Plants 30-70 cm tall, glabrous. Stem erect, swollen in lower part, branched in upper part. Leaves alternate; petiole 1-2 cm; leaf blade whitish abaxially, dark green adaxially, ovate, 4-8 × 2-3 cm, setose between teeth, lateral veins 5 or 6 pairs, base cuneate, attenuate into petiole, margin crenate or crenulate, apex acuminate. Inflorescences many, usually crowded at apices of branches, corymbose, 3-10-flowered; peduncles erect, 2-4 cm, very slender. Pedicels 5-15 mm, elongate at fruiting, bracteate at base; bracts caducous, ovate-lanceolate or setose spreading. Flowers yellow, small, ca. 5 mm wide. Lateral sepals 2, falcate-ovate, ca. 4 mm, 3-veined, apex obtuse or slightly acute. Lower sepal navicular, limb 7-8 mm deep, base gradually narrowed into an incurved spur 2-2.5 cm; mouth suboblique, tip acute. Upper petal orbicular, ca. 8 mm in diam., abaxial midvein narrowly cristate, cuspidate, apex retuse; lateral united petals not clawed, 1-4 cm, 2-lobed; basal lobes orbicular; distal lobes dolabriform or lunar, ca. 2 × as long as basal lobes, apex obtuse; auricle inflexed, small, narrow. Filaments linear; anthers small, apex acute. Seeds few, obovoid, ca. 4 mm, smooth. Fl. Aug-Sep.
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