Dioscoreaceae Dioscorea batatas Deene.
Source: Magness et al. 1971
The plant is a vine with stems reaching 10 to 30 feet, with cordateovate, shiny leaves. It is grown in the tropics for the edible tubers, which develop deep in the ground, so are difficult to dig. In the U.S., most varieties of sweet potato are often erroneously termed yams. The true yams are not grown in continental U.S. as food crops, but may be found in tropical areas to a limited extent. In culture and exposure of edible parts they resemble sweet potato.