Branchlets terete, glabrous, with sparse arachnoid tomentum when young; tendrils 2- or 3-branched. Leaves simple; stipules brown, 4-8 × 3-5 mm, membranous, entire, apex obtuse; petiole 4-14 cm, with sparse arachnoid tomentum when young, eventually glabrate; leaf blade broadly oval, 6-24 × 5-21 cm, adaxially with sparse arachnoid tomentum when young, then glabrescent, basal veins 5, lateral veins 5 or 6 pairs, veins raised abaxially, conspicuous or slightly impressed adaxially, abaxial veinlets conspicuous, ± raised, usually pubescent or glabrescent, base cordate, notch rounded to obtuse, base of lobes usually constricted or mixed with broad ones, notch rounded, rarely acute or obtuse, margin 28-36-toothed on each side, teeth sharp, slightly irregular, apex acute or acuminate. Panicle leaf-opposed, loose, 5-13 cm, basal branches well developed, with sparse arachnoid tomentum when young, eventually glabrescent. Pedicel 2-6 mm, glabrous. Buds obovoid, 1.5-3 mm, apex rounded. Calyx 0.2-0.3 mm, glabrous, subentire. Petals calyptrate. Filaments filiform, 0.9-2 mm; anthers yellow, ovoid-elliptic, 0.4-0.6 mm, conspicuously short and abortive in female flowers. Disk 0.3-0.5 mm. Ovary conical; style obvious, slightly thick at base. Seeds obovoid, apex retuse, chalazal knot elliptic, ventral holes furrowed upward to middle or near apex from base.