Part 10

"The abundance of Lonchopteris Mantelli is a character of the Wealdean formations of the south of England and the department of the Oise, where this fossil seems to make its appearance, at least in fragments, in the greater number of localities, where these beds are exposed by the excavation of potter's clay in this formation, near Savignies. In Germany, on the contrary, this species is wanting, and _Abietites Linkii_ becomes the predominating plant. With regard to Brachyphyllum, I have not yet had it in my power to study them in a natural state; but the figures given of them leave little doubt as to their analogy with the species of the Oolitic epoch.

"The abundance of the Cycadeæ likewise forms a distinctive character of the Wealdean formations of Germany. Still there are, as has been seen, many species common to the two basins; and I may add, that probably the Sphenopteris Goepperti, _Dunk._, does not differ from Sphenopteris Phillipsii, _Mant._

"I have not included in this list some marine plants mentioned as belonging to the beds of this epoch; _1st_, because it appears to me doubtful whether they really belong to the Wealdean and not to the Glauconian epoch; _2dly_, because it still appears to me uncertain, whether the species mentioned, Chondrites æqualis and intricatus, are quite identical, specifically with the species of this name belonging to the fucoidal sandstone lying above the chalk.

"III. REIGN OF THE ANGIOSPERMS.--The dominating character of this last transformation of the vegetation of the globe, is the appearance of Angiospermous dicotyledons, those vegetables which actually constitute more than three-fourths of the vegetable creation of our epoch, and which appear to have acquired this predominance from the commencement of the Tertiary formations. For a long period I was of opinion that these vegetables did not begin to appear till after the chalk, with the earliest beds of the Tertiary formations; but more recent investigation has shewn that beds belonging to the Chalk formation present some very distinct examples.

"These vegetables appear even at the beginning of the Chalk formation; for it is certain that many well-determined species exist in the quadersandstein and planerkalk of Germany, which appear to correspond to the green sandstone of France, or green sand of English geologists; although this formation in France and England has never yielded any of them, but only some examples of Cycadeæ, Coniferæ, and marine plants. But in southern Sweden, at Kopingue in Scania, some specimens of dicotyledonous leaves appear associated with a species of Cycadeæ, in beds which have been referred to the greensand; so that the whole Chalk formation would appear to constitute a first period in the reign of the Angiosperms, forming, so to speak, the passage between the vegetation of the Secondary and that of the Tertiary formations, still presenting, as the first, a few Cycadeæ, as the following, some Angiospermous dicotyledons, and thus paving the way to the considerable development of these vegetables in the succeeding period. This period is besides characterised by many Coniferæ peculiar to it, and which appear very distinct from those of the Wealdean formations, and from those of the Eocene epoch of the Tertiary formations; and such in particular are the _Cunninghamites_.

"We can therefore distinguish two great periods in the reign of the Angiosperms:

"_1st_, The Cretaceous period, a kind of period of transition.

"_2dly_, The Tertiary period, presenting all the characters arising from the predominance of Angiosperms, Dicotyledons, and Monocotyledons, and divisible into many epochs, the characters of which will not be well established until we have removed all doubts as to the agreement of the different local series of the Tertiary formations.

"V. _Cretaceous Period._--The Cretaceous period, properly so called, comprehends perhaps many distinct epochs; but the beds where fossil vegetables have been observed, not having been always classified with precision in the different subdivisions of this formation, it is impossible to establish their chronology with certainty. Besides, we must distinguish an epoch which appears immediately to precede this formation, and one which follows it, and yet differs from the Eocene period.

"We are acquainted with fossil vegetables of the Cretaceous period:--

"_1st, Sub-Cretaceous Epoch_.--In the subcretaceous marine lignites of the Isle of Aix, near La Rochelle, and of Pialpinson, in the department of the Dordogne; these are the most ancient beds of the Cretaceous formation, or the last of the Jurassic period. Here have been found only marine plants, wood, and branches of Coniferæ.

"_2d_, In the chloriteous chalk or greensand of southern England, the neighbourhood of Beauvais and Maus; only Cycadeæ and marine plants have been observed there.

