DIV. I 



PTERIDOPHYTA 



535 



(Cordaiteae, Cycadeae) ; they have thus great importance in the 



FIG. 506. Lyginodendron oldhamium. Transverse section of stem, (x 2. After SCOTT.) 



FIG. 507. Lyginodendron oldhamium. A, Microsporangia (OossoMeca). B, Macrosporangium 

 (Lagenostoma). Reconstruction. The open cupule bears stalked glands. (After SCOTT.) 



phylogeny of the higher plants. They became extinct in the Permian 

 period. 



In their vegetative organs the Pteridospenns resembled especially the 



