512 



A TEXTBOOK OF THEORETICAL BOTANY 



Placenta 



Stalk 



Stomium 



Indusium 



Annulus 



Fig. 507. — Pteris serridoto. Section through marginal 

 sorus with mature sporangia. 



Fig. 508. — Pteris serrulata. Metaphase stages of meiosis 

 in spore mother cells. 