"_3d_, In the same formation in Scania, where M. Nilson has observed leaves of Dicotyledons mixed with leaves of Cycadites.

"_4th_, At Niederschoena, near Freyberg, in Saxony, beds, analogous to greensand or quadersandstein, containing fossils of considerable variety, Cycadeæ, Coniferæ, and Dicotyledons, particularly _Credneria_.

"_5th_, In the quadersandstein of Bohemia and Silesia, at Blankenburg, at Teifenfurth, Teschen, &c., where this sandstone is characterised by the presence of dicotyledonous leaves of the genus _Credneria_, by Cyeadeæ, and particularly by Coniferæ of considerable variety, described by M. Corda in Reuss' work on the Chalk of Bohemia.

"_6th_, In France, in the iron sands connected with the green sandstones, near Grand-Pré, in the department of Ardennes, where M. Buvignier has found two fossil vegetables of a very remarkable character, a stalk of an arborescent fern, and a cone previously observed in England in the same formation.

"But in other places, and in beds belonging to epochs certainly different, this period has presented only marine vegetables; such more especially are those fucoidal sandstones or macigno, characterised by Chondrites targionii, æqualis, intricatus, &c., now designated by the name of fucoidal sandstone or flysch--the geological epoch of which has long been doubtful, but which observers seem to agree in considering as a distinct formation, superior to the chalk, and inferior to the most ancient beds of the Tertiary formations.

"These fucoidal sandstones form a very distinct epoch, which hitherto appears to be characterised only by marine vegetables, and what, at least in a botanical point of view, would form the line of demarcation between the Cretaceous and Tertiary formations; for it is remarkable that the fuci found there in such great numbers have little connection with those of the Chalk, properly so called, and none whatever with those of the most ancient beds of the Tertiary formations, such as those of Monte-Bolca.

"From the study and comparison of these fossils, derived from such various sources, we may divide the Cretaceous period into three epochs, of which the middle one is the true Cretaceous epoch. The others, characterised almost exclusively by marine vegetables, are somewhat doubtful with regard to their true geological position; the one, more ancient than the Chalk, contains only the subcretaceous lignites of the neighbourhood of La Rochelle, and the Department of Dordogne; the other, superior to the Chalk, corresponds to the Sandstone with fucoides."

The _subcretaceous_ epoch comprehends Algæ, Naiadeæ, and Coniferæ.

"This small Flora is almost entirely founded on fossil plants, collected among the marine lignites of the Isle of Aix, near La Rochelle, long since described by M. Fleureau de Bellevue.

"The difference of the vegetables does not appear to admit of connecting this Flora with that of the inferior chalk or greensand; but it would require to be more completely examined, both with regard to its precise geological epoch and the entire amount of vegetable species which it contains. The most abundant and characteristic of these species is the _Rhodomelites strictus_, whose branches, crossed and mingled with _Zosterites_, constitute the mass of these lignites with the wood of Coniferæ, which have not yet been studied, and small branchlets, very rare, of _Brachyphyllum orbignianum_.

"I have referred to this period the two _Cystoseirites_, described by M. de Sternberg, and mentioned by him as found in the beds between the jurassic slates and the chalk in Transylvania.

"Does this fossil Flora correspond to a formation almost entirely marine, but cotemporary with the Wealdean epoch? New investigations can alone determine this, but we may suppose an analogy between the Brachyphyllum of the epochs."

_2d_, _Cretaceous Epoch_.--The Cretaceous epoch presents us, among the amphigenous cryptogams, with Algæ, some of which are doubtful; among the Acrogenous cryptogams, with ferns; the Monoctyledons are here represented by two species of palms; the Gymnospermous dicotyledons by the cycadeæ and coniferæ; the Angiospermous dicotyledons by a species of Acerineæ, a betulaceæ, a cupulifera, salicineæ, an acerineæ, and a juglandeæ; lastly, a few dicotyledons remain, but the determination of the families to which they belong is uncertain.

"We ought, moreover, to notice at least from ten to twelve species of dicotyledonous leaves, indeterminate, and often imperfect, figured by Geinitz, Reuss, Corda, and Goeppert, or existing in collections.

