Corm

Corm, a short, fleshy, underground stem, generally consisting of a single internode and enclosed in a few sheathing membranous leaves. It bears buds on its upper surface or laterally and adventitious roots below; but differs from a bulb, which it resembles externally, in being a solid stem, and not being mainly made up of fleshy leaf-scales. Corms occur in the snowdrop, Crocus, Gladiolus, and Arum among Monocotyledons, and in Cyclamen among Dicotyledons. In some Ariods corms reach an enormous size. Such a rhizome (q.v.) as that of the onion-couch may well be considered as a chain of corms, and the corm of Arum, is sometimes termed a shortened rhizome.