J. SMITH ON THE GENERA OF FERNS. 151 



veins of Elaphoglossum, being generally internal, and in their 

 having a distinct thickened apex, terminating within a thick- 

 ened margin. From StenocMcBna, the most obvious distinc- 

 tion is the petioles not being articulated with the racliis ; but 

 that is not always general; for in a species from Luzon, which 

 I have placed under Polyhotrya, the pinnules are truly arti- 

 culated with the rachis, but in other respects this species par- 

 takes more of the habit of Polyhotrya than of Stenochlcena. 



Sect. II. Svmplophlebie/E. 



Veins direct, their apices combined by a transverse mar- 

 ginal straight or angular vein ; or unifoi-m and reticulated; or 

 costceforra and pinnate, the venules simply or compoundly 

 anastomosing. 



41. Aconiopteris, Presl. 



Acrostichi, Sp. Hook, et Grev. 



Veins simple or forked, elevated, parallel, their apices bifid, 

 and angularly anastomosing, forming a continuous zig-zag 

 marginal vein, and producing a short excurrent veinlet from 

 the angular junctions, which terminate within the margin. 



Fronds simple, linear-lanceolate, squamose ; sterile slightly 

 plicate and marginate ; margin of the fertile membraneous, in- 

 dusiiform. 



Species. 1. A. subdiaphanum, Presl. (Acrostichum, Hook. 

 et Grev.) lllust. Hook, et Grev. Ic. Fil. t. 205. Hook. Gen. Fil 

 t. 79. h. 



Obs. This genus is formed upon a single species which, in 

 habit, is similar to Elaphoglossum, but differing in the veins, 

 being prominently elevated, and angularly combined at the 

 margin. The same characters distinguish it from Olfersia, 

 which differ also in having sporangia on both sides of the 

 segments. 



42. Olfersia, Radd. 



Veins forked, internal, parallel, their apices combined by a 

 transverse, continuous marginal straight vein ; fertile seg- 

 ments sporangiferous on both sides ! 



