Roots conical or cylindrical, 15-30 × 1-1.4 cm, ± branched. Stems twining, more than 1 m; branches and branchlets short, no more than 5 cm, leafy, sterile or with terminal flowers, sparsely villous or eventually glabrescent. Leaves alternate or opposite; petiole 1-8 cm, villous or hirsute; blade abaxially gray-green, adaxially green, deltoid or broadly ovate, 3-10 × 4-10 cm, both surfaces sparsely puberulent or hirsute, base shallowly cordate, truncate, or rounded, margin coarsely dentate, apex acuminate or acute. Flowers terminal on main stems, branches, and/or branchlets, solitary or sometimes in few-flowered cymes; pedicels 1-2 cm, villous. Calyx tube adnate to ovary up to middle, semiglobose or broadly obconic, 4-5 × 7-8 mm, glabrous; lobes ovate-lanceolate or triangular, 9-13 × 3-7 mm, margin denticulate, often white ciliate, apex acuminate or acute. Corolla pale yellow-green, with purple veins, tubular, 2-2.5 × 0.9-1.5 cm; lobes deltoid, ca. 1/3 as long as tube. Filaments slightly dilated at base, ca. 6 mm, glabrous; anthers ca. 3 mm. Capsules semiglobose below, broadly conical above. Seeds numerous, yellow-white, ovoid, wingless, smooth. Fl. and fr. Jul-Oct.
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