hymenophyllum

from The Century Dictionary.

• noun A genus of usually small and sometimes very minute ferns, including a large number of species with filmy pellucid fronds, found chiefly in hot and damp tropical forests; the filmy ferns or lace-ferns.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun type genus of the Hymenophyllaceae: filmy ferns