THE FILM PERNS. 



87 



FIG. 25. 



pinnae pinnatifid or bipinnatifid, and having their branches 

 mostly produced on the upper side, though sometimes alter- 

 nately on each side the pinna. The fronds are virtually, as 

 is the case with the Trichomanes, a branched series of rigid 

 veins, winged throughout, except on the lower part of the 

 short stipes, by a narrow, membranous, leafy margin. The 

 clusters of spore-cases are produced around the axis of a vein, 

 which is continued beyond the margin of the fronds, this 

 vein or receptacle being enclosed within an urn-shaped in- 

 volucre, consisting of two nearly orbicular compressed valves, 

 which are spinosely serrate on the upper margin. 



This species is widely distributed throughout the United 

 Kingdom, and is found in many other parts of the world. 



The Hymenophyllums require the same conditions for their 

 successful cultivation as does the Trichomanes, to which 

 genus the reader is referred. 



WILSON'S FILM FERN. 



The name of this species is Hymenophyllum unilaterale. 

 It is perhaps more commonly known as If. Wilsoni, 



It is a small moss-like plant, with 

 numerous creeping filiform stems, 

 generally growing in dense tufts, and 

 producing a crowded mass of semi- 

 drooping, brown-green, half-trans- 

 parent fronds, averaging three or 

 four inches in height. The fronds are 

 cf a linear-lanceolate form, and pin- 

 nate ; the rachis is usually somewhat 

 curved, and the pinnae are convex 

 above, all turned one way, so that 

 the fronds become more or less uni- 

 lateral ; the outline of the pinnae is 

 wedge-shaped, cut in a digitate-pin- 

 natifid way, the lobes being linear- 

 obtuse with a spinulose-serrate mar- 

 gin. The rigid veins, branching 

 from the principal rachis, which is 

 very slightly winged in the upper 

 part, become themselves branched 

 so as to produce one venule to each 

 segment; or, in other words, the 

 veins are twice branched, and 

 throughout their entire length after 

 they leave the central rib they are furnished with a narrow 



Hymenophyllum unilaterale. 



