178 J. SMITH ON THE GENERA OF FERNS. 



Fronds pinnate, 12 to 14 feet long; pinnae sessile cordate, 

 from \ to \\foot long by 4 — 5 inches wide. Sori linear, produced 

 on the straight parallel portion of the venule, from near the 

 midrib to their point of anastomosing. 



Species. 1. H. marginatum, {Linn.) Illust. Plum.fil. t 

 106. Hook, gen.fl. t. 55. 



Obs. The technical character that distinguishes this fine 

 fern as a genus distinct from the preceding is, in the exterior 

 margin of the reticulated venation being combined by a con- 

 tinuous vein, parallel with and close to the margin, and also 

 by its plane indusium. 



75. OxYGONiOM, Presl, J. Sm. 

 (Diplazii sp. Presl, Wall. Callipteris, J. Sm. in Journ. ofBot.) 



Veins pinnately-forked ; venules parallel till near the mar- 

 gin, then anastomosing, and reticulated, terminating with free 

 marginal veinlets. Sporangia bilateral, constituting binate 

 linear sori. Indusia plane. 



Fronds pinnate, rarely simple; pinna entire, ovate-lanceolate, 

 and acuminate. 



Species, i. O. vittaeformis, J. Sm. (Callipteris, J. Sm.) 

 2. O. ovatum, (Walt.) 3. O. alismaefolium, Presl. 4. O. ele- 

 gans, J. Sm. Illust. Presl, Reliq. Hank. t. 8.f. 3. 



Obs. From an examination of specimens of DipldZium 

 ovatum of Wallich, and D. cdismcefolium of Presl, I originally 

 considered them as not generically distinct from the following 

 genus; but the recent possession of ample specimens of the 

 above four species have now induced me to consider them as 

 forming a distinct group, distinguished from the following by 

 their entire and broader habit, as also by the fascicles of 

 venules being nearly uniform and parallel, and not anasto- 

 mosing till near the margin, as in the preceding genus, and 

 differing from it only in the sori being binate. 



Oxygonium ovatum and alismcBfolium, have hitherto been 

 observed and described as having only simple fronds; but 1 

 possess specimens with both simple and pinnate fronds grow- 



