Bulb
An underground storage organ made of fleshy layers, holding next season's shoot and flower.
A true bulb is a short stem wrapped in swollen leaf bases, like an onion. Cut one in half and you see the layers, with the future flower already formed in the middle. The bulb feeds the plant through its resting season and powers the flower. Tulips, daffodils, hyacinths, lilies and alliums grow from bulbs. In shops, the word is used loosely for corms, tubers and rhizomes as well, since all are sold dry and planted the same way.