Sargassum occurs. "Sargassum muticum" is a large brown seaweed of the class Phaeophyceae. It grows attached to rocks by a perennial holdfast up to 5 cm in diameter. From this holdfast the main axis grows to a maximum of 5 cm high. The leaf-like laminae and primary lateral branches grow from this stipe. In warm waters, it can grow to 12 m long, however in British waters it gives rise to a single main axis with secondary and tertiary branches that the plant sheds annually. Numerous small 2–6 mm stalked air vesicles provide buoyancy. The reproductive receptacles are also stalked, and
Sargassum to cover the entirety of the Sargasso Sea, making navigation impossible, it has since been found to occur only in drifts. "Sargassum" species ares also cultivated and cleaned for use as an herbal remedy. Many Chinese herbalists prescribe powdered "Sargassum"—either the species "S. pallidum", or more rarely, hijiki, "S. fusiforme"—in doses of 0.5 gram dissolved in warm water and drunk as a tea. It is called in traditional Chinese medicine, where it is used to resolve "heat phlegm". Species of this genus of algae may grow to a length of several metres. They are generally brown or dark green in