石山薯蓣 shi shan shu yu

Rhizome usually 3--10-branched, to 20 cm, each end enlarged into a globose or ellipsoid tuber ca. 5 cm in diam.; cork yellowish white; transverse section white. Stem twining to left, brown or white puberulent, glabrescent except at nodes, sparsely prickly. Leaves alternate, palmately 3-foliolate, simple distally on stem; middle leaflet lanceolate or subelliptic, 7--20 × 3--11 cm, pinnately veined, veins white pubescent, base cuneate, margin entire, apex acuminate; lateral leaflets ovate-elliptic, base obliquely cuneate, apex acute. Male spike branched, to 20 cm. Male flowers: sessile or subsessile; bract and bracteole broadly triangular-ovate, margin white pubescent abaxially; stamens 3. Capsule straw-colored at maturity, long ellipsoid, 2--3 cm, base slightly cordate, apex rounded; wings ca. 0.8 cm wide. Seeds inserted near apex of capsule; wing pointing toward capsule base. Fl. Sep--Oct, fr. Dec--Feb.

* Evergreen broad-leaved forests, scrub forests; 900--1500 m. W Yunnan.

This species includes material misidentified as Dioscorea arachidna Prain & Burkill in earlier accounts, including that in FRPS. True D. arachidna though sharing the same distinctive rootstock, differs from D. menglaensis in its much narrower leaflets and lack of prickles, and much more closely resembles members of the D. kamoonensis complex.