ONE-SIDED (OR WILSON’S) FILM FERN. 
Hymenophyllum unilaterdle , — Willdenow. 
In Hymenojphyllum unilaterale the pinnae are what 
is called decurrent in the upper part — that is to say, 
they are prolonged beyond their points of insertion, as 
if running downwards, so that the fronds appear to be 
one-sided, or unilateral. The name of One-sided 
might therefore be employed to designate it just as 
well as if not better than the cognomen of its dis¬ 
coverer. Like H. Trunbridgense , it grows from numer¬ 
ous slender thready stems, into dense tufts, from 
which spring a crowded mass of half-drooping brown, 
green, or olive-coloured, semi-transparent fronds, 
averaging from three to four inches in height. The 
fronds are lanceolate and pinnate, the rachis is usually 
somewhat curved, the pinnae are one-sided, convex 
above, and all turned one way, as already described, 
the outlines of the pinnae wedge-shaped, digitately 
pinnatifid (like the fingers of a hand notched almost 
to the bone). The extreme or ultimate lobes are 
linear-obtuse with a spinulose-serrated margin. The 
fronds when luxuriant have a tendency to become 
branched. The veins are twice-branched, branching 
