tuber

A swollen part of a stem or root, usually modified for storage, and lasting for one year only, those of the succeeding year not arising from the old ones, nor bearing a position relative to them. Examples of such perennating organs are the stem tubers of potato (Solanum tuberosum) and the root tubers of Dahlia. Root tubers develop from adventitious roots (compare taproot ). A stem tuber may be distinguished from a root tuber by the presence of buds or 'eyes'.