PTERIDOPHYTA 



269 



FIG. 234. Botrychium Virginianum. Development of the sporangium. A,B, young 

 sporangia ( X 480) . C, an older one ( X 240) ; all median sections ; the sporogenous 

 cells have the nuclei shown. 



FIG. 235. Marattia Douglasii; development of sexual organs. A, B, C, arche- 

 gonium. D-F, antheridium. F, surface view of antheridium, showing opercular 

 ceil. 6, two sperm-cells, containing ripe spermatozoids. H, free spermatozoid. 

 (A-F, X400; G, H, X 800.) 



