Dictyota naevosa (Suhr) Mont.

Scientific Description

Habit and structure. Thallus medium to dark brown, occasionally light brown when fresh, usually 20–40 cm long with branches 1–2.5(–3) cm broad, subdichotomously branched (2–)5–10 cm apart, commonly with unbranched upper parts often 10–15 cm long, with rounded axils and apices; proliferations present only after damage. Holdfast of rhizoids and sometimes with a few, subterete, short, stolons; epilithic. Cortical cells (15–)20–30(–40) µm across, L/B 1–2(–3),with the medullary cell outlines usually conspicuous in dried specimens. Cortex forming compact, short, filaments of 2–6 cells in the central part very close to the base. Medulla monostromatic, rarely 2 cells thick very near the base. Hair tufts often more or less in lines across the branches, hairs 15–20 µm in diameter.

Reproduction. Tetrasporangia 80–120(–180) µm in diameter, grouped into elongate-ovoid sori mostly 2–4 mm long and 1–2 mm across, centred around hair tufts, often with other scattered sporangia. Sexual reproduction unknown.

Distribution.In southern Australia, from Horrocks Beach, W. Aust., to Port Willunga, S. Aust.

Habitat. D. naevosa is apparently a deep water species, known from the drift and to 31 m deep.

[After Womersley, Mar. Benthic Fl. Southern Australia II: 190–192 (1987)]