horizontally; but their structure 
is very imperfectly preserved. The stem being old and probably 
long deprived of its leaves, they may have been partially disorganised 
before it was fossilised. The outer surface of the axis is striated 
longitudinally, and in some places marked with impressions of tort- 
uous fibres, apparently those of the inner bark. In the cross-sec- 
tion, where weathered, it shows concentric rings; but under the 
microscope these appear rather as bands of compressed tissue than 
as proper lines of growth. They are about twenty in number. This 
tree has an erect, ribbed trunk, twelve feet in height and fifteen 
inches in diameter, swelling to about two feet at the base. 

2. Favularia Type.—tThis has been well described by Brongniart 
and by Renault,* and differs from the above chiefly in the fact that 
the outer exogenous woody zone is composed of reticulated instead 
of scalariform tissue, and the inner zone is of the peculiar form 
which I have characterised as psendo-scalariform. 

3. Sigillaria Proper.—This I have illustrated in my paper in 
the “Journal of the Geological Society” for May, 1871, and it ap- 
pears to represent the highest and most perfect type of the larger 
ribbed Sigillaria. This structure I have described as follows, bas- 
ing my description on a very fine axis found in an erect stem, and 
on the fragments of the woody axis found in the bases of other erect 
stems: 

a. A dense cellular outer bark, usually in the state of compact 
coal—but when its structure is preserved, showing a tissue of thick- 
ened parenchymatous cells. 

&. A very thick inner bark, which has usually in great part 
perished, or been converted into coal, but which, in old trunks, con- 
tained a large quantity of prosenchymatous tissue, very tough and 
of great durability. This “bast-tissue” is comparable with that of 
the inner bark of modern conifers, and constitutes much of the min- 
eral charcoal of the coal-seams. 

ce, An outer ligneous cylinder, composed of wood-cells, either 
with a single row of large bordered pores,} in the manner of pines 


* “ Botanique Fossile,” Paris, 1881. 

+ These are the same with the wood-cells elsewhere called discigerous 
tissue, and to which I have applied the terms uniporous and multiporous. 
The markings on the walls are caused by an unlined portion of the cell- 
wall placed in # disk or depression, and this often surrounded by an 


THE CARBONIFEROUS FLORA. 161 


and cycads, or with two, three, or four rows of such pores sometimes 
inscribed in hexagonal areoles in the manner of Dadoxylon. This 
woody cylinder is traversed by medullary rays, which are short, and 
composed of few rows of cells superimposed. It is also traversed by 
oblique radiating bundles of pseudo-scalariform tissue proceeding to 
the leaves. In some Sigtllari@ this outer cylinder was itself in part 
composed of pseudo-scalariform tissue, as in Brongniart’s specimen 
of S. elegans ; and in others its place may have been taken by mul- 
tiporous tissue, as in a case above referred to; but I have no reason 
to believe that cither of these variations occurred in the typical 
tibbed species now in question. The woody fibres of the outer 
cylinder may be distinguished most readily from those of conifers, 
as already mentioned, by the thinness of their walls, and the more 
irregular distribution of the pores, Additional characters are fur- 
nished by the medullary rays and the radiating bundles of scalari- 
form tissue when these can be observed. 

d, An inner cylinder of pseudo-scalariform tissue. I have 
adopted the term pseudo-scalariform for this tissue, from the con- 
viction that it is not homologous with the scalariform ducts of ferns 
and other acrogens, but that it is merely a modification of the dis- 
cigerous wood-cells, with pores elongated transversely, and sometimes 
separated by thickened bars, corresponding to the hexagonal areo- 
lation of the ordinary wood-cells. A similar tissue exists in cycads, 
and is a substitute for the spiral vessels existing in ordinary ex- 
ogens. : 

e. A large medulla, or pith, consisting of a hollow cylinder of 
cellular tissue, from which proceed numerous thin diaphragms to- 
wards the centre of the stem. 

These structures of the highest type of Sigillaria are on the 
one hand scarcely advanced beyond those of Calamopitus, as de- 
scribed by Williamson, and on the other approach to those of 

' Cordattes, as seen in specimens presented to me by Renault. 

Finally, as to the fruit of Sigillarie, I have no new facts to 
offer. The strobiles or spikes associated with these trees have been 
variously described as gymnospermous (Renault) or cryptogamous 
(Goldenberg and Williamson). I have never seen them in place. 
Two considerations, however, have always weighed with me in refer- 
ence to this subject. One is the constant abundance of Trigonocarpa 


hexagonal rim of thickened wall; but in all cases these structures are 
less pronounced than in Dadozylon, and less regular in the walls of the 
same cell, as well as in different layers of the tissues of the axis. 


162 THE GEOLOGICAL HISTORY OF PLANTS. 


and Cardiocarpa in the soil of the Sigillaria forests, as I have studied 
this at the South Joggins. The other is that the rings of fruit-scars 
on the branches of Sigillaria are homologous with leaf-scars, not 
with branches, and therefore should have borne single carpels and 
not cones or spikes of inflorescence. These are merely suggestions, 
but I have no doubt they will be vindicated by future discoveries, 
which will, I have no doubt, show that in the family Stgillariacee 
we have really two families, one possibly of gymnospermous rank, 
or at least: approaching to this, the other allied to the Lepidodendra, 


CRYPTOGAMIA, 
(Acrogenes.) 
Family LeriwopEnDREzZ; Genus LEPIDODENDRON, Sternberg. 


These are arboreal Lycopods having linear one-nerved leaves, 
stems branching dichotomously, and with ovate or rhombic leaf-bases 
bearing rhombic leaf-scars, often very prominent. The fruit is in 
scaly strobiles, terminal or lateral, and there are usually, if not 
always, macrospores and microspores in each strobile. The young 
branches and stems have a central pith, a cylinder of scalariform 
tubes sending out ascending bundles to the leaves through a thick 
cellular and fibrous inner bark, and externally a dense cortex conflu- 
ent with or consisting of the leaf-bases, Older stems havea second or 
outer layer of scalariform fibres in wedges with medullary rays, and 
strengthening the stem by a true exogenous growth, much as in the 
Diploxylon type of Sigillaria. The development of this exogenous 
cylinder is different in amount and rate in different species.* This 
different development of the exogenous axis is accompanied with 
appropriate external appearances in the stems, and the changes 
which take place in their markings. These are of three kinds, In 
some species the areoles, at first close together, become, in the pro- 
cess of the expansion of the stem, separated by intervening spaces of 
bark ina perfectly regular manner; so that in old stems, while widely 
separated, they still retain their arrangement, while in young stems 
they are quite close to one another. This is the case in L. corruga- 
tum, In other species the leaf-scars or bases increase in size in the 
old stems, still retaining their forms and their contiguity to each 
other. This is the case in L. undulatum, and generally in those 
Lepidodendra which have large leaf-bases. In these species the 


* See “ Memoirs of Dr. Williamson,” in “ Philosophical Transactions,” 
for ample details. 


THE CARBONIFEROUS FLORA. 163 


continued vitality of the bark is shown by the occasional production 
of lateral strobiles on large branches, in the manner of the modern 
red pine of America. In other species the areoles neither increase in 
size nor become regularly separated by growth of the intervening 
bark; but in old stems the bark splits into deep furrows, between 
which may be seen portions of bark still retaining the areoles in 
their original dimensions and arrangement. This is the case with 
LL. Pictoense. This cracking of the bark no doubt occurs in very old 
trunks of the first two types, but not at all to the same extent. 

As a type of Lepidodendron, I may describe one of the oldest 
Carboniferous species characteristic of the Lower Carboniferous in 
America, and corresponding to L. Veltheimianum of Europe. 

