Plants annual, 30-80 cm tall, glabrous, with few supporting roots. Stem erect, long naked in lower part, branched in upper part; branchlets spreading, slender. Leaves alternate, petiolate, upper leaves subsessile; petiole 2-3.5 cm; leaf blade pale green abaxially, dark green adaxially, ovate or ovate-oblong, 4-12 × 2.5-5 cm, membranous, lateral veins 2-4 pairs, base broadly cuneate, gradually attenuate into petiole, margin crenate, teeth mucronulate, apex caudate. Inflorescences in upper leaf axils, 3-5-flowered; peduncles shorter than petioles, 2-3 cm. Pedicels 5-7 mm, bracteate at base; bracts persistent, ovate, 2-3 × ca. 1.5 mm, membranous. Flowers yellowish, 1.5-2 cm deep. Lateral sepals 2, broadly ovate or subcordate, ca. 4 × 3-4 mm, 5-veined, apex mucronulate. Lower sepal navicular, ca. 5 mm deep, gradually narrowed into an incurved or involute spur; spur 1.4-1.5(-2) cm, slender; mouth oblique, ca. 1 cm wide, tip acute. Upper petal broadly cordate, 5-6 mm, apex mucronulate, abaxial midvein triangular cristate; lateral united petals not clawed, 1.5-1.6 cm, 2-lobed; basal lobes suborbicular; distal lobes dolabriform, ca. 2 × as long as basal lobes, apex obtuse; auricle inflexed. Filaments linear, ca. 3 mm; anthers broadly ovoid, apex acute. Ovary erect, fusiform. Capsule linear, ca. 1.5 cm. Seeds few, oblong. Fl. Aug.
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