OF PLANTS AND ANIMALS. 171 



nerogamia, and formed for a long succession of ages a lead- 

 ing feature in tlie flora of the antediluvian world, is evident, 

 if we consult the pages of geological history. It is true 

 that the cellular Cryptogamia, such as lichens and mosses, 

 are very seldoia found in a fossil state ; hut this is not to 

 be wondered at, when we remember that the preservation 

 of plants in this condition necessarily depends on their 

 structure. The fossil Cryptogamia, which have a woody 

 and vascular structure, have however, been preserved in 

 the greatest abundance. 



The absence of organic remains in rocks is not al\yays 

 sufficient to enable us to state that these rocks wer6 formed 

 before animals or vegetables existed, since the late Prof. 

 Eorbes has shown that, even in the present day, there are 

 depths in the ocean which are destitute of organic life. 

 Hence rocks deposited at such depths might contain no 

 organic remains. ' 



Fossil plants are found in the aqueous and stratified for- 

 mations, which have been divided into three great groups, 

 the Paleozoic, the Secondary, and the Tertiary. The Paleo- 

 zoic rocks include the Silurian, Cambrian, and Old Ked 

 Sandstone and Carboniferous formations. In the Silurian, 

 Cumbrian, and Old Red Sandstone we meet with the remains 

 of marine plants, and also a few terrestrial species. In the 

 Old Red Sandstone of Scotland, Miller has detected fucoid 

 ferns, and in the same formation at Oporto, Bunburyhas 

 found Pecopteris cyathea, P. muricata, and Neuropteris 

 tenuifolia, ferns which are closely allied to those of the car- 

 boniferous period. There was land, therefore, as well as 

 water at this remote epoch, although the abundance of fishes 

 and marine plants seems to indicate that the sea covered 

 the greater part of the earth's surface. 



Towards the close of the paleozoic period, however, land 



