Sodium alginate is a gum, extracted from the cell walls of brown algae. They appear to be the closest relatives of the brown algae. This genus contains the largest of all the phaeophyceae or brown algae. Macrocystis is a monospecific genus of kelp (large brown algae). Other groups of brown algae grow to much larger sizes. Laminaria is a genus of 31 species of brown algae commonly called "kelp". They are sometimes served on edible seaweed, such as brown algae. Between 1,500 and 2,000 species of brown algae are known worldwide. Hormones occur in multicellular organisms (plants, animals, fungi, brown algae, and red algae). Oil from brown algae (kelp) is a source of EPA. Second, all brown algae are multicellular. It is also produced by brown algae and bacteria. The latter of these pigments is not found in red or brown algae. Alginic acid, or alginate, is extracted from brown algae. The photosynthetic system of brown algae is made of a P700 complex containing chlorophyll a.