The Origin of Land Plants 105 



Selaginella comes nearer the seed-bearing plants 

 than does any other living pteridophyte. 



Paleozoic Pteridophytes. The horsetails and 

 club-mosses were once very much better developed 



FIG. 13 



A A club-moss, Lycopodium, showing the spore-bearing 

 cone, or strobilus, sp. 



B A sporophyll with its single sporangium. 



C A horsetail, Equisetum, showing the sheath-like leaves, 

 v, and the terminal cone made up of the sporangiophores, a 

 single one of which is shown in D sp, sporangia. 



than at the present time, this being especially the 

 case in the Paleozoic types. Many of the Paleozoic 

 pteridophytes reached tree-like dimensions and 

 showed a secondary growth in thickness of their 

 stems comparable to that which is found in most 



