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| Figure 120.—Wild yam (Dioscorea villosa) |
Other common names.—Dioscorea, colicroot, rheumatism root, devil's-bones.
Habitat and range.—Wild yam grows in moist thickets, trailing over adjacent shrubs and bushes, its range extending from Rhode Island to Minnesota and south to Florida and Texas. It is most common in the central and southern portions of the United States.
Description.—The wild yam is a vine growing to a length of 15 feet with a smooth stem and heart-shaped leaves from 2 to 6 inches long and 1 to 4 inches wide, hairy on the under side, borne on long, slender stems. The small, greenish-yellow flowers are produced from June to July, the male flowers being borne in drooping clusters about 3 to 6 inches long and the female flowers in drooping, spikelike heads. The fruit, which is a yellowish-green 3-lobed capsule, ripens in September and remains on the vine for some time during the winter. The rootstock runs horizontally underneath the surface of the ground. It is only about one-fourth to one-half inch in diameter.
Part used.—The rootstock, generally collected in autumn.