Description from Flora of China
Annuals, 20-35(-55) cm tall, black when dry, subglabrous to sparsely villous, mostly with eglandular hairs. Stems 1 or 2-7-fascicled, quadrangular, winged along ribs. Leaves early deciduous below, sessile, linear, rarely linear-lanceolate, 1.5-4.5 cm X 2-6 mm, herbaceous, subglabrous to sparsely pubescent, base cuneate, margin entire, apex narrowly acute; midvein abaxially raised. Racemes 1/4-1/2 of stem length. Flowers 4-6, often paired. Bracteoles linear. Calyx 1.2-1.5 cm X 6-9 mm; lobes 5, subtriangular. Corolla yellow, 1.4-1.6 cm, outside sparsely pubescent; tube 8-10 mm; lower lip 4-5 mm, lobes suborbicular; upper lip emarginate. Stamens included; anther locules narrowly ovate, ca. 1.5 mm. Capsule ovoid-globose, 8-10 mm. Seeds black, reniform, less than 0.5 mm. Fl. Jul-Oct.
* Edge of forests, grassland on mountain slopes, trailsides; 1000-2800 m. Guangxi, Sichuan, Yunnan.