"This Flora, which contains from sixty to seventy species, is, as we perceive, remarkable in this respect, that the Angiospermous dicotyledons nearly equal the Gymnospermous dicotyledons, and in the existence of a pretty considerable number of well characterised Cycadeæ, which cease to appear at the Eocene epoch of the Tertiary formations.

"The genus _Credneria_, containing dicotyledonous leaves, with a very peculiar nervation, but the affinities of which are doubtful, is likewise one of the characteristic forms of this epoch, in a pretty considerable number of localities. With regard to the species of dicotyledonous leaves, referred to determined families, I may remark that these supposed relations, founded on very imperfect specimens, and very few in number, are still very uncertain, and incapable of furnishing a basis for comparison with the other Floras, nor any certain conclusion.

"_3d_, _Fucoidian Epoch_.--This epoch, which seems to me to form the most natural limit between the Cretaceous and Tertiary periods, is characterised by those deposits, so rich in Algæ, of a very peculiar form, that they have been called the sandstones or macignos à fucoïdes, or the flysch of Switzerland,--a formation very widely spread, especially in southern Europe, from the Pyrenees, as far as the vicinity of Vienna, and even to the Crimea.

"I have not hitherto found land plants mingled with these marine species. I do not believe that fossil woods have been met with.

"Almost all these Algæ appear to belong to the same group, the genus _Chondrites_; and although the species are pretty numerous, they pass from one to another by almost insensible shades. The Algæ of the neighbourhood of Vienna, placed in the genus _Munsteria_, are very ill characterised, and perhaps are not congenerous with those of the jurassic limestone of Solenhofen; but they appear to me to have been found in the same formation, designated by the name of gray calcareous slate, of the sandstone of Vienna, as the Chondrites of the same country."

The Flora of the fucoidean sandstone is constituted by twelve species of Algæ (_Chondrites_ and _Munsteria_.)

"What is remarkable in this series of species is, that they have nothing in common, either with the Algæ of the Subcretaceous epoch, or with those of the Eocene epoch, and particularly of Monte-Bolca, with which this Flora should be almost cotemporary, according to many geologists. The identity of these species of Algæ is likewise remarkable in all the localities, however distant from each other--localities so numerous, in regard to the greater number of these species, that I have been unable to enumerate them.

"The Chondrites targionii, or perhaps a distinct species, but very nearly related, is the only one presented in another formation, in the greensand and gault of the Isle of Wight, in England, according to M. Fitton; and in this same formation, in the department of the Oise, according to M. Graves.

"M. Kurr has likewise described and figured, under the name of _Chondrites bollensis_, a fucus of the Lias--the very varied forms of which are almost identical with the Chondrites targionii, æqualis, and difformis.

"VI. _Tertiary Period._--Considered as a whole, the vegetables of this period, cotemporary with all the Tertiary deposits, and continued even in the vegetation which now covers the earth's surface, is one of the best characterised. The abundance of Angiospermous dicotyledons, that of the monocotyledons of diverse families, but especially the Palms, during a part at least of this period, immediately distinguish it from the most ancient periods. Yet the observations made on the Cretaceous epoch have established a kind of transition between the forms of the Secondary epochs and those of the Tertiary epochs, which was not suspected a few years ago. But while, at this period, the Angiosperms appear nearly to equal the Gymnosperms, in the Tertiary period, they greatly exceed them; while at the Cretaceous epoch, there are still Cycadeæ and Coniferæ allied to the genera inhabiting tropical regions; during the Tertiary period, the Cycadeæ appear to have been completely wanting in Europe, and the Coniferæ belong to the genera of the temperate regions.