LEpmopENDRON Corrucatum, Dawson.—(See Fig. 438, supra.) 
“Quarterly Journal of Geological Society,” vol. xv. ; “‘ Acadian Geol- 
ogy,” page 451. 

Habit of Growth—Somewhat slender, with long branches and 
long, slender leaves having a tendency to become horizontal or 
drooping. 

Markings of Stem.—Leaf-bases disposed in quineunx or spirally, 
elongate, ovate, acute at both ends, but more acute and slightly 
oblique. at the lower end; most prominent in the upper third, and 
with a slight vertical ridge. Leaf-scars small, rounded, and showing 
only a single punctiform vascular scar. The leaf-scar on the outer 
surface is in the upper third of the base; but the obliquity of the 
vascular bundle causes it to be nearly central on the inside of the 
epidermis. In young succulent shoots the leaf-scars are contiguous 
and round as in Cyclostigma, without distinct leaf-bases. In this 
state it-closely resembles Z. Olivieri, Kichwald.* 

In the ordinary young branches the leaf-scars are contiguous, 
and closely resemble those of .L. elegans, Brongt. (Fig. 43 C). As the 
branches increase in diameter the leaf-scars slightly enlarge and 
sometimes assume a verticillate appearance (Fig. 43 D). As they 
still further enlarge they become separated by gradually increasing 
spaces of bark, marked with many waving strie or wrinkles (Fig. 
431,N). At the base of old stems the bark assumes a generally 
wrinkled appearance without distinct scars. 

Knorria or Decorticated States.—Of these there is a great variety, 
depending on the state of preservation, and the particular longi- 
tudinal ridges. Fig. 43 D shows a form in which the vascular bun- 
dles appear as cylindrical truncate projections, Other forms show 


* Lethea Rossica, Plate Y, Figs. 12, 13. 


164 THE GEOLOGICAL HISTORY OF PLANTS. 


the leaf-bases prominent, or have an appearance of longitudinal rib- 
bing produced by the expansion of the bark. 

Structure of Stem—tThis is not perfectly preserved in any of 
my specimens, but one flattened specimen shows a central medulla 
with a narrow ring of scalariform vessels surrounding it, and consti- 
tuting the woody axis. The structure is thus similar to that of L, 
Harcourtii, which I regard as probably the same with the closely 
allied European species L. Veltheimianum. 

Leaves.—These are narrow, one-nerved, curving somewhat rap- 
idly outward (Figs. 48, B, C, D). They vary from one to two inches 
in length. 

Roots.—I have not seen these actually attached, but they occur 
very abundantly in the underclays of some erect forests of these 
plants at Horton Bluff, and are of the character of Stigmarie (Figs. 
30, 81). In some of the underclays the long, flattened rootlets are ex- 
cessively abundant, and show the mark of a central vascular bundle. 

Fructification.—Cones terminal, short, with many small, acute 
imbricate scales, Spore-cases globular, smooth (Fig. 43 C). On 
the surface of some shales and sandstones at Horton there are innu- 
merable round spore-cases of this tree about the size of mustard-seed 
(Fig. 48 F). Large slabs are sometimes covered with these, and thin 
layers of shale are filled with flattened specimens, 

This is the characteristic species of the Lower Carboniferous coal- 
measures, occurring in great profusion at Horton Bluff and its 
vicinity, also at Sneid’s Mills near Windsor, Noel and Five-Mile 
River, at Norton Creek and elsewhere in New Brunswick (Matthew’s 
collection), and at Antigonish (Honeyman’s collection). 

I have received from the lowest Carboniferous beds of Ohio speci- 
mens of this species.* According to Rogers and Lesquereux similar 
forms occur in the Vespertine of Pennsylvania and in the Lower 
Carboniferous of Illinois. L. Veltheimianum of western Europe 
and L. glincanwm of Russia are closely allied Lower Carboniferous 
species.t+ 

A very different type is furnished by a new species from the 
middle coal-formation of Clifton, New Brunswick. 

LEPIDODENDRON CLIFTONENSE, Dawson.— Habit of Growth.— 
Robust, with thick branches, and leaves several inches in length. 
Terminal branches becoming slender, with shorter leaves, 


* “ Journal of Geological Society,” November, 1862, p. 313. 
+ For comparisons of these see “Report on Plants of Lower Carbon- 
iferous of Canada,” p. 21. 


THE CARBONIFEROUS FLORA. 165 


Markings of Stem.—Leaf-bases long oval, pointed at ends, en- 
larging with growth of stem. lLeaf-scars central, rhombic, trans- 
verse. 

Leaves,—One-nerved, acutely pointed, from four inches in length 
on the larger branches to one inch or less on the branchlets. 

Fructification.—Cones large, cylindrical or long oval, with large 
scales of trigonal form, and not elongated but lying close to the sur- 
face. Borne on lateral, slender branchlets, with short leaves, 


Genus LeripopHioros, Sternberg; ULopenpRon, L. and H.; 
Lomatopstoios, Corda. 


Lepidophloios.—Under this generic name, established by Stern- 
berg, I include those lycopodiaceous trees of the coal-measures 
which have thick branches, transversely elongated leaf-scars, each 
with three vascular points and placed on elevated or scale-like pro- 
tuberances, long one-nerved leaves, and large lateral strobiles in ver- 
tical rows or spirally disposed. Their structure resembles that of 
Lepidodendron, consisting of a Sterndergia pith, a slender axis of 
large scalariform vessels, giving off from its surface bundles of 
smaller vessels to the leaves, a very thick cellular bark, and a thin 
dense outer bark, having some elongated cells or bast-tissue on its 
inner side. In these trees the exogenous outer cylinder is less de- 
veloped than in the Lepidodendra, and is sometimes wanting in 
stems or branches of some thickness. 

Regarding ZL. laricinum of Sternberg as the type of the genus, 
and taking in connection with this the species described by Golden- 
berg, and my own observations on numerous specimens found in 
Nova Scotia, 1 have no doubt that Lomatophloios crassicaulis of 
Corda, and other species of that genus described by Goldenberg, 
Ulodendron and Bothrodendron of Lindley, Lepidodendron ornatis- 
simum of Brongniart, and Halonia punctata of Geinitz, all belong 
to this genus, and differ from each other only in conditions of 
growth and preservation. Several of the species of Lepidostrobus 
and Lepidophyilum also belong to Lepidophiotos. 

The species of Lepidophioios are readily distinguished from 
Lepidodendron by the form of the areoles, and by the round sears on 
the stem, which usually mark the insertion of the large strobiles, 
though in barren stems they may also have produced branches; still, 
the fact of my finding the strobiles im sitw in one instance, the ac- 
curate resemblance which the scars bear to those left by the cones of 
the red pine when borne on thick branches, and the actual impres- 
sions of the radiating scales in some specimens, leave no doubt in my 

16 


166 THE GEOLOGICAL HISTORY OF PLANTS. 


mind that they are usually the marks of cones; and the great size of 
the cones of Lepidophloios accords with this conclusion. 

The species of Lepidophiotos are numerous, and individuals are 
quite abundant in the coal formation, especially toward its upper 
part. Their flattened bark is frequent in the coal-beds and their 
roofs, affording a thin layer of pure coal, which sometimes shows the 
peculiar laminated or scaly character of the bark when other charac- 
ters are almost entirely obliterated. The leaves also are nearly as 
abundant as those of Sigzlaria in the coal-shales. They can readily 
be distinguished by their strong, angular mid-rib. 

