192 J. SMITH ON THE GENERA OF FERNS. 



respect analogous to the genus Cyathea^ but from which 

 Woodsia differs in not having the elevated receptacle and 

 compressed sporangia, which characterize Cyathea, besides 

 being entirely different in habit, which is similar to the fol- 

 lowing genus. 



91. Cystopteris, Bernh. Presl. J. Sm. 



(Aspidii sp. Sw. Cyathea sp. S7mth.) 



Veins forked; venules free; sporangia medial; sori round; 

 indusium lateral, oblong-reniform, inflated, cucullate. 



Fronds slender, M-tripinatifid, from a few inches to 1 foot 

 high, idtimate segments dentate or laciniated ; sori usually 

 hecoming confluent, the free margin of the indusium dentate 

 or fmhnate. 



Examp. 1. C. atomaria, {Sw.) 2. C. alpina. Link, 3. 

 C dentata, Hook. 4. C. fragilis, Bernh. 5. C. bulbifera, 

 Bernh. 6. C. fumarioides, Schott. Illust. Schott. Gen. Fil t. 

 8. Schk. Crypt, t. 54, 57, 62. Hook. Gen. Fd. t. 52. B. 



Obs. The habit and inflated indusium of this genus indi- 

 cates some affinity with the Athyrimn section of Aspleninm; 

 but the attachment of the indusium being across, and not 

 longitudinally on the side of the venule as in Athyrium, dis- 

 tinguishes them; and from Woodsia it is known by its lateral 

 semicalyciform indusium. 



92. Lastrea, Bory, Presl, J. Sm. 

 (Aspidii sp. Auth. Nephrodii sp. Anth. Polystichii sp. Both. 



Dryopteris, Schott. Thelypteris, Schott. Arthobotrys, 



Wall. Hypodematium, Kunze. Polypodii, §. Lastrese 



sp. Bory.) 



Veins forked or costaeform and pinnate; venules direct, 

 free; sporangia medial or terminal; sori round; industvm 

 reniform, lateral. 



Fronds varying from pinnate to decompound, the pilin<B 

 or ultimate segments, entire, sinuous, or pinnatifid, fertile 

 frond sometimes contracted, the lower exterior venule of 

 forked veins, and usually all the venules of pinnate veins 



