FERN TRIBE 153 
16. Firmy Fern (Hymenophillum). 
1, Tunbridge Filmy Fern (H. tunbridgénse). — Fronds pinnate ; 
pinne pinnatifid, forming a wing on each side of the rachis; the segments 
serrated and spinous. This delicate, flaccid, membrane-like fern grows in 
matted tufts, looking rather like a withered than a living plant, on account 
of its olive-brown tint, though when really dried in the herbarium it retains 
much elasticity. The slender, delicate Filmy Ferns are the smallest of our 
native species, and are somewhat like delicate mosses. The veins are so 
strongly marked, that, as in Trichomanes, they seem to form the fronds, the 
filmy cellular portion surrounding them like a wing. Their length is from 
one to three inches, they grow almost erect, and their outline is lanceolate, 
or somewhat egg-shaped. They are flat, and their pinne once or twice 
pinnatifid, their branches mostly on the upper side, though sometimes alter- 
nately on each side of the pinna. The clusters of capsules are formed round 
the axis of a vein, which runs beyond the margin of the frond—this vein, or 
receptacle, being enclosed in a kind of cup forming the involucre. This con- 
sists of two compressed valves, which are nearly round, and are swollen 
slightly at the base, and have a notched and spinous upper margin; and it 
is by this two-valved involucre that the genus is distinguished from the 
nearly allied Bristle Ferns. The rhizomes are creeping and very slender. 
This fern is not peculiar to Tunbridge Wells, though found on several 
moist rocks in that neighbourhood ; and having been first discovered there, 
the plant is known by the trivial name tunbridgénse. It is not a rare fern, as 
it grows amongst moss in damp and shady places, especially in mountainous 
or rocky districts in several parts of this country—as in Tilgate Forest, 
Sussex ; on Dartmoor, in Devonshire ; in many parts of Cornwall; in several 
localities of Cumberland, Westmoreland, Kent, Cheshire, Yorkshire, and 
Lancashire. It is also of frequent occurrence in Wales and Ireland, and in 
the latter country is sometimes very luxuriant. In Scotland it occurs as far 
north as Argyll, Stirling and Mull. 
2. Wilson’s Filmy Fern or Scottish Filmy Fern (H. wnildterale). 
—Fronds pinnate ; pinne curving backwards; segments linear, entire, or 
two-cleft. This is a small film-like fern, growing on wet rocks in various 
parts of England and Wales, and very abundant in the Highlands of Scot- 
land, as well as in many parts of Ireland, in similar situations and localities as 
those given for H. tunbridgense. 'Though it grows, like the Tunbridge Fern, 
in matted tufts, and the two plants are often found on the same rock, yet it 
is a very distinct species. The fronds are much more rigid, of a darker 
brownish-green tint, somewhat drooping in attitude, and the pinnz turning 
back in a direction contrary to that of the fructification. They are about 
two or three inches long; their outline is linear-lanceolate and pinnate. 
They last for several years, and continue their growth even after the first 
season. The rachis is somewhat arched, and the pinne are convex above, 
all turning one way, so that the fronds are more or less one-sided. The 
wedge-shaped pinnz are cut into slender, blunt, pinnatifid segments, having 
a serrated and slightly spinous edge. The rigid veins are twice branched, 
and have a narrow leafy wing; but the main stalk of the fern is not winged, 
Iv.— 20 