The markings of Lepidophiotos may easily be mistaken for those 
of the Clathraria type of Sigillaria, When the stem only is seen, 
they can be distinguished by the length of the leaf-bases in Lepi- 
dophloios, and by the dominant central vascular scar; also by the 
one-nerved and ribbed leaves. Where the large, round marks of the 
cones are present, these are an infallible guide, never being present 
in Sigillaria. As the cones grew on the upper sides of the branches, 
the impression of the lower side often shows no cone-scars, or only 
two lateral rows, whereas on the upper side of the same branch they 
appear spirally arranged. I may describe as an example— 

Lepidophloios Acadianus, Dawson. Leaf-bases broadly rhom- 
bic, or in old stems regularly rhombic, prominent, ascending, termi- 
nated by very broad rhombic scars having a central point and two 
lateral obscure points. Outer bark laminated or scaly. Surface of 
inner bark with single points or depressions. Leaves long, linear, 
with a strong keel on one side, five inches or more in length, Cone- 
scars sparsely scattered on thick branches, either in two rows or 
spirally, both modes being sometimes seen on the same branch. 
Scalariform axis scarcely an inch in diameter in a stem five inches 
thick. Fruit, an ovate strobile with numerous acute scales covering 
small globular spore-cases. This species is closely allied to Uloden- 
dron majus and Lepidophloios laricinus, and presents numerous 
varieties of marking. Coal-formation, Nova Scotia. 


Family Caramirem; Genus CALAMiItes, Suckow. 


The plants of this genus are unquestionably allied to the mod- 
ern Hquisetacew, but excel these so much in variety of form and 
structure, and are so capricious in their states of preservation, and so 
liable to be mistaken for parts of plants generically different, that 
they have given rise to much controversy. The following considera- 
tions will enable us to arrive at some certainty. 

The genus Calamites was originally founded in the longitu- 


™ 


THE CARBONIFEROUS FLORA. 167 


dinally ribbed and jointed stems so frequent in: the: coal-formation, 
and of which the common C. Suckovtt is a typical form. The most 
perfect of these stems represent the outer surface immediately within 
the epidermis, in which case transverse lines or constrictions 
mark the nodes, and at the nodes there are rounded spots, some- 
times indicating radial processes of the pith, first described by 
Williamson ; in other cases, the attachment’ of branchlets, or in some 
specimens both. But some specimens show the outer surface of the 
epidermis, in which case the transverse nodal lines are usually in- 
visible, though the scars of branchlets may appear. In still other 
examples the whole of the outer tissues have perished, and the so- 
called Calamite is a cast of the interior of the stem, showing merely 
longitudinal ribbing and transverse nodal constrictions. In study- 
ing these plants in situ in the erect Calamite brakes of the coal- 
formation of Nova Scotia, one soon becomes familiar with these ap- 
pearances, but they are evidently unknown to the majority of palao- 
botanists, though described in detail more than twenty years ago. 

When the outer surface is preserved it is sometimes seen to bear 
verticils of long needle-like leaves (C. Cistiz), or of branchlets with 
secondary whorls of similar leaves (C. Suckovti and C. undulatus). 
No Calamite known to me bears broad one-nerved leaves like those 
of Asterophyliites and Annularia, though the larger stems of these 
plants have been described as Calamites, and theterm Calamocladus 
has been used to include both groups. The base of the Calamite 
stem usually terminates in a blunt point, and may be attached to a 
rhizome, or several stems may bud out from each other in a group or 
stool. The roots are long and cylindrical, sometimes branching. 
The fruit consists of spikes of spore-cases, borne in whorls and sub- 
tended by linear floral leaves. To these strobiles the name Calamo- 
stachys has been given. 

Williamson has shown that the stem of Calamites consists of a 
central pith or cavity of large size surrounded by a cylinder con- 
sisting of alternate wedges of woody and cellular matter, with ver- 
tical canals at the inner sides of the wedges, and slender medullary 
rays. The thick cellular wedges intervening between the. woody 
wedges he calls primary medullary rays; the smaller medullary 
rays in the wedges, secondary medullary rays. There is thus a 
highly complex exogenous stem based on the same principle with 
the stem of a common Hguisetum, but with much greater strength 
and complexity. 

Williamson has also shown that there are different sly pe of 
these stems, More especially he refers to the three following: 


168 THE GEOLOGICAL HISTORY OF PLANTS. 


(a) Calamites proper, which has the woody wedges of scalari- 
form or barred tissue with thin medullary rays, and the thick pri- 
mary medullary rays are cellular. 

(0) Calamopitus has reticulated or multiporous tissue in the 
woody wedges with medullary rays, and the primary medullary 
wedges are composed of elongated cells. 

(c) Calamodendron has the woody wedges of barred tissue as in 
a, with medullary rays, but has the intervening medullary wedges 
of an elongated tissue approaching to woody fibre, and also with 
medullary rays. 

To these I would adda fourth type, which I have described, from 
the coal-formation of Nova Scotia,* 

(d@) Eucalamodendron differs from Calamodendron in having 
true bordered pores or pseudo-scalariform slit-pored tissue, and cor- 
responds to the highest type of calamitean stem. 

I would also add that under a and 0 there are some species in 
which the woody cylinder is very thin in comparison to the size of 
the stem. In cand d the woody cylinder is thick and massive, and 
the stems are often large and nodose. 

As an example of an ordinary Calamite in which the external 
surface and foliage are preserved, I may quote the following from 
my report on the “ Flora of the Lower Carboniferous and Millstone 
Grit,” 1873: 

Catamites Unpunatvs, Brongniart.—This species is stated by 
Brongniart to be distinguished from the C. Suckovti, the character- 
istic Calamite of the middle coal-formation, by its undulated ribs 
marked with peculiar cellular reticulation. He suggests that it may 
be merely a variety of C. Suckovit, an opinion in which Schimper 
coincides; but since I have received large additional collections from 
Mr. Elder, containing not only the stems and branches, but also the 
leaves and rhizomes, I am constrained to regard it as a distinct 
though closely allied species. 

The rhizomata are slender, being from one to two inches in 
diameter, and perfcctly flattened. They are beautifully covered with 
a cellular reticulation on the thin bark, and show occasional round 
areoles marking the points of exit of the rootlets. I have long been 
familiar with irregular flattened stems thus reticulate, but have only 
recently been able to connect them with this species of Calamite. 

The main stems present a very thin carbonaceous bark reticu- 
lated like the rhizomes, They have flat, broad ribs separated by deep 


*“ Quarterly Journal of the Geological Society,” 1871, 


THE CARBONIFEROUS FLORA. 169 


and narrow furrows, and undulated in « remarkable manner even 
when the stems are flattened. This undulation is, however, perhapsan 
indication of vertical pressure while the plant was living, as it seems 
to have had an unusually thin and feeble cortical layer, and the un- 
dulations are apparently best developed in the lower part of the stem. 
At the nodes the ribs are often narrowed and gathered together, 
especially in the vicinity of the rounded radiating marks which ap- 
pear to indicate the points of insertion of the branches. At the top 
of each rib we have the usual rounded areole, probably marking the 
insertion of a primary branchlet. 

The branches have slender ribs and distant nodes, from which 
spring secondary branchlets in whorls, these bearing in turn small 
whorls of acicular leaflets much curved upward, and which are ap- 
parently round in cross section and delicately striate. They are 
much shorter than the leaves of Calamites Suckovit, and are less 
dense and less curved than those of C. nodosus, which [ believe to be 
the two most closely allied species. 

* Lesquereux notices this species as characteristic of the lower part 
of the Carboniferous in Arkansas. 

