THE FIRST FORESTS OF MODERN TYPE.
For a long time it was believed by geologists that a great and
mysterious gap separated the Upper Cretaceous from the oldest Tertiary
formations; and in Western Europe, in so far as physical conditions and
animal life are concerned, the severance seemed nearly complete. Oceanic
deposits, like the Upper Chalk, are succeeded by beds of littoral and
estuarine characters. The last and some of the greatest of the Mesozoic
Saurians have their burial-places in the Upper Cretaceous, and appear no
more on earth. The wonderful shell-fishes of the Ammonite group, and the
cuttle-fishes of the Belemnite type, share the same fate. With the
earliest deposits of the Eocene Tertiary came in multitudes of large
Mammalia heretofore unknown, and the Cetaceans appear in the sea instead
of the great marine lizards; while shells, corals, and crustaceans of
modern types swarm in the waters. Thus it is true that a great and
apparently somewhat abrupt change takes place at the close of the
Cretaceous, and terminates for ever the reptilian age. Even in regions
like Western America, where physically the later Cretaceous shades
gradually into the earlier Tertiary, so that there have been doubts as
to the limits of these several periods, the same great change in animal
life occurs.
But a link of connection has at length been found in the history of the
vegetable kingdom. The modern flora came in with its full force in the
later Cretaceous, before the end of the reptilian age, and continued
onward to the present time. Thus the plant takes precedence of the
animal, and the preparation was made for the mammalian life of the
Eocene by the introduction of the modern flora in the Cretaceous period.
In like manner it is possible that the great graphite deposits of the
Laurentian indicate a vegetation which preceded the swarming marine life
of the Cambrian; and it is not improbable that the PalA|ozoic land flora
existed long before the first land animals. Thus the plant, as in the
old Mosaic record, ever appears on the day before the animal, in each
stage of the development of the world.
In Chapter IV. we traced the history of the old and rich vegetation of
the Coal period. But this vegetation consisted principally of cryptogams
and those lowest phA|nogams, of the pine and cycad groups, which have
naked seeds. In the modern flora we may arrange the several groups of
plants, somewhat naturally, as follows:aEuro"
_Series I._, CRYPTOGAMS:aEuro"
Class 1, _Thallophytes_, sea-weeds, lichens, fungi.
aEuroŁ 2, _Anophytes_, mosses, &c.
aEuroŁ 3, _Acrogens_, ferns, lycopods, horsetails.
_Series II._, PHAćNOGAMS:aEuro"
Class 4, _Gymnosperms_, pines, cycads, &c.
aEuroŁ 5, _Endogens_, palms, grasses, &c.
aEuroŁ 6, _Exogens_, oaks, maples, &c.
With reference to the history of these groups the record stands as
follows:aEuro"In the PalA|ozoic age classes 3 and 4 culminated, and
constituted the great mass of the arboreal vegetation. On entering the
Mesozoic, No. 3 becomes somewhat diminished, but No. 4 continues with
unabated prevalence, so that the Mesozoic has sometimes been
characterized as emphatically the age of Gymnosperms. With these appear
some Endogens, allied to the modern Yuccas and Screw pines and Arums.
But in the lower Mesozoic rocks we have no representatives of the
broad-leaved Exogens (Angiosperms), which constitute the great mass of
ordinary forest vegetation; and it is only in the Cretaceous that we
find them appearing in force, and that the monotonous vegetation of the
older style was replaced by the more beautiful and varied forms of our
modern woods.
In Europe, in the lower part of the Upper Cretaceous of Bohemia
(_Cenomanian_), have been found some leaves which indicate the beginning
of this change. These have been referred to CA|salpinias or Brasilettos,
pod-bearing trees of India and tropical America, _Aralias_ or Ginsengs,
_Magnolias_, Laurels, an Ivy, and a peculiar and uncertain genus
(_Credneria_). With these are noble palms, both of the types with
pinnate and palmate leaves, and trees allied to the Giant _Sequoias_ of
California, and to the Araucarian pines of the southern hemisphere. (See
Frontispiece to this Chapter.) These ancient Cretaceous forests of
Eastern Europe are compared by Saporta with those which now live in the
warmer portions of China or in South AmericaaEuro"truly a marvellous change
from the sombre and uniform vegetation by which they seem to have been
immediately preceded. A still further development of modern vegetation
takes place in the next or highest member of the Cretaceous, the
Maestricht beds (_Senonian_), where we find a crowd of modern types. On
this great change Count Saporta remarks with truth that there seem to
have been periods of pause and of activity in the introduction of
plants. The Jurassic period was one of inactivity; and a new and
vigorous evolution, as he regards it, is introduced in the middle of the
Cretaceous.
