Sphacelaria rigidula Kutzing 1843

    Thalli medium to dark brown, 0.5-2 cm high, profusely branched tufts or cushions. Basal portion stoloniferous or pseudofilamentous disc with branched rhizoids. Branching of erect filaments more or less richly branched with narrow angle, ending in long colourless phaeophycean hairs 7-22 µm broad and 90-180 µm long. Apical cells long and rounded to slightly pointed apex, 50-90 µm long and 20-33 µm broad. Segments of the main axis divide one to three times longitudinally. Filament 15-24 µm broad, segments 18-32 µm long usually longer than broad, but occasionally equal to or shorter than broad.

    Propagules mostly with 2-3, slender, cylindrical to slightly tapering arms, 110-132 µm long and 14-20 µm broad. Length of the propagules from the pedicel to the lens-shaped top cell varies between 150-190 µm long.