"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 considered 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.