THE FILM FERNS. 
THE TUNBRIDGE FILM FERN. 
Hymenophylhm Tunbridgense. —Smith. 
The Film Ferns — Hymenophyllum, so called from 
the two Greek words hymen —a film or membrane, 
and phyllon — a leaf, belong to the same group (Tri- 
chomanine2e) as the Bristle Ferns — Trichomanes. 
They are all small moss-like plants, the smallest of 
our native Ferns, distinguished from other (foregoing) 
Ferns by having their fructification on the margins of 
the fronds, and from each other by the form and nature 
of the involucres which surround the fructification. 
These involucres are deep urn-shaped pits, in which 
are contained the spore-cases, clustered around hair¬ 
like or bristly receptacles, which bristles are indeed 
the ends of the frond-veins projecting into the urns. 
In Hymenophyllum these bristles are always shorter 
than the urn; while in Trichomanes (a British genus 
