The New Student's Reference Work/Cotyledon

Cotyledon (kŏt′ĭ-lē′dŏn), the first leaf or leaves developed by an embryo. In seed-plants the cotyledons are developed in the seed, and are more or less different from the usual leaf-form, often being fleshy from containing stored food, as in the bean and acorn. Generally the cotyledons escape from the seed during its germination, but in some cases, as in the acorn, they never leave the seed. See Embryo.