Tt will be observed that I regard the striated and ribbed stems not 
as internal axes, but as representing the outer surface of the plants. 
This was certainly the case with the present species and with C. 
Suckovit and C. nodosus. Other species, and especially those which 
belonged to Calamodendron, no doubt had a smooth or irregularly 
wrinkled external bark; but this gives no good ground for the man- 
ner in which some writers on this subject confound Calamites with 
Calamodendra, and both with Asterophyllites and Sphenophyllum. 
With this no one who has studied these plants, rooted in their native 
soils, and with their appendages still attached, can for a moment 
sympathise. One of the earliest geological studies of the writer was 
a bed of these erect Calamites, which he showed to Sir C. Lyell in 
1844, and described in the “ Proceedings of the Geological Society ” 
in 1851, illustrating the habit of growth as actually seen well ex- 
posed. in a sandstone cliff. Abundant opportunities of verifying 
the conclusions formed at that time have since occurred, the results 
of which have been summed up in the figures in Acadian Geology, 
which, though they have been treated by some botanists as merely 
restorations, are in reality representations of facts actually observed. 

On these subjects, without entering into details, and referring 
for these to the elaborate discussions of Schimper, Williamson, and 
McNab, and to my paper on the subject, “Journal of the Geological 
Society,” vol. xxvii, p. 54, I may remark : 


170 TIE GEOLOGICAL HISTORY OF PLANTS. 


1. That the aérial stems of ordinary Calamites had a thin cortical 
layer, with lacunz and fibrous bundles and multiporous vessels—the 
whole not differing much from the structure of modern Equiseta. 

2. Certain arborescent forms, perhaps allied to the true Calamites, 
as well as possibly the old underground stems of ordinary species,* 
assumed a thick-walled character in which the tissues resembled the 
wedges of an exogen, and abundance of pseudo-scalariform fibres were 
developed, while the ribbing of the external surface became obsolete 
or was replaced by a mere irregular wrinkling. 

8. Sufficient discrimination has not been exercised in separating 
casts of the internal cavities of Calamites and Calamodendron from 
those representing other surfaces and the proper external surface. 

4, There is no excuse for attributing to Calamites the foliage of 
Annularia, Asterophyllites, and Sphenophyllum, since these leaves 
have not been found attached to true Calamite stems, and since the 
structure of the stems of Asterophyllites as described by Williamson, 
and that of Sphenophyllum as described by the writer,} are essen- 
tially different from those of Calamites. 

5. As the species above described indicates, good external char- 
acters can be found for establishing species of this genus, and these 
species are of value as marks of geological age. 


Genus ARCHAOCALAMITES, Sternberg. 


This genus has been established to include certain Calamites of 
the Devonian and Lower Carboniferous, in which the furrows on the 
stem do not altérnate at the nodes or joints, and the leaves in one 
species at least bifurcate. C. radiatus, Brongniart, is the typical 
species. In North America it occurs in the Erian, probably as low 
as the Middle Erian. In Europe it has so far been recognised in the 
Lower Carboniferous only. I have, however, seen stems from alleged 
Devonian beds in Devonshire which may have belonged to this species, 


Family ASTEROPHYLLITEZ; Genus ASTEROPHYLLITES, Brongniart. 


Stems ribbed and jointed like the Calamites, but with inflated 
nodes and a stout internal woody cylinder, which has been described 
by Williamson. Fyrom the joints proceeded whorls of leaves or of 
branchlets, bearing leaves which differed from those of Calamites in 
their having a distinct middle rib or vein. The fructification con- 


* Williamson, “Transactions of the Royal Society.” McNab, in 
“ Proceedings of the Edinburgh Botanical Society.” 
+ “Journal of the Geological Society,” 1866. 


THE CARBONIFEROUS FLORA. 171 


sisted of long slender cones or spikes, having whorls of scales bear- 
ing the spore-cases. Some authors speak of Asterophyllites as only 
branches and leaves of Calamites; but though at first sight the re- 
semblance is great, a close inspection shows that the leaves of As- 
terophyllites have a true midrib, which is wanting in Calamites. 

Genus ANNULARIA—It is perhaps questionable whether these 
plants should be separated from Asterophyllites. The distinction is 
that they produce branches in pairs, and that their whorls of leaves 
are one-sided and usually broader than those of Asterophyllites, and 
united into a ring at their insertion on the stem. One little species, 
A. sphenophylloides, is very widely distributed. 

PinnuLaRia—a provisional genus—includes slender roots or stems 
branching in a pinnate manner, and somewhat irregularly. They 
are very abundant in the coal shales, and were probably not inde- 
pendent plants, but aquatic roots belonging to some of the plants 
last mentioned. The probability of this is farther increased by their 
resemblance in miniature to the roots of Calamites, They are always 
flattened, but seem originally to have been round, with a slender 
thread-like*axis of scalariform vessels, enclosed in a soft, smooth, 
cellular bark, 


Family RuwocarPes; Genus SPHENOPHYLLUM,. 


Leaves in whorls, wedge-shaped, with forking veins. Fructi- 
fication on spikes, with verticils of sporocarps. These plants are 
by some regarded as allied to the Calamitee and Asterophyllitee, by 
others as a high grade of Rhizocarps of the type of Marsilia. The 
stem had a star-shaped central bundle of scalariform or reticulato- 
scalariform vessels. 


Genus SporaNneiTEs. (Sporocarpon, Williamson.) 


Under this name we may provisionally include those rounded 
spherical bodies found in the coal and its accompanying beds, and 
also in the Erian, which may be regarded as Macrospores or Sporo- 
carps of Protosalvinia, or other Rhizocarpean plants akin to those de- 
scribed above in Chap.er III, which see for description. 

Genus PRotosaLvinta.—Under this we include sporocarps allied 
to those of Salvinia, as described in Chapter IIT. 


Family Fruices. 


Under this head I shall merely refer to a few groups of special 
interest, and to the provisional arrangement adopted for the fronds 
of ferns when destitute of fructification, 


172 THE GEOLOGICAL HISTORY OF PLANTS. 


The external appearances of trunks of tree-ferns have been al- 
ready referred to. 

With respect to tree ferns, the oldest. known examples are those 
from the Middle Devonian of New York and Ohio, which I have de- 
scribed in the “Journal of the Geological Society,” 1871 and 1881. 
As these are of some interest, I have reproduced their descriptions 
in a note appended to Chapter III, which see. 

The other forms most frequently occurring in the Carboniferous 
are Caulopteris, Palewopteris, and Megaphyton.* Stems showing 
merely masses of aérial roots are known by the name Psaronius. 

With reference to the classification of Paleozoic ferns, this has 
hitherto been quite arbitrary, being based on mere form and vena- 
tion of fronds, but much advance has recently been made in the 
knowledge of their fructification, warranting. a more definite at- 
tempt at classification. The following are provisional genera usu- 
ally adopted : 

1. Cyclopteris, Brongniart.—Leaflets more or less rounded or 
wedge-shaped, without midrib, the nerves spreading from the point 
of attachment. This group includes a great: variety of fronds evi- 
dently of different genera, were their fructification known ; and some 
of them probably portions of fronds, nite other parts of which may 
be in the next genus. 

2. -Neuropteris, Brongniart.—Fronds pinnate, and with the 
leaflets narrowed at_the base; midrib often not distinct, and disap- 
pearing toward the apex. Nervures equal, and rising at an acute 
angle. Ferns of this type are among the most abundant in the coal- 
formation. 

3. Odontopteris, Brongniart.—In these the frond is pinnate, and 
the leaflets are attached by their whole base, with the nerves either 
proceeding wholly from the base, or in part from an indistinct mid- 
rib, which soon divides into nervures. 

4, Dictyopteris, Gutbier.—This is a beautiful style of fern, with 
leaflets resembling those of Veuropter?s, but the veins arranged in a 
network of oval spaces. Only a few species are known in the coal- 
formation. 

