CHARACTERS OF TRIBES AND GENERA. 229 



late with the rachis. Veins radiating, forked, costa ex- 

 centric ; venules direct free, their apices clavate, the 

 anterior one sporangiferous. Receptacles oblong. Sori 

 terminal, elliptical, sub-marginal. Indusium oblong, 

 attached longitudinally. 



Type, Aspidiwm trttncatulum, Sw. 



Illust Hook, and Bauer. Gen. Fil., 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 NepJirolepis, 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 Aspideoe besides Mesochlcena 

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

 in the u Synopsis Filicum," has united Mesochlcena with 

 Didymochlcena, thus making a second species, which he 

 names D. polycarpa. 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 Mesocklcena scarcely differs 

 from the group to which Nephrodium 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 Didymochlaena. 

 Upon the same principle the simple fronded Fern Fadyenia 

 prolifera is referable to Didymochlcena. 



Sp. D. lunulata (Vesv.} (v v.), Hook. Sp. Fil., Hoolc. 

 Gard. Ferns., pi. 17. 



