After flowering plants and ferns, mosses are the most diverse group of plants today, with more than 10,000 species in 700 genera. This makes mosses almost twice as diverse as mammals.
Mosses don't receive as much attention from us as other groups of plants, such as flowers, ferns, or conifers, because most mosses are small and inconspicuous. They have no vascular tissue or wood to lend them structural support, nor do they have large leaves or showy cones or flowers. This does not mean that mosses are not important; in fact, mosses play important roles in reducing erosion along streams, water and nutrient cycling in tropical forests, and insulating the arctic permafrost. They also provide habitat for a variety of microscopic animals that live among their leaves.
Mosses are also much older than most groups of plants you are probably familiar with. The oldest known moss fossils come from the early Carbonifeorus of England, predating conifers and most ferns.
For more information about mosses, try the resources listing at the ABLS website. The American Bryological and Lichenological Society is devoted to the scientific study of all aspects of bryophyte biology.
You may also be interested in the Bryological Resources at the Missouri Botanical Garden, including a literature database, index of moss names, and bryological glossary.
