Description from Flora of China
Ruellia anagallis N. L. Burman, Fl. Indica 135. 1768; Gratiola cordifolia Colsmann; Lindernia cordifolia (Colsmann) Merrill; Vandellia anagallis (N. L. Burman) T. Yamazaki; V. callitrichifolia H. Léveillé; V. cordifolia (Colsmann) G. Don.
Annuals, 10-40 cm. Roots fibrous. Stems creeping, often branched, striate, glabrous, rooting from nodes. Leaves short petiolate to subsessile; leaf blade triangular-ovate, ovate, or oblong, 0.4-2 X 0.7-1.2 cm, glabrous, base truncate to subcordate, margin shallowly crenate, apex rounded to acute; lateral veins 3 or 4 on each side of midrib, spreading at an angle of 45°. Flowers axillary, solitary. Pedicel 6-10 mm, to 2 cm in fruit, glabrous. Calyx ca. 5 mm, basally connate; lobes narrowly lanceolate, glabrous. Corolla white or light purple, 0.8-1.2 cm; lower lip slightly longer than upper lip, spreading flat, 3-lobed, lobes subequal; upper lip ovate, 2-lobed. Filaments of anterior stamens basally with a clavate appendage. Stigma 2-lobed. Capsule linear-ovoid, ca. 2 X as long as persistent calyx. Seeds ovoid, tuberculate. Fl. Apr-Sep, fr. Jun-Nov.
Edge of forests, along streams, rice fields, wet places; ca. 1500 m. Fujian, Guangdong, Guangxi, Guizhou, Hunan, Jiangxi, Sichuan, Taiwan, Yunnan [Bhutan, Cambodia, India, Japan, Laos, Malaysia, Myanmar, Philippines, Sikkim, Thailand, Vietnam; Australia].