5. Lonchopteris, Brongniart.—Ferns with netted veins like the 
above, but with a distinct midrib, and the leaflets attached by the 
whole base. Of this, also, we can boast but few species, 

6. Sphenopteris, Brongniart.—These are elegant ferns, very nu- 
merous in species, and most difficult to discriminate. Their most 


* See my “ Acadian Geology,” also below. 


THE CARBONIFEROUS FLORA. 173 


distinctive characters are leaflets narrowed at the base, often lobed, 
and with nervures dividing in a pinnate manner from the base. 

%. Phyllopteris, Brongniart.—These are pinnate, with long lan- 
ceolate pinnules, having a strong and well-defined midrib, and 
nerves proceeding from it very obliquely, and dividing as they pro- 
ceed toward the margin. The ferns of this genus are for the most 
part found in formations more recent than the Carboniferous; but I 
have referred to it, with some doubt, one of our species. 

8. Alethopteris, Brongniart.—This genus includes many of the 
most common coal-formation ferns, especially the ubiquitous .A. Zon- 
chitica, which seems to have been the common brake of the coal- 
formation, corresponding to Pteris aguilina in modern Europe and 
America. These are brake-like ferns, pinnate, with leaflets often 
long and narrow, decurrent on the petiole, adherent by their whole 
base, and united at base to each other. The midrib is continuous to 
the point, and the nervures run off from it nearly at right angles. 
In some of these ferns the fructification is known to have been mar- 
ginal, as in Preris. 

9. Pecopteris, Brongniart.—This genus is intermediate between 
the last and Neuwropteris. The leaflets are attached by the whole 
base, but not usually attached to each other; the midrib, though 
slender, attains to the summit; the nervures are given off less ob- 
liquely than in Neuropteris, This genus includes a large number of 
our most common fossil ferns. 

10. Beinertia, Goeppert.—A genus established by Goeppert for a 
curious Pecopteris-like fern, with flexuous branching oblique ner- 
vures becoming parallel to the edge of the frond. 

11. Hymenophyllites, Goeppert.—These are ferns similar to 
Sphenopteris, but divided at the margin into one-nerved lobes, in the 
manner of the modern genus Hymenophyllum, 

12. Paleopteris, Geinitz.—This is a genus formed to include cer- 
tain trunks of tree-ferns with oval transverse scars of leaves. 

18. Caulopteris, Lindley and Hutton.—Is another genus of fossil 
trunks of tree-ferns, but with elongate scars of leaves. 

14, Psaronius, Cotta.—Includes other trunks of tree-ferns with 
alternate scars or thick scales, and ordinarily with many aérial roots 
grouped round them, as in some modern tree-ferns. 

15. Megaphyton, Artis——Includes trunks of tree-ferns which 
bore their fronds, which were of great size, in two rows, one on each 
side of the stem. These were very peculiar trees, less like modern 
ferns than any of the others. My reasons for regarding them as 
ferns are stated in the following extract from a recent paper: 


174 THE GEOLOGICAL HISTORY OF PLANTS. 


“Their thick stems, marked with linear scars and having two 
rows of large depressed areoles on the sides, suggest no affinities to 
any known plants. They are usually ranked with Lepidodendron 
and Ulodendron, but sometimes, and probably with greater reason, 
are regarded as allied to tree-ferns. At the Joggins w very fine 
species (If. magnificum) has been found, and at Sydney u smaller 
species (1. hwmile); ‘but both are rare and not well preserved. If 
the large scars bore cones and the smaller bore leaves, then, as Bron- 
guiart remarks, the plant would much resemble Lepidophiotos, in 
which the cone-scars are thus sometimes distichous. But the scars 
are not round and marked with radiating scales as in Lepidophloios ; 
they are reniform or oval, and resemble those of tree-ferns, for which 
reason they may be regarded as more probably leaf-scars; and in 
that case the smaller linear scars would indicate ramenta, or small 
aérial roots. Further, the plant described by Corda as Zippea dis- 
ticha is evidently a Megaphyton, and the structure of that species is 
plainly that of a tree-fern of somewhat peculiar type. On these 
grounds I incline to the opinion of Geinitz that these curious trees 
were allied to ferns, and bore two rows of large fronds, the trunks 
being covered with coarse hairs or small aérial roots. At one time I 
was disposed to suspect that they may bave crept along the ground; 
but a specimen from Sydney shows the leaf-stalks proceeding from 
the stem at an angle so acute that the stem must, I think, have been 
erect. From the appearance of the scars it is probable that only a 
pair of fronds were borne at one time at the top of the stem; and, if 
these were broad and spreading, it would be a very graceful plant. 
To what extent plants of this type contributed to the accumulation 
of coal I have no means of ascertaining, their tissues in the state of 
coal not being distinguishable from those of ferns and Lyco- 
podiacee.” 

16. For descriptions of the genus Archwopieris and other Erian 
ferns, see Chapter IIT. 


CHAPTER V. 
THE FLORA OF THE EARLY MESOZOIC. 


Great physical changes occurred at the close of the 
Carboniferous age. The thick beds of sediment that had 
been accumulating in long lines along the primitive con- 
tinents had weighed down the earth’s crust. Slow sub- 
sidence had been proceeding from this cause in the coal- 
formation period, and at its close vast wrinklings occurred, 
only surpassed by those of the old Laurentian time. 
Hence in the Appalachian region of America we have the 
Carboniferous beds thrown into abrupt folds, their shales 
converted into hard slates, their sandstones into quartzite 
and their coals into anthracite, and all this before the 
deposition of the Triassic Red Sandstones which consti- 
tute the earliest deposit of the great succeeding Mesozoic 
period. In like manner the coal-fields of Wales and 
elsewhere in western Europe have suffered similar treat- 
ment, and apparently at the same time. 

This folding is, however, on both sides of the Atlantic 
limited to a band on the margin of the continents, and to 
certain interior lines of pressure, while in the middle, as 
in Ohio and Illinois in America, and in the great interior 
plains of Europe, the coal-beds are undisturbed and un- 
altered. In connection with this we have an entire 
change in the physical character of the deposits, a great 
elevation of the borders of the continents, and probably 
a considerable deepening of the seas, leading to the estab- 
lishment of general geographical conditions which still 
remain, though they have been temporarily modified by 
subsequent subsidences and re-elevations. 


176 THE GEOLOGICAL HISTORY OF PLANTS. 


Along with this a great change was in progress in 
vegetable and animal life. The flora and fauna of the 
Palxozoic gradually die out in the Permian and are re- 
placed in the succeeding Trias by those of the Mesozoic 
time. Throughout the Permian, however, the remains 
of the coal-formation flora continue to exist, and some 
forms, as the Calamites, even seem to gain in importance, 
as do also certain types of coniferous trees. The Triassic, 
as well as the Permian, was marked by physical disturb- 
ances, more especially by great volcanic eruptions dis- 
charging vast beds and dykes of lava and layers of volcanic 
ash and agglomerate. This was the case more especially 
along the margins of the Atlantic, and probably also on 
those of the Pacific. The volcanic sheets and dykes as- 
sociated with the Red Sandstones of Nova Scotia, Con- 
necticut, and New Jersey are evidences of this. 

At the close of the Permian and beginning of the 
Trias, in the midst of this transition time of physical 
disturbance, appear the great reptilian forms character- 
istic of the age of reptiles, and the earliest precursors of 
the mammals, and at this time the old Carboniferous 
forms of plants finally pass away, to be replaced by a 
flora scarcely more advanced, though different, and con- 
sisting of pines, cycads, and ferns, with gigantic equiseta, 
which are the successors of the genus Calamites, a genus 
which still survives in the early Trias. Of these groups 
the conifers, the ferns, and the equiseta are already famil- 
jar to us, and, in so far as they are concerned, a botanist 
who had studied the flora of the Carboniferous would 
have found himself at home in the succeeding period. 
The cycads are a new introduction. The whole, how- 
ever, come within the limits of the cryptogams and the 
gymnosperms, so that here we have no advance.* 


* Fontaine’s “ Early Mesozoic Flora of Virginia” gives a very good 
summary of this flora in America. 


