Sphacelaria cirrosa (Roth) C.Agardh

Thallus filiform, forming olive brown, stiff, feather-like tufts, to 50 mm long.  Filaments segemented, each segment with (1-) 4-10 (-24) longitudinal walls, but very rarely with secondary transverse walls.  Branches numerous, in one plane; apical cells large and conspicuous.  Attached by a minute basal disc; rhizoids sparse or absent.  Propagules common, stalk of the propagule narrows to the base, often with an apical hair and usually 3 cigar-shaped arms. Unilocular sporangia pedicellate; plurilocular sporangia oval, rare, pedicellate. 

Habitat: Littoral, Infralittoral; usually epiphytic on Halidrys siliquosa or Cystoseira baccata, sometimes epilithic. Occasionally forming free-floating balls on sheltered shores (below).