Plants annual, 30-50 cm tall. Leaves alternate, often crowded at apices of stem and branches; petiole 1-2.5 cm; leaf blade oblong-ovate or oblong-lanceolate, 5-17 × 2.5-4 cm, setose between teeth, lateral veins 7-11 pairs, base cuneate, margin coarsely crenate, apex caudate-acuminate. Inflorescences axillary, racemose, 4-6-flowered; peduncles 6-8 cm. Pedicels 2-2.5 cm, bracteate at middle; bracts caducous, linear. Flowers yellow, small. Lateral sepals 4; outer 2: broadly ovate, apex acute; inner 2: linear, minute. Lower sepal narrowly funnelform, narrowed into an erect, slender spur; mouth tip rostellate. Upper petal obovate, apex mucronulate, abaxial midvein not carinate; lateral united petals ± clawed, 2-lobed; basal lobes triangular, apex acuminate; distal lobes lanceolate, longer; auricle small. Anthers obtuse. Capsule linear. Fl. and fr. Jul-Oct.
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