Corms

A corm is a short, swollen underground or underwater plant stem whose inner structure is made up of solid tissue. From the vertical top of the corm, one or a few buds grow into shoots that produce leaves and flowers. What distinguishes corms from true bulbs is the inner structure. A halved corm reveals a solid interior, while a halved bulb exposes fleshy layers. Compare the tissue layers of a shallot (a bulb) with the solid heart of a water chestnut.