76 



which it is in general easily separated in mat-like masses. The 

 fronds vary from one to three or four inches in length, springing 

 singly at short intervals from the creeping rhizoma ; they are of a 

 very thin, almost filmy texture, and composed, like those of 7H- 

 chomanes, of the winged upper portion of the wire-like rachis and 

 its branches. The pinnae are alternate, connected throughout by 

 the wing of the rachis, and deeply once or twice pinnatifid, chiefly 

 on the anterior or upper side ; the ultimate segments are linear, 

 obtuse, and margined with sharp spiny serratures. The fructifi- 

 cation is sessile, terminating a vein, and occupying the place of 

 the first upper segment of each pinna, as expressed in our lower 

 figure ; the involucre being apparently formed by a modification of 

 the segment it supplants, similar to that of the last genus. The 

 involucre in this species is somewhat orbicular, but a little com- 

 pressed, especially toward the apices of the irregularly and sharply 

 serrated valves, and includes a short central column or receptacle 

 bearing around it the sessile thecse ; this receptacle is, as in the 

 previous instance, the extremity of the branch vein, but instead of 

 being filiform, it is thickened so as to become almost club-shaped, 

 and never extends beyond the involucre. 



The figures of this beautiful little fern represent it as growing 

 on the ground, erect; but if inverted would better display the ordi- 

 nary habit, and that in which it appears to the greatest advantage ; 

 or, clothing with a tapestry of deep olive-green the shaded perpen- 

 dicular faces of dripping rocks and caverns, when its filmy fronds 

 are nearly pendulous, and the several series overlie each other at 

 the base like the half-ruffled plumage of a bird : much of its beauty 

 is lost when growing in a horizontal position. 



It maybe cultivated in the open air by imitating its natural site, 

 and very successfully in the house under glass, on the same plan 

 as recommended for the Bristle Fern ; the chief object to be at- 

 tended to being the retention of a moist atmosphere about its 

 fronds, which, being short, do not require when grown apart from 

 other species a glass of the same elevation as the latter ; but it 

 may be planted around other larger ferns in the closed cases, and 

 vegetates luxuriantly under either circumstance, producing its 

 fructification copiously at all seasons. It is little, if at all suscep- 

 tible of injury from cold, a fact rather opposed to some of the 

 recorded habitats within the tropics, which probably refer to 

 different though perhaps nearly allied species. 



HYMENOPHYLLUM UNILATERALE. Wilson's Film Fern. TAB. 

 XLIII. 



Fronds pinnate : pinnae subunilateral, recurved, pinnatifid ; the 

 segments linear, undivided or bifid, spinosely serrated. Involucre 



