Moss

(class Bryopsida, or Musci), any of at least 10,000 species of small, spore-bearing land plants (division Bryophyta) distributed throughout the world except in salt water. Valvate mosses constitute the subclass Andreaeidae, and peat mosses compose the subclass Sphagnidae. The large subclass Bryidae constitutes most species of mosses, but the subclass Polytrichidae