Rhizome horizontal, ginger-shaped, variable in length, ca. 2 cm thick; transverse section yellow; roots slender, fibrous. Stem twining to left, glabrous, sometimes densely and shortly yellow hairy. Leaves alternate, simple; petiole 4--7 cm; leaf blade drying blackish, triangular to ovate or ovate-lanceolate, 5--19(--22) × 3--13(--16) cm, usually membranous, abaxially sometimes hispidulous especially along veins, base cordate to subtruncate, margin subentire or slightly undulate, sometimes transparent, apex acuminate. Male spikes solitary or 2 or 3 together. Male flowers: solitary or in cymules of 2 or 3, sessile; bracts ovate-lanceolate; bracteoles ovate; perianth yellow, usually drying black, saucer-shaped; stamens 3, inserted in perianth tube, filaments short, anthers ovoid, connectives elongate at anthesis, fork-shaped; staminodes filiform. Female spike solitary, to 5 cm. Female flowers: staminodes present; ovary terete. Capsule reflexed, brown, shiny, broadly obovoid or ellipsoid, usually somewhat angular, 1.6--2.1 cm, apex truncate; wings 0.8--1.1 cm wide. Seeds inserted near middle of capsule, winged all round. Fl. May--Aug, fr. Jun--Oct.
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