106 HISTORY OF BRITISH FEIINS. 



CYSTOPTERIS FRAGILIS, Bernhardi. The Brittle Bladder- 

 Pern. (Plate X. fig. 1.) 



This is a tufted-growing plant, spreading, if undisturbed 

 under congenial circumstances, into large patches of nume- 

 rous crowns, each of which throws up a tuft of several 

 fronds, growing from six inches to a foot, sometimes 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 form of the frond is lanceolate ; it is 

 bipinnate, the pinnse 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 pinnse 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 venule to each of the lobes into which the margin 

 is cut, these venules branching again into two, three, four, 

 or more veinlets, according to the size of the lobes, and each 