This new and grand elevation of the vegetable kingdom in the Cretaceous
age was not local merely. In Moravia, in the Hartz, in Belgium and
France, even in Greenland, the same great renewing of the face of the
earth was in progress. In America it was proceeding on a grand scale,
and seems to have set in earlier than in Europe.[71] In the Dakota group
of the West, one of the lower members of the Cretaceous, and covering a
vast area, a rich angiospermous flora has been discovered by Hayden, and
described by Lesquereux and Newberry, and beds of coal have been formed
from its remains. In VancouveraEuro(TM)s Island in British Columbia, Cretaceous
coal measures occur, comparable in value and in the excellence of the
fuel they afford with those of the true coal formation. Some of the beds
of coal are eight feet in thickness, and the shales associated with them
abound in leaves of exogenous trees generally similar to those still
living in America. In these beds are also found mineralized trunks,
which present under the microscope the familiar structures of our oaks,
birches, and other modern trees. Thus all over the northern hemisphere
the elevation of the land out of the waters of the great Cretaceous
subsidence was signalized by a development of noble and exuberant forest
vegetation, of the types still extant. The following list of families
found in the Cretaceous, after Saporta, will show the botanist how fully
our modern Exogens are represented:aEuro"
APETALAć.
_MyricaceA|._
_CupuliferA|._
_BetulaceA|._
_SalicaceA|._
_MoreA|._
_ProteaceA|._
_LauraceA|._
GAMOPETALAć.
_ApocynaceA|._
_EricaceA|._
_EbenaceA|._
_MyrsineA|._
POLYPETALAć.
_AraliaceA|._
_HamameliaceA|._
_HelleborineA|._
_MagnoliaceA|._
_TiliaceA|._
_CelastraceA|._
_AnacardiaceA|._
_MyrtaceA|._
Of the plants in this list, some, like the oaks, birches, willows, and
heaths, are common and familiar members of the flora of the northern
hemisphere to-day, and even of the European flora. Some, like the
_Magnolias_, _Myricas_, and witch-hazels, are characteristically American,
and a few, like the ProteaceA|, are now confined to the southern
hemisphere. Some of these families have dwindled since the Cretaceous
time, so as to be represented by very few species, or at least have not
advanced, while others have multiplied and prospered; and on the whole
the flora of the northern hemisphere seems to have been as rich in this
early beginning of our modern forests as it is at the present day.
LesquereuxaEuro(TM)s results, with reference to the American flora of the Dakota
group, are very similar, and present some surprising features of
resemblance to modern American forests, though he remarks that these
Cretaceous trees are generally characterized by the even or unserrated
edges of their leaves; and the same remark seems to apply to the oldest
Cretaceous leaves of Europe.
A very singular feature of the Cretaceous flora is the number of species
of some genera now represented by few or even a single species; and this
is the more remarkable when we consider how few species, comparatively,
of the older flora, are known to us. For example, Lesquereux, though
aware of the great variability of the modern _Sassafras_ of America,
recognizes eight species of this genus in the Dakota Cretaceous, one of
which seems to be that still living in America, so that it has continued
unchanged, while the others have perished (Fig. 155). Thus this genus
culminates at once in the Cretaceous, but continues still in one of its
species. Again, the tulip-tree, _Liriodendron_, one of the most
beautiful, unique, and invariable of American trees, is represented by
one sole species in the present world. There seem to be no less than
four in the Dakota beds, besides others in the Cretaceous of New Jersey,
and one species is found in the Tertiary of Greenland as well as in that
of Europe (Fig. 156). There are probably four or five species of
plane-tree (_Platanus_) now extant, of which but one occurs in America,
unless _P. Mexicana_, the Mexican plane-tree, is a good species as
distinct from the ordinary, more northern, form. There are seven
species, according to Lesquereux, in the Cretaceous of Dakota alone.
This sort of evolution backward, or from many species to few, would
probably be greatly increased, had we fuller knowledge of the Cretaceous
flora, as there are several genera already represented by as many
species as they can boast in modern times. We have already seen that
this abrupt and sudden culmination of genera and families, and their
subsequent decadence, is no rare thing in geology, and it connects
itself with that idea of periods of creative activity which we have
already had occasion to notice.
