What occurs during fertilization? Each ovule of a typical flowering plant contains a megaspore mother cell. This cells divides meiotically to produce 4 haploid megaspores, only one of which survives. This megaspore divides mitotically to produce the embryo sac (female gametophyte) which usually has 8 nuclei. The 2 center nuclei are called the polar nuclei and one of the 3 cells next to the micropyle is an egg cell. The anthers contain microspore mother cells, each of which divides meiotically to produce 4 haploid microspores. Each of these divides mitotically to give a 2-celled pollen grain. One cell is the tube cell, and the other is the generative cell. The generative cell later divided to give 2 sperm. The pollen grain is the male gametophyte. After pollination, the pollen grain germinates, and as the pollen tube grows, the sperm nuclei travel to the embryo sac. Angiosperms undergo double fertilization. One sperm nucleus unites with the egg nucleus, forming a 2N (diploid) zygote, and the other unites with the polar nuclei. This union produces a 3N (triploid) endosperm cell. After fertilization, the endosperm cell divides to form the endosperm and the zygote becomes the sporophyte embryo. The ovule matures into the seed and the ovary becomes the fruit.