220 THE EVOLUTION OF PLANTS 



decidedly worse off than the zoologist, for fossil 

 animals go further back than fossil plants. At 

 present we cannot for our purposes get beyond 

 the Devonian; previous records are still doubt- 

 ful as regards Vascular Plants; they are of some 

 value for the evolution of certain groups of Sea- 

 weeds, but these facts do not in any way con- 

 nect with the later Palaeozoic history, and have 

 no bearing on the descent of the higher plants. 



A remark of Darwin's applies with special 

 force to fossil plants: "The geological record, 

 at all times imperfect, does not extend far enough 

 back, to show with unmistakable clearness that 

 within the known history of the world organisa- 

 tion has largely advanced" (Origin of Species, 

 p. 308). 



In the Devonian period the Vegetable Kingdom 

 had already reached a very high level of organisa- 

 tion. The following main groups of the higher 

 plants are known to have existed at that tune , 



Cordaitese, Pteridosperms, 



Ferns, Lycopods, 



Horsetails, Sphenophylls. 



As regards the Seed-plants, we have found 

 such strong evidence of affinity between the 

 Pteridosperms and the Ferns as to leave no rea- 

 sonable doubt that they were derived from a 

 common stock; the Cordaitese have so much in 



