[4] The stramenopiles diverged from other major eukaryotic groups such as the opisthokonts (animals and fungi) and the archaeplastida (which includes land plants) over a billion years ago.

[1] The brown algae are also important because they are one of only a small number of eukaryotic groups that have evolved complex multicellularity.

[4] The alga is unbranched and filamentous;[4] it forms soft beards on larger plants or other firm substrata and grows up to 2 feet long.

[6] Filaments on E. siliculosus can grow up to 30μm in diameter, tapering toward the apices and sometimes forming terminal pseudo hairs.

[6] E. siliculosus reproduction and growth involves two different patterns of early development, which begin with either a symmetric or an asymmetric division of the initial cell.

[2] Asymmetric division leads to the immediate development of an erect thallus without the formation of a prostrate, basal structure (immediate differentiation).

With the study of Ectocarpus came the discovery of multiple genetic and genomic resources that apply to all species of brown algae.

[3] The carbon storage system of brown algae is unusual, involving the accumulation of reserves of mannitol and the β-1,3-glucan laminarin rather than α-1,4-glucans such as starch or glycogen.