Plants annual, 30-40 cm tall. Stem erect, slender, branched or simple, glabrous. Leaves alternate. Lower and middle leaves petiolate; petiole 2-3 cm, slender; leaf blade broadly ovate or ovate-orbicular, 3-5 × 1-2 cm, thinly membranous, base abruptly attenuate into petiole, apex obtuse. Upper leaves sessile or subsessile, oblong, glabrous, setose between teeth, lateral veins 4-6 pairs, glabrous, base cordate, slightly amplexicaul, margin coarsely crenate. Inflorescences in upper leaf axils 1-5-flowered; peduncles 2-3 cm, slender. Pedicels slender, bracteate below flowers; bracts persistent, ovate. Flowers purplish or dirty yellow, large, 2-3 cm deep. Lateral sepals 2, obliquely ovate or ovate-orbicular, inequilateral, apex acute. Lower sepal saccate, abruptly narrowed into an incurved spur; spur short, shallowly 2-fid. Upper petal cucullate, orbicular, abaxial midvein thickened, slightly cristate middle; lateral united petals 2-lobed; basal lobes subtetragonous, small; distal lobes dolabriform, large, apex acute; auricle large. Anthers obtuse. Capsule linear, 3-4 cm. Seeds brown, elliptic-oblong, tuberculate. Fl. Jul-Sep.
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