Description from Flora of China
Plants helophytic, small. Aerial shoots creeping, unbranched or dichotomously branched, terete, sparsely leafy. Leaves spirally arranged, dimorphic or monomorphic, lanceolate, linear, or scalelike, papery, midrib indistinct, base cuneate, decurrent, sessile, margin entire, apex acuminate. Strobili solitary, erect, terete, stalked. Sporophylls different from trophophylls, dimorphic or monomorphic, subulate to lanceolate, imbricate, margin membranous and irregularly toothed, apex acute, acuminate, or obtuse. Sporangia yellow, reniform.
About 18-25(-40) species: cosmopolitan, with centers of diversity in New World tropics and New Guinea; two species in China.