A nutritive tissue, characteristic of flowering plants, that surrounds the developing embryo in a seed. It develops from nuclei in the embryo sac and its cells are triploid. In endospermic seeds it remains and increases in size; in nonendospermic seeds it disappears as the food is absorbed by the embryo, particularly the cotyledons. Many plants with endospermic seeds, such as cereals and oil crops, are cultivated for the rich food reserves in the endosperm.