"Notwithstanding this assemblage of characters common to the whole Tertiary period, there are evidently notable differences in the generic and specific forms, and in the predominance of certain families at different epochs of this long period; but here we often experience serious difficulties in establishing a uniformity as to time among the numerous local formations which constitute the different Tertiary formations. In assigning the different localities where fossil vegetables have been observed to the principal divisions of the Tertiary series, I have not followed exactly the bases admitted by M. Unger in his Synopsis; I have approached nearer to the distribution adopted by M. Raulin, in his Memoir on the Transformations of the Flora of Central Europe during the Tertiary period (Ann. Sc. Nat., t. x., p. 193, Oct. 1848), which refers many of the formations, classified by M. Unger in the Miocene division, to the Pliocene, or most recent epoch. Yet, according to the advice of M. Elie de Beaumont, I have not placed all the Lignite formations of Germany in the Pliocene division, as M. Raulin has done, nor all of them in the Miocene division, like M. Unger; but, conformably to the old opinion of my father, I have left the Lignites from the shores of the Baltic, which include amber, in the inferior division of the old basins of Paris, London, and Brussels, considering them cotemporary with the Soisson Lignites. Those of the banks of the Rhine, of Wetteravia and Westphalia, are arranged in the Miocene division; those of Styria, and part of Bohemia, on the contrary, are placed among the recent or Pliocene formations.

"This distribution agrees pretty generally with the nature of the vegetables contained in them. One important point only leaves me in doubt: this relates to the Lignites of the environs of Frankfort or Wetteravia, the plants of which are pretty generally analogous to those of OEningen or Partschlug in Styria; although their geological position seems to call upon us to refer them to a more ancient formation.

"It is probable that a more complete knowledge of these diverse deposits would lead to a division into distinct epochs more numerous; but I think that, in the meantime, the division into three principal epochs, which I shall designate, with the majority of geologists, by the names Eocene, Miocene, and Pliocene, is sufficient for a comparison of the successive changes of the vegetable kingdom. I shall point out for each of them the localities which I think should be comprehended under these different designations.

"With regard to the general characters which result from the comparative examinations of these Floras, we find that the number of species, in the great divisions, are thus distributed in these three Floras:--

Eocene Miocene Pliocene Epoch. Epoch. Epoch. -------- -------- -------- Cryptogams, 33 ... 10 ... 13 ... Amphigenous, ... 16 ... 6 ... 6 Acrogenous, ... 17 ... 4 ... 7 Phanerogams, ... ... ... ... ... ... Monocotyledons, 33 33 26 26 4 4 Dicotyledons, 143 ... 97 ... 195 ... Gymnosperms, ... 40 ... 19 ... 31 Angiosperms, ... 103 ... 78 ... 164 --------- -------- -------- Total, 209 ... 209 ... 212 ...

"It may only be remarked that, in the first column, or Eocene formation, the fossil fruits of the Isle of Sheppey--a part only of which have been described by M. Bowerbank--have a great influence on the numbers of the different divisions of Phanerogams, and that this locality appears altogether exceptional, and is, perhaps, an example of the effect of currents conveying exotic fruits from remote climates, and accumulating them on a point of the shores of Europe.

"In this point of view, the enumeration of the plants of this first epoch is in no way comparable to that of the other epochs, where I have refrained even from introducing the small number of fossil plants from the Tertiary formations of the equatorial regions that are known, in order to confine myself to a comparison of the Tertiary Floras of Europe.

"With regard to the characters drawn from vegetable forms during these three epochs, the most remarkable appear to me, 1_st_, In the Eocene period, the presence, but rarity, of the palms, limited to a small number of species.

"The predominance of Algæ and marine Monocotyledons, which must be ascribed to the great extent of marine formations during this epoch.

"The existence of a great number of extra European forms, resulting especially from the presence of the fossil fruits of Sheppey.

"2_d_, In regard to the Miocene epoch, the abundance of palms in the greater number of localities belonging, without doubt, to this epoch; the existence of a considerable number of non-European forms, in particular of the genus _Steinhauera_, which appears to me to be a rubiaceæ allied to _nauclea_, found in many localities of these formations.

"3_d_, In regard to the Pliocene epoch, the great predominance and variety of Dicotyledons, the rarity of Monocotyledons, and, above all, the absence of Palms; lastly, the general analogy of the forms of these plants with those of the temperate regions of Europe, North America, and Japan.

