Dioscorea nipponica Makino

The rhizome is an important source of steroids for the drug industry.

Rhizome horizontal, many branched, cylindric, more than 1.5 cm thick; cork layer persistent or readily detached. Stem twining to left, drying green or reddish brown, to 5 m, glabrescent. Leaves alternate, simple; petiole 10--20 cm; leaf blade shiny, drying yellowish green, broadly cordate to palmately unequally 3--7-lobed, very variable in shape, 7--15 × 4--13 cm, glabrous or sparsely minutely setose especially along veins, basal veins 7 or 9, outermost ones often forked, base cordate, margin undulate to prominently bluntly toothed or lobed, apex acuminate. Male spike solitary, to 17 cm, rarely with occasional cymules expanded to form lateral branches. Male flowers: usually in cymules or umbellules of 2--4(--7), solitary distally on inflorescence, sessile or shortly pedicellate; bracts lanceolate, slightly shorter than perianth; bracteoles ± obsolete; perianth saucer-shaped, lobes obtuse at apex; stamens 6, inserted at middle of perianth lobes, anthers introrse. Female flowers: staminodes filiform; stigma 3-lobed. Capsule reflexed at maturity, light brown, purplish speckled, ellipsoid-oblanceolate, 1.5--2 cm, base rounded, apex shallowly emarginate; wings 0.7--0.8 cm wide. Seeds inserted near base of capsule, sometimes only 1 fertile, winged all round but wing much wider toward capsule apex. Fl. Jun--Aug, fr. Aug--Oct.

Anhui, Gansu, Guizhou, Hebei, Heilongjiang, Henan, Hubei, N Jiangxi, Jilin, Liaoning, Nei Mongol, Ningxia, S Qinghai, Shaanxi, Shandong, Shanxi, NW Sichuan, N Zhejiang [Japan, Korea, Russia].

Mixed forests, scrub forests, warm-temperature transitional areas; 100--1800 m.