Description from Flora of China
Capraria crustacea Linnaeus, Mant. Pl. 1: 87. 1767; Vandellia bodinieri H. Léveillé; V. crustacea (Linnaeus) Bentham.
Annuals, 10-20 cm tall, much branched. Branches widely spreading, subquadrangular, deeply sulcate, glabrous. Petiole 1-8 mm; leaf blade triangular-ovate to broadly ovate, 1-2 X 0.5-1.1 cm, abaxially pilose along veins to subglabrous, adaxially subglabrous, base broadly cuneate to rounded, margin shallowly crenate or serrate, apex obtuse to subacute. Flowers axillary and solitary or in short apical racemes. Pedicel slender, 0.5-2.2 cm, subglabrous. Calyx urnlike, 3-5 mm, shallowly lobed; lobes triangular-ovate, outside sparsely pubescent. Corolla purple, 5-8 mm; tube slightly longer than calyx; lower lip 3-lobed, middle lobe larger and slightly longer than upper lip; upper lip ovate, sometimes shallowly 2-lobed. Stamens didynamous. Style fugacious. Capsule broadly ellipsoid, almost as long as persistent calyx. Seeds pale yellow-brown, subglobose, scrobiculate. Fl. and fr. year round.
Moist areas, rice fields, grassland, trailsides; below 1300 m. Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hainan, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Sichuan, Taiwan, Xizang, Yunnan, Zhejiang [widely distributed in tropics and subtropics].