THE PTERIDOPHYTA : FILICALES, THE FERNS 



5" 



There are only two genera in the family : Hymenophyllum with a two- 

 lobed indusium and Trichomanes with an indusium in one piece. We shall 

 deal in detail only with the former genus. 



Outtr cortex 



Phloem 



Fig. 505. — Pteridium aquilinum. Transverse section 

 of the root. 



Placenta 



Sporangium 



Indusium 



Fig. 506. — Pteris serrulata. Transverse section through 

 marginal sorus showing developing sporangia. In 

 the genus Pteris no second indusium is present. 



