The Gulf-weed itself has so peculiar a history that it forms not the least remarkable point of interest in the description of the Sargasso Sea. It is one of the numerous species of the genus Sargassum, which is among the most natural and readily distinguished genera of the family of Fucaceæ. The great cryptogamist, Agardh, enumerates sixty-two species of Sargassum, of which the one concerning which we are speaking is the Sargassum bacciferum, called Fucus natans by Linnæus, and Fucus sargasso by Gmelin. The Spanish word Sargazo, or Sargaço, meaning sea-weed, supplies its common English name. The integument is leathery and the general color brown, of varying shades, sometimes light and sometimes dark. The most striking peculiarity, on a cursory view, is the abundance of globular cells, which have been taken by the unlearned for fruit, but which are in reality merely receptacles of air, by means of which the plant not only floats upon the surface of the ocean, but also is enabled to support vast numbers of marine animals, which find shelter among its tangled fronds. Columbus, the first discoverer of the Sargasso Sea, described the meadows as yellow like dry hay-seed, bearing leaves of common rue, with numerous berries, which turn black in drying like juniper berries. These berries have received the name of rasins de tropique. There is one point in the history of the Sargassum which has excited the attention of all observers, and more particularly of botanists. It is the fact that the Sargassum is always found floating upon the deep sea, and is yet destitute of any apparent means of propagation. Agardh remarked that no fruit nor root could be detected; and expressed his belief that it grew in the depths of the ocean and was torn up by the waves. This belief was very general at one time, and it was supposed that the perfect plant was unknown; but that the Gulf Stream collected together the torn-off masses of its vesicular summits. Rumphius suggested that the Sargassum fed upon the fat exhalations and oily effluvia of dead fish, and other organic substances entangled in it. Even modern publications state that there is reason to think that it is first attached to the bottom of the comparatively shallow parts of the sea; but the Gulf-weed is never found so attached. It always floats; and is healthy and abundant in that condition, never exhibiting any organs of fructification, though constantly putting out new fronds.