(brown algae) A division consisting predominantly of marine *algae
and including many of the large seaweeds, such as the wracks (*Fucales
) and kelps (*Laminariales
). The organization of the thallus is more advanced than in other algae and growth is truly parenchymatous in many species. Sexual reproduction is usually oogamous. In addition to chlorophylls a and c, the brown algae contain carotin and xanthophyll pigments, including fucoxanthin. The main storage products are laminarin, mannitol, and fucosan. The Phaeophyta contains one class, the Phaeophyceae, divided into three subclasses: the Isogeneratae, in which there is an isomorphic alternation of generations (e.g. Ectocarpus, Dictyota); the Heterogeneratae, with a heteromorphic alternation of generations (e.g. Laminarid); and the Cyclosporae, with no alternation of generations (e.g. Fucus).