The table provides examples of plant structures and their classifications:
Following this pattern, a корневище (rhizome) is also a modified plant structure. Rhizomes are typically underground stems that grow horizontally and can sprout new shoots and roots. Therefore, it fits the classification of a modified shoot.
The ellipses "..." for "корневище" should be replaced with видоизменённый подземный побег, consistent with the classification of "луковица".
Ответ: видоизменённый подземный побег