Plants annual, 30-40 cm tall, glabrous. Stem erect; branches and branchlets spreading. Leaves often crowded at apex of stem, alternate; petiole 2-7 mm; leaf blade pale green abaxially, dark green adaxially, ovate, ovate-lanceolate, or oblong, 5-10 × 2-3 cm, membranous, lateral veins 7 or 8 pairs, fine, base acute, abruptly attenuate into petiole, margin crenulate or crenate-serrate, apex acute or acuminate. Inflorescences 2-4-flowered; peduncles 3-6 cm, very slender. Pedicels 1-1.5 cm, fibrous, bracteate at base; bracts caducous, ovate-lanceolate, 1-2.5 mm. Flowers yellow, small, 7-8 mm wide. Lateral sepals 2, broadly ovate, ca. 4 mm, 7-veined, base subequilateral, apex acuminate, abaxial midvein carinate. Lower sepal navicular, ca. 6 mm deep, narrowed into an incurved or involute spur ca. 1.5 cm, tip rounded, mucronulate. Upper petal orbicular, ca. 7 mm in diam., base retuse, apex rostellate, abaxial midvein shortly cornute; lateral united petals ± clawed, ca. 1.4 cm; basal lobes orbicular, small; distal lobes oblong or narrowly dolabriform, ca. 2 × as long as basal lobes, apically 2-lobed, each lobe subacute at apex; auricle small. Filaments linear; anthers acute. Ovary erect, fusiform. Capsule erect, ca. 1.8 cm, slender. Seeds few, oblong, 3-5 mm, smooth, shiny. Fl. Aug-Sep.
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