32 EDWARD WILBER BERRY 



anatomy and segregated into five families, are referred to the 

 Pteridospermae {Cladoxylon, Volkelia, Lyginoderidron, Heteran- 

 gium, Megaloxylon, Calamopitys, Medullosa, Sutcliffia, Sieloxylon, 

 Cycadoxylon, Ptychoxylon, Protopitys). The fern like fronds 

 involved in this group with their corresponding seed forms are 

 as follows: 



Sphenopteris — Lagenostoma Callipteris — Carpolithus (in part) 



Neuropteris — Rhabdocarpus (in part) Callipteridium — Tripterospermum 



Alethopteris — Pachytesta Doleropteris — Codonospermum 



Odontopteris — Odontopterocarpus Aneimites — Wardia 



Linopteris — Trigonocarpus (in part) Dicksonites — Carpolithus (in part) 



According to Scott, the Pteridosperms exhibit two lines of 

 evolution, — one toward polystely, which becomes elaborated 

 (MeduUosaceae) and then extinct; and another in which a single 

 stele becomes elaborated (Lyginodendraceae), the latter type is 

 considered as approaching the Cycadophytes. According to 

 Chodat, Lyginodendron is a specialized fern, an end product not 

 concerned with cycad ancestry, which group originated from the 

 MeduUosaceae (which he renames Protocycadaceae). 



We know too few members of what was really a great group 

 to be dogmatic, but there can be no question but that our whole 

 conception of Paleozoic floras and ancestral seed plants has been 

 profoundly altered by what has thus far been demonstrated. 



The other great group of Paleozoic gymnosperms, exempli- 

 fied by the genus Cordaites, while they also show in their structure 

 the evidences of a fern ancestry, had travelled the evolutionary 

 road much farther than the Pteridosperms. They had lost all of 

 the more obvious fern characters and were tall trees with a thick 

 cylinder of secondary wood (Dadoxylon) of the araucarian type, 

 differing from modern conifers merely in their larger pith. Their 

 foliage consisted of a dense crown of spirally arranged, invari- 

 ably simple and elongated, and sometimes very large leaves. 

 The fructifications were small catkin-like cones, the cf and 9 

 separate as in modern conifers. The cones were small, with 

 thick spirally bracteate axes, in the one case bearing micro- 

 sporophylls, and except for the bracts comparable to Ginkgo; 

 and in the other case bearing short-stalked ovules. The pollen 