[Illustration: FIG. 155.aEuro"_Sassafras cretaceum_ (Newberry).]
[Illustration: FIG. 156.aEuro"_Liriodendron primA|vum_ (Newberry). A
Cretaceous Tulip-tree.]
[Illustration: FIG. 157.aEuro"_Onoclea sensibilis._ Eocene.aEuro"After
Newberry.]
[Illustration: FIG. 158.aEuro"_Davallia tenuifolia._ Eocene.aEuro"After Dawson.
Natural size and enlarged.]
I have dwelt principally on the phA|nogamous plants of the Cretaceous, as
presenting the most noteworthy and new features of the time; but we must
not forget that though cryptogams were deposed from the high position
they held in the PalA|ozoic, they still existed; and there are more
especially many interesting species of ferns and equisetums in the
Cretaceous and Eocene rocks. These are, however, of modern types; and
it is remarkable that some of them appear to have continued without even
specific change from the later Cretaceous up to the present time. A
striking illustration of this is afforded by two ferns discovered side
by side in the oldest Eocene beds[72] of the plains west of Red River,
and described in Dr. G. M. DawsonaEuro(TM)s report on the 49th parallel. One of
these is the well-known and very common _Onoclea sensibilis_ (Fig. 157),
or sensitive fern of Eastern America.[73] This species came into
existence at latest at the close of the Cretaceous, and has apparently
been continued in America up to the present time. In Europe, where it
does not now live, it occurs as a fossil in Eocene beds in the Isle of
Mull. The other is _Davallia tenuifolia_ (Fig. 158), a delicate little
plant belonging to a genus not now represented in America, and to a
species at present found only in Asia. Yet this species also lived in
America in early Eocene times, but has since been banished, though its
former companion, the _Onoclea_, still holds its ground. Such cases of
specific persistence along with great changes of habitat are very
instructive as to the permanence of species.
Count Saporta, whose just remarks on the marvellously sudden incoming of
the Cretaceous flora we have already referred to, also notices the fact
that the families and genera represented in this flora are a most
miscellaneous and unconnected assemblage, showing either the
simultaneous appearance of many dissimilar types, or requiring us to
believe in the existence of these and of intermediate forms for a very
long period before that in which they are first found. This may,
however, be placed in connection with the appearance of an exogenous
tree (_Syringoxylon_) in the Devonian, referred to in a previous
chapter. It would be a strange and now little suspected case of
imperfection of the record, if it should be found that trees of this
type were lurking in exceptional corners through all the vast periods
between the Devonian and the Cretaceous, to burst forth in unwonted
variety and luxuriance in the latter period.
The new Cretaceous flora appears first in beds which had been recently
elevated from the ocean of the great Cretaceous subsidence; and when it
first flourished, in temperate regions at least, the continents were of
small dimensions, and broken up into groups of islands. Farther, America
would seem to have had precedence of the Eastern Continent, and the
Arctic of the Temperate regions. Thus on the elevation of the later
Cretaceous land, plants previously established in the far north spread
themselves southward, over newly-raised lands, radiating from the polar
regions into Europe, Asia, and America. This seems the only way of
accounting for the similarity of the plants in these distant countries.
The new flora of the Upper Cretaceous in its journey southward met with
a climate probably warmer than the present, yet not so warm as to
prevent trees similar to those now living in the same latitudes from
flourishing.
Let us now trace this flora through the succeeding ages, in which I
shall follow pretty closely some general statements made by Count De
Saporta in memoirs recently published.
[Illustration: FIG. 159.aEuro"Eocene Leaves. From Aix.
_a_, _Quercus antecedens_ (Saporta). _b_, _Diospyros pyrifolia_
(Saporta). _c_, _Myrica Mathesonii_ (Saporta).]
