3. Elatine ambigua Wight in Hooker, Bot. Misc. 2: 103. 1830.
长梗沟繁缕 chang geng gou fan lü
Plants 1.5-3 cm tall. Stem richly branched. Leaves subsessile or shortly petiolate; stipules lanceolate, ca. 1 mm, membranous, margin dentate, apex acute; petiole (if present) ca. 1 mm; leaf blade spatulate, lanceolate to ovate-lanceolate, or elliptic, 2-5 × ca. 0.7 mm, margin entire, apex subacute. Flowers axillary, solitary; pedicel conspicuous, curved downward at fruiting stage, 1.5-2.5 mm. Calyx 3-fid; lobes oblong-ovate or broadly lanceolate, ca. 0.5 × 0.3 mm, apex obtuse. Petals 3, reddish, long elliptic, elliptic, or ovate, 1-1.5 × ca. 0.5 mm, 2-3 × as long as sepals. Stamens 3, shorter than petals. Ovary obovoid, 3-loculed; styles 3. Capsule cylindric-ovoid, 3-septicidal. Seeds nearly straight or slightly curved, ca. 0.5 mm, reticulate-striate.
Lakes, pools, marshy places. Yunnan [Bhutan, India, Indonesia, Malaysia, Vietnam; naturalized in Australia, Europe, and North America (California)].