Small annual herbs, 5–60 cm tall; stems thin, creeping, sometime erect, ascending, quadrangular, rooting at nodes, glabrous or occasionally puberulous at nodes. Leaves pinnately nerved; sessile or petiole 1–2 mm long, lamina ovate to deltoid-ovate, 7–3 x 0.3–1.5 cm, apex obtuse or acute, base subcordate, obtuse, truncate or cuneate, margins serrate, glabrous. Flowers solitary and axillary, rarely terminal; pedicel 0.7–5 cm long, glabrous. Calyx 3–7 mm long, 5-lobed; lobes divided almost to the base, linear-lanceolate to lanceolate, apex acute, glabrous. Corolla white, pink to pale purple, 8–13 mm long; glandular outside; upper lip ovate or rounded, apex emarginsate, margins undulate, glabrous, 2.5–5 mm wide; lower lip broadly 3-rounded lobes, 7–1.6 mm wide. Stamens 4, all fertile; filaments glabrous, posterior filaments straight, ca. 1.5 mm long, connective of posterior extending a long tail, anterior filaments curved, 3–4 mm long, geniculate or short spure near the base, papillose, ca. 0.5 mm long. Capsules cylindric, apex usually style joined or acuminate, glabrous, 6–15 x 1–2 mm, longer than calyx lobes, acuminate. Seeds numerous, narrowly ovoid, cylindrical, 0.25‒0.45 x 0.16‒0.25 mm, scorbiculate-foveolate
India, China, Laos, Cambodia, Vietnam, China, Malaysia, Indonesia, Philippines, New Guinea and Australia
Open areas, in swampy or marshy grounds, paddy fields, riversides, grassland, at 0–1600 m altitudes; flowering and fruiting throughout the year