Zonaria crenata J.Agardh

Scientific Description

Habit and structure. Thallus light to medium brown, occasionally dark brown, (5–)10–25(–35) cm long, much branched, branches complanate but often displaced, denuded below with stupose axes 1–3(–5) mm thick and a matted rhizoidal holdfast 5–20(–25) mm across and 5–15 mm long; epilithic. Fronds irregularly branched from apical splitting, margin below the apices usually irregularly spinous, upper parts (2–)4–10(–12) mm broad, narrowing to 2–4 mm broad near the stupose central axis where the lateral wing has disintegrated; upper fronds covered with a network of the hydroid Scoresbia