At the beginning of the Eocene we find a humid and warm climate in
Europe, with great forests of oaks, chestnuts, laurels, giant pines, and
other genera, some of them still European, others Asiatic or American,
and many of them survivors of the Cretaceous (Figs. 159 to 162); and at
the same period similar forests overspread those great plains of North
America which were rising from out the Cretaceous sea, and there vast
swampy beds were formed of vegetable _dA(C)bris_, giving origin to beds of
brown coal, some of them eighteen feet in thickness. Then came in Europe
and Asia that great subsidence under the sea, during which the Nummuline
limestones were deposited, and when the old continent was resolved again
into an archipelago of islands, perhaps closely connected with more
southern lands. This led to a great increase of southern forms of
plants, which does not seem to have occurred to the same extent in
America, where the flora is more continuous, though showing a warmer
climate in the older than in the newer Eocene. At this period Palms,
Screw pines, Proteaceous shrubs, Myrtles, _Acacias_, and other plants of
the character of those of more southern climates were dominant in Europe
(Fig. 163). The well-known beds of Bournemouth, in the south of
England,[74] contain a rich flora of the Eocene age, perhaps of its
middle period, and reminding us of the forests of sub-tropical India or
Australia.
[Illustration: FIG. 160.aEuro"An Ancient Clover (_Trifolium palA|ogA|um_,
Saporta). Eocene. Aix.]
[Illustration: FIG. 161.aEuro"An Eocene Maple (_Acer sextianus_, Saporta).
Aix.]
[Illustration: FIG. 162.aEuro"A European Magnolia of the Eocene (_M. dianA|_,
Saporta). Aix.]
[Illustration: FIG. 163.aEuro"Flower and Leaf of _Bombax sepultiflorum_.
Eocene of Aix.aEuro"After Saporta.
A European representative of the Silk-cotton-tree of the East Indies and
Tropical America.]
Gradual elevation of the land favoured for a time the extension of these
plants, and the warmth of the climate allowed them to extend even into
Arctic latitudes. But in the middle of the Eocene another subsidence
occurred, which exterminated much of the Eocene flora, and was perhaps
accompanied with a reduction of temperature, in which the more northern
lands became covered with great forests of trees allied to the Pines. In
England a remarkable deposit of this age is that of Bovey Tracey, in
Devonshire, where beds of clay and brown coal have afforded a rich flora
of American and southern types. The _Sequoia_ shown in Fig. 164 abounds
at this place, and is a near relation to the celebrated aEurooebig treesaEuroŁ of
California; the _Cinnamomum_ in Fig. 165 is a type equally foreign from
modern England. It is a curious feature of the Bovey deposit that
immediately above these Eocene beds, holding a rich flora of warm
temperate character, are glacial clays with leaves of Arctic willows and
of the dwarf birch, indicating a climate much more severe than that of
the British Islands at present.[75]
[Illustration: FIG. 164.aEuro"Branch and Fruit of _Sequoia CouttsiA|_ (Heer).
Eocene. England.]
In the Miocene period the land again rose, and the northern flora spread
itself southward equally over Europe, Asia, and America, so that the
Miocene flora of all these regions is very similar; and this Miocene
flora continues substantially to this day in Eastern America and Eastern
Asia, except that it has been greatly reduced in number of species by
the intervention of the cold glacial period; but in Europe and Western
America it has been largely replaced by other apparently more modern
species.
[Illustration: FIG. 165.aEuro"_Cinnamomum Scheuchzeri_ (Heer). Eocene.
England.]
A striking result of recent discoveries is the fact that in Cretaceous
and Eocene times a very warm climate prevailed in the extreme Arctic
regions, and trees of temperate latitudes grew there freely. In the
recent Arctic expedition, Captain Fielden found in latitude 81A deg. 40aEuro(TM),
within 600 miles of the Pole, a bed of lignite, from twenty-five to
thirty feet in thickness, associated with remains of plants such as now
grow only in temperate latitudes.
aEurooeFrom the character of the plant-remains, Dr. Heer infers that the
lignite of this locality represents an ancient peat-moss, which must
have been of wide extent, with reeds, sedges, birches, poplar, and
certain conifers growing on its banks; while the higher and drier ground
in the neighbourhood probably supported a growth of pines and firs, with
elms and hazel-bushes. The remains of water-lilies suggest the existence
of a fresh-water lake in the old peat-moss, which must have remained
unfrozen during a great part of the year.aEuroŁ
It is to be observed with reference to the age of these beds, that as
the Later Cretaceous and Eocene flora of Europe and America migrated
from the north, the plants found in the beds of that age in the
temperate latitudes may really be somewhat older in the Arctic regions,
a fact which produces some uncertainty as to their actual age.
