The New Student's Reference Work/Sargassum

Sargas′sum, a genus of brown seaweeds whose species are often observed floating in great masses in the large eddies formed by oceanic currents.  These regions of comparatively stagnant water covered by sea-weeds are known as Sargasso Seas, the prevailing type being a species of Sargassum.  See Phæophyceæ.