Dioscorea prazeri Prain & Burkill

Rhizome branching freely, short and stout, gray-brown or nearly black; flesh white and very poisonous. Stem smooth, ridges very indistinct, climbing to 4 m. Leaves cordate or long-cordate, usually to 12 (-20) cm in either dimension, 7-11-nerved; secondary nerves differing a little from the network; both surfaces shining; petiole half as long as the lamina. Male flowering branches 1-3 together, from upper leaf-axils or sometimes collected on branches with reduced leaves, cymes 1-3 mm apart; the axis between the cymes apt to be flexuous; narrow wings descend from the bracts; bracts broadly ovate and abruptly long acuminate. Perianth-cup less than 1 mm deep. Tepals 1½ mm long, ovate and almost rounded above. Anthers turned outwards, much shorter than their filaments. Female flowering axes solitary, directed downwards, with about 20 flowers and to 30 cm long. Tepals shorter and thicker than those of the male flower, only just united at the base. Capsules, though rarely more than 8 mature, near enough to each other to imbricate, becoming a satiny chestnut brown; wings broadly semi-obcordate or subrhom-boidal, rarely semicircular, the base of the capsule obtuse as it passes into the short curved stipe and the apex cordate with shoulders (Fig. 5a). Seeds ovate-oblong, to 12 by 8 mm, reddish at maturity but the wing pale.

At its southern limits it grows on limestone. It ascends the mountains of NW. India from near sea-level to 1600 m. It approaches in the Himalaya D. deltoidea WALL, but does not mingle with it. It is noteworthy that D. deltoidea which produces shorter blades, has longer petioles than D. prazeri; also that it requires less humidity.

Uses. The rhizome of both is used for soap in India, particularly for washing the hair as the saponin in it kills lice.