The yam is a tuber of the genus Dioscorea, a group of climbing plants indigenous to tropical climates. It is oblong and in some cases grows to a length of 3 ft. It may weigh as much as 30lbs. It contains a large proportion of starch. When boiled or roasted it forms a mealy, palatable and wholesome food. It is not sweet like the sweet potato and keeps better. A species brought from China to France is still cultivated there., supplying a vegetable of a starchy sort all the year round.
Some species of yam are poisonous. Church gives the approximate composition as follows:
From The Baker’s ABC by John Kirkland, formerly Head Teacher of National School of Baking, published 1927 by Gresham