Corm

A corm is a modified plant stem some plants use as a storage organ or for hibernation. Corms are structurally plant stems, and can produce roots. On the top of the corm, one or a few buds grow into shoots that produce normal leaves and flowers.
Some plants with corms regularly replace their older corms with a stack of younger ones. In other species their corms simply grow larger in most seasons. Yet others split when multiple buds or stolons on a large corm sprout independently.
Corms can be dug up and used to multiply or redistribute the plant (see, for example, taro). Plants with corms generally can be propagated by cutting the corms into sections and replanting. 
Examples.
Plants that form corms include the following species: