432 PHARMACEUTICAL BOTANY 
the land ferns have underground stems or rhizomes from which 
fronds arise. 
Fic. 325.—Dryopteris marginalis, a fern whose rhizome and stipes constitute the drug, 
American Aspidium. 
The main axis of the majority of the typical land-growing 
ferns is a creeping underground stem or rhizome which at its 
various nodes bears rootlets below and fronds above. These 
fronds are highly developed, each being provided with a petiole- 
