CYSTOPTEKIS. 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 lengtli of 

 the frond, and generally erect. The frond is lanceolate, 

 bipinnate ; the pinnce 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, 



