Sphacelaria tribuloides Menegh.

Scientific Description

Habit and structure. Thallus medium to dark brown, 5–20 mm long, densely tufted and spreading from a restricted base, usually epilithic, sometimes on seagrasses, attached by stoloniferous filaments. Branching of erect filaments relatively sparse with laterals similar to parent filaments and indeterminate, all filaments growing to an equal height; phaeophycean hairs frequent, 10–16 µm in diameter. Filaments straight, 20–30 µm in diameter above, 25–45 (–50) µm in diameter below, with segments L/B 1–1.5 and showing 1–2(–3) longitudinal walls; secondary transverse walls absent.

Reproduction. By tribuliform propagula, 150–180 µm long and 100–130 µm across the arms, borne on a uniseriate, 1–3 celled pedicel, with the two arms distinct, tapering, with their terminal cells cut off by a straight cross wall, and a small lenticular cell mid way between the arms. Zooidangia unknown for Australian plants; in Europe (Prud'homme van Reine 1982, p. 182) unilocular sporangia subspherical, 65–80 µm in diameter, and plurilocular sporangia ovoid, 55–100 µm long and 30–55 µm in diameter, with either large or small loculi.

Distribution. From tropical, W.Aust., around southern Australia to Tuggerah Lakes, N.S.W.

Habitat. S. tribuloides is a common species on rock at or just below low tide level.

[After Womersley, Mar. Benthic Fl. Southern Australia II: 160–162 (1987)]