Yam

Yam, the tuber of various species of the monoeotyledonous genus Dioscorea, the type of the order Dioscoreaceae. They sometimes reach a height of 30, 40, or even 100 lbs., and closely resemble potatoes in composition and flavour, though richer in nitrogenous matter. D. sativa and D. alata are natives of India; and D. Batatas, the Chinese yam, yields large crops in France and Algeria and is hardy in England, but is not appreciated, partly owing to the depth to which its roots penetrate.