the numerous impressions of which M. Unger has collected, studied, and determined, partly published by him in his Chloris Protogea, and presented altogether in a special enumeration of these species recently published under the title of Flora of Parschlug. In this locality alone, M. Unger has recognised and classified 140 different species; it is the most numerous local Flora with which we are acquainted, and the geological epochs. If we compare, namely, the Tertiary fossil plants of Europe with those living on the spot now, we shall be struck with the differences of about the same value as those already mentioned between the eastern and western coasts of the continents under the same latitudes. Compare, for instance, a list of the fossil trees and shrubs from Eningen, with a catalogue of trees and shrubs of the eastern and western coasts, both of Europe, Asia, and North America, and it will be seen that the differences they exhibit scarcely go beyond those shewn by these different Floræ under the same latitudes. But what is quite extraordinary and unexpected is the fact, that the European fossil plants of that locality resemble more closely the trees and shrubs which grow at present in the eastern parts of North America, than those of any other part of the world; thus, allowing us to express correctly the differences already mentioned between the vegetation of the eastern and western coasts of the continents, by saying that the present eastern American flora, and I may add, the fauna also,* and probably also that of eastern Asia, have a more ancient character than those of Europe and of western North America. The plants, especially the trees and shrubs growing in our days in this country and in Japan, are, as it were, old fashioned; they bear the mark of former ages-a peculiarity which agrees with the general aspect of North America; the geological structure of which indicates that this region was a large continent long before the extensive tracts of land had been lifted above the level of the sea in any other part of the world. "The extraordinary analogy which exists between the present Flora and Fauna of North America, and the fossils of the Miocene period in Europe, would also give a valuable hint with respect to the mean annual temperature of that geological period. Eningen, for instance, whose fossils of all classes have perhaps been more fully studied than those of any other locality, could not have enjoyed, during that period, a tropical or even a subtropical climate, such as has often been assigned to it, if we can at all rely upon the indications of its Flora; for this is so similar to that of Charleston, South Carolina, that the highest mean annual temperature we can ascribe to the Miocene epoch in central Europe must be reduced to about 60° Fah. ; that is to say, we infer from its fossil vegetation that Eningen had, during the Tertiary times, the climate of the warm temperate The characteristic genera Lagomys, Cheldyra, and the large Salamanders with permanent gills, remind us of the fossils of Eningen, for the present fauna of Japan, as well as the Liquidambar, Carya, Taxodium, Gleditschia, &c., &c. identity of a great number of species with those of Eningen, indicates well the synchronism of these two local formations. Such other points in Styria appear likewise to be of the same epoch, as well as many localities in Hungary so rich in silicified wood. In Bohemia, the tripoli slates of Bilin and Comothau, which contain a pretty considerable number of plants described by M. de Sternberg, are no doubt referrible to this epoch, according to the nature of these plants. Lastly, the Tertiary hills, called the sub-appennine hills of Plaisantin, of Tuscany, and a part of Piedmont, as well as the gypseous formation of Stradella, near Pavia, so rich in impressions of leaves, form part of this epoch; but, with the exception of this latter point, these formations contain, in general, few vegetables. "In France, the Pliocene epoch probably comprehends a part of the fresh-water deposits of Auvergne and Ardêche. Thus, the slates of Menat and those of Rochesauve appear to me to furnish a Flora very similar to those of Eningen and Parschlug. With regard to the marls of Gergovia and Merdogne, near Clermont, I think they ought rather to be classed in the Miocene epoch; but this question can be settled only by a more attentive determination of the species. The Flora, which recapitulates all that has been described or named in these formations, is, however, essentially founded, zone, the climate of Rome, for instance, and not even that of the northern shores of Africa. We are led to this conclusion by the following argument:-The same isothermal line which passes at present through ningen, at the 47th degree of northern latitude, passes also through Boston, lat. 42°. Supposing now (as the geological structure of the two continents and the form of their respective outlines at that period seem to indicate), that the undulations of the isothermal lines which we notice in our days existed already during the Tertiary period, or, in other words, that the differences of temperature which exist between the western shores of Europe and the eastern shores of North America, were the same at that time as now, we shall obtain the mean annual temperature of that age by adding simply the difference of mean annual temperature which exists between Charleston and Boston (12° Fah.) to that of Œningen, which is 48° Fah., as modern Eningen agrees almost precisely with Boston, making it 60° Fah.; far from looking to the northern shores of Africa for an analogy, which the different character of the respective vegetations would render still less triking. The mean annual temperature of Eningen, during the Tertiary pe would not therefore differ more from its present mean than that of CharlesMers from that of Boston."