THE FLORA OF THE EARLY MESOZOIC. ‘177 


As we ascend, however, in the Mesozoic, we find new 
and higher types. Even within the Jurassic epoch, the 
next in succession to the Trias, there are clear indica- 
tions of the presence of the endogens, in species allied to 


the screw-pines and grasses; and the palms appear a 

little later, while a few exogenous trees have left their 

remains in the Lower Cretaceous, and in the Middle and 

Upper Cretaceous these higher plants come in abund- 

antly and in generic forms still extant, so that the dawn 

of the modern flora belongs to the Middle and Upper 
17 


178 THE GEOLOGICAL HISTORY OF PLANTS. 


Cretaceous. It will thus be convenient to confine our- 
selves in this chapter to the flora of the earlier Mesozoic. 
Passing over for the present the cryptogamous plants 
already familiar in older deposits, we may notice the new 
features of gymnospermous and phenogamous life, as they 
present themselves in this earlier part of the great rep- 
tilian age, and as they extended themselves with remark- 
able uniformity in this period over all parts of the world. 
For it is a remarkable fact that, if we place together in 
our collections fossil plants of this period from Australia, 
India, China, Siberia, Europe, or even from Greenland, 
we find wonderfully little difference in their aspect. This 
uniformity we have already seen prevailed in the Palxo- 
zoic flora; and it is perhaps equally marked in that of 
the Mesozoic. Still we must bear in mind that some 
of the plants of these periods, as the ferns and pines, 
for example, are still 
world-wide in their 
distribution; but this 
does not apply to oth- 
ers, more especially 
the cycads (Fig. 65). 
The cycads consti- 
tute a singular and ex- 
ceptional type in the 
modern world, and 
are limited at present 
to the warmer cli- 
mates, though very 
generally distributed 
Fra. 65.—Pod: ites lanceolatus, Sternb. in these, as they OC- 
SS acidosis cur in Africa, India, 

Japan, Australia, Mexico, Florida, and the West Indies. 
In the Mesozoic age, however, they were world-wide in 
their distribution, and are found as far north as Green- 
land, though most of the species found in the Cretaceous 


THE FLORA OF THE EARLY MESOZOIC. 179 


of that country are of small size, and may have been of 
low growth, so that they may have been protected by the 
snows of winter. The cycads have usually simple or un- 
branching stems, pinnate leaves borne in a crown at top, 
and fruits which, though somewhat various in structure 
and arrangement, are all of the simpler form of gymno- 
spermous type. The stems are exogenous in structure, 
but with slender wood and thick bark, and barred tissue, 
or properly as tissue intermediate between this and the 
disc-bearing fibres of the pines. 

Though the cycads have a considerable range of or- 
ganisation and of fructification, and though some points 
in reference to the latter might assign them a higher 
place, on the whole they seem to occupy a lower position 
than the conifers or the cordaitez of the Carboniferous. 
In the Carboniferous some of the fern-like leaves assigned 
to the genus Noeggerathia have been shown by Stur and 
Weiss to have been gymnosperms, probably allied to 
cycads, of which they may be regarded at least as pre- 
cursors. Thus the cycadean type does not really consti- 
tute an advance in grade of organisation in the Mesozoic, 
any further than that, in the period now in question, it 
becomes much more developed in number and variety of 
forms. But the conifers would seem to have had preced- 
ence of it for a long time in the Paleozoic, and it replaces 
in the Mesozoic the Cordaites, which in many respects 
excelled it in complexity. 

The greater part of the cycads of the Mesozoic age 
would seem to have had short stems and to have consti- 
tuted the undergrowth of woods in which conifers at- 
tained to greater height. An interesting case of this is 
the celebiated dirt-bed of the quarries of the Isle of Port- 
land, long ago described by Dean Buckland. In this 
fossil soil trunks of pines, which must have attained to 
great height, are interspersed with the short, thick stems 
of cycads, of the genus named Cycadoidea by Buckland, 


180 THE GEOLOGICAL HISTORY OF PLANTS. 


and which from their appearance are called “fossil 
birds’ nests” by the quarrymen. Some, however, must 
have attained a considerable height so as to resemble 
palms. 

The cycads, with their simple, thick trunks, usually 
marked with rhombic scars, and bearing broad spreading 
crowns of large, elegantly formed pinnate leaves, must 
have formed a prominent part of the vegetation of the 
northern hemisphere during the whole of the Mesozoic 
period. A botanist, had there been such a person at the 
time, would have found this to be the case everywhere 
from the equator to Spitzbergen, and probably in the 
southern hemisphere as well, and this throughout all the 
long periods from the Early Trias to the Middle Cre- 
taceous. In a paper published in the “ Linnean Trans- 
actions” for 1868, Dr. Carruthers enumerates twenty spe- 
cies of British Mesozoic cycads, and the number might 
now be considerably increased. 

The pines present some features of interest. We have 
already seen their connection with the broad-leaved Cor- 
daites, and in the Permian there are some additional 

types of broad-leaved conifers. 

In the Mesozoic we have great 

numbers of beautiful trees, 

with those elegant fan-shaped 

leaves characteristic of but one 

living species, the Salisburia, 

or gingko-tree of China. It is 

SN curious that this tree, though 

Me ee {Cinek) now limited to eastern Asia, 

geous, Siberia and North will grow, though it rarely 

fruits, in most parts of tem- 

perate Europe, and in America as far north as Montreal, 

and that in the Mesozoic period it occupied all these re- 

gions, and even Siberia and Greenland, and with many 
and diversified species (Fig. 66). 


THE FLORA OF THE EARLY MESOZOIC. 181 


Salisburia belongs to the yews, but an equally curious 
fact applies to the cypresses. The genus Sequoia, limited 
at present to two species, both Californian, and one of 
them the so-called “big tree,” celebrated for the gigantic 
size to which it attains, is represented by species found as 
far back at least as the Lower Cretaceous, and in every 
part of the northern hemi- 
sphere.* It seems to have 
thriven in all these regions 
throughout the Mesozoic 
and early Kainozoic, and 
then to have disappeared, 
leaving only a small rem- 
nant to represent it in 
modern days. A number 
of species have been de- 
scribed from the Mesozoic 
and Tertiary, all of them 
closely related to those now 
existing (Fig. 67). 

The following notice of 
these trees is for the most 
part translated, with some 
modifications and abridg- 
ment, from a paper read 
by the late Prof. Heer be- 
fore the Botanical Section 
of the Swiss Natural His- 
tory Society : 

The name itself deserves *%- 9% —Sequaia Smithiana, Heer. 
consideration. It is that 
of an Indian of the Cherokee tribe, Sequo Yah, who in- 
vented an alphabet without any aid from the outside world 
of culture, and taught it to his tribe by writing it upon 


* In the Eocene of Australia. 


182 THE GEOLOGICAL HISTORY OF PLANTS. 


leaves. This came into general use among the Chero- 
kees, before the white man had any knowledge of it ; and 
afterward, in 1828, a periodical was published in this 
character by the missionaries. Sequo Yah was banished 
from his home in Alabama, with the rest of his tribe, and 
settled in New Mexico, where he died in 1843. 

