Plants evergreen, small. Rhizome siphonostelic, creeping or suberect, covered with septate hairs. Fronds linear and grasslike, or dichotomously branched and fan-shaped. Sporangia borne in 2-4 rows on extended fertile sporophores; spores monolete; gametophytes filamentous, algae-like.

More than 20 species: mainly in the tropics; two species in China.