CHAPTER IX. 
THE BLADDER FERNS 
(Cystopteris). 
YSTOPTERIS signifies, literally, Bladder Fern, 
tlie indusium or spore-cover of this family re- 
sembling a bladder or cap — a peculiarity so 
marked as to render recognition of fertile plants 
very easy. The spore-heaps are round, and 
scattered freely over the backs of the fronds. 
There are several species indigenous to Great 
Britain, the commonest being 0. fragilis; the 
others are rare. All are deciduous, with one 
doubtful exception, hereafter mentioned. Their roots are more 
or less creeping, and, their size being small, they speedily, under 
favourable conditions, make very pretty patches, subject, 
however, to the drawback that the fronds are very apt to 
turn brown as soon as they attain full size under cultivation. 
The Brittle Bladder Fern 
( Cystopteris fraaiUs). 
As its name implies, this Fern is of very delicate texture; 
the fronds are twice divided, roughly spear-shaped, and about 
6in. high. It is found growing in chinks in walls and rocks, 
and under cultivation demands the same treatment as its 
companions. It needs, however, more protection from the 
isun, which turns it speedily brown, and from wind, which 
breaks its tender fronds. It is not so impatient of moisture 
or close treatment as wall Ferns generally, and hence is not 
