Major entries:
Dioscorea aculeata Linn. Birch-Rind Yam. Goa Potato.
Dioscorea alata Linn. White Yam.
Dioscorea bulbifera Linn. Air Potato.
Dioscorea pentaphylla Linn. Yam.
Dioscorea sativa Linn. Yam.

Dioscorea. Dioscoreaceae. Yams.

Related entry: Oncus

Under the general name of yams the large, fleshy, tuberous roots of several species of Dioscorea are cultivated in tropical and subtropical countries. Many varieties known only in cultivation are described as species by some authors. In the Fiji Islands alone, says Milne, there are upwards of 50 varieties, some growing to an enormous size, occasionally weighing from 50 to 80 pounds but the general average is from two to eight pounds. In Australia, according to Drummond, there is a native yam which affords the principal vegetable food of the natives.

Dioscorea aculeata Linn. Birch-Rind Yam. Goa Potato.

Tropical Asia. This yam is said to be a native of tropical, eastern Asia, and is cultivated in the Indian Archipelago, the Pacific islands and the West Indies. The root is of a sweetish taste and Dr. Seemann regarded it as one of the finest esculent roots of the globe. It is cultivated in India and the tubers are dug, in the cold season, in the forests and sold in the bazaars. A variety cultivated at Caracas has a very delicious taste, though Lunan, at Jamaica, says this yam is slightly bitter. This yam is said by Seemann, at Viti, never to flower or fruit.

Dioscorea alata Linn. White Yam.

Tropical Asia. This plant is cultivated in the tropics of the whole earth. Unger says the Indian Archipelago and the southern portions of the Indian continent is the starting point of this yam, thence it was carried first to the eastern coast of Africa, next to the west coast and thence to America, whence the names yam and igname are derived from the negroes. In the negro dialect of Guinea, the word yam means "to eat." This is the species most generally cultivated in the Indian Archipelago, the small islands of the Pacific and the Indian continent. It is universally cultivated in the Carnatic region. There are several varieties in Jamaica, where it is called white yam.

Dioscorea atropurpurea Roxb. Malacca Yam. Rangoon Yam.

Siamese countries. The Malacca yam is cultivated in India and is known in Calcutta as the rangoon yam. It is called in Burma myouk-nee and is cultivated.

Dioscorea bulbifera Linn. Air Potato.

Tropical Asia. Less cultivated than many others, this yam is found wild in the Indian Archipelago, upon the Indian continent as far as Silhet and Nepal to Madagascar. Grant found it in central Africa. The bulbs are like the Brazil-nut in size and shape cut like a potato when unripe and are very good boiled. Schweinfurth says it is called nyitti and the bulbs which protrude from the axils of the leaves, in shape like a great Brazil-nut, resemble a potato in taste and bulk. In the Samoan and Tonga group of islands, the root is not considered edible. In India, the flowers and roots are eaten by the poorer classes, the very bitter root being soaked in lye to extract the bitterness, but a variety occurs which is naturally sweet. In Jamaica, it is cultivated by the negroes for the bulbs of the stem. It was seen in a garden at Mobile, Alabama, by Wm. Bartram, about 1733, under cultivation for its edible roots.

Dioscorea cayenensis Lam.

Tropical South America. The root is edible.

Dioscorea daemona Roxb.

East Indies. The plant is called kywae and its very acrid root is eaten by the Karens in times of scarcity.

Dioscorea decaisneana Carr.

China. The root is edible and was introduced into France as a garden plant but is now forgotten, although it is perhaps valuable.

Dioscorea deltoidea Wall.

East Indies. This species occurs both wild and cultivated in the Indian Archipelago; its roots are eaten.

Dioscorea divaricata Blanco. Chinese Potato. Chinese Yam. Cinnamon Vine. Yam.

Philippine Islands, China and everywhere cultivated in several varieties. This yam was received in France in 1851 from Shanghai, and was introduced into the United States, in 1855, by the Patent Office Department. It has not fulfilled expectation in the United States and is now grown principally as an ornamental climber. It was observed in Japan by Thunberg.

Dioscorea fasciculata Roxb. Yam.

Tropical eastern Asia. This species is cultivated largely about Calcutta, and a starch is made from its tubers. Firminger says this is a very distinct kind of yam, the tubers about the size, form and color of large kidney potatoes; when well cooked, it has a greater resemblance in mealiness and flavor to the potato than any other yam he knows of. It is much cultivated in the Philippines by the natives and is much esteemed.

Dioscorea globosa Roxb. Yam.

East Indies. This species is much cultivated in India as yielding the best kind of yam and is much esteemed both by Europeans and natives. Roxburgh says it is the most esteemed yam in Bengal, but Firminger thinks it not equal in quality to other varieties. In Burma, Mason says it is the best of the white-rooted kinds.

Dioscorea hastifolia Nees. Yam.

Australia. The tubers are largely consumed by the aborigines for food, and this is the only plant on which they bestow any kind of cultivation.

Dioscorea japonica Thunb.

Japan. The roots, cut into slices and boiled, have a very pleasant taste.

Dioscorea nummularia Lam. Tivolo Yam.

Moluccas. This yam has cylindrical roots as thick as an arm and of excellent quality.

Dioscorea oppositifolia Linn. Yam.

East Indies. This is one of the edible yams.

Dioscorea pentaphylla Linn. Yam.

Tropical Asia. In India, this yam is common in jungles and is found in the South Sea Islands. Wight has never seen it cultivated in India, although the natives dig the tubers to eat. It is cultivated in Amboina and sometimes in Viti. In India, the male flowers are sold in the bazaars and eaten as greens. The tubers are eaten in Viti and Hawaii. It is a good yam. Graham says the tubers are dreadfully nauseous and intensely bitter even after being boiled. They are put into toddy to render it more potent, as they have intoxicating properties, and a few slices are sufficient. In China, the "nauseous tubers are sometimes cooked and eaten."

Dioscorea piperifolia Humb. & Bonpl.

South America. This species has edible roots.

Dioscorea purpurea Roxb. Pondicherry Sweet Potato.

East Indies. The Pondicherry sweet potato is known only in a cultivated state, and was brought to India from the Mauritius, where it is much grown. The tuber is of a dull, crimson-red outside and of a glistening white within.

Dioscorea quinqueloba Thunb. Yam.

Japan. This species is an edible yam of Japan.

Dioscorea rubella Roxb. Yam.

East Indies. This is a common but very excellent yam of India, as good perhaps as any in cultivation. The tuber is of great size, crimson-red on the outside and of a glistening white within.

Dioscorea sativa Linn. Yam.

Tropics. Pickering states that this species is found in tropical America and is cultivated by the Waraus of the delta of the Orinoco. The word igname was heard by Vespucius on the coast of Para and was found by Cabral, in 1500, applied in Brazil to a root from which bread was made. This yam was carried by European colonists to the Malayan Archipelago. Its roots, says Seemann, are acrid and require to be soaked before boiling. Browne says it is cultivated in the southern United States for its large, flattened and sometimes palmated roots, which are boiled, roasted and eaten like the potato.

Dioscorea spicata Roth.

East Indies. It has edible roots.

Dioscorea tomentosa Koen. Doyala Yam.

East Indies. This is the Doyala yam of India.

Dioscorea trifida Linn. Indian Yam.

Guiana and Central America. This species is cultivated as an edible yam.

Dioscorea triloba Lam. Yam.

Guiana. This is the smallest and most delicate of the yams grown in Jamaica. It seldom exceeds eight or nine inches in length and two or three in diameter and is generally smaller. The roots have a pleasant, sweetish taste, very agreeable to most palates.

Sturtevant's Edible Plants of the World, 1919, was edited by U. P. Hedrick.