The name seaweed incorrectly implies that these organisms have little value. Actually, many seaweeds are rich in vitamins and minerals and are eaten in various parts of the world. Seaweeds also have many industrial uses. Brown algae yield a gummy substance called algin and red algae produce jellylike substances called agar and carrageenin. Manufacturers add these substances to various foods and drugs to give them a smooth texture and help them retain moisture.
Manufacturers also use algins in lipsticks, soaps, photographic film, paint, varnish, and buttons.
Agar serves as a culture medium, a base on which bacteria are grown in scientific laboratories. See Bacteriology . Algae, including the common seaweeds, traditionally have been classified in the plant kingdom, Plantae. Today, many scientists classify these organisms in the kingdom Protista. The giant kelp is Macrocystis pyrifera.