Yam, a large starchy tuber.
Dioscorea alata
The plant is a vine which climbs trees. It is similar to sweet potatoes but the inside of the tuber may be white, yellow, or deep purple (the most common variety). In good soil the tuber may grow to about two handspans in diameter. A part of the tuber may be cut off and used. The remaining tuber will continue to grow. The tuber is peeled, and boiled in water.