140 Plant Life and Evolution 



from such seed-bearing lycopods is by no means 

 improbable. This is, however, by no means so obvi- 

 ous as the derivation of the cycads from fern-like 

 forms; but if it should be demonstrated, of course 

 it would indicate that the two orders of gymno- 

 sperms conifers and cycads are absolutely un- 

 related. Some students of the fossil gymnosperms 

 consider the Cordaitales, which are the oldest of 

 all known seed-plants, to be a composite type with 

 affinities both with conifers and cycads; but the 

 arguments brought forward in favor of this theory 

 are not entirely convincing, and it is quite as likely 

 that there is no direct relationship between the Cor- 

 daitales and any living gymnosperms. 



The earliest known Conifers, which were proba- 

 bly allied to the living genus Araucaria, which in- 

 cludes the Norfolk Island pine, are met with in the 

 later Paleozoic, from which time they increase rap- 

 idly in number and importance, until by the end of 

 the Mesozoic, practically all of the existing genera 

 are met with. With the advent of the angiosperms, 

 which began to be prominent by this time, the 

 conifers decline in importance but still have held 

 their own pretty well, and are important constitu- 

 ents of the floras of many parts of the world; but 

 their importance is due rather to number of indi- 

 viduals than to any great variety of species. The 

 conifers have shown themselves to be far more 

 adaptable than the cycads, which at present very 

 seldom occur anywhere in large numbers, while the 



