128 Remarks on the Ancient Flora of the Earth. 



limestone, in which at least twenty species have been distinguish- 

 ed, the more perfectly organised mammalia on the other side of 

 the chalk, that is below it, seem to possess only a single repre- 

 sentative ; but on this side of it, that is above it, there occurs a 

 state perfectly comparable with the character of the Fauna of the 

 present creation, if we abstract the difference of climate. Such, 

 also, is tlie case in the extensive range of the vegetable kingdom. 

 M. Brongniart has himself explained the character of the vegeta- 

 tion of his fourth period, as perfectly similar to that now in exist- 

 ence. The dicotyledonous plants which appear here, belong, for 

 the most part, to the most perfectly developed families. In the 

 period of formation, below the chalk, M. Brongniart found among 

 the more highly organized vegetables only varieties of the na- 

 tural families of the Cycadecc and Coniferoe prevailing, — a fact 

 of very great importance, the knowledge of which we owe ex- 

 clusively to the laborious researches of this distinguished ob- 

 server. The influence which these exercise in the present crea- 

 tion onlv through a small number of genera upon the Flora of 

 these periods, seems to have induced M. Brongniart to raise 

 them to the rank of a distinct class ; for he distinguished them 

 both in the tabular survey before us, and in his History of Ve- 

 getable Fossils (livr. i. p. 20), under the denomination of 

 Phanerogamous Gymnospermes, and gave them a position be- 

 tween the Vascular Cryptogamia and the Monocotyledona. 

 However important the grounds may have been that enabled 

 the author to act thus, we can neither give an assent to the prin- 

 ciples hence deduced by him, nor consider the place assigned to 

 his new class as the right one. 



. Regarding the name of Phanerogamous Gymnospermes, occa- 

 sioned bv the remarkable researches of R. Brown, it does not 

 become us to decide on the accuracy of the fact here brought for- 

 ward. We may, however, have recourse to the opinions of two 

 botanists of the first rank, Decandolie and Richard, who consider 

 it by no means proven that the female flowers belonging to these 

 plants can be regarded as a simple ovttla, without pericarpium. 

 If further investigations, however, should shew us that the 

 families of the Cycadea and Conifera, in the numerous devia- 

 tions -which moreover so much distinguish them, still preserve 



