CYSTOFTERIS. 
151 
Fronds lanceolate, bipinnate. Pinnae triangular. Leaflets ovate, 
toothed. 
Cystopteris is derived from two Greek words, kystos , 
bladder, and pteris , fern, and refers to the form of the 
involucre. 
The common form of this elegant little fern has an 
elongated eaudex, which throws out a number of fibrous 
roots, and from which plen- 
tiful clusters of fronds ascend. 
The numerous stems are 
brittle, dark red shading to 
black, shiny, and slender ; 
they occupy about a third of 
the length of the frond, and 
are scaly at the base. The 
fronds are lanceolate in form, 
of delicate herbaceous texture, 
and attain a height varying 
from 6 inches to 1 foot. The 
pinnse have the form of a long 
triangle ; they are divided to 
the stem, so as to be beset with pinnules, which are 
cut into more or less distinct leaflets. The delicate 
texture of the leaflets affords a good opportunity of noti- 
cing the venation 3 the mid- vein is waved and branched 
two or more times, and the sori are situated on the lower 
side branches. The sori are numerous, presently throw- 
ing back the hood-like involucres and becoming con- 
fluent, so as to cover the back of the frond with dark 
brown powder. 
This delicately-beautiful fern is a pleasant object in 
hilly districts, projecting its feathery tufts of fronds 
from rocky precipices and from beneath stranded boulder- 
