2. Dioscorea quaternata (Walter) J.F. Gmel. (wild yam)
88 a–c; Map 334
D. quaternata var. glauca (Muhl.) Fernald
Aerial stems from horizontal rhizomes, these 10–15 mm in diameter when fresh,
contorted and with many knobs or short side-branches. Leaves in whorls of 3–9
below, becoming alternate above, 4–26 cm long, heart-shaped, the base cordate
and the tip acuminate. Aerial tubers not produced. Fruits 18–26 mm long. Seeds
9–13 mm wide including the wing. 2n=36, 54, 60. April–June.
Scattered in the Ozark and Ozark Border counties (eastern U.S. west to Missouri
and Texas). Mesic bottomland and upland forests, frequently on mesic, rocky
slopes, thickets along creeks.
Aside from characters of the rhizomes and the lower leaves mentioned in the key
to species, D. quaternata and D. villosa can be difficult to
distinguish vegetatively. One useful feature best observed on fresh material is
that the aerial stems of D. quaternata are round or nearly so in
cross-section, whereas those of D. villosa tend to be 8–14-angled or
ridged. The flowers and fruits of these species are nearly identical.