Sargassum vestitum (Turner) C.Agardh

Scientific Description

Habit and structure. Thallus dark brown, 10–150 cm long, with a simple or branched stipe 1–4 cm long, terete, 2–4 mm in diameter, with no or slight branch residues, bearing apically 1–4(–6) primary branches. Holdfast discoid-conical, 5–15 mm across, usually with a single stipe; epilithic. Primary branches 10–50 cm long, axes slender to moderately robust, triquetrous, bearing tristichously arranged, simple (rarely branched) laterals, denuded below on old branches. Laterals (lower) (3–)5–10 cm long, 0.5–1.5(–2) cm broad, smooth, margins entire; upper laterals distinctly smaller than lower laterals, 2–4 cm long and 1–3 mm broad (becoming filiform above), smooth, entire, often lost from older fertile branches. Vesicles usually absent, occasionally profuse, clustered, petiolate, ovoid to ellipsoid, (3–)4–8 mm long, (2–)3–5 mm in diameter, with a small mucro.

Reproduction. Thalli monoecious. Receptacles bisexual, in open to dense clusters on upper laterals, (1–)2–3(–5) mm long and 0.5–1(–2) mm broad, petiolate, simple, compressed and occasionally slightly triquetrous above, with prominent spines on their upper half and especially at the apex, with scattered ostioles on the flat surfaces. Conceptacles unisexual or bisexual; oogonia sessile, ovoid, 100–200 µmlong and 80–130 µmin diameter, few per conceptacle; antheridia sessile or on branched paraphyses, ovoid, 15–25 µmlong and 8–12 µm in diameter.

Distribution.From Two Rocks, W. Aust., to Mallacoota Point, Vic., and around Tas.

Habitat. S. vestitum is common just below low tide level and in pools on rough-water coasts.

[After Womersley, Mar. Benthic Fl. Southern Australia II: 434–436 (1987)]