The parts of the flower involved in reproduction are the stamen and the carpel, which contain the anther and the ovary, respectively. The anther at the top of the stamen has numerous microspore mother cells that undergo meiosis to produce microspores. Within the ovule, the megaspore mother cell in the carpel undergoes meiosis to produce four megaspores. The megaspore then undergoes mitosis to produce the embryo sac, which contains two cells: the tube cell and the egg cell. One megaspore undergoes mitosis and develops into a nucleus, and the other polar nuclei join with two sperm cells. The fertilized egg becomes a seed, which is protected by the seed coat. In angiosperms, seeds are triploid (3n). When animals eat fleshy fruits, they may ingest the seeds enclosed by the fruit and disperse them by defecation sometime later.