TricTiomanes.] XCIV. FILICES. 571 



localities, in western Spain, South Wales, Yorkshire, Argyleshire, and 

 Killarney in Ireland. Fr. summer. \T. Andrewsii, Newm., is a pretty 

 form with a narrower frond, many-winged involucres, and larger 

 receptacles.] 



XVII. HYMENOPHYLLUM. FILMY FERN. 



Half-pellucid Ferns, closely resembling Trichomanes, but usually 

 smaller ; the involucres deeply divided into 2 lobes, and the bristle or 

 receptacle usually concealed within them.' 



A large genus, with nearly the same range as Trichomanes. 



1. H. tunbridgense, Linn. (fig. 1314). Tunbridge F. Rootstock 

 very slender, creeping, and much branched with numerous fronds, 

 forming broad, dense, almost moss-like patches. Fronds pinnate, 

 seldom above 2 or 3 inches long, lanceolate in general outline ; the 

 stem very slender ; the segments deeply divided into 3 or 8 or more 

 oblong-linear lobes, which appear minutely toothed when seen through 

 a lens. Involucres at the base of the segments or their lobes, on their 

 inner edge, ovate, about a line long, deeply divided into 2 flattish lobes, 

 often minutely toothed round the edge. 



In moist, rocky, or shady situations, dispersed over most of the 

 warmer mountain districts of the Old World, especially in the southern 

 hemisphere, more rare in America, extending from the Canary Islands 

 and western Europe to Belgium and Norway, but not recorded from 

 eastern Europe or any part of the Russian dominions, nor from North 

 America. Generally distributed over the greater part of Britain, but 

 more frequent in Scotland, northern and western England, and Ireland, 

 than in eastern England. Fr. summer and autumn. A variety with the 

 valves of the involucre entire, not toothed, is usually distinguished as 

 a species, under the name of H. unilateral, Willd. (fig. 1315), or H. 

 Wilsoni, Hook. , but the other characters, said to accompany this one, 

 such as the narrow involucres, the different direction of the lobes of the 

 fronds, &c., do not appear to me to be so constant as they are supposed 

 to be ; and the teeth of the valves, when present, are very variable. 

 The entire-valved form is the most common in Scotland and Ireland, 

 but the two are often intermixed. 



