THE EILM EEIINS. 



THE TUNBRIDGE FILM FEEN. 



Hymenoptyllum 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- 

 CHOMANINE^;) as the Bristle Ferns Trichoinanes. 

 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 TTy- 

 menopliyllum these bristles are always shorter than the 

 urn ; while in Trichomanes (a British genus also, but 

 not found in the Lake Country) they project more, so 

 that the fronds become bristly when very full of spores. 

 Hence the name of Bristle Fern. They are known 

 also by the farther difference that the involucres of 



