Annual herb, with long-running, trailing or ± scrambling stems bearing branched tendrils, finely puberulent and with scattered long hairs. Petioles long, hollow, with indumentum as on stems. Lamina variable in size and shape, to c. 30 × 30 cm (sometimes more in cultivation), sinuate or shallowly lobed, very broad-ovate, scabridulous above and on veins beneath, otherwise ± densely hairy below; margins denticulate; base broad-cuneate, situated in the deep, rather rounded sinus. ♂ fls on long, hispid peduncles. Calyx mostly 2-2.5 cm long, lobed to > 1/2 way; lobes ± subulate, densely pilose. Corolla 5-7-(8) cm long, with prominent veins, hairy on both sides, especially the veins outside; lobes ovate, acute or short-acuminate, ± apiculate. ♀ fls larger than ♂; peduncle short and stout, at fruiting becoming very thick, spongy, and corky on the outside, nearly terete, expanded along whole length. Fr. very variable in size and shape but never scalloped, always developing a fairly hard rind (although never shell-like), usually wider than long and of circular and flattened form; rind grey, dark green, orange or red, usually smooth except for grooves, sometimes rather rough; pulp yellow to orange. Seed whitish, ellipsoid; margin raised and obtuse.