Sphagnum's a genus of between 151-350 species of mosses commonly called peat moss, due to its prevalence in peat bogs and mires. A distinction's made between sphagnum moss, the live moss growing on top of a peat bog, and sphagnum peat moss, the decaying matter underneath. Bogs are dependent on precipitation as their main source of food and nutrients, thus making them a favourable habitat for sphagnum as it can retain water and air quite well. Members of this genus can hold large quantities of w… (More on Sphagnum)