Description from Flora of China
Herbs annual, glabrous, 25--50 cm tall. Stems arcuately erect to ascending, obscurely quadrangular, simple or branched from base, sparsely black glandular punctate. Leaves alternate, occasionally opposite at base of stem; petiole 1/4--2/3 as long as leaf blade, narrowly winged; leaf blade ovate to rhomboid-ovate, rarely ovate-lanceolate, 1.5--5 X 1--1.3 cm, submembranous when dry, sparsely dark purple or black glandular striate near margin or along midvein, base short attenuate to subrounded, rarely cuneate, apex acute. Racemes terminal; bracts subulate, usually ca. 1/2 as long as pedicels, rarely ca. as long as pedicel. Pedicel 5--12 mm, elongating slightly in fruit. Calyx lobes ovate-lanceolate, ca. 3 mm, black striate outside, margin membranous, apex acute. Corolla white or pink; tube ca. 2 mm; lobes spatulate to oblong obovate, 4--4.5 X 1.6--2 mm, apex obtuse. Stamens long exserted; filaments adnate to base of corolla lobes, free parts to 6 mm; anthers ovate, dorsifixed, ca. 1 mm. Ovary sparsely puberulous; style ca. 7 mm. Capsule subglobose, ca. 4 mm in diam. Fl. Apr-May.
Damp places on grassy mountain slopes, streamsides; 1000--2300 m. W Guangxi, Guizhou, SW Sichuan, Yunnan [Bhutan, India, Laos, Myanmar, Nepal, Thailand].