. 21. 



78 BRITISH FERNS. 



into large patches of numerous crowns, each of which throws 

 up a tuft of several fronds, growing from six inches to afoot, 

 sometimes more, in height. The 

 stipes is very brittle and shining, 

 with a few small scales at the base. 

 The frond is lanceolate, bipinnate, 

 the pinnae 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 pin- 

 natifid, almost pinnate, the lobes 

 themselves then resembling the 

 smaller pinnules nearer the apex of 

 the pinnae and frond. The vena- 

 tion in ordinary-sized pinnules con- 

 sists of a somewhat tortuous mid- 

 vein, which gives off a lateral branch 

 or yenule to each of the lobes into 

 which the margin is cut, these ve- 

 nules branching again into two, 

 three, four, or more veinlets, accord- 

 ing to the size of the lobes ; and 

 each branch generally bearing a 

 sorus at about midway its length. 

 The sori are thus generally nume- 

 rous, and rather irregularly dis- 

 posed; and it often occurs that 

 they are so numerous as, when fully 

 grown, to become confluent into a 

 mass of fructification covering the 

 whole under surface of the frond. 



Cystopterit fragile, 

 DieMeana. 



The sori, which are nearly circular, are covered while young 

 by a concave or hood-shaped indusium, which usually 

 becomes torn or split at the point into narrow segments, 

 and the whole soon becomes pushed back or cast off by the 

 growing spore-cases. 



The variety dentcda is generally smaller, and almost 

 always blunter in the form of its parts ; this grows from six 

 to eight inches high, and has ovate-lanceolate pinnae, with 

 ovate, obtuse, pointless pinnules, which are again divided on 

 the margin into a series of short blunt notches or teeth ; the 

 venation is more simple, and the fructification is more 



