Description from Flora of China
Dioscorea mairei H. Léveillé (1913), not R. Knuth (1924); D. praecox Prain & Burkill.
Tubers vertical, cylindric, mucilaginous. Stem twining to left, white or light brown woolly, glabrescent. Leaves alternate, simple; petiole 3--6 cm; leaf blade broadly cordate to ovate, 4--8.5 × 5--10.5 cm, adaxially sparsely woolly, abaxially white woolly, ± glabrescent, basal veins 7 or 9(or 11), base shallowly cordate, apex acuminate or caudate-acuminate. Male inflorescence not known with certainty, but apparently indistinguishable from that of Dioscorea yunnanensis. Female spikes sometimes produced with new leaves, to 3 cm; rachis often shorter than mature capsule. Female flower: bracts reddish brown dotted, lanceolate; perianth lobes ovate-triangular, ca. 1.2 mm; style 3-ribbed, base enlarged, stigma 3-fid, reflexed. Capsule erect, ovoid-oblong or oblong, 1.1--2 cm, densely pubescent; wings 0.8--1.3 cm wide, entire, rarely undulate. Seeds inserted near base of capsule; wing pointing toward capsule apex. Fl. Jul--Aug, fr. Sep--Oct.
Dioscorea hemsleyi has an extremely distinctive, short infructescence, with the capsules ± erect and often longer than the rachis. It is otherwise very difficult to distinguish from D. yunnanensis which is found in the same areas. It has not yet been possible to correlate any male material with the two species, and all male collections have been placed under D. yunnanensis in the present account. This problem will only be resolved by growing plants from seed of known origin.
Open scrub forests, mountain slopes; 1000--3000 m. Guangxi, Guizhou, Sichuan, Yunnan [Cambodia, Laos, Myanmar, Vietnam].