SELECTED DIVISIONS OF ALGAE 1. Brown algae (kelp) are macroscopic and may reach lengths of 50 meters. Most are found in coastal waters and grow very rapidly. Algin, a thickener used in foods such as ice cream, is extracted from the cell walls. This product is also used in hand lotions. 2. Red algae—these live deeper in the ocean than other algae. Agar is extracted from them. Another product, carageenan, comes from a species of red algae known as Irish moss and is used as a thickening agent in evaporated milk, ice cream and drugs. Some of these produce a lethal toxin. 3. Green algae—these have cellulose walls and store starch. Green algae may have given rise to terrestrial plants. Most green algae are microscopic, and may be either unicellular or multicellular. Some form grass-green scum in ponds.
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