When Endlicher was preparing his synopsis of the 
conifers, in 1846, and had established a number of new 
genera, Dr. Jacbon Tschudi, then living with Endlicher, 
brought before his notice this remarkable man, and asked 
him to dedicate this red-wooded tree to the memory of a 
literary genius so conspicuous among the red men of 
America. Endlicher consented to do so, and only en- 
deavored to make the name pronounceable by changing 
two of its letters. - 

Endlicher founded the genus on the redwood of the 
Americans, Taxodium sempervirens of Lamb; and named 
the species Sequoia sempervirens. These trees form large 
forests in California, which extend along the coast as far 
as Oregon. Trees are there met with of 300 feet in height 
and 20 feet in diameter. The seeds have been brought 
to Europe a number of years ago, and we already see in 
upper Italy and around the Lake of Geneva, and in Eng- 
land, high trees; but, on the other hand, they have not 
proved successful around Zurich. 

In 1852, a second species of Sequoia was discovered in 
California, which, under the name of big tree, soon at- 
tained a considerable celebrity. Lindley described it, in 
1853, as Wellingtonia gigantea; and, in the following 
year, Decaisne and Torrey proved that it belonged to 
Sequoia, and that it accordingly should be called Sequoia 
gigantea. 

While the Seguota sempervirens, in spite of the de- 
structiveness of the American lumbermen, still forms 
large forests along the coast, the Sequoia gigantea is con- 
fined to the isolated clumps which are met with inland at 


THE FLORA OF THE EARLY MESOZOIC. 183 


a height of 5,000 to 7,000 feet above sea-level, and are 
much sought after by tourists as one of the wonders of 
the country. Reports came to Europe concerning the 
largest of them which were quite fabulous, but we have 
received accurate accounts of them from Prof. Whitney. 
The tallest tree measured by him has a height of 325 
fect, and in the case of one of the trees the number of the 
rings of growth indicated an age of about 1,300 years. 
It had a girth of 50 to 60 feet. 

We know only two living species of Sequoia, both of 
which are confined to California. The one (S. semper- 
virens) is clothed with erect leaves, arranged in two rows, 
very much like our yew-tree, and bears small, round 
cones; the other (S. gigantea) has smaller leaves, set 
closely against the branches, giving the tree more the ap- 
pearance of the-cypress. The cones are egg-shaped, and 
much larger. These two types are therefore sharply de- 
fined. 

Both of these trees have an interesting history. If we 
go back into the Tertiary, this same genus meets us with 
a long array of species. ‘Two of these species correspond 
to those living at present: the 8. Langsdorfii to the 8. 
sempervirens, and the S. Coutisie to the S. gigantea.* 
But, while the living species are confined to California, in 
the Tertiary they are spread over several quarters of the 
globe. 

Let us first consider the Sequoia Langsdorfii. This 
was first discovered in the lignite of Wetterau, and was 
described as Taxites langsdorfii. Heer found it in the 
upper Rhone district, and there lay beside the twigs 
the remains of a cone, which showed that the Tazites 
Langsdorfii of Brongniart belonged to the Californian 
genus Sequoia established by Endlicher. He afterward 


* §. Couttsie has leaves like S.-gigantea,; and cones like those of & 
sempervirens, 


184 THE GEOLOGICAL HISTORY OF PLANTS. 


found much better preserved cones, together with seeds, 
along with the plants of east Greenland, which fully 
confirmed the determination. At Atanekerdluk in 
Greenland (about 70° north latitude) this tree is very 
common. The leaves, and also the flowers and numerous 
cones, leave no doubt that it stands very near to the 
modern redwood. It differs from it, however, in hay- 
ing @ much larger number of scales in the cone. The tree 
is also found in Spitzbergen at nearly 78° north latitude, 
where Nordenskidld has collected, at Cape Lyell, wonder- 
fully preserved branches. From this high latitude the 
species can be followed down through the whole of Eu- 
rope as far as the middle of Italy (at Senegaglia, Gulf of 
Spezia). In Asia, also, we can follow it to the steppes 
of Kirghisen, to Possiet, and to the coast of the Sea of 
Japan, and across to Alaska and Sitka. It is recognized 
by Mr. Starkie Gardner as one of the species found in 
the Eocene of Mull in the Hebrides.* It is thus known 
in Europe, Asia, and America, from 43° to 78° north 
latitude, while its most nearly related living species, per- 
haps even descended from it, is now confined to Cali- 
fornia. 4 

With this §. Langsdorfii, three other Tertiary species 
are nearly related (S. brevifolia, Hr., 8. disticha, Hr., 
and S. Nordenskiéldi, Hr.). These have been met with in 
Greenland and Spitzbergen, and one of them has lately 
been found in the United States. Three other species, in 
addition to these, have been described by Lesquereux, 
which appear to belong to the group of the 8. Langsdorfit, 
viz., S. longifolia, Lesq., S. angustifolia, and S. acu- 
minata, Lesq. Several species also occur in the Creta- 
ceous and Eocene of Canada. 

These species thus answer to the living Sequoia sem- 
pervirens ; but we can also point. to Tertiary represen- 


* It is Fareites Campbelli of Forbes. 


THE FLORA OF THE EARLY MESOZOIC. 185 


tatives of the S. gigantea. Their leaves are stiff and 
sharp-pointed, are thinly set round the branches, and lie 
forward in the same way: the egg-shaped cones are in 
some cases siniilar. 

There are, however, in the early Tertiary six species, 
which fill up the gap between S. sempervirens and S. 
gigantea. They are the S. Coutisia, S. affinis, Lesq., 
S. imbricata, Hy., S. sibirica, Hr., S. Heerit, Lesgq., and 
S. biformis, Lesq. Of these, 8. Couttsiw, Hr., is the 
most common and most important species. It has short 
leaves, lying along the branch, like 8. gigantea, and 
small, round cones, like S. Langsdorfii and sempervirens. 
Bovey Tracey in Devonshire has afforded splendid speci- 
mens of cones, seeds, and twigs, which have been described 
in the ‘‘ Philosophical Transactions.” More lately, Count 
Saporta has described specimens of cones and twigs from 
Armissan. Specimens of this species have also been found 
in the older Tertiary of Greenland, so that it must have 
had a wide range. It is very like to the American &. 
affinis, Lesq. 

In the Tertiary there have been already found fourteen 
well-marked species, which thus include representatives 
of the two living types, S. sempervirens and S. gigantea. 

We can follow this genus still further back. If we go 
back to the Cretaceous age, we find ten species, of which 
five occur in the Urgon of the Lower Oretaceous, two in 
the Middle, and three in the Upper Cretaceous. Among 
these, the Lower Cretaceous exhibits the two types of the 
Sequoia sempervirens and 8. gigantea. To the former 
the S. Smithiana answers, and to the latter, the Reichen- 
bachit, Gein. The S. Smithiana stands indeed uncom- 
_ monly near the S. Langsdorfii, both in the appearance of 
the leaves on the twigs and in the shape of the cones. 
These are, however, smaller, and the leaves do not become 
narrower toward the base. The S. pectina, Hr., of the 
Upper Cretaceous, has its leaves arranged in two rows, and 


186 THE GEOLOGICAL HISTORY OF PLANTS. 


presents a similar appearance. The S. Reichenbachit is a 
type more distinct from those now living and those in 
the Tertiary. It has indeed stiff, pointed leaves, lying 
forward, but they are arcuate, and the cones are smaller. 
This tree has been known for a long time, and it serves 
in the Cretaceous as a guiding star, which we can follow 
from the Urgonian of the Lower Cretaceous up to the 
Cenomanian. It is known in France, Belgium, Bohemia, 
Saxony, Greenland, and Spitzbergen (also in Canada and 
the United States). It has been placed in another genus 
—Geinitzia—but we can recognise, by the help of the 
cones, that it belongs to Sequoia. 

Below this, there is found in Greenland a nearly re- 
lated species, the 8S. ambigua, Hr., of which the leaves 
are shorter and broader, and the cones round and some- 
what smaller. 

The connecting link between S. Smithiana and Reich- 
enbachit is formed by S. subulata, Hr., and S. rigida, 
Hr., and three species (S. gracilis, Hr., 8. fastigiata and 
S. Gardneriana, Carr.), with leaves lying closely along the 
branch, and which come very near to the Tertiary species 
S. Couttsie. We have therefore in the Cretaceous quite 
an array of species, which fill up the gap between the &. 
sempervirens and gigantea, and show us that the genus 
Sequoia had already attained a great development in the 
Cretaceous. This was still greater in the Tertiary, in 
which it also reached its maximum of geographical dis- 
tribution. Into the present world the two extremes of 
the genus have alone continued ; the numerous species : 
forming its main body have fallen out in the Tertiary. 

If we look still further back, we find in the Jura a 
great number of conifers, and, among them, we meet in 
the genus Pinus with a type which is highly developed, 
and which still survives ; but for Sequoia we have till now 
looked in vain, so that for the present we can not place 
the rise of the genus lower than the Urgonian of the Cre- 


THE FLORA OF THE EARLY MESOZOIC. 18% 


taceous, however remarkable we may think it that in that 
period it should have developed into so many species ; and 
it is still more surprising that two species already make 
their appearance which approach so near to the living 
Sequoia sempervirens and S. gigantea. 

Altogether, we have become acquainted, up to the 
present time, with twenty-six species of Sequoia. Four- 
teen of these species are found in the Arctic zone, and 
have been described and figured in the ‘‘ Fossil Flora 
of the Arctic Regions.” Sequoia has been recognised by 
Ettingshausen even in Australia, but there in the Eocene. 

This is, perhaps, the most remarkable record in the 
whole history of vegetation. ‘The Sequoias are the giants 
of the conifers, the grandest representatives of the family, 
and the fact that, after spreading over the whole northern 
hemisphere and attaining to more than twenty specific 
forms, their decaying remnant should now be confined to 
one limited region in western America and to two species 
constitutes a sad memento of departed greatness.* The 
small remnant of S. gigantea still, however, towers above 
all competitors, as eminently the ‘‘big trees”; but, had 
they and the allied species failed to escape the Tertiary 
continental submergences and the disasters of the glacial 
period, this grand genus would have been to us an extinct 
type. In like manner the survival of the single gingko 
of eastern Asia alone enables us to understand that 
great series of taxine trees with fern-like leaves of which 
it is the sole representative. 

Besides these peculiar and now rare forms, we have in 
the Mesozoic many others related closely to existing yews, 
cypresses, pines, and spruces, so that the conifers were 
probably in greater abundance and variety than they are 
at this day. 


¥ 

* The writer has shown that much of the material of the great lignite 
beds of the Canadian Northwest consists of wood of Sequoia of both the 
modern types, 


188 THE GEOLOGICAL HISTORY OF PLANTS. 


In this period, also, we find the earliest representatives 
of the endogenous plants. It is true that some plants 
found in the coal-formation have been doubtfully re- 
ferred to these, but the earliest certain examples would 
seem to be some bamboo-like and screw-pine-like plants 
occurring in the Jurassic rocks. Some of these are, it is 
true, doubtful forms, but of others there seems to be no 
question. The modern Pandanus or screw-pine of the 
tropical regions, which is not a pine, however, but a 
humble relation of the palms, is a stiffly branching tree, 
of a candelabra-like form, and with tufts of long leaves 
on its branches, and nuts or great hard berries for fruit, 
borne sometimes in large masses, and so protected as to 
admit of their drifting uninjured on the sea. The stems 
are supported by masses of aérial roots like those which 
strengthen the stems of tree-ferns. These structures and 
habits of growth fit the Pandanus for its especial habitat 
on the shores of tropical islands, to which its masses of 
nuts are drifted by the winds and currents, and on whose 
shores it can establish itself by the aid of its aérial roots. 

Some plants referred to the cycads have proved veri- 
table botanical puzzles. One of these, the Williamsonia 
gigas of the English odlite, originally discovered by my 
friend Dr. Williamson, and named by him Zamia gigas, a 
very tall and beautiful species, found in rocks of this age in 
various parts of Europe, has been claimed by Saporta for 
the Endogens, as a plant allied to Pandanus. Some 
other botanists have supposed the flowers and fruits to be 
parasites on other plants, like the modern Raffesia of 
Sumatra, but it is possible that after all it may prove to 
have been an aberrant cycad. 

The tree-palms are not found earlier than the Middle 
Cretaceous, where we shall notice them in the next chap- 
ter. In like manner, though a few Angiosperms occur 
in rocks believed to be Lower or Lower Middle Cretaceous 
in Greenland and the northwest territory of Canada, and 


THE FLORA OF THE EARLY MESOZOIC. 189 


in Virginia, these are merely precursors of those of the 
Upper Cretaceous, and are not sufficient to redeem the 
earlier Cretaceous from being a period of pines and cycads. 

On the whole, this early Mesozoic flora, so far as 
known to us, has a monotonous and mean appearance. 
It no doubt formed vast forests of tall pines, perhaps re- 
sembling the giant Sequoias of California ; but they must 
for the most part have been dark and dismal woods, 
probably tenanted by few forms of life, for the great rep- 
tiles of this age must have preferred the open and sunny 
coasts, and many of them dwelt in the waters. Still we 
must not be too sure of this. The berries and nuts of the 
numerous yews and cycads were capable of affording 
much food. We know that in this age there were many 
great herbivorous reptiles. like Iguanodon and Hadrosau- 
rus, some of them fitted by their structure to feed upon 
the leaves and fruits of trees. There were also several 
kinds of small herbivorous mammals, and mach insect 
life, and it is likely that few of the inhabitants of the 
Mesozoic woods have been preserved as fossils. We may 
yet have much to learn of the inhabitants of these forests 
of ferns, cvcads, and pines. We must not forget in this 
connection that in the present day there are large islands, 
like New Zealand, destitute of mammalia, ard having a 
flora comparable with that of the Mesozoic in the northern 
hemisphere, though more varied. We have also the re- 
markable example of Australia, with a much richer flora 
than that of the early Mesozoic, yet inhabited only by 
non-placental mammals, like those of the Mesozoic. 

The principal legacy that the Mesozoic woods have 
handed down to our time is in some beds of coal, locally 
important, but of far less extent than those of the Car- 
boniferous period. Still, in America, the Richmond coal- 
field in Virginia is of this age, and so are the anthracite 
beds of the Queen Charlotte Islands, on the west coast of 
Canada, and the coal of Brora in Sutherlandshire. Valu- 

18 


190 THE GEOLOGICAL HISTORY OF PLANTS. 


able beds of coal, probably of this age, also exist in China, 
India, and South Africa ; and jet, which is so extensively 
used for ornament, is principally derived from the car- 
bonised remains of the old Mesozoic pines. 

In the next chapter we have to study a revolution in 
vegetable life most striking and unique, in the advent of 
the forest-trees of strictly modern types. 


NOTE TO CHAPTER V. 


I appenD to this chapter a table showing the plant-bearing series 
of the Cretaceous and Laramie of North America, from a paper in 
“Trans. R. 8. C.,” 1885, which see for further details: 


(In DESCENDING ORDER.) 


Perioda. Floras and subfloras. References, 
Transition | Upper Laramie or Poreu-| {™Gaigary. ‘Report of Geol, Sur 
ocene pine Hill. 0! nion . 
Cretaceous. | group, U.S. territory. vey er aap Ye for 1879, and Me- 
Middle Laramie or Willow 
> 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. 


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