Description from Flora of China
Vandellia nummulariifolia D. Don, Prodr. Fl. Nepal. 86. 1825; Lindernia sessiliflora (Bentham) Wettstein; Vandellia chinensis T. Yamazaki; V. sessiliflora Bentham.
Annuals, 1-15 cm tall. Roots fibrous. Stems erect, subquadrangular, sparsely spreading hairy on angles. Leaf blade broadly ovate to orbicular-ovate, 5-12 X 4-8 mm, abaxially glabrous or sparsely hairy only on midrib, base broadly cuneate to cordate, margin shallowly crenate to undulate or acuminate toothed, apex obtuse; veins parallel from base. Inflorescences terminal or axillary subumbels, few flowered. Central flowers sessile or short pedicelled, cleistogamous; other flowers on pedicels ca. 2 cm, sometimes sterile. Calyx ca. 3 mm, lobed to middle or 2/3 of length; lobes ovate to lanceolate-ovate. Corolla violet, rarely blue or white, ca. 7 mm; lower lip spreading flat, 3-lobed; upper lip ovate. Filaments of anterior stamens basally small appendaged. Capsule narrowly ellipsoid, ca. 2 X as long as persistent calyx, apex acuminate. Seeds brown. Fl. Jul-Sep, fr. Aug-Nov.
Edge of rice fields, along streams, wet places; below 1800 m. Gansu, Guangxi, Guizhou, Hubei, Hunan, Jiangxi, Shaanxi, Sichuan, Xizang, Yunnan, Zhejiang [Kashmir, Myanmar, Nepal, Sikkim, Thailand, Vietnam].