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The Collaborative International Dictionary
Melanosperm

Melanosperm \Me*lan"o*sperm\, n. [Gr. me`las, me`lanos, black + spe`rma 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.

Wiktionary
melanosperm

n. An alga of any kind that produces blackish spores, or seed dust.