I/O THE LIVING WORLD. 



plants tells somewhat of a similar story, and we may 

 thus conclude that even in plants, embryology re- 

 peats past history, at least in a measure. Of the 

 early history of plants, however, we know practically 

 nothing, and of the history of later ages it is neces- 

 sary to combine all sources of evidence in order to 

 get anything like a connected account. 



Plants have not left so complete a fossil record as 

 have animals. Particularly is this true of the lower 

 forms which almost universally agree in having no 

 hard parts adapted for preservation. So imperfect 

 is their preservation that it is impossible in many 

 cases to determine whether a given specimen in 

 the earliest rocks is a plant or simply a crystalli- 

 zation, a worm track, or mud crack. There is no 

 doubt that plants were in existence during the long 

 Archean (i) age. The immense beds of graphite 

 belonging to these times give us almost certain 

 proof of the fact. But no traces of them except 

 the graphite beds have survived the metamorphosis 

 of the rocks. 



In the Silurian (2) age, however, plants were un- 

 doubtedly abundant, and our first record of them is 

 thus nearly contemporaneous with that of animals. 

 But the plants were all of the lower types. 



Marine algae were doubtless in great numbers in the seas of this 

 period, and everything seems to indicate that they were not unlike 

 their descendants of to-day, which form the slimes of fresh water and 

 some of the sea mosses. Their poor preservation makes it impossible 

 to say much about them. During the Silurian (2) there were also in 

 existence at least two types of land plants, living perhaps in swamps 

 or shallow water. There was a delicate little plant named Psilophy- 

 ton, thought to be a link between two later groups (rhizocarps and 



