GULFWEED, in botany, a popular name for the seaweed Sargassum bacciferum, one of the brown seaweeds (Phaeophyceae), large quantities of which are found floating in the Gulf of Mexico, whence it is carried northwards by the Gulf Stream, small portions sometimes being borne as far as the coasts of the British Isles. It was observed by Columbus, and is remarkable among seaweeds for its form, which resembles branches bearing leaves and berries; the latter, to which the species-name bacciferum refers, are hollow floats answering the same purpose as the bladders in another brown seaweed, Fucus vesiculosus, which is common round the British Isles between high and low water.