^» ASPIDIUM. 



the others anastomosing angularly, and forming on their exterior 

 sides or angular junctions excurrent fertile free veinlets. 



Sporangia medial. 



Sori circular, transversely-multiserial, abundant. 



Indusiam orbicular, central. 



Fronds pinnate. 



Distinguished from Polystichum in the anastomosing venules. 

 Habit and texture very similar to Polystichum. 



The venation of Cyrtomium and the position of its sori is 

 nearly similar to the sections Gonioplilebium and Cyrtophlehium 

 in Polypodium. Distinguished by having an indusium. 



NEPHRODIUM. Schott. 



Veins pinnate, costEeform, the lowest pair or pairs of venules 

 fertile, and angularly anastomosing; their points of meeting 

 combined by an excurrent anastomosing sterile veinlet. 



Sporangia medial. 



Sori circular, a row on either side of the veins. 



Indusium mostly reniform, rarely orbicular. 



Fronds simple or pinnate; pinnae entire, serrate, or sinuously- 

 pinnatifid. 



Distinguished by the anastomosing venules. 



Nephrodium in venation is similar to the section Goniopteris 

 in Polypodium, and only distinguished by having an indusium. 



LASTREA. BoRY. 



Veins pinnate, forked, or costeeform; venules direct and free. 



Sporangia medial or terminal. 



Sori circular. 



Indusium lateral, reniform, smooth, or pilose. 



Fronds varying from pinnate to decompound. 



Only distinguished from the true form of Polypodium by the 

 presence of an indusium, being similar in habit and venation. 

 Those with bipinnatifid fronds only distinguishable from 

 Nephrodium by not having anastomosing venules. 



POLYSTICHUM. Roth. 



Veins pinnately-forked; venules direct and free, the lower 

 exterior one or more, fertile. 



