Epiphytic or growing on rocks, etc., with short creeping rhizome bearing clathrate scales, numerous matted roots and clustered or closely spaced fronds. Fronds stipitate or sessile, linear to round, mostly without a differentiated midrib; veins anastomosing to form large elongate areoles, without included veinlets. Sori superficial or in grooves, 2 or more very long sori between the midrib and margin, or usually many on the anastomosing veins, without an indusium; paraphyses present in species without a midrib (subgen. Antrophyum to which nearly all Old World and one Central American species belong) but absent in all but 1 species with a midrib. Spores monolete or trilete.