sphagnum

from WordNet (r) 3.0 (2006)

sphagnum
    n 1: any of various pale or ashy mosses of the genus Sphagnum
         whose decomposed remains form peat [syn: {sphagnum},
         {sphagnum moss}, {peat moss}, {bog moss}]

from The Collaborative International Dictionary of English v.0.48

Sphagnum \Sphag"num\, n. [NL., fr/ Gr. ??? a kind of moss.]
   (Bot.)
   A genus of mosses having white leaves slightly tinged with
   red or green and found growing in marshy places; bog moss;
   peat moss.
   [1913 Webster]