Marsh Moss, or Mnium, L. a genus of perennial plants, comprising 32 species, most of which are natives of Britain.—The following only deserves to be mentioned, namely, the fontanum, or Fountain Marsh Moss; it grows in low wet meadows, turf-bogs, and springs ; where it flowers from May till August. This kind of moss, which may be seen at a considerable distance, serves as an excellent guide for discovering clear and cold springs : wherever it thrives, fresh water may be found, without the trouble of sinking deep wells.