The mature embryo sac consisting of antipodals, egg apparatus and a large endosperm mother cell. The two polar nuclei usually fuse prior to fertilization. Fertilization occurs in the apical ovules of the ovary approximately 24 hours after the open flower stage and the basal ones are being fertilized at 32 hours. Double fertilization takes place and the entire endosperm is triploid from its inception. Two "x-bodies" remain in the tip of the pollen tube following discharge of the male gamete nuclei.