Myriodesma quercifolium (Bory) J.Agardh

Scientific Description

Habit and structure. Thallus medium to dark brown, 20–50 cm long, with few to several complanately branched fronds from the branched stipe. Holdfast discoid-conical, 3–8 mm across; epilithic. Stipe 8–15(–25) cm long, with 2–5 di- or trichotomies at intervals of 1–4(–8) cm, each 2–5 mm in diameter. Fronds 15–30 cm long, irregularly alternately pinnate with laterals 2–6 cm apart, (0.7–)1–2.5(–4) cm broad, usually with coarsely serrate margins especially above, rarely with few or no serrations; serrations with rounded ends; midrib conspicuous below, disappearing above. Structure of fronds 250–500 µm and mostly 8–10 cells thick, with a medulla of elongate cells and a cortex of isodiametric cells with an inactive phaeoplastic meristoderm.

Reproduction. Thalli monoecious. Conceptacles densely scattered over the fronds, bisexual, with a basal group of phaeophycean hairs becoming paraphyses; oogonia sessile, ovoid, 80–140 µm long and 40–65 µm in diameter; antheridia mostly sessile, or on short branched paraphyses, elongate-ovoid, 20–30 µm long and 6–10 µm in diameter.

Distribution. From Kalbarri, W. Aust., to Port Elliot, S. Aust.

Habitat. M. quercifolium is a deep water western species.

[After Womersley, Mar. Benthic Fl. Southern Australia II: 416 (1987)]