Plants annual, 30-90 cm tall, glabrous. Stem erect, slender, naked in lower part, branched in upper part. Leaves alternate; petiole long, 2-3 cm; leaf blade gray-green abaxially, dark green adaxially, ovate or ovate-lanceolate, 3-7(-9) × 2-4 cm, membranous, lateral veins 6-8 pairs, curved, abaxially glabrous, adaxially adpressed strigose, base cuneate, attenuate into petiole, margin crenate or serrate, teeth glandular-mucronulate, apex subcaudate-acuminate. Inflorescences in upper leaf axils, 2-flowered; peduncles erect or slightly spreading, longer than or ca. equal to leaves, 4-7 cm, slender. Pedicels fibrous, 1-1.5 cm, slightly elongate at fruiting, bracteate at base (but appearing as if at middle in upper flowers); bracts caducous, ovate-lanceolate or lanceolate, 3-5 mm, midvein puberulent, apex long acuminate. Flowers yellow, 2-2.5 cm deep. Lateral sepals 2, ovate, 5-6 mm, 6-or 7-veined, apex mucronulate, abaxial midvein fine, not thickened. Lower sepal navicular, 0.8-1 cm, abruptly narrowed into an incurved spur ca. 2 × as long as limb; mouth vertical, 0.8-1 cm wide, tip acute. Upper petal subtetragonous-orbicular, 0.8-1 cm in diam., base cordate, apex retuse, rostellate, abaxial midvein thickened, narrowly carinate; lateral united petals not clawed, 1-1.5 cm, 2-lobed; basal lobes orbicular; distal lobes oblong-dolabriform, longer, apex rounded; auricle rounded. Filaments broadly linear, 3-4 mm; anthers ovoid, apex acute. Ovary erect, fusiform. Capsule linear, 2-3 cm. Seeds many, brown, orbicular, compressed, ca. 3 mm, smooth. Fl. Jul-Aug.
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