Any of at least 12,000 species of small, spore-bearing land plants in the bryophyte division, found worldwide except in salt water. Mosses are simple and ancient plants that have survived nearly unchanged since the Permian Period (290–248 million years ago). Commonly found in moist, shady locations (e.g., forest floors), mosses may range in size from microscopic to more than 40 in. (1 m) long. They prevent erosion and release nutrients from the substrates on which they grow. The life cycle shows clear alternation of generations between the sexual gametophyte, with stemlike and leaflike structures that produce eggs and swimming sperm, and the sporophyte, a raised stalk that ends in a spore case (sporangium). Mosses also reproduce asexually by branching. The economically important genus Sphagnum forms peat. Many so-called mosses are not bryophytes, including Irish moss (a red form of algae); beard moss, Iceland moss, oak moss, and reindeer moss (all lichens); Spanish moss (a name used variously for a lichen or an air plant of the pineapple family); and club moss (an evergreen herb of the family Lycopodiaceae).