62 EERNS OP GREAT BRITAIN. 



sium is hooded, and not round and flat, and it is also 

 sufficiently like a bladder to have given this name to the 

 plants. The clusters of capsules are at first distinct, but 

 they increase very rapidly, in some cases -finally crowd- 

 ing into a mass. 



This fern is very widely distributed throughout the 

 United Kingdom, preferring moist rocky places and 

 walls in mountainous districts, and attaining the greatest 

 luxuriance on limestone soils. It forms most beautiful 

 patches of somewhat pale green verdure, springing from 

 rocky crevices, its numerous fronds growing in tufts 

 from its rhizome, and its black and wiry roots pene- 

 trating into the clefts. This plant has received much 

 attention from botanists, as it has several forms or 

 varieties, which are however intimately connected. That 

 termed C. angustdta, which is the most distinct, is, 

 however, by some writers on ferns, considered as a 

 variety of C. dentdta. The frond in this variety is oblong- 

 lanceolate, twice pinnate ; the pinnules linear lanceolate, 

 more or less forming a wing, acutely pinnatifid or 

 toothed. It is rather longer than the ordinary form, 

 and tapers more towards the point of the frond, and 

 also towards the points of the pinnae. The Brittle 

 Bladder-fern has been termed Cystea frdffilis, Cyathea 

 frdgilis, or Polypddium frdgile. 



2. C. dentdta (Toothed Bladder-fern). — Fronds ob- 

 long-lanceolate, twice pinnate ; pinnules egg-shaped, ob- 

 tuse, bluntly toothed. This plant is so similar to the 

 Brittle Bladder-fern that some writers describe it merely 

 as a variety of that plant, but Mr. Babington and several 

 of our recent writers on Perns consider it a distinct 



