The sporophyte produces free-swimming haploid spores by meiosis that germinate into haploid gametophytes. Sporophytes produce haploid spores by meiosis, that grow into gametophytes. The sporophyte produces spores by meiosis which in turn develop into gametophytes. Both types of spores develop into gametophytes inside sporangia. Within seed plants, male gametes are produced by extremely reduced multicellular gametophytes known as pollen. These undergo mitosis to form male gametophytes, each of which contains two haploid cells. The haploid generation consists of male and female gametophytes. For example, plants produce gametes through mitosis in gametophytes. Microsporangia are sporangia that produce microspores that give rise to male gametophytes when they germinate. At least one of the spores develop into haploid female gametophytes (megagametophytes). Flowers contain sporangia and are the site where gametophytes develop. Smaller spores tend to germinate into gametophytes which produce only sperm-producing antheridia. Their spores develop into underground, mycotrophic gametophytes. The anther produces pollen grains which contain the male gametophytes that produce sperm nuclei. Carpospores germinate into gametophytes, which produce sporophytes.