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Small perennial herbs, prostrate to ascending, often rooting at the nodes, mainly branched at the base. Stems terete to quadrangular, sometimes with scattered enatia as are also found on the leaves. Leaves opposite, or in 4, rarely in 2 rows, rarely subverticillate, simple, entire to dentate. Flowers polygamous, rarely monoecious, 4-merous, in axillary congested clusters of 1-11 flowers, consisting out of 1 ♂ and 2-10 ♀ and/or 1 ☿ and 2-10 ♀, rarely with either 1-3 ♂ or 1-7 ♀ flowers. ♂ Flowers: long-stalked; sepals as in ♀; stamens 8 or (not in Mal.) 4; ovary rudimentary, conical, sometimes with some reduced ovules; style often rudimentary. ☿ Flowers: shortly to long-stalked; petals and anthers as in ♂, for the rest as in ♀. ♀ Flowers: subsessile to shortly stalked; sepals connate at the very base, mostly triangular; ovary urceolate with (4-)8 ribs, imperfectly 4-celled^when young, later 1-celled with a central columella. Fruit nut-like, pericap hard, enlarging to fruit-size long before the seed is set.
Flowers in axillary 3–11(15)-flowered fascicles, or rarely solitary; fascicles sometimes of 1–3 pedicellate central hermaphrodite flowers with the others female and sessile or subsessile, or sometimes having 1 long-pedicellate central male flower with the others female and sessile or subsessile, or sometimes having 1–3 long-pedicellate male flowers in the upper leaf-axils and 1–7 sessile or subsessile female flowers in the lower leaf-axils.
Perennial low-growing herbs, sometimes weakly suffruticose plants, with a ± creeping rhizome and rooting at the lower nodes; stems usually branching at the base, often reddish.
Calyx-tube urceolate or ellipsoid, with longitudinal nerves which sometimes alternate with often strongly mamillate ribs; calyx-lobes 4, triangular, persistent.
Leaves simple, opposite or in (3)4 rows, rarely verticillate or alternate, usually small; leaf-lamina entire to dentate, sessile or shortly petiolate.
Gynoecium 4-locular, becoming 1-locular by resorption of septa; ovules 4; styles 4 or absent; stigmas papillose.
Nutlets small, with or without 4 or 8 tuberculate longitudinal ribs.
Petals 4, sometimes rudimentary or absent in female flowers.
Seeds 1, pendulous; embryo cylindric.
Stamens 4 or 8, or absent.
