Phaeophyta Brown algae are characterized by multicellular thalli with mostly uninucleate cells. They are generally found in intertidal or upper subtidal zones. The primary photsynthisizing pigment is cholorophyl a. However, fucoxanthin is the major accessory pigment and contributes to their olive to gold-brown coloring. Growth of the thalli is usually intercalary or apical.
Sexual reproduction can be isogamous, anisogamous, or oogamous.
The motile spores and male gametes are typically diflagellated. This is the only class in the Phaeophyta, so it shares the same characteristics as the division. The sporophyte is the dominant field phase and is made up of a holdfast, stipe, and one or more blades. Gametophyte thalli are not known to exist in nature. Unlike most algae, the Laminariales have tissues that are differentiated into an epidermis, cortex, and medulla.