Corm
A solid, swollen underground stem base that stores food, replaced by a new one each year.
A corm looks like a bulb from outside but is solid inside, with no layers. It is a swollen piece of stem with a papery tunic. Each year the plant uses up the old corm and forms a new one on top of it, often with small cormlets around the base that can be grown on. Crocuses, gladioli, freesias and crocosmias grow from corms. The saffron crocus is raised entirely from corms, since it sets no seed.