CHAEACTEES OF TEIBBS AND GENERA. 229 



late witli the rachis. Yeins radiating, forked, costa ex- 

 centric ; venules direct free, their apices clavate, the 

 anterior one sporang-iferous. Ji^iceptades oblong. Sori 

 terminal, elliptical, sub-marginal. Indusium oblong, 

 attached longitudinally. 



Type, Aspidiuiii iruncatuluni, Sw. 



Illust. Hook, and Bauer. Gen. Pil., t. 8 ; Moore Ind. 

 Fil, p. 43 A ; J. Sm. Ferns Brit, and For,, fig. 81 ; 

 Hook. Syn. Fil, t. 4, fig. 41. 



Obs. — The habit and general appearance of the Fern 

 forming this genus is so peculiar and unique that it is diffi- 

 cult to point out its place in any natural sequence. Its 

 texture, its articulated pinnules, and its terminal sori, indi- 

 cate some connection with NephroJfpis, with which it also 

 agrees in the apices of the veins being marked by white 

 dots, which form a conspicuous row on the superior side of 

 the pinnules. 



In my observation on this genus in 1841 I have said 

 that "this is the only genus in A^pidece besides MesocMceim, 

 that has elongated sori," upon this character Mr. Baker, 

 in the " S^^nopsis Filicum," has united MesoMcena with 

 Didijmochkena, thus making a second species, which he 

 names D. piolycarpa. In doing this he entirely sets aside 

 natural habit, as well as the position of the sori, and nature 

 of the venation, for in habit Mesoohlcena scarcely diflfers 

 from the group to which h eplirodiam molle belongs, with 

 which it agrees in the lower pair of venules anastomosing, 

 and the sori being medial on the venules, and which is 

 entirely at variance with the character of Didijm.o(ddaiia. 

 Upon the same principle the simple fronded Fern Fadyenia 

 pirolifera is referable to Didymochlcena. 



Sp. D. Innnlata (Desv.) (v v.), Hooh. Sp. Fil., Hool:. 

 Gard. Ferns., pi. 17. 



