Description from Flora of China
Vines [or shrubs], lacking cystoliths. Leaves petiolate; leaf blade margin entire to lobed to dentate. Flowers solitary or paired in leaf axils, or in terminal dichasiate thyrses, pedunculate; bracteoles leaflike, paired, enclosing calyx and most or all of corolla tube, distinct or fused along one side, persistent. Calyx much shorter than bracteoles, cupular with 10-20 subulate lobes or reduced to an entire ring. Corolla funnel-shaped, large; tube with short cylindric base then widened; limb ± equally 5-lobed. Stamens 4, often didynamous, inserted near base of corolla tube, included; anthers 2-thecous; thecae oblong or ovoid, parallel, spurred or not at base, sometimes bearded. Disk shortly annular or pulvinate. Ovary fleshy; ovules 2 per locule, collateral; style glabrous or pubescent; stigma 2-cleft, entire, or fringed. Capsule basally subglobose, apically prominently beaked, 2-4-seeded; retinacula absent. Seeds compressed to spherical, lacking trichomes.
Some species of Thunbergia are naturalized in the New World tropics.
Thunbergia erecta (Bentham) T. Anderson and T. laurifolia Lindley, both cultivated in gardens, are not treated here.
More than 100 species: Old World tropical regions; six species (one introduced) in China.
(Authors: Hu Jiaqi (胡嘉琪 Hu Chia-chi), Deng Yunfei (邓云飞); Thomas F. Daniel)