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DescriptionTerrestrial or epiphytic herbs, annual or perennial. Stems erect or creeping and mat forming, alternate or dichotomously branched, glabrous or pubescent; roots arising basally or throughout the lenght of the stem, mainly from the branch axils. Leaves ligulate, thin, numerous, small, simple with an unbranched central vein, glabrous or hairy, either spirally arranged and ± similar in shape and size or dimorphic and 4-ranked, the lower (lateral leaves) patent, the upper (median leaves) appressed and pointing forwards. Sporangia dehiscent with 2 valves, borne singly in the axils of the leaves, sporophylls arranged in ± compact terminal cones, heterosporous.