Vines woody, turning black on drying. Branches shallowly 4-grooved, appressed puberulous. Leaves ternate; petiole 2--4 cm; leaflet blades elliptic-ovate to ovate, 4.2--6.8 × 1.6--3 cm, subleathery, both surfaces strigose only on basal veins, base rounded to subcordate, margin entire, apex acute, acuminate, or short caudate; basal veins abaxially ± prominent, adaxially impressed. Cymes axillary, 1-flowered; peduncle slender, 1--2.5 cm, appressed puberulous; bracts linear, 3--4 mm, densely puberulous. Flowers 2.5--3 cm in diam. Pedicel 1.8--2.2 cm. Sepals 4, white, spreading, elliptic-oblong, 12--15 × 5--7 mm, abaxially densely sericeous-puberulous, adaxially glabrous, margin abaxially velutinous, apex obtuse. Stamens 8--10 mm, glabrous; anthers oblong, ca. 1.5 mm, apex apiculate. Ovaries pubescent. Style ca. 6 mm, densely brownish villous. Fl. Apr--May.
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