have successively occupied the surface of the Earth, 75 



II. Reign of the Gymnosperms. 



3. Vosgesian Period. 

 (Constituting a single epoch.) 



4. Jwassic Period. 



Keupric epoch. Oolitic epoch. 



Liassic epoch. Wealden epoch, 



III. Reign of the Angiosperms. 



5. Cretacean Period, 

 Subcretacean epoch. Cretacean epoch, Fucoidian epoch. 



6. Tertiary Period. 



Eocene epoch. Miocene epoch. Pliocene epoch. 



In reviewing these different epochs, I shall enumerate the 

 different species of fossil plants which have been observed in the 

 formations corresponding to them. In the carboniferous period, 

 I shall only indicate the genera and the approximative number 

 of species comprised in each of these genera, the characters of 

 the vegetation of this period being strongly marked and resting 

 essentially on the nature of the genera. The number of species, 

 especially in those genera rich in species, cannot be established 

 very accurately, because many of the species described by authors 

 often require a fresh examination in order to suppress synonyms, 

 and because even many of these species have only been indicated 

 by names and have not yet been described or figured. In the 

 other periods I shall give, as far as possible, the complete list of 

 described species belonging to each particular epoch, because the 

 same genera are not unfrequently perpetuated through several 

 successive epochs, the differences depending in great part on 

 specific distinctions. 



I. Reign of the Acrogens. 



The great predominance of the Acrogenous division, and in 

 particular of the families of Ferns and Lycopodiacese, the con- 

 siderable number of species of the first of these families, the 

 great development of the plants of the second, and the arbores- 

 cent form of the Lepidodendron, form part of the most striking 

 characters of this epoch; but we must nevertheless add the 

 presence of families, altogether anomalous, which we arrange in 

 the Gymnospermous division, but which differ in an evident 

 manner from the actually existing families of this division. 

 These families ceased to exist at the close of this reign of the 



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