Annual or biennial herb, up to 200 mm high. Stems slender, erect. Leaves in relatively few pairs, internodes prominent; blade linear to narrowly ovate, 12 x 1.0-1.5 mm. Flowers: in 1-few-flowered cymes; filaments inserted in corolla sinuses; anthers with a minute apical gland; style with small stigmatic swelling near base, style and stigma 5-7 mm long; calyx keeled or very narrowly winged, joined for 2-4 mm at base; corolla with tube 5.0-7.5 mm long, yellow or pale yellow; Oct., Feb.-Jun.