4. Thunbergia lutea T. Anderson, J. Linn. Soc., Bot. 9: 448. 1866.
羽脉山牵牛 yu mai shan qian niu
Thunbergia salwenensis W. W. Smith.
Vines to 5 m or longer, climbing. Stems glabrous except for a circle of trichomes on nodes. Petiole 5-7.5 cm, glabrous; leaf blade ovate to lanceolate-ovate, 4-13 × 2-6 cm, abaxially subglabrous, adaxially pubescent or setose, base rounded to broadly cuneate and decurrent onto petiole, margins obscurely toothed to sometimes irregularly denticulate, apex acuminate. Flowers axillary, solitary; bracteoles elliptic, 2.1-2.4 × 1.5-1.7 cm, abaxially glabrous, adaxially gland-tipped hairy, palmately 7-veined, apex mucronate. Calyx minute, 10-toothed. Corolla pinkish or white; tube basally cylindric for ca. 7 mm, throat ca. 3.5 cm; lobes orbicular, ca. 1.2 cm in diam., equal. Staminal filaments glabrous, ca. 1 cm; anther thecae ca. 7 mm, barbate, spurred at base, spurs hairlike. Ovary glabrous; style ca. 2.5 cm, glabrous; stigma funnel-shaped, 2-cleft. Capsule glabrous, basal part ca. 1 × 1.8 cm, beak ca. 1.8 cm. Seeds reniform, ca. 8 × 5 mm. Fl. Aug-Dec, fr. Mar-May.
Forests or thickets; 1000-2500 m. SE Xizang, Yunnan [Bhutan, India, Myanmar].