"II. REIGN OF THE GYMNOSPERMS.--During the preceding periods, and particularly during the Carboniferous period, the Acrogenous cryptogams predominated, and the Gymnospermous dicotyledons, less numerous, shewed themselves in unusual forms, and sometimes so anomalous that we are in doubt whether to place them in this or the preceding department; such are the Asterophylliteæ. At a later period, on the contrary, these anomalous and ambiguous forms, whose classification is often obscure, disappear; Acrogenous cryptogams and Gymnospermous dicotyledons evidently enter into families still existing, differing from them only in generic forms; the Ferns and Equisetaceæ, which represent the acrogens, are less numerous; the Coniferæ and Cycadeæ almost equal them in number, and usually exceed them in frequency, especially in the second period; by their abundance and size they afford the essential character of all these formations; lastly, the Angiospermous dicotyledons are wholly wanting, and the monocotyledons are in very small numbers. "This reign of the Gymnospermous dicotyledons is divided into two periods; the first, in which the Coniferæ predominate, and in which the Cycadeæ scarcely appear; the second, in which this family becomes predominating in the number of species, in frequency and variety of generic forms. The latter may be divided into many epochs, each presenting peculiar characters. "III. _Vosgian Period._--This period, which does not appear to have been of long duration, and comprehends only the _variegated_ sandstone properly so called, presents the following characters; _1st_, The existence of ferns, pretty numerous, of forms very often anomalous, evidently constituting genera now extinct, and which are not found even in the most recent formations; such are the Anomopteris and the Crematopteris. Stems of arborescent ferns are more frequent than during the Jurassic period; true Equisetums are very rare; the Calamites, or rather perhaps the Calamodendrons, are abundant. _2d_, The Gymnosperms are represented by two genera of Coniferæ, _Voltzia_ and _Haidingeria_, of which the species and specimens are very numerous. The Cycadeæ, on the contrary, are very rare. M. Schimper mentions only two species founded on two unique specimens of a very imperfect character, and the determination of which may be considered doubtful. "This consideration appears to me to separate completely, in a botanical point of view, the period of the variegated sandstone from that of the Keuper, although both are placed by geologists in the trias-formation. For the Cycadeæ become very abundant in the Keuper, are perfectly characterised, and often analogous to those of the Jurassic period; while the Coniferæ of the variegated sandstone are, on the contrary, wanting in this formation.