The Encyclopedia Americana (1920)/Sargassum

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SARGASSUM, the most highly organized genus of the marine algæ, Fulcaceæ, or rock weeds. They are seaweeds which are either attached to stones by a discoid hold-fast or are floating, with long filiform stems, much branched and bearing long, narrow, leaf-like fronds with distinct midribs. The air-bladders are little, stalked globes, with slender projecting tips, and stand out from the axils of the fronds, like solitary grapes. It is to this characteristic that the generic name remotely refers and which has given rise to the common names, tropical grapes and grape-weed. Sargasso stems are much employed in South America under the name of goitre-sticks, for the cure of goitre. Sargassum bacciferum is the famous gulf-weed, which forms rafts or islands floating together on vast areas of the various oceans and called “sargasso seas.” The one lying in the North Atlantic Ocean, between the Azores and the Antilles (roughly 20° to 38° north latitude and 30° to 65° west longitude), its exact position being determined by the central whirl of the Gulf Stream, is so dense as to be often a hindrance to navigation. It covers a territory nearly equal to the European continent and was discovered by Columbus on his first voyage, he and the succeeding Spanish navigators calling it the Mar de Sargaço; it is connected by a narrow belt with a smaller sea between the Bermudas and the Bahamas. There is still another sea in the Pacific and one in the Antarctic Ocean. It is a disputed question whether the weeds have been torn from the shore and blown to their final resting place or whether they live and propagate themselves on the high seas. At any rate these floating islands furnish a permanent home to many small pelagic animals and of predaceous animals seeking them as food.