Plants 50-70 cm tall, rigid, glabrous, with few, thick roots. Stem erect, long naked in lower part, ± simple or rarely branched. Leaves alternate, shortly petiolate; leaf blade purple-tinged abaxially, green adaxially, oblong-lanceolate or oblanceolate, 12-15 × 2-3 cm, papery, stipitate glandular-ciliate near base, lateral veins 7 pairs, base slightly cordate or cuneate, margin sharply serrate, teeth mucronulate, apex caudate-acuminate. Inflorescences in upper leaf axils, pendulous, or ± curved, elongate, 4-6 cm, 2-4-flowered. Pedicels spreading or pendulous, bracteate below flowers; bracts persistent, lanceolate. Flowers yellow, large, ca. 4 cm deep. Lateral sepals 2, ovate-lanceolate, 3-4 mm. Lower sepal broadly funnelform, incurved, constricted into a slender spur ca. 1 cm. Upper petal orbicular, small, apex cuspidate; lateral united petals not clawed, ca. 15 cm, 2-lobed; basal lobes very small; distal lobes oblong, apex rounded. Filaments linear; anthers obtuse. Ovary fusiform, ca. 3 mm. Capsule linear, 4-6 cm. Seeds many, oblong, ca. 2.5 mm, glabrous. Fl. Aug, fr. Oct.
Home