A

David

Darling

nucellus

The nucellus is the central tissue of an ovule. The nucellus contains the embryo sac and is almost totally surrounded by integuments except for a small channel, the micropyle, through which the pollen tube may grow prior to fertilization. At fertilization the nucellus may be reabsorbed as the embryo develops or it may persist to form a nutritive perisperm in some seeds.