BRITISH FERNS. 79 



usually intermixed with the almost ubiquitous Asplenium 

 Trichomanes ; in England, its geographical range is very limited, 

 being confined to the extreme northern counties, and in Ireland, 

 I believe, to a single mountain, Ben Bulben ; but here, Mr. 

 Moore informs me, it is abundant. 



The root is fibrous, black, and rather tender ; the rhizoma 

 black, scaly, and tufted ; the fronds appear in May and June, 

 arrive at maturity in August, and remain green through the 

 winter: they are fertile only. 



The rachis is naked for about a third of its length : half the 

 naked portion is black or purplish ; the remainder to the apex 

 of the frond, and all the pinnae, are of a bright vivid green: 

 the form of the frond is narrow, elongate, linear, and simply 

 pinnate ; the pinnae are not so numerous as in A. Trichomanes ; 

 they are somewhat quadrate, but without angles, and more or 

 less crenate at the- margin : they are mostly placed alternately 

 on the rachis, are usually very distinct, and separate, but some- 

 times crowded ; they are attached to the rachis by their stalks 

 only. 



The lateral veins are either simple or forked ; they bear an 

 elongate linear mass of thecae, almost immediately on leaving the 

 midvein ; and, if forked, the division takes place beyond the mass 

 of thecae ; this is the most decided specific character possessed by the 

 plant : the veins do not reach the margin of the pinna ; the 

 thecae are at first covered by a linear, elongate indusium ; this 

 soon disappears, and they become confluent in a ferruginous 

 mass, occupying the centre of the pinna, and concealing the 

 midvein : the masses at first are four or six in number. 



