Polysiphonia bipinnata, Pterosiphonia robusta

Description: Thallus is fine, profusely branched, dark red to reddish-brown, reaching at least 12 cm (5 in) tall. Branching near tips is all in one plane, spreading out easily on your finger. This species requires a microscope for accurate identification of its polysiphonous habit of 10-12 pericentral cells surrounding the axial cell. Habitat: This common perennial grows on rock in the mid to low intertidal of protected to semi-exposed habitats in spring but gets grazed back by herbivores. Similar taxa: Polysiphonia spp., Antithamnionella pacifica.