CHAPTER XVIII. 
THE FILMY FERNS. 
these beautifully delicate forms of vegetable 
life the families all over the world are com- 
paratively few, though the species are fairly 
numerous. In Britain we have three species, 
representing two families — viz., Hymenophyllum 
tunhridgense and H. unilaterale, commonly called 
the Tunbridge Filmy Fern and the one-sided 
Filmy Fern, and Trichomanes radicans, or the 
Killarney Fern, frequently called also the Bristle 
Fern — of which we will give a short description under each 
heading, referring our readers to Chapter YI., in our first 
section, for remarks regarding their cultivation. 
The Tunbridge Filmy Fern 
(Hymenophyllum tunhridgense). 
This very delicate and charming little Fern is admirably 
illustrated in Fig. 32, and hence we need not describe its 
form. In colour it is a very dark, semi-transparent green, 
and when well grown it forms a dense mat, the tiny, hair- like, 
creeping roots interlacing thickly with each other, and throwing 
up an immense number of fronds. This species, like all its 
relations, only thrives within the humid influences of running 
water, and is at home within reach of the spray of mountain 
cascades, where it may be found lining the crevices of the 
rocks, and forming a lovely tapestry upon their surfaces. It 