The warmth required for the growth of luxuriant forests near the Pole
might be secured by a different distribution of land and water, and of
the oceanic currents, but the requirements of plants as to light seem
more difficult to meet, and it has been doubted whether species similar
to those which are accustomed in modern times to regular alternations of
day and night could submit to the long Arctic winter darkness. It is
known, however, that in conservatories in Northern Russia plants
supplied with heat and moisture can endure in winter great deprivation
of light, and at Disco, in Greenland, roses and fuchsias flourish as
house plants.[76] These facts show that if there were sufficient light
and heat in summer, a great number of the plants of temperate latitudes
could endure extreme cold and much deprivation of light in winter.
It may be well here to inform the reader that some confusion as to the
succession of the Cretaceous and Tertiary floras in America has arisen
from the fact that the plants which are evidently Eocene in Greenland
and America have been until lately incorrectly regarded as Miocene in
Europe. In the Western States, the Dakota group of Lesquereux is
overlain by 2000 feet of Cretaceous beds, containing the marine shells
characteristic of that age, but no plants. But in VancouveraEuro(TM)s Island
these same Upper Cretaceous beds contain an abundant flora, which some
botanists have called Tertiary for the reason already mentioned. Above
the 2000 feet of marine beds overlying the Dakota group is the Lower
Lignite group of Lesquereux, holding many fossil plants, including Palms
and other evidences of a warmer climate than that of the Cretaceous, and
which constitute a Lower Eocene flora corresponding in some respects to
that of Europe. This is succeeded by an Upper Lignite group, also
Eocene, but representing a more temperate climate, and therefore
resembling more nearly the Cretaceous flora. This is nearly identical
with the so-called Miocene of Greenland, Alaska, and Mackenzie River,
which the facts collected by the Canadian geologists have shown to be
really Eocene.[77] But the Canadian reports containing these facts are
comparatively little known in Europe, hence incorrect ideas as to the
succession of these floras have been handed from one writer to another.
To those who adopt extreme views as to the refrigeration of the northern
hemisphere in so-called glacial times, there is great difficulty in
accounting for the continued existence of the early Tertiary flora; but
if we adopt moderate views as to this, and demand merely a great
subsidence, with much reduction of mean temperature, we may suppose that
the plants previously existing were preserved on insular spots, whence
they were ready to recolonize the land on its emergence from the sea. It
seems certain, however, that our continents never regained, after the
Glacial period, the exuberance of plant life which they presented in the
Miocene and earlier Pliocene; and we shall find that this statement
applies to the world of animals as well as to that of plants. This
reduction was more extreme in Europe than in Eastern Asia and Eastern
America, and the fact is thus accounted for in a recent lecture by Prof.
Asa Gray:aEuro"
aEurooeI conceive that three things have conspired to this loss. First,
Europe, hardly extending south of latitude 40A deg., is all within the limits
generally assigned to severe glacial action. Second, its mountains trend
east and west, from the Pyrenees to the Carpathians and the Caucasus
beyond, near its southern border; and they had glaciers of their own,
which must have begun their operations, and poured down the northward
flanks, while the plains were still covered with forest, on the retreat
from the great ice-wave coming from the north. Attacked both on front
and rear, much of the forest must have perished then and there. Third,
across the line of retreat of those which may have flanked the
mountain-ranges, or were stationed south of them, stretched the
Mediterranean, an impassable barrier. Some hardy trees may have eked out
their existence on the northern shore of the Mediterranean and the
Atlantic coast. But we doubt not, _Taxodium_ and _Sequoias_, _Magnolias_
and _Liquidambars_, and even Hickories and the like, were among the
missing. Escape by the east, and rehabilitation from that quarter until
a very late period, were apparently prevented by the prolongation of the
Mediterranean to the Caspian, and thence to the Siberian ocean. If we
accept the supposition of NordenskiAÂld, that, anterior to the Glacial
period, Europe was aEuro~bounded on the south by an ocean extending from the
Atlantic over the present deserts of Sahara and Central Asia to the
Pacific,aEuro(TM) all chance of these American types having escaped from or
re-entered Europe from the south and east is excluded. Europe may thus
be conceived to have been for a time somewhat in the condition in which
Greenland is now, and indeed to have been connected with Greenland in
this or in earlier times.[78] Such a junction, cutting off access of the
Gulf Stream to the Polar Sea, would, as some think, other things
remaining as they are, almost of itself give glaciation to Europe.
