52 BRITTLE BLADDER FERN. 



inches high, growing in tufts. They are lanceolate 

 and twice pinnate. The stalk is erect, slender, dark- 

 coloured, and almost without scales. The veining in 

 the fronds is very evident, owing to their delicate and 

 almost transparent texture. The mid-vein of the 

 pinnules is somewhat winding, with a venule simple 

 or divided, branching off to each lobe, one branch 

 extending to the point of each marginal tooth. 

 Almost each vein bears at its termination a cluster of 

 capsules of a roundish form, which contain the seeds : 

 these increase very rapidly, and at last become con- 

 fluent. 



This beautiful little fern is distributed widely over 

 the United Kingdom, and prefers moist and moun- 

 tainous districts, in the fissures of rocks, or the inter- 

 stices of stone walls. It is rare in Ireland. It is 

 found all over the world in favourable situations, ex- 

 tending even to the Arctic regions. The varieties are 

 easily distinguished. They are : 



CYSTOPTERIS FRAGILIS DENTATA, which is smaller 

 than the original fern, and always blunter in form. 

 The veining is similar, but the fructification is at the 

 margin and not near the middle of the secondary vein. 

 One great distinction from the Brittle Bladder Fern 

 is that the clusters of sori as they ripen form a brown 

 ridge on the under surface of the pinnules. It is 

 found in the North of England chiefly. 



CYSTOPTERIS DICKIEAKA is a variety of fragilis 

 having a very compact frond. It may be dis- 

 tinguished by its deflexed over-lapping pinnae ; the 

 pinnules decurrent, broad, obtuse, with a few shallow 



