WAYSIDE AND WOODLAND FERNS. 



Filmy Ferns (Hymenophyllea). 



This tribe of Ferns is represented in Britain by three species 

 only : the Tunbridge Filmy-fern, the One-sided Filmy-fern, 

 and the Bristle Fern. They are characterized by very thin 

 translucent fronds that are only one cell thick, and by the 

 spore-cases being girt by a complete ring, and enclosed in 

 an urn-shaped indusium (Plate 10). 



Tunbridge Filmy-fern (Hymenophyllum tunbridgense). 



Our two Hymenophylhims grow in continuous sheets of matted 

 threads from which arise the small pellucid fronds. They are 

 more like mosses in their habit than ferns, clinging .to the 

 surfaces of rocks and tree-roots rather than rooting in them. 

 The rootstock is long and slender, no thicker than a piece of 

 fine thread, and the fronds arise from it singly at intervals. 

 Those of the Tunbridge Fern are of such delicate texture that 

 they require to be perpetually bathed in an atmosphere heavily 

 charged with moisture, and where no stray sunbeam, nor, 

 indeed, any strong light can fall upon them. Their favourite 

 habitat is the near neighbourhood of a waterfall where the 

 spreading branches of tall trees shut out all light that has not 

 been filtered by passing through their tender foliage. Here, 

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