Morphology highly variable: thallus <15 cm tall, flattened; varies in width with tips divided ~dichotomously; flattened faces of thalli covered thickly or sparsely with papillae of various sizes; dark brown to reddish black. There are separate male and female plants that produce haploid gametes. Male plants lack papillae & are light rose to yellowish in color. In the pictures I think we are looking at a female gametophyte since it has many little papillae. Papillae is where fertilization occurs.
Tidal pools, next to Morro Rock. Morro Bay, CA.
Description: Thallus is a branched blade, reddish brown (almost black) to yellowish brown, tough, reaching 15 cm (6 in) tall; branching dichotomous to irregular. This perennial species arises from a Petrocelis-like base; female thalli have distinct bumps (papillae), like a rough washcloth. Habitat: One of our most common seaweeds, growing on rocks from the high to mid intertidal of semi-protected to semi-exposed habitats. Similar taxa: Mastocarpus spp., including unnamed low intertidal and tidepool.. more