DESCRIPTION OF SPECIES. 43 



a great tendency to vary without losing its essential characters, I have 

 thought it best to unite it with this somewhat abnormal form. Plate XXIII, 

 Fig. 4 a, is an enlarged portion of Fig. 4, giving the form of the sori which is 

 the same as that found in the sori of Figs. 1 and 2. Plate XXII, Fig. 1, 

 gives the normal form and size of the pinnules from the upper part of the 

 frond, where the pinnatifid pinna? of the lower part of the frond are 

 reduced to simple pinnules. Fig. la, gives the nervation of one of these 

 pinnules. Plate XIX, Fig. 4, represents a character sometimes seen where 

 the middle nerve of the pinnules becomes very broad and fiat, almost rib- 

 bon-like. Plate XXI, Fig. 2, gives normal pinnules somewhat more remote 

 than usual, and broader. Plate XIX, Fig. 5, represents a portion near the 

 upper end of one of the ultimate pinnae. It shows that the pinnules here 

 are very decurrent, and are united for a considerable distance. I have not 

 in a single instance seen the end of one of these large upper pinnae. Plate 

 XIX, Fig. 3, gives a portion of one of the pinna? near its end, where the 

 pinnules are united for a considerable distance. It, as well as Fig. 5, shows 

 the manner in which the lateral nerves go off from the rachis of the pinnae 

 in these uppermost pinnules. Plate XXIII, Fig. 3, gives a portion of one 

 of the pinnae with very long pinnules, the lowest of which are undulate on 

 the margin. In Plate XXI, Fig. 1, we have 7 pinnae which evidently go 

 off from a rachis not shown in the specimen. They show the graduation 

 from simple pinnules to undulate and crenate pinnules. Fig. 1 gives an 

 enlarged pinnule of this specimen to show the nervation and Fig. 1 a a por- 

 tion of another. In Plate XX, Fig. 1, we have three pinnae from a lower 

 portion of the frond which show the increasing depth of the lobation. Fig. 

 lb is an enlarged portion of the upper pinna to show the nervation, and 

 Fig. la is from a lower pinna likewise enlarged to show the nervation. 

 Plate XIX, Fig. 2, represents the pinnatifid pinnae from the lower part of 

 the frond corresponding to the simple pinnules of the upper part, and Fig. 

 2 a gives enlarged lobes of a portion of one of these pinnae to show the 

 nervation. Plate XXII, Fig. 3, represents what is probably a portion of 

 the stipe, and the branch a may be the base of a rachis bearing pinnae such 

 as those in Plate XX, Fig. 1. This would make the plant at least quadri- 

 pinnatifid. 