"A remarkable character of the Floras of these three epochs, but which is most striking in regard to the last, in which the dicotyledonous plants are most numerous, is the absence of the most numerous and characteristic families of the division of Gamopetalis. Thus, among the numerous impressions of Partschlug, OEningen, Hoerring, Radoboj, &c., there is nothing to indicate the existence of the Compositæ, Campanulaceæ, Personneæ, Labiaceæ, Solaniæ, Boraginaæ, &c.

"The only Monopetales mentioned in great numbers are the Ericaceæ, Ilicineæ, some Sapotaceæ, and Styraceæ, families which belong almost as much to the Dialypetales as to the Gamopetales.

"In the Miocene flora only have been pointed out many Apocyneæ, and Rubiaceæ, which I have mentioned above.

"1. _Eocene Epoch._--This epoch, in the most precise limits, comprehends plastic clay with its lignites, the coarse Parisian limestone and gypsum which lie above it in the same basin; but I have not thought it worth while, in the meantime, to separate from it some formations which, according to the investigations of modern geologists, are placed between the Cretaceous formations and the inferior parts of the formations mentioned; such are the Nummulitic formations of the Vicentin, comprehending the celebrated locality of Monte-Bolca, and probably some others near it, such as Salcedo, in the Vicentin. I have likewise joined to this Flora of the Eocene formations a very remarkable locality of the basin of Paris, the relations of which with the Tertiary beds are not yet perfectly determined,--these are the beds of a species of ancient Travertin which, near Sezanne, contain numerous fossil vegetables still undescribed, and of which I shall here notice the most remarkable. These plants have very peculiar remains, and belong probably to a special Flora, unless the differences can be ascribed to a diversity of station.

"Besides the different members of the Eocene formation, properly so called, of the Paris basin, I comprehend in this Flora the fossils of the same formation in England, at the Isle of Wight, and Isle of Sheppey in the London basin. These latter fossils, consisting almost solely of fruits transformed into pyrites, constitute a whole which has no analogue in any other of the Tertiary basins of Europe; not only in the number and diversity of these fruits, but in their peculiar characters, which remove them widely from the plants whose leaves occur in the other beds of the same geological epoch. Everything, therefore, would lead us to suppose that these fruits, although belonging to plants cotemporaneous with the Eocene deposits of Europe, have been brought from distant countries by marine currents, just as fruits are still brought from the equatorial regions of America to the coasts of Ireland or Norway by the great current of the Atlantic. The deposit in the Isle of Sheppey appears therefore to be an accidental case in the Eocene deposits, and the Paris basin presents none of these fossils.

"The Tertiary basin of Belgium, which follows that of London, has yielded, near Brussels, some fossil fruits in very small numbers, but which appear identical with one of the genera most abundant at Sheppey. This is the _Nipadites_, considered at first as a species of Coco, under the name of _Cocus burtini_.

"Lastly, following the advice of my learned associate, M. Elie de Beaumont, I have included in the same Flora the plants contained in the Lignites of the shores of the Baltic and Pomerania, so rich in amber, in which these vegetables have often been preserved. It is to the labours of M. Goeppert that we are indebted for a knowledge of these vegetables, most frequently represented by very small fragments, the relations of which he has determined with much skill and accuracy."

With materials collected in these various localities, but of which the greater part are still unpublished, we may construct the Flora of the Eocene epoch; but the list, comprehending only the species described, or at least determined, is only a mere sketch.

M. Brongniart then gives the names of the vegetables belonging to the Eocene epoch; these are, for the Amphigenous cryptogams, algæ, and mushrooms; for the Acrogenous cryptogams, hepatici, mosses, ferns, equisetaceæ, and characeæ. The Monocotyledons present Naiades, Nipaceæ, and palms. The Gymnospermous dicotyledons are represented by Coniferæ (Cupressinæ, Abietineæ, Taxineæ, and Gnetaceæ.) Lastly, among the Angiospermous dicotyledons, we find examples of Betulaceæ, Cupuliferæ, Juglandeæ, Ulmaceæ, Proteaceæ, Leguminosæ, OEnothereæ, Cucurbitaceæ, Sapindaceæ, Malvaceæ, Ericaceæ, and three doubtful families (Phyllites, Antholithes, and Carpolithes.)

"The most remarkable characters of this Flora are,--