23 . 
TEE MOUNTAIN BLADDER FERN. 
Cystopteris montana. 
Plate 5 , Fig. 3 , Page 225 . 
Amongst our British Bladder Ferns this is not only the 
rarest species; it is, of all our native Ferns,. the rarest of the 
rare. Its common and its botanical name both indicate that 
this is a Fern of mountainous regions. It loves to grow in 
rocky crevices and on dripping rocky ledges in mountain 
ravines. From the fact that it has a creeping rootstock, or 
rhizoma, and not a tufted caudex, like the other Bladder 
Ferns, it might seem more appropriate to rank it as a 
Polypody ; and, were the form of the rhizoma the mark by 
which the Polypodies are known, there would be sufficient 
reason, perhaps, for including it in that genus. Indeed, the 
generic name of Polypodium is given to it by some botanical 
writers. But the distinguishing mark of the Polypodies is 
the uncovered or non-indusiate spore clusters, and this Fern 
has the hoodlike cover peculiar to the genus Cydopteris. 
Hence there is a sufficient reason for ranking it as a species 
under that genus. 
Description. — The general outline of the fronds, with 
the exception of the indentations of the lobes, singularly 
resembles the Three-branched Polypody. Like it, Cystopteris 
montana is very distinctly three-branched in appearance, in 
