Rhizome horizontal, irregularly branched, cylindric; cork black-brown, rough. Stem twining to left, slender, hard, grooved, glabrous. Leaves alternate, simple to 3-foliolate, more divided distally on stem; leaf blade of simple leaves triangular or triangular-ovate, 5--16 × 1.5--5 cm, glabrous, smooth, reticulate veins prominent abaxially, base rounded, apex acute; middle leaflets of palmate leaves lanceolate, base attenuate, lateral leaflets ovate, smaller than middle ones, base slightly oblique. Male spikes solitary or 2--4 together, occasionally few branched, lax, 12--15 cm. Male flowers: solitary or in cymules of 2--4; perianth purple, lobes spreading at anthesis, long ovate; stamens 6, inserted at base of perianth, filaments short, anthers alternately larger and smaller. Female spikes 7--10 cm. Capsule dark-brown at maturity, shiny, obovoid, 1--1.5 cm, apex slightly emarginate or truncate; wings 0.5--1 cm wide. Seeds inserted near middle of capsule, winged all round. Fl. May--Aug, fr. Jul--Oct.
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