CHAP. VII. FOSSIL BOTANY. 311 



ancient and present flora of our planet must be insti- 

 tuted, it will be evident that such data must generally 

 be far too imperfect to admit of any accurate deter- 

 mination of specific differences, though they may afford 

 us sufficient materials for ascertaining several truths of 

 high interest. The class, order, sometimes the precise 

 genus, may be ascertained to which a fossil vegetable 

 belongs, even though we posses only a small fragment 

 of the plant. More frequently, these fossils bear an 

 analogy to some recent genera, which they closely re- 

 semble, but to which they cannot be accurately referred. 

 In such cases this resemblance is indicated by referring 

 them provisionally to a genus whose name is a modifi- 

 cation of the recent genus : thus " Lycopodites" is a 

 genus of fossil plants allied to " Lycopodium," but too 

 imperfectly known to have its characters fully pointed 

 out. 



(316.) Botanical Epochs. It was soon remarked, 

 when the study of fossil vegetables began to attract the 

 attention of botanists, that those from the coal-measures 

 were distinct from the plants now existing on the sur- 

 face of the earth, and that they more nearly resembled 

 the species of tropical climates than such as grew in 

 the temperate zones. Subsequent researches have shown 

 that the species embedded in different strata likewise 

 differ from each other, and that on the whole there are 

 about fourteen distinct gealogical formations in which 

 traces of vegetables occur. According to Mons. Bron- 

 gniart they first appear in the schists and limestones 

 below the coal. These contain a few cryptogamic 

 species (about thirteen), of which four are marine 

 AlgiE, and the rest ferns, or the allied orders. In the 

 coal itself above 300 distinct species have been re- 

 cognised, among which those of the higher tribes of 

 cryptogamic plants are the most abundant, amounting 

 to about two thirds of the whole. Many of them are 

 arborescent, and parts of their trunks are found stand- 

 ing vertically in the spots where they grew. There are 

 no marine plants in the formation. A few palms and 

 x 4 



