Vines perennial, herbaceous. Stems shallowly 4--6-grooved, sparsely puberulous, glabrescent. Leaves 1-or 2-ternate or pinnate; petiole 1.8--4 cm; leaflet blades ovate, broadly ovate, or ovate-elliptic, 0.8--6 × 0.5--1.8(--3.2) cm, papery, abaxially sparsely puberulous, adaxially sparsely puberulous on veins, both surfaces ± reticulate, base rounded, cuneate, or subcordate, margin entire or to 3-denticulate on each side, apex acute to acuminate; basal veins abaxially prominent. Cymes axillary, 1-flowered; peduncle 2--8.5 cm; bracts shortly petiolate, ternate or simple, 3-parted or undivided. Flowers 3--9 cm in diam. Pedicel 3.5--11 cm, apically puberulous to subglabrous. Sepals (4 or)5 or 6, white, spreading, elliptic to narrowly elliptic, 2.7--4.8 × 0.8--2.8 cm, abaxially densely velutinous along midvein, adaxially glabrous, margin glabrous, apex acute. Stamens 0.6--1.8 cm, glabrous; anthers linear, 3--4.8(--6) mm, apex minutely apiculate. Ovaries pubescent. Style 5--7.5 mm, basally densely brownish villous, apically glabrous. Fl. May.
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