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Mosses
Mosses are among the simplest true land plants. In the gametophyte generation, a moss plant has multicellular sex organs that protect the gametes-sperm and eggs.
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Each gametophyte, male and female, makes many haploid gametes by mitosis. Sperm that are made by the antheridium, the male sex organ, must swim through a film of moisture to the egg. The egg stays in the female sex organ, the archegonium , where fertilization and zygote formation occur. The diploid zygote, still embedded, then begins to divide by mitosis to become a sporophyte. The sporophyte carries on some photosynthesis but also obtains nourishment from the female gametophyte. When mature, the sporophyte produces many spores by meiosis. If conditions are favorable, each spore develops into a small structure, the protonema , that grows into a mature gametophyte.
แหล่งข้อมูล : Biology living system. Page 416.
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