324 
HYMENOPHYLLACE.E. 
the longest receptacles at present stand in Trichomanes, those 
with the most distinctly bivalved involucres in Hymenophyllum. 
These, however, are mere questions of degree, and are quite in- 
sufficient to guide the botanist who — without a prior knowledge 
of a plant — seeks, by means of books, to ascertain its generic 
and specific names. It must not, however, be understood that 
I object to the subdivision of the Linnean genus Trichomanes ; 
so far from this, I trust the time is not far distant when some 
competent botanist shall rearrange the entire group, pointing out 
characters that admit of no dispute, and leading us on to a far 
more accurate knowledge of these beautiful plants than we can 
hope to glean from any works yet before the public. 
The roots are black, wiry, and very slender ; the rhizoma 
long, black, slender, wiry and creeping. The fronds consist of 
branched series of veins, each being clothed with a membranous 
or filmy wing, the structure in this respect being exactly similar 
to that of Trichomanes ; the branches or pinnae are alternate, 
and each is more or less subdivided ; the divisions or pinnules 
are mostly in pairs ; the margin of the wing is crenate or 
denticulate. The clusters of capsules are nearly round, and 
each is seated almost at the extremity of a short vein, which in 
each pinna is next adjoining the midrib of the frond. The 
wing, or membranous portion of the frond, is divided below the 
cluster of capsules, and encloses it as in a kind of cup, which is 
usually called the involucre : the upper margin of this involucre 
is notched and uneven ; the capsuliferous vein or receptacle 
does not extend beyond the margin of the involucre. In exotic 
species, scarcely distinguishable in other respects, the involucre 
is discernible just beyond the margin, and such species are con- 
sequently allowed to retain the Linnean name of Trichomanes. 
