196 J. SMITH ON THE GENERA OF FEIINS. 



91. DiDYMOCHLiENA, DeSV. 



(Aspidii sp. Su>> Tegularia, Reinw.) 



Feins radiating, forked; venw/es direct, free, the exterior 

 one fertile; sporangia termina] ; son elliptical ; indusiutn ob- 

 long, central, and longitudinally attached. 



Fronds bipinnate ; pinnules ohlong, elliptical, truncate, 

 oblique at the base, the midnb eccentric, vanishing towards 

 the apex ; petiole articulated with the rachis, apex of sterile 

 venules, thickened and clavate. 



Species. D. truncatula, {Sw.) (D. sinuosa, Desv. Aspi- 

 dium squamatLim, IVilld. Tegularia adiantifolia, Reinw.) 

 lUust. Hook, et Bauer Gen. Fit. t. 8. 



Obs. This genus is founded upon a very fine, beautiful, 

 and distinct fern, a native of Brazil, and the islands of Java 

 and Luzon : its fronds are usually from two to five or six 

 feet in length, and produced from a short arboreous caudex. 

 It is the only genus in Aspidiece besides Mesochlcena, that has 

 elongated sori. It belongs to that peculiar group of ferns 

 which have the pinnae or ultimate segments of the fronds 

 articulated with the rachis, and therefore deciduous as in 

 some species of Drynaria, Stenochlana^ Adiantum, and some 

 of the immediate following genera; and which structure is 

 analogous to a similar articulation which forms the attach- 

 ment between the base of the stipes and rhizoma of many 

 ferns, especially those which have a creeping rhizoma pro- 

 ducing the fronds in an alternate manner from the sides ; and 

 it is worthy of notice, that the whole of the species so charac- 

 terized, have a great affinity in many other respects. 



95. Nephrolepis, Schott. 

 (Aspidii sp. Sw. and Auth. Nephrodii sp. R. Br. and Auth.) 



Veins forked ; venules direct, free, the lower exterior one 

 fertile ; sporangia terminal ; sori round ; indusiiim reniform^ 

 or sometimes nearly orbicular. 



Fronds pinnate, linear; pinnce lanceolate, crenate, ser- 

 rate or auricidate at the base ; costce sometimes slightly/ ec- 