-Agassiz, on Lake Superior, p. 150. as may be seen by the indication of localities, on the two basins of Parschlug and Eningen. "The Flora of the Pliocene formations is constituted by Amphigenous cryptogams, comprehending alge and mushrooms; by Acrogenous cryptogams, including a muscite, ferns, lycopodiaceæ, and equisitacea; by Monocotyledons, naiades, gramineæ, cyperaceæ, and liliaceae; by Gymnospermous dicotyledons, coniferæ, represented by cupriessineæ, abietineæ, and taxineæ; finally, by Angiospermous dicotyledons, comprehending myriceæ, betulaceæ, cupuliferæ, ulmaceæ, balsamifluæ, salicineæ, laurineæ, thymaleæ, santalacea, corneæ, myrtaceæ, calycantheæ, pomaceæ, rosaceæ, amygdaleæ, leguminosa, anacardeæ, juglandeæ, rhamneæ, celastrineæ, sapindaceæ, acerineæ, tiliaceæ, magnoliaceæ, capparideæ, sapoteæ, styraceæ, oleaceæ, ebenacea, ilicines, and ericaceæ. "The Pliocene epoch, considered in relation to Europe, for I have intentionally excluded from the preceding list some fossils of the Antilles referred to these formations, offers as peculiar characters an extreme analogy to the existing Flora of the temperate regions of the northern hemisphere; I do not say of Europe, for this Pliocene flora comprehends many genera strangers in the present time to Europe, but proper to the vegetation of America or temperate Asia. Such are, if we admit the accuracy of the generic relations established by the botanists to whom these determinations are owing, taxodium, salisburia, comptonia, liquidambar, nyssa, robinia, gleditschia, bauhinia, cassia, acacia, rhus, juglans, ceanothus, celastrus, sapindus, liriodendron, capparis, sideroxylon, achras, and symplocos, all genera foreign to temperate Europe, but in which they have been found in a fossil state, but which, for the most part, still occur in the temperate regions of other parts of the globe. "As to other genera still existing in Europe, but which contain only a small number of species, we find many more of them in a fossil state; such are the Erables, of which 14 species are enumerated in this Flora of the Pliocene epoch, and the Oaks, which are 13 in number. It ought to be remarked, that these species come from two or three very circumscribed localities which, in the present time, probably would not furnish, in a circuit of many leagues, more than three or four species of these genera. Lastly, another character, which I have already spoken of, and which makes this Flora to differ still further from that of our epoch, is the absence, or at least the small number and nature of the plants with Gamopetalous corollas. "Thus, there are only twenty plants of this Flora arranged in the families of this division, and all are referrible to this group of Hypogynous gamopetales, which I have distinguished by the name of Isogynes; in the general organization of the flowers, they approach nearest to the dialypetales. "Is this absence of Anisogynous gamopetales, and with irregular ovaries, the result of chance; or does it arise from this, that many of these plants, particularly among the species of temperate regions, are herbaceous, and that herbaceous plants are generally in conditions less favourable for passing into a fossil state? Or, lastly, did those families, which some botanists have been led to consider the most elevated in organization, not yet exist? These are points which cannot be positively determined in the present state of our knowledge. "We may however remark, that at the Miocene epoch, these plants were still less numerous, but belonging to other families; and that at the Eocene period, no one is mentioned by the authors who have shewn the connection between the fossil and living plants, without having any preconceived idea on the subject. "Another fact to be noticed, but which likewise probably depends on the herbaceous nature of these vegetables, and their leaves not being shed, is the almost complete absence of Monocotyledons, ferns, and mosses, which establishes, in regard to these families, a very great difference between the Pliocene flora and that of modern Europe. "A difference not less important distinguishes this Flora from that of the most ancient epochs ; namely, the absence, in all these formations, of the family of Ferns, which, on the contrary, furnishes so prominent a feature in the Miocene epoch. No trace of them occur in Europe in the Pliocene formations I have enumerated; while the woods of this family are very abundant in the formations of the West Indies, which is con 97 Glacial Theory of Erratics. -79 sidered as an epoch at least as recent as the Pliocene formation, which appears to indicate that at this period the zones of vegetation were distributed nearly as at present. "Indeed, in these modern formations of the Antilles, we find among the fossil woods, the only portions of their vegetables that have hitherto been collected, specimens which indicate the existence, not only of numerous and varied palms, but of many other families of the equatorial zone, such as Lianes, nearly related to Bauhinia and Menispermeæ, Pisonia, &c. The vegetation of the Antilles had therefore at this period the characters of the equatorial zone, as in Europe it had then the characters of the temperate zone. "Lastly, and to terminate our observations on this Flora of the latter geological epoch which preceded the present one, we would remark that, notwithstanding the general analogies which exist between the vegetables of these formations and those now living in the temperate regions, no species appears to be identical, at least with the plants that still grow in Europe; and if, in some rare cases, complete identity appears to exist, it is between these vegetables and American species. Thus the Flora of Europe, even at the most recent geological epoch, was very different from the European Flora of the present day."—L'Institut. Glacial Theory of the Erratics and Drift of the New and Glacialists and Antiglacialists.-Erratic basins of Switzerland.Similar phenomena observed in other parts of Europe.—Points necessary to be settled; first, the relation in time and character between the Northern and the Alpine erratics.—Traced in North America.-Not yet settled whether any local centres of distribution in America; but the general cause must have acted in all parts simultaneously.-This action ceased at 35° north latitude; this incompatible with the notion of currents.— In both hemispheres a direct reference to the Polar Regions.—Difficulty * Vide Lake Superior, its physical character, vegetation, and animals. By Professor Louis Agassiz. 1850. VOL. XLIX. NO. XCVII.-JULY 1850. G |