THE PTERIDOPHYTA : LYCOPSIDA, ETC 



615 



■^ tV^^ ^" 



Bract 





\ t 





Synang'tum 



■-**■• ,^ • 



Axis 



Fig. 625. — Psilotum triquetnini. 

 Transverse section of a syn- 

 angium showing three united 

 sporangia with thick walls. 



i. 





^Sk. 



:%. 



t\ 



^ 



« 



/ 



f 



Fig. ezb.-Psilotum triqueUum. Prothallus with rhizoids, antheridia and 

 archegonia. Enlarged about ten times. {From Zimmermann, Uie 

 Phylogenie der Pfianzen.") 



