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THE FERN PARADISE. 
2 . 
THE ONE-SIDED EILMY FERN. 
Hymenophyllum unilaterale. 
Plate 8, Fig. 2. 
E two Filmy Ferns resemble eacb other 
closely in many important respects. 
But Unilaterale is chiefly distinguished 
from Tunbridgense by haying the leafy filaments 
on the primary branches of the fronds produced 
on the upper surface only of the branches, instead 
of on both sides, above and beneath, which is the 
case in the Tunbridge Filmy Fern. In Unilaterale 
as in Tunbrigense, what corresponds in ordinary 
Ferns to the leaflets of the fronds are branched 
veins, with filmy, semi-transparent, wing-like 
borders. The distinction between the two Ferns 
is somewhat slight. But both are found growing 
under the same conditions, often in company, their 
thin wire-like rhizomas densely interlacing with 
each other, and with the roots of the mosses which 
