172 HISTORY OF BRITISH FERNS. 



pearance. This sort is usually barren, though we have 

 seen it, when somewhat less curled, produce the usual fruc- 

 tification. 



Another variety is called polysckides, or angustifolium 

 by some. The fronds of this are linear, and blunt at the 

 apex, much narrower than in the common sort, and the 

 margin is deeply and irregularly lobed, and crenated. This 

 sort is fertile, and its sori are short, and instead of being 

 ranged in a single series on each side the midrib, as is 

 usual in the common sort, they form two irregular lines 

 on each side. A very curious form, lobed in the same 

 manner as this variety, but having more the outline of the 

 common sort, has been found by Sir W. C. Trevelyan, in 

 Somersetshire; it is remarkable in having a longitudinal 

 ridge on each side between the midrib and margin, on the 

 exterior of which ridge the short interrupted sori are pro- 

 duced. 



A third variety is multifidum. This has the fronds forked 

 either near the apex or sometimes near the base; each 

 branch is again more or less repeatedly forked, and the 

 apices of all the forks are developed into irregular fan- 

 shaped leafy expansions, to which the term multifid is ap- 

 plied. Sometimes the fronds are merely forked once or 



