Myriodesma serrulatum (J.V.Lamour.) Endl.

Scientific Description

Habit and structure. Thallus medium to dark brown, 15–30 cm long, with usually two complanately branched fronds from the branched stipe. Holdfast discoid-conical; probably epilithic. Stipe 2–18 cm long, with 1–4 di- or trichotomies at intervals of 1–6 cm, each (1–)2–3 mm in diameter. Fronds 10–25 cm long, irregularly pinnate with long, alternate, laterals (2–)3–6(–10) cm long, 2–4(–5) mm broad, linear but tapering above, coarsely and regularly serrate along their length with teeth 1–1.5 mm long; denuded below; midrib present, inconspicous near apices. Structure of fronds 0.4–0.6 mm and 10–20 cells thick, with a medulla of elongate cells in older parts and a cortex of isodiametric cells with a surface phaeoplastic meristoderm.

Reproduction. Thalli monoecious. Conceptacles prominent, conspicuously raised above the surface, forming an irregular line on each side of midrib, bisexual, with a basal group of phaeophycean hairs and also sterile, simple or once-branched paraphyses; oogonia sessile, ovoid, 90–140 µmlong and 60–80 µmin diameter; antheridia sessile or on branched paraphyses, elongate, 22–36 µmlong and 8–15 µmin diameter.

Distribution. From Port Denison to Cape Riche,W. Aust.

[After Womersley, Mar. Benthic Fl. Southern Australia II: 410–412 (1987)]