a genus of marine brown algae of the order Laminariales. They are the largest algae, measuring up to 45 m. They consist of a flexible branching stalk with rhizoids and leaflike blades with air bladders that support the branches and blades near the surface. There are three species. They are distributed in temperate waters of the southern and northern (only near the shores of California) hemispheres. They are mainly used to obtain salts of alginic acids.