SAPROLEGNIALES 



179 



Fig. 68. — Rhipidium americanum Thaxter. (a) Typical plant, the branches 

 showing occasional segmentation, (^e) Sporangium with papilla of dehiscence 

 extruding swarmspores into a thin-walled vesicle which finally ruptures freeing 

 biciliate swarmspores. (/) Oogonium in which the exospore is being formed 

 by the periplasm, (g) Mature oospore. {After Thaxter 1S96.) 



