Ovule

Ovule means "small egg". In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: The integument(s) forming its outer layer(s), the nucellus (or megasporangium), and the megaspore-derived female gametophyte (or megagametophyte) in its center. The megagametophyte (also called embryo sac in flowering plants) produces an egg cell (or several egg cells in some groups) for fertilization. After fertilization, the ovule develops into a seed.