Tuber
A swollen underground stem or root that stores food and carries buds for new growth.
A tuber is a thickened storage organ. A potato is the familiar example of a stem tuber, with buds, called eyes, across its surface. Among flowers, tuberous begonias, cyclamens and anemones grow from tubers. Dahlias grow from clusters of swollen roots, which gardeners also call tubers. In cold climates dahlia tubers are dug up after the first frost, stored dry and frost-free over winter, and replanted in spring.