Ferns of the Moors and Mountains 



the genus Cystopteris, whose distinguishing mark is the 

 very fine-toothed indusia, swollen or inflated near their 

 centre, covering the small globular sori. These indusia 

 are ovate in shape, and are attached to the frond by 

 their bases below the sori, over which they form a 

 kind of hood, tapering away to a toothed point. When 

 the spores are ripe the indusia are reflexed. Cystopteris 

 is formed from the Greek word kystos, " a bladder," and 

 pteris, Greek for " fern." " Bladder " is a reference to 

 the inflated centres of the indusia. 



Both ferns of this genus are very delicate in texture, 

 the membranous character of the fronds being alone 

 sufficient to distinguish them from all other mountain 

 ferns. 



The small fronds of the Brittle Bladder Fern, which 

 are about 6 inches in length and lanceolate in outline, 

 grow in tufts from a rootstock clad with almost trans- 

 parent brownish scales. These fronds are once or twice 

 pinnate, the pinnae having wedge-shaped bases and 

 being about I inch long. The pinnules are cut into 

 toothed lobes. 



This fern is named Cystopteris fragilis. It owes its 

 specific name to the delicacy and fragile nature of its 

 fronds, fragilis being a Latin word meaning " easily 

 broken." 



There are one or two varieties of this fern dis- 

 tinguished from each other by their more or less finely- 

 cut leaf segments. Many botanists, however, are 

 unwilling to declare them distinct species. 

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