Greenland may be referred to, by way of comparison, as a country which,
having undergone extreme glaciation, bears the marks of it in the
extreme poverty of its flora, and in the absence of the plants to which
its southern portion, extending six degrees below the Arctic Circle,
might be entitled. It ought to have trees, and might support them. But
since destruction by glaciation no way has been opened for their return.
Europe fared much better, but suffered in its degree in a similar way.
aEurooeTurning for a moment to the American continent for a contrast, we find
the land unbroken and open down to the tropic, and the mountains running
north and south. The trees, when touched on the north by the on-coming
refrigeration, had only to move their southern border southward, along
an open way, as far as the exigency required; and there was no
impediment to their due return. Then the more southern latitude of the
United States gave great advantage over Europe. On the Atlantic border,
proper glaciation was felt only in the northern part, down to about
latitude 40A deg.. In the interior of the country, owing doubtless to greater
dryness and summer heat, the limit receded greatly northward in the
Mississippi Valley, and gave only local glaciers to the Rocky Mountains;
and no volcanic outbreaks or violent changes of any kind have here
occurred since the types of our present vegetation came to the land. So
our lines have been cast in pleasant places, and the goodly heritage of
forest-trees is one of the consequences.
aEurooeThe still greater richness of North-east Asia in arboreal vegetation
may find explanation in the prevalence of particularly favourable
conditions, both ante-glacial and recent. The trees of the Miocene
circumpolar forest appear to have found there a secure home; and the
Japanese islands, to which most of these trees belong, must be
remarkably adapted to them. The situation of these islandsaEuro"analogous to
that of Great Britain, but with the advantage of lower latitude and
greater sunshinetheir ample extent north and south, their diversified
configuration, their proximity to the great Pacific gulf-stream, by
which a vast body of warm water sweeps along their accentuated shores,
and the comparatively equable diffusion of rain throughout the year, all
probably conspire to the preservation and development of an originally
ample inheritance.aEuroŁ
The comparative paucity in species of the west coast of America, though
the _Sequoias_ and some other forms which have perished elsewhere are
retained there, is admitted to be exceptional, and not easily explained,
except by the supposition of peculiar local conditions affecting the
comparatively narrow strip of land between the Rocky Mountains and coast
ranges, and the Pacific.
To such widely-distributed and varied and complex phenomena as those
which have been discussed in the present chapter, it is impossible to do
justice in the space at our command. Details in relation to them will be
found in the publications of Heer, of Saporta, and of Lesquereux, and
are well worthy of study by botanists, to whom alone they can be made
fully intelligible. In general, with reference to now prevalent theories
of derivation, they present two very dissimilar aspects. No difficulty
can be greater to the evolutionist than to account for the simultaneous
appearance of so many modern generic forms in the Cretaceous; and the
fact of many of the genera presenting more and more species the farther
we trace them back is a strange anomaly of evolution. On the other hand,
the number of species continuing unchanged from the Eocene to the
Modern, the others only slightly modified, and the representative
species occurring in the floras of the old and new continents, appear to
many to give great support to the doctrine of gradual transformation of
species. Farther facts and farther comprehension of the difference
between species and races will be necessary to the settlement of these
questions. In the meantime it would appear that the Jurassic flora
rapidly gave place, at a particular point of geological time, to that
of the modern world, and this not merely in one locality, but over the
whole northern hemisphere; and there are apparently similar facts in the
southern hemisphere as well. It farther appears that each genus was at
first represented by many species, and that as time went on these were
gradually reduced to a few best suited to survive; and that the changes
of climate and level which occurred distributed these over different
parts of the continents in a way at first sight very anomalous, but
which Prof. Gray somewhat quaintly represents as follows:aEuro"
aEurooeIt is as if Nature, when she had enough species of a genus to go round
the four floral regions (Europe, East Asia, West America, and East
America), dealt them fairly one at least to each quarter of our zone;
but when she had only two of some peculiar kind, gave one to us, and the
other to Japan, Mantchuria, or the Himalayas; and when she had only one,
divided it between the two partners on the opposite sides of the table.aEuroŁ
Lastly, it seems very probable that many so-called species are nothing
more than varietal forms, which may very well be modified descendants of
Miocene or Eocene plants now figuring in our lists under different
names.
[Illustration: SIVATHERIUM GIGANTEUM.
A Great Ruminant of the Miocene of India.
Copied by special permission of James Murie, M.D., F.G.S., &c.]