page_title: Brown algae
section_title: Growth
hierarchical_section_title: Brown algae / Morphology / Growth
caption_attribution_description: Area Marina Protetta Capo Gallo, Palermo, Sicily Dictyota dichotoma
context_page_description: The brown algae, comprising the class Phaeophyceae, are a large group of multicellular algae, including many seaweeds located in colder waters within the Northern Hemisphere. Most brown algae live in marine environments, where they play an important role both as food and as a potential habitat. For instance, Macrocystis, a kelp of the order Laminariales, may reach 60 m in length and forms prominent underwater kelp forests. Kelp forests like these contain a high level of biodiversity. Another example is Sargassum, which creates unique floating mats of seaweed in the tropical waters of the Sargasso Sea that serve as the habitats for many species. Many brown algae, such as members of the order Fucales, commonly grow along rocky seashores. Some members of the class, such as kelps, are used by humans as food.
  Between 1,500 and 2,000 species of brown algae are known worldwide. Some species, such as Ascophyllum nodosum, have become subjects of extensive research in their own right due to their commercial importance. They also have environmental significance through carbon fixation.
context_section_description: The brown algae include the largest and fastest growing of seaweeds. Fronds of Macrocystis may grow as much as 50 cm (20 in) per day, and the stipes can grow 6 cm (2.4 in) in a single day.
  Growth in most brown algae occurs at the tips of structures as a result of divisions in a single apical cell or in a row of such cells. they are single cellular organisms. As this apical cell divides, the new cells that it produces develop into all the tissues of the alga. Branchings and other lateral structures appear when the apical cell divides to produce two new apical cells. However, a few groups (such as Ectocarpus) grow by a diffuse, unlocalized production of new cells that can occur anywhere on the thallus.
caption: Growth in Dictyota dichotoma occurs at each frond tip, where new cells are produced.
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