Family Description:
Plants are composed of unilateral branched filaments that grow upright as well as creep along the substratum. Usually, the phases are isomorphic, and sexual reproduction is isogamous. Chloroplasts can be single or numerous in each cell.

Some members of Family Ectocarpaceae secrete a pheromone called ectocarpene, which both stimulates male gametophytes to release sperm and causes the sperm to be attracted to the eggs, thus increasing the effectiveness of fertalization.

Species description:
Fine yellowish-brown to dark brown twisted and richly branched filaments measure about 2 to 5 cm (about 0.8 to 2 in) tall. They form a dense feltwork growing on rocks, wood, or other algae. We have seen Sea Felt most often growing on Rockweed (Fucus gardneri). The tiny side branches can be opposite or alternate. If you have a microscope, examine some of the filaments carefully and you will see swellings scattered along them; these are intercalary sporangia (spore-forming organs) or gametangia (gamete-producing organs) and are very characteristic of this genus (other genera of filamentous browns have terminal sporangia; that is, their spore-forming organs occur at the tips of the branches).

The morphology of Sea Felt is highly variable and influenced by temperature, growth and age.

Sea Felt seems to prefer the lowered salinity present near the mouths of streams (or, maybe its predators don't like low salinity and so it escapes predation there). It is common in our area, especially in summer.

Source:  North Pacific Seaweeds