Plants epiphytic, terrestrial, or on rock. Stems long-creeping, often threadlike and intertwining, or short-erect, protostelic, bearing brown hairs of 1--2 types. Roots sparse or absent. Leaves small, 0.5--20 × 0.2--5 cm, often forming dense mats. Petiole short, threadlike to wiry, often winged part or entire length. Blade ovate or oblong to lanceolate, simple to decompound, usually 1 cell thick between veins (except Trichomanes membranaceum Linnaeus), entire or dentate; scales or simple and/or stellate hairs often borne on veins or leaf margins. Veins free and divergent, occasionally present as unattached "false" veins. Sori marginal on vein ends, enclosed by 2-valved or conic involucres. Sporangia borne on moundlike receptacle or on elongate "bristle," sessile or short-stalked; annulus oblique. Spores green, globose, trilete. Gametophytes filamentous or ribbonlike or a combination of both, much branched, 0.2--1 cm, often bearing gemmae, persistent, clone-forming by vegetative reproduction.