Description: Thallus is a tuft of mostly unbranched, pigmented, uniseriate filaments growing on Fucus, up to 0.7 cm (0.28 in) tall. Large, elongate unilocular sporangia commonly occur on colorless branched basal filaments, but these can be seen only with a microscope. This species can co-occur with Pylaiella sp., which is usually much longer and is always branched. Habitat:This species usually occurs on Fucus or Palmaria in the mid intertidal of moderately protected shores in mid to late summer. Similar taxa: Pylaiella, Ectocarpus.