Assuming these data as the basis of a philosophical generalization, M. Brongniart arranges the known species of fossil plants into three grand systems, which correspond with the great geological periods, comprehended in the palæozoic, secondary, and tertiary formations. The first or most ancient flora is characterized by the predominance of _Cryptogamic Acrogens_--the _Ferns_ and _Club-mosses_; the second by the large development of the _Dicotyledonous Gymnosperms_--the _Cycads_ and _Conifers_: the third by the appearance and prevalence of the _Angiosperms_, both dicotyledonous and monocotyledonous. The following table presents a concise view of the results of M. Brongniart's investigation.[184] [184] For details, and a masterly review of the subject, the original Memoir must be consulted. See Tableau des Genres de Végétaux Fossiles, considérés sur le point de vue de leur Classification Botanique et de leur Distribution Géologique, par M. Adolphe Brongniart. Paris, 1849. CHARACTER OF THE FLORAS. GEOLOGICAL EPOCHS. I. Règne des Acrogènes; the Flora } The _Devonian_, _Carboniferous_, of Vascular Cryptogamia. } and _Permian_, Formations. II. Règne des Gymnospermes; the } The _Triassic_, _Jurassic_ (or Flora of Cycadaceæ and Coniferæ. } _Lias_ and _Oolite_), and } _Wealden_, Formations. III. Règne des Angiospermes. } The _Cretaceous_, and _Tertiary_ Flora of Dicotyledonous and } (_Eocene_, _Miocene_, and Monocotyledonous flowering } _Pliocene_), Formations. plants, or Angiosperms. } It must be observed that this table is only designed to indicate the successive _predominance_ of each of the three classes of the vegetable kingdom, in the respective epochs, and not the entire exclusion of the others. Thus, in the two first, both Acrogens and Gymnosperms existed; but in the first period the former greatly exceeded the latter, both in number and magnitude; while in the next the Gymnosperms acquired the ascendancy; but in both these epochs, from the Devonian to the Wealden inclusive, very few if any Angiosperms, or flowering dicotyledons, existed. With the Cretaceous period the Angiosperms appear in great numbers, and in the Tertiary epochs acquire the importance they possess in the existing floras. The following analysis of the flora of the Carboniferous epoch, by M. Brongniart, will exemplify these remarks.[185] [185] See Wonders of Geology, vol. ii. pp. 726-733, for an account of the Carboniferous floras and deposits. ANALYSIS OF THE CARBONIFEROUS FLORA