Carpospores germinate into gametophytes, which produce sporophytes. The life cycle is of the large diploid sporophytes and microscopic gametophytes. This is based on the position of the perichaetia and sporophytes. The mature sporophytes form the reproductive organs called sori. The fertilised zygotes germinate into young sporophytes which will grow into the mature seaweed. Ferns mostly produce large diploid sporophytes with rhizomes, roots and leaves. Mature sporophytes remain attached to the gametophyte. The moss is autoicous, and its sporophytes are exerted. In infected sporophytes, cells undergo meiosis and produce haploid spores. The gametophytes produce sperm and eggs to create new sporophytes. These plants are reared into young sporophytes for up to 60 days. Like the sporophytes of seed plants, those of ferns consist of stems, leaves and roots. Microthalli formed in this way then detach from the gametophyte to form separate sporophytes. Unlike plants at the bryophyte grade, their sporophytes were branched. Unlike bryophytes, fern sporophytes are free-living and only briefly dependent on the maternal gametophyte.