Yama Yang-Chow Fu
YAMA YANG-CHOW FU weigh more than ii ft. The plant grows freely in deep sandy soil, moderately enriched. The sets, consisting of pieces of the roots, may be planted in March or April, and require no other culture than the staking of the climbing stems. They should not be dug up before November, the chief increase in their size taking place in autumn. They sometimes strike downwards 2 or 3 ft. into the soil, and must be carefully dug out, the upper slender part being reserved for propagation, and the lower fleshy portion eaten after having been allowed a few days to dry. The tubers of D. alata sometimes weigh 100 ft. Most of the yams contain an acrid principle, which is dissipated in cooking.
The only European Dioscorea is that known as D. pyrenaica, a native of the Pyrenees, a remarkable instance of a species growing at a long distance from all its congeners. True yams must not be confounded with the sweet potato, Ipomoea Batatas, as they sometimes are in London markets. The common black bryony (Tamus communis) of hedges in England is closely allied to the yams of the tropics, and has a similar root-stock, which is reputed to be poisonous.
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)