THE BRISTLE FERN. x 289 
which the spore-cases are developed. The peculiarity resides in its 
being entire or monophyllous as it is sometimes described, or truly 
urn-shaped ; while that of Hymenophyllum is split down to the base 
into two divisions, and hence becomes two-valved. 
The plants referred to this genus are widely distributed over the 
warmer regions of both hemispheres, but are more especially abun- 
dant in tropical America. They grow only in situations where 
shade and moisture abound; indeed their structure is not adapted 
for situations which are exposed or influenced by a drying atmosphere, 
and exposure for a few hours to conditions like these, would suffice to 
shrivel up their fronds. Their natural habitats are the deep recesses 
of tropical forests, where they luxuriate on the trunks of trees or on 
dripping rocks, surrounded by an atmosphere loaded with vapour. 
The species of Trichomanes, excluding one or two which have 
spicate fructification (Fees, Bory) and reticulated veins (Hymeno- 
stachys, Bory), range under two sections, namely, $ Hutrichomanes, 
and $ Didymoglossum. The first of these groups contains those 
species which have the involucres equally truncate and plane or 
spreading at the mouth, as in T. radicans; the second which com- 
prises those in which the mouth of the involucre becomes two-lipped 
from the unequal extension of its margin, is well represented by the 
T. Filicula òf India and the East. 
The name Trichomanes is an ancient Greek word, which is sup- 
posed to belong to Asplenium Trichomanes. It is said to be derived 
from thrix, trichos a hair or bristle, and manos soft thin or porous; 
the former term, it has been suggested in regard to its present ` 
application, alluding to the hair-like receptacles, and the latter to 
the texture of the frond. Another derivation, at least as applicable 
as the foregoing, is from riz, trichos a hair, and mania excess, in 
allusion to the long hair-like exserted receptacles. 

BRITISH SPECIES AND VARIETY. 
T. radicans: fronds ovate or triangular ovate, the divisions usually crowded. 
var. Andrewsii: fronds narrow lanceolate-ovate, the primary divisions 
narrow and distant. ` 

