cotyledon

Cotyledon

The cotyledon(s) make up the bulk of the seed. They are a source of stored carbohydrates that are the fuel for germination. The word cotyledon comes from the Greek for "seed leaf." They are commonly referred to as "seed leaves." Plants are divided into two major groupings based on cotyledon structure: monocots and dicots. Monocots include grasses and lilies. When these seeds germinate, there is only one seed leaf.

There are two types of germination. In one case, the cotyledons remain within the testa and fuel the growth of the embryo. In the second case, the cotyledons emerge as the first leaves of the seedling and carry out photosynthesis until the true leaves form.

[|Wikipedia Entry for Cotyledon]