Annual herb, 12–40 cm high. Stem branched, or simple and branched at inflorescence, distinctly winged. Leaves sessile, lanceolate to ovate-lanceolate, 7–32 mm long, 3–9(–12) mm wide, acute, cuneate, with 3 distinct nerves on the lower surface. Inflorescences usually many-flowered dichasial cymes; bracts 2.5–8.5 mm long, 1–2 mm wide, ovate-lanceolate, acute; pedicels 4–14 mm long, 4-winged. Flowers irregular, white or pale-pinkish. Calyx dorsally distinctly winged, wing to ± 0.7 mm wide; tube 4.5–9.2 mm long; teeth sharply triangular, ovate or ovate-lanceolate, ± 1.5–2.9 mm long, 0.5–1.1 mm wide at base, acuminate. Corolla tube cylindrical, 5–11.6 mm long; lobes obovate, unequal, 2 longer and wider than the other 2, 3.6–5.6 mm long, 1–2.2(–4) mm wide, obtuse or emarginate. Stamens inserted beneath the corolla sinuses at different positions; filaments unequal in length, 0.6–1.4 mm long; anthers 0.7–1.1 mm long, oblong, 1–2(–3) sterile, fertile anther on the filament inserted on the shorter and narrower corolla lobes, 3 anthers well below stigma, ± 1.8 mm between the tips of anthers and stigma, 1 anther slightly below stigma, ± 0.9 mm from tip of the stigma. Ovary ovoid to ellipsoid, 5–6.4 mm long, ± 1.5 mm diameter; style ± 3.6–5 mm long; stigma lobes 0.8–1.4 mm long, papillate. Capsule ellipsoid, 5.7–6.8 mm long, 1.8–2.9 mm diameter, included in the corolla tube. Seeds numerous, 0.2–0.3 mm in diameter, surface reticulate-pitted.
