They contain two unlike flagella, chlorophyll a and c and fucoxanthin pigments. Some lake dwelling golden algae are both heterotrophic and autotrophic. These algae are all multicellular. They contain chlorophyll a and c and fucoxanthin pigments. Since the pigments and stored foods are identical with those of the Chrysophyta, it is thought that the brown algae evolved from the less complex golden algae.
Most brown algae live in the cool waters off the temperate and sub polar areas.
Members of the genus Fucus are good examples. Their algal body is the thallus , a multicellular structure that looks like a plant but has no vascular tissue. It is attached to the surface of rocks by a structures called a holdfast . The chloroplast of the red algae show strong evidence of descent from cyanobacteria. The arrangement of photosynthetic membranes are similar.