Cotyledon

Noun

(Gr. kotylêdon: cavity, hollow) The first leaf or leaves of a seed plant, found in the embryo of the seed which may form the first photosynthetic leaves or may remain below ground. A part of the embryo in a seed plant. The number of cotyledons is an important feature in classifying plants. Among the flowering plants, the class known as Monocotyledonae have a single cotyledon and Dicotyledonae have two. Conifers have either two cotyledons, as in Taxus (yews), or five to ten, as in Pinus (pines). In seeds without an endosperm, e.g. garden pea and broad bean, the cotyledons store food, which is used in germination. In seeds showing epigeal germination, e.g. runner bean, they emerge above the soil surface and become the first photosynthetic leaves.