Moss, primitive plants related to the liverworts. The mosses and liverworts together make up the phylum bryophyta. Of the 2 groups, the mosses are the more advanced because they have a vertical stem with simple leaves and roots. From the tip of the leafcovered stem springs a tall stalk bearing a capsule containing the spores. Mosses display alternation of generations, with both sexual and asexual stages in their life cycles. Mosses are dependent on water for their life and reproduction. They are found in damp woods, crevices, bogs, and a few live underwater in ponds. They play an important part in preventing erosion and in the formation of soil. The peat mosses, are of considerable economic importance. They are extremely absorbent, taking up over 100 times their weight of water, and have been used in surgical dressings. Their rotted remains collect in bogs to form peat, which is used in many parts of the world as fuel and in garden cultivation.