Membranaceous, mostly tropical small ferns, with slender often filiform creeping or rarely suberect rootstocks, the leaves usually much divided, the leaf-tissue pellucid, usually of a single layer of cells. Sporanges sessile upon a filiform, usually elongate receptacle, within an urn-shaped or tubular truncate or two-lipped marginal indusium, terminal upon the veins; ring complete, transverse, opening vertically.

Two genera, Hymenophylhun and the following, comprising some 450 or more species, abundant in the humid tropics and mainly epiphytic.