TRICHOMANES. 
191 
it comes from two Greek words, meaning hair^ and excess^ 
in reference to these projecting hair-like receptacles. 
Trichomanes radicans, Swartz. 
The Bristle Fern. (Plate XVIIL fig. 1.) 
This very beautiful plant exists only in the immediate 
neighbourhood of waterfalls, and in situations where a 
constant moisture is maintained. Such conditions are, 
indeed, quite necessary to it, on account of its semi-mem- 
branous texture, which shrinks before an arid atmosphere ; 
and hence it can only be successfully cultivated when kept 
quite close, and constantly wetted over head. This species 
has a creeping, wiry, black-looking stem, clothed with 
pointed scales. The fronds are three or four times pinna- 
tifid, cut up into small linear segments, which are entire or 
bifid at the apex, and have a stout nerve or vein running 
up their centre, and rendered very conspicuous in conse- 
quence of the thin pellucid texture of the leafy expansions 
which surround it. Or the frond may be described as con- 
sisting of a series of three or four times branched rigid 
veins, margined throughout by a thin, pellucid, cellular 
expansion, or wing, a greater or less number of the apices 
of the veins becoming surrounded by the cellular membrane 
