NUMBER OF KNOWN FOSSIL PLANTS. 595 



the extinct ones ; while in the Pliocene (v^eiuv, more) the recent shells 

 outnumber the extinct ones. The differences between the organic 

 contents of one system and another, are in proportion to the interval 

 of geological time elapsed between them ; and the older the rocks, the 

 more are the fossils distinct from the plants of the present day. The 

 systems of organic life have always been adjusted to the actual condi- 

 tion of land and sea. 



1177. The number of fossil plants known to M. Adolphe Brong- 

 niart, in 1836, was 527. In 1845, Goeppert and Bronn stated the 

 number to be 1,792 ; and as in the 100,000 plants now known to 

 exist in different parts of the globe, a large proportion consists of cel- 

 lular plants, which would disappear in the process of fossilization, it 

 would seem that the total number of known fossil species bears a con- 

 siderable proportion to those now existing. Their numerical distribu- 

 tion in the different rocks is stated by Goeppert to be as follows : 



Older and Middle Palaeozoic, ........................................ 5fc 



Carboniferous, ............................................................. 819 



Permian, .................................................................... 58 



Triassic, ................................................................... 86 



Oolitic, ..................................................................... 234 



Wealden, ................................................................... 16 



Cretaceous, ................................................................ 62 



Tertiary, ..................................................................... 454 



Unknown, ................................................................... 11 



1792 



From this table, Murchison remarks, it appears that the newer Palaeo- 

 zoic group contains more than half the known species of fossil plants, 

 a remarkable circumstance when it is considered that the great herbi- 

 vorous land quadrupeds had no existence before the tertiary period. 

 The small number of plants in the Cretaceous system is probably 

 owing to the depth of the sea in which these formations were deposited. 



1178. Among Dicotyledonous fossils there are numerous Amenta- 

 cea3, Coniferae, and Cycadaceae, besides many doubtful species. Among 

 Monocotyledons, there appear to be plants belonging to Liliaceae, 

 Smilacese, Palmae, Potamae, Pandanaceae, &c. Among Acotyledons 

 there is a vast number of genera and species belonging to Equise- 

 taceae, Lycopodiaceae, and Filices, and a few Marsileaceae, Musci, and 

 Algae. 



1179. It is impossible in a short treatise like this to allude to many 

 of the fossil species of plants. It will be sufficient to indicate some of 

 the more important genera. The vegetable remains met with in the 

 Silurian and Devonian rocks are few and unimportant, compared with 

 those which characterize the Carboniferous period ; and their structure 

 seems to indicate either that they have been longer exposed to the 

 agency of moving water, or that they are cellular marine species. 



