beyond the margin of the fronds, this vein or receptacle
being enclosed within an urn-shaped involucre, consisting
of two nearly orbicular compressed valves, which are spi-
nosely serrate on the upper margin.
It is a species widely distributed throughout the United
Kingdom, and is found in many other parts of the world.
It requires the same conditions for its successful cultivation
as does the Trichomanes, to which genus the reader is
referred.
I t is the Trichomanes tunbridgense of Liunmus.
H ym en o ph y l l um u n il a t e r a l e , Willdenow. — Wilson’s
Eilmy Eern. (Plate XV. fig. 3.)
This plant is by English botanists most commonly called
Hymenophyllum Wilsoni, hut there is-no ground to doubt
that it is identical with H. unilaterale, a name published
by Willdenow long before that of Wilsoni ; we have, therefore,
adopted Willdenow’s name on the ground of priority.
The species 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-transparent fronds, averaging three or four
inches in height. The fronds are of a linear-lanceolate
form, and pinnate; the rachis is usually somewhat curved.
and the pinnæ are convex above, all turned one way, so
that the fronds become more or less unilateral ; the outline
of the pinnæ is wedge-shaped, cut in a digitate-pinnatifid
way, the lobes being linear-obtuse with a spinulose-serrate
margin.
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
primary rachis they are furnished with a narrow membranous
leafy wing or border, the primary rachis itself being
almost quite without any such border. The clusters of spore-
cases are collected around the free ends of veins, which
usually occupy the place of the lowest anterior segment, and
are included wdthin an urceolate involucre, which is divided
into two oblong convex inflected valves, which are quite
entire at the flattened edges where they meet.
This Eilmy Eern seems equally diffused with its allied
species, and they are often found in company. This,
however, seems to be the more common of the two in some
parts of Scotland, and in Ireland. It is widely distributed
in other parts of the world.-