356 M. Brongniart on llie Vegetation of' 



and all the naturalists, who have paid attention to the subject, 

 appear now to adopt this opinion. 



There existed, at this epoch, Equiseta upwards of ten feet 

 high, and from five to six inches in diameter ; tree Ferns of 

 from forty to fifty feet in height ; and arborescent Lycopodia- 

 ceoe, of from sixty to seventy feet high. 



The essential characters of this first vegetation of the globe 

 are, therefore, the numerical predominance of vascular crypto- 

 gamic plants, and the great development of these vegetables. 



The second period of vegetation, which comprehends the 

 plants whose remains have been enveloped in the variegated 

 sandstone, is yet very little known. The terrestrial plants, 

 to the number of twenty, which have been found in this depo- 

 sit, differ toially from those of the older or newer formations, 

 and evidently indicate a particular vegetation peculiar to this 

 epoch. The numerical relations of the different classes are also 

 very different, in as far as can be determined with so small a 

 number of species. Thus the cryptogamic plants are less nu- 

 merous, and appear of smaller size. 'J 'hey do not form the half 

 of the Flora. Four or five plants belong to a ])articular genus 

 of the family of Coniferas ; but no plant of the family of Cyca- 

 deae, appears to exist at this epoch. Lastly, some monocotyle- 

 donous plants of singular appearance, but difficult to be ap- 

 proximated to living species, complete the flora. 



We see that of the four classes of vegetables which we parti- 

 cularly consider, making abstraction of the agamic and cellular 

 cryptogamic plants, three make their appearance at this epoch, 

 in place of only two which existed in the preceding period. 

 The dicotyledones are still wanting. 



The flora of the third period of vegetation is much better 

 known. Seventy species have been discovered in the formations 

 included between the shell limestone and the chalk. These 

 species are totally different from those of the older formations, 

 and give to the vegetation of this epoch very peculiar charac- 

 ters, depending upon the nature of these plants, and their nu- 

 . merical relations to each other.. 



These seventy plants still belong only to three of the great 

 classes of the vegetable kingdom. These classes are the same, 

 it is true, as those of the preceding period ; but the species, ge- 



