DESCRIPTFOX OF THE SPECIKS. 97 



placed on the lower portion of the pinimles in a row on each side of the 

 niidnerve, and extend nearly to the summits of the pinnules. Tiu-y are 

 reniform, proportionally large, and inserted in the end of the u})per branch 

 of a forking nerve. 



Locality : Fredericksburg. 



This beautiful fern is not very rare at Fredericksburg. It has afforded 

 the most perfect specimens found of the ferns of the Potomac Hora, and a 

 sufficient number of them has been obtained to give a pretty good idea of 

 the character of the plant. From the size of some of the specimens we 

 may conclude that it attained the dimensions of a tree, for all the speci- 

 mens seem to be fragments of compound pinnae, which were probably ncit 

 of primary rank. PI. XIV, Fig. 1, seems to show a portion of the upper 

 part of a compound pinna, and Fig. 2 to I'epresent a portion of a pemdtimate 

 pinna coming from a part of the frond lower than Fig. 1, and hence 

 larger. Fig. 3 seems to show the summit of a compound pinna like Fig. 1, 

 and the same may be said of PI. XV, Fig. 2. Portions like PI. XIV, Fig. 

 h, and PI. XV, Fig. 4, appear to belong to the lower part of the frond, 

 where the pinnules begin to show division into teeth. 



This plant is not very near any described fern. The sterile portion 

 reminds one of Cladophlchis parva for this part of the fern beh)ngs to 

 the type of Cladophlehis. The plant is a little like Aspidium Ocrstedi Ileer, 

 but cau not be identified with that species. 



Aspidium Vikginicum, sp. nov. 



Plate XV, Fis. 7; Plate XXI, Fig. 14. 



Frond bipinnate or tripinnate; arborescent?; rachis of the principal 

 pinna stout and rigid ; pinnse of ultimate order reduced to pinnules in the 

 terminal portions of the penultimate pinnai, alternate, linear lanceolate, 

 passing through pinnately lobed pinna* into pinnules with entire margins ; 

 leaf-substance thick and leathery ; nerves slender, immersed in the leaf- 

 substance, and seen with difficulty ; pinnules of the lower piniuc opposite, 

 separate to the base ; attached by the entire base, elongate oblong, sub- 

 acute, with denticulate margins ; sterile form of the frond not seen ; sori 

 comparatively small, reniforru, in two rows, one on each side of the niid- 



MON XV 7 



