Large, woody, glabrous, twining perennial. Stems becoming woody, the younger ones slender, herbaceous, terete, usually distinctly muricate with reddish papillae (as are the petioles, the peduncles and the pedicels). Leaf lamina, pentagonal in outline, 4–13 cm., as long and as wide, palmately dissected nearly to the base (base cordate with a narrow-sinus); lobes 5–7, elliptic, lanceolate or oblong-lanceolate, up to 6·5 × 2 cm.; acute, entire or minutely crenulate in var. kentrocaulos or deeply pinnatifid in var. pinnatifida; petiole 3–7 cm. long, often muriculate. Inflorescence cymose, few-flowered or reduced to a single flower. Peduncle patent to suberect, 3–8 cm. long, often muricate; bracteoles ovate, acute, early deciduous, occasionally larger and dissected like the leaves in var. pinnatifida; pedicels up to 3 cm. long at first deflexed, patent to suberect when the flowers open and ultimately cernuous in fruit. Sepals ovate-oblong, up to 3 cm. long, obtuse edges, glabrous, concave, somewhat unequal, enlarging in fruit. Corolla funnel-shaped, yellow or white dark purple centre, glabrous, 3·5–5·5 cm. long; limb faintly petagonal, plicate, lobes bluntly triangular. Capsule narrowly ellipsoid at first enclosed in the accrescent, brown and coriaceous calyx, but ultimately exposed just before dehiscence when sepals spread out, pale brown. Seeds brown to black, minutely hairy.