Description from Flora of China
Plants 2-10 cm tall. Stem richly branched, terete, weak; internodes short. Leaves opposite; stipules caducous, triangular or ovate-lanceolate, 0.7-1 mm, membranous, apex acute; petiole 0.5-3 mm or absent; leaf blade ovate-oblong or lanceolate to linear-lanceolate, 3-10 × 1.5-3 mm, submembranous, adaxially glabrous, base attenuate, margin entire, apex obtuse; lateral veins 2- or 3-paired, minute. Flowers axillary, solitary, sessile, subsessile, or shortly pedicellate and then pedicel 0.3-0.4 mm at fruiting stage. Sepals 2 or 3, ovate, 0.5(-0.7) mm, connate at base, apex obtuse. Petals 3, white or reddish, broadly ovate or elliptic, slightly longer than sepals. Stamens 3, shorter than petals. Ovary compressed globose, 3-loculed; styles 3, erect, free, short. Capsule compressed globose, 1-1.5 mm in diam., 3-septicidal. Seeds oblong, nearly straight or slightly curved, ca. 0.5 mm, finely and densely hexagonal reticulate-striate.
Pools, streams, paddy fields, marshy places. Guangdong, Heilongjiang, Jilin, Taiwan [India, Indonesia, Japan, Malaysia, Nepal, Philippines; Australia, Europe, North America, Pacific islands (New Zealand)].