THE FEKN PARADISE. 



2. 



THE ONE-SIDED FILMY FERN. 



Hymenophyllum unilaterale. 



PLATE 8, FIG. 2. 



[HE two Filmy Ferns resemble each other 

 closely in many important respects. 

 But Unilaterale is chiefly distinguished 

 from Turibridgense by having 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 



402 



