Perennial, climber with tuberous roots, tubers purple or pale yellow; stem terete, green or purple, usually hairy; leaves ovate-cordate, more or less lobed, glabrous or sparingly hairy; flowers axillary, solitary or in few to many-flowered cymes; peduncles long; bracts ovate, acute, cauducous; sepals oblong, acuminate, cuspidate, glabrous; corolla pale violet, campanulate, tube 2-3 cm long, throat darker; limbs 5 plaited, margins shortly lobed; stamens 5, unequal, epipetalous, included, filament filiform, ciliated at base, glabrous or often hairy; disk annular; ovary 4-celled, 4-ovuled, style filiform, stigma entire or 2-lobed, globose; capsule ovoid, 2-4 locular, 2-4 seeded; seeds rotundate, glabrous.