86 BRITISH FEENS. 



The variety and elegance of this plant make it a favourite 

 species for cultivation. The conditions of success are, a close 

 atmosphere, shade, moderate warmth, constant but not stag- 

 nant moisture, and a porous surface to which the roots may 

 cling. 



CHAPTEK XIX 



THE FILM FEENS. 



THE British Hymenophyllums, or Film Ferns, are small 

 moss-like plants, with pellucid fronds, distinguished, along 

 with Trichomanes, by having their fructification at the edges 

 of the fronds ; and known from that genus by having the in- 

 volucres which surround the clusters of spore-cases, two- 

 valved instead of urn-shaped or entire. They are the smallest 

 of all our native Ferns, and, being somewhat rare, or at 

 least local in their distribution, they have always been re- 

 garded with much interest. Two native species are recog- 

 nised, much like each other in general aspect, and distin- 

 guished by one or two rather minute technicalities, which, 

 however, are sufficiently obvious to those who have learned 

 how to look for them. 



The name Hymenophyllum is compounded from the two 

 Greek words which mean a membrane, and a leaf; and is ap- 

 plied to those plants with much propriety, from the mem- 

 branous texture of their leaves or fronds. 



TUNBETDGE FILM FERN. [Plate XII. fig. 2.] 



The name of this species is Hymenophyllum tunbridffense, 

 the Trichomanes turibridgense of older writers, so named in 

 consequence of its having been found in the neigbourhood of 

 Tunbridge, though occurring also in many other parts of the 

 United Kingdom. 



It grows in the form of matted tufts, on the surface of 

 damp rocks, in the sheltered humid localities which are 

 congenial to it : the black, wire-like, creeping stems being 

 entangled together, and interlaced with the mosses and allied 

 plants which are often found in its company. The fronds 

 are very short, from one to three or fix inches long, mem- 

 branous and semitransparent, almost erect, and of a dull 

 brownish-green even when fresh, which gives them in some 

 measure the appearance of being dead. These fronds are 

 lanceolate, or somewhat ovate ; they are pinnate, with the 



