Hair moss. Hair moss, Polytrichum commune, growing on stones on the floor of a birch wood. This star- shaped moss is common in wet moorland and by woodland streams where it grows in green clumps. Another yellow green moss can also be seen. Mosses produce spores which germinate into gametophytes, the green part of the moss. Male and female sex organs develop on the gametophyte, and produce sperm and eggs. The male sperm migrate to the female cells through a film of water on the plant's surface. Damp conditions are also needed because mosses have no true roots and absorb water and minerals through their leaves. Photographed in Northumberland National Park, England.