Japanese name: ニガカシュウ（苦何首烏） Scientific name:Dioscorea bulbifera
[Overview]
A climbing perennial found in hills and fields.
It has a large, flattened spherical tuber, and the outer skin of the tuber is black.
The leaves are simple and alternate, round-heart-shaped, 5–13 cm both in length and width, with a abruptly pointed tip, and hairless on both sides.
The leaf margin is entire.
The leaf stalk is 3–9.5 cm long, and bulbils form in the leaf axils.
The plant is dioecious.
Both male and female inflorescences hang down.
Both male and female flowers are yellowish green tinged with purple; there are 6 tepals, lanceolate, which do not open flat.
The fruit is an oblong capsule 1.5–2.5 cm long and 1–1.5 cm wide, with 3 wings.
