THE MAIDENHAIR FERN. Í 245 
liarities of venation, have given rise to their being distributed in 
three sectional groups, which are the following :—$ Mesopleuria, 
represented by the West Indian A. Wilsoni, and the South American 
A. lucidum, in which there is a medial costa, and the sori are 
linear elongate and. continuous; $ Synechia, represented by the West 
Indian A. pulverulentum, and. A. villosum, in which the costa is 
wanting, and the sori are elongate and continuous: and $ Adian- 
tellum, represented by the native A. Capillus- Veneris, and the 
Brazilian A. cuneatum, in which the costa is wanting, and the sori 
are short, of a rounded or oblong form. These three sections embrace 
a considerable number of species widely dispersed over the earth. 
At first sight, the two forms of sori which are found among the 
species of this genus, appear to be the one like that of Pteris, and 
the other like that of Cheilanthes; and there is undoubtedly much 
outward resemblance between them. There can be, however, no 
difficulty in distinguishing either of these genera from the corres- 
pondent series of Adiantum, when it is remembered, that whilst in 
Pteris the receptacle is linear and marginal, and the indusiform 
margin overles the line of spore-cases attached thereto, and in 
Cheilanthes, the receptacle is a point close to the margin at the apex 
of a vein, also covered by a reflexed roundish lobe-like marginal 
scale, the spore-cases in Adiantum are attached to the cover itself 
and are turned over along with it. 
The name Adiantum is a latinised form of the Greek adianton, 
derived from adiantos, dry or unmoistened, and seems to apply to a 
property possessed by these plants of repelling water from the 
surface of their fronds, so that they cannot easily be wetted. - 
BRITISH SPECIES. 
A. Capillus-Veneris : a perennial, with bi-tri-pinnate fronds of which the wedge- 
shaped pinnules are set on black hair-like stalks. 


