Sirophysalis trinodis (Forssk.) Kütz.

Scientific Description

Habit and structure. Thallus medium brown, to 65 cm tall, with a solitary or clustered growth form, erect from a crustose holdfast 7.5–10.0 mm wide. Primary axis terete, branched, covered in scars from previously shed laterals, 13–19 mm long, 2–4 mm wide. Primary branches radial, terete, crowded, 1.0–1.5 mm diam., with sparse to very crowded narrow spines with acute forked or infundibuliform, 0.25–0.40 mm long. Secondary branches radial, terete, 0.5–1.0 mm diam., with spines 0.3–0.4 mm long. Lower laterals linear-lanceolate to broadly lanceolate, 12–120 mm long, 1.5–15.0 mm wide; margins smooth to serrulate; apices acute; midrib percurrent; cryptostomata scattered and numerous. Upper laterals distinctly smaller, linear-lanceolate, 12–65 mm long, 0.5–15.0 mm wide; apices tapering to a very narrow point; midrib percurrent; base sharply cuneate, oblique with pedicels 0.25–0.50 mm; cryptostomata minute, scattered or in rows. Vesicles slightly elongate, 0.5–2.5 mm diam., solitary or in chains of 2–4 embedded mid-leaf or crowned with a linear-serrate leaf. Receptacles alternate on determinate reproductive branches, often associated with vesicles, smooth to coarse, terete or slightly compressed, simple or divided up to twice, with vesicles arising mid-receptacle in some plants. Monoecious with bisexual conceptacles.

Distribution. Known from Egypt to South Africa, Pakistan, India and Sri Lanka and east to Indonesia, New Caledonia and Chile. Occurs in W.A., S.A., N.T., Qld and Lord Howe Island; it is possibly a recent adventive in Tas.

Habitat. Epilithic in the shallow subtidal.

[After Dixon & Huisman, Algae of Australia: Mar. Benthic Algae of North-western Australia, 1. Green and Brown Algae 271 (2015)]