208 THE MEDALS OF CREATION. Cuap. VI. 
and variety ;—are phenomena, which the facts brought be-— 
fore us in the course of this argument, present in a ee ‘ 
point of view. j 
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 pala- 
ozoic, secondary, and tertiary formations. g 
The first or most ancient flora is characterized by the — 
predominance of Cryptogamic Acrogens—the Ferns and © 
Olub-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. * ; 
CHARACTER OF THE FLORAS. GEOLOGICAL EPOCHS. 
I. Régne des Acrogénes ; the Flora The Devonian, Carboniferous, and — ‘| 
of Vascular Cryptogamia. Permian, Formations. ; 
Il. Régne des Gymnospermes ; the The Triassic, Jurassic (or Lias 
Flora of Cycadacez and Co- \ and Oolite), and Wealden, — 
nifere, Formations. : 
III. Réegne des Angiospermes ; the » 
Flora of Dicotyledonous and 
Monocotyledonous flowering 
plants, or Angiosperms. 
The Cretaceous, and Tertiary 
(Locene, Miocene, and Pliocene), 
Formations. 
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 — 
* 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 Bo- 
tanique et de leur Distribution Géologique, par M. Adolphe Brongniart. ~ 
Paris, 1849. 
