Tendrilled lianas, glabrate in age; stems ribbed, minutely appressed-pubescent; wood composite, usually with 3 flattened peripheral bundles, the bundles moder-ately large, sometimes irregular; sap often drying dark and resinous; tendrils bifid. Leaves biternate; petiole, rachis, and petiolule ribbed to narrowly winged; leaf-lets elliptic to lanceolate to oblanceolate, obtuse to acuminate at the apex, the acumen often blunt with a sharp apiculum, acute to obtuse or attenuate at the base, 4-8.5 cm long, 1.5-3 cm wide, to 15 cm long and 6 cm wide on juvenile leaves, usually dentate above the middle, with distinct, irregular black lines on the lower surface, these sometimes inconspicuous when fresh, the juvenile leaves sometimes with pubescent midribs; stipules minute, ovate. Thyrses small, race-mose and either solitary in leaf axils or on tendrils, or in open terminal panicles. Flowers white, 3-4 mm long; sepals densely tomentose; sepals, petals, and scales with reddish black lines like those of the leaves; petals to 3 mm long, each sub-tended by a broad green gland, those of the anterior petal with an ear-shaped orange lobe, the scales of the anterior petals ca. 2 mm long, yellow, the crest emarginate, held in front of and slightly below the cluster of stamens, the de-flexed appendage densely villous, pendent to almost the base of the petal; stamens 7-9, the filaments pubescent; staminate flowers with the stamens equalling petals, ca. 3 mm long, the pistil very reduced; bisexual flowers with the stamens ca. 2 mm long, the ovary, style and stigma together 3-3.5 mm long, the stigmas 3, ca. 1 mm long, the ovary tomentose. Fruits ovate-cordate, 2-2.5 cm long, the cells blackened and densely birtellous, the wings hirtellous on the inner margin, conspicuously marked with irregular black lines, gradually constricted usually well below the seed-bearing part.