Source : Webster's Revised Unabridged Dictionary (1913)

Melanosperm \Me*lan"o*sperm\, n. [Gr. me`las, -anos, black + ?
   seed.] (Bot.)
   An alga of any kind that produces blackish spores, or seed
   dust. The melanosperms include the rockweeds and all kinds of
   kelp. -- {Mel`a*no*sper"mous}, a.