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The Bryophytes: Mosses and Liverworts Mosses also belong to the bryophyte division of the plant kingdom. They are less sensitive to drying out than liverworts. Some mosses can dry out and will revive once they become wet again. As we shall see, however, water is essential for their reproduction.
Mosses grow in spreading mats or in tightly packed cushions. Their bodies consist of a stem covered in tiny leaflets. It is at the end of these stems that the sperm cells and egg cells are produced. This usually happens in early springtime. The sperms and eggs are not always produced on the the same stem. In the case of some mosses the sex cells are produced by different plants; in other words there may be male and female moss plants. When the moss plants are showered with drops of water from a rain storm or from a waterfall, the sperms swim through the water to the stems which support the eggs. After the sperm has fertilized an egg a spore case grows out of the moss on a stem. The spore case is often protected by a cap which blows off when the case ripens and dries out. The spores are microscopic and are carried away on the wind. If they land in a suitable habitat they will eventually germinate and grow into new moss plants. The diagram above shows the life cycle of a moss called Polytrichum. This is a moss which has separate male and female plants.
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