nucellus The mass of tissue in the ovule of a plant that contains the embryo sac. Following fertilization, it may be absorbed by the developing embryo or persist to form a perisperm. The size and shape of the nucellus is a diagnostic feature of some species.

nucellus The tissue that makes up the greater part of the ovule of seed plants. It contains the embryo sac and nutritive tissue. It is enclosed by the integuments except for a small gap, the micropyle. In certain flowering plants it may persist after fertilization and provide nutrients for the embryo.