DESCRIPTION OF THE SPECIES, 91 



placed, cuneate at base, those in the lower part of the from! cut more or 

 less deeply into oblong acnte to obtuse lobes, passing- towards the tips of 

 the ultimate pinn;c into lol)ed piiuuiles like those of the upper part of tlie 

 frond, and at tlie tips into ovate or oblong lobes and teeth. In the upper 

 part of the frond they are elliptical, three lobed, or entire; all the pinnules 

 and segments are broad. The ultimate pinmB and the pinnules of the 

 lower part of the frond usually terminate in three lobed segments or in 

 broad elliptical jjinnules. The nerves are copiously branched, diverge 

 flabellately into the lobes and teeth, and are very distinct and strong. 



Localities: Fishing hut above Dutch Gap Canal, rather connnon; 

 Fredericksburg ; Deep Bottom ; near Telegraph Station ; at all except the 

 first rare. 



This is the most common fern at the fishing hut above Dutch Gap 

 Canal, and a number of good specimens were found there, although none 

 of them are of large size. CI. XXXV, Fig. 4, is somewhat different from 

 the normal forms in showing a keeled principal rachis, and in the narrower 

 segments of the i)innules. It resembles PI. XXXVII, Fig. 1, the only 

 specimen found at Deep Bottom. In PI. XXXVI, Figs. H-S, are given the 

 normal forms which are most common at the fishing hut locality. None 

 of the specimens .show apparently anvtliing more than fragments of a com- 

 pound pinna, which, in the case of the stoutest forms, may be a primary 

 pinna. The rachi.ses of the compound penultimate piniiie are sometimes 

 swollen at the insertion of the ultimate ])inna'. Tlie plant is a very well 

 characterized one, and can usually be distinguished at a glance. It is one 

 of the more widely diffused ferns of the Potomac flora. It is not nearly 

 allied to any previously described plant known to me. 



Sphenopteris ^Iantklli Brongn. 



Plate L, Fi^s. 1/2. 



Frond bipinnate or tripinnate ; primary pinnjic in outline ovate-lance- 

 olate, acuminate; secondary pinna?, alternate, approximate, erect, fasti- 

 giate; pinnules alternate and opposite, straight, linear, or linear- cuneate, 

 at base adnata and decurrent, at the apex acuminate, very entire, the 

 lower ones often dentate or pinnatifid. 



