CYSTOPTERIS. 
177 
Cystopteris fragilis, Bernhardi, 
The Brittle Bladder Fern, (Plate X. fig. 1.) 
This is a tufted-growing plant, spreading, if undis- 
turbed, under congenial circumstances, into large patches 
of numerous crowns, each of which throws up a tuft of 
several fronds, growing from six inches to a foot, some- 
times more, in height. The stipes, which is very brittle, 
dark-coloured, and shining, with a few small scales at the 
base, is usually rather more than a third of the length of 
the frond, and generally erect. The frond is lanceolate, 
bipinnate ; the pinnas lanceolate, the pinnules ovate-acute, 
cut more or less deeply on the margin, the lobes furnished 
with a few pointed teeth. In some of the plants, and 
usually owing to their vigour, the pinnules are so very 
deeply cut as to become pinnatifid, almost pinnate, the 
lobes themselves then resembling the smaller pinnules 
nearer the apex of the pinnae and frond. 
The venation is very readily seen, owing to the delicate 
texture of the frond. In the ordinary-sized pinnules there 
is a somewhat tortuous midvein, which gives off a lateral 
branch or vein to each of the lobes into which the 
margin is cut, these veins branching again into two, 
2 ^ 
