Erect, 20-70 cm high, annual, solitary, glabrous herb. Stem quadrangular. Leaves 0.75-2.5 x 0.5-2.0 cm, ovate-spathulate, obtuse, amplexicaule. Inflorescence 3-8 flowered clusters, terminal or axillary. Flowers tetramerous, spurred, long pedicellate; pedicels of inflorescence unequal. Calyx 4-lobed, deeply partite, smaller than corolla; lobes lanceolate-ovate, acute-mucronate, spathulate, reticulately nerved. Corolla 4-lobed, deeply partite; lobes obovate-lanceolate or elliptic, obtuse-mucronate, 3.5-6.5 (7.0) x 2-4 mm; purplish nectariferous glands at base of lobes, protruding in 1 mm wide, 3-8 mm long spurs. Stamens 4; anthers ovate, obtuse, cordate. Ovary 2.5-6.5 x 1.5-4.5 mm, ovate-elliptic; stigma bibbed, papillose. Capsule subexserted, 20-25 seeded. Seeds ellipsoid-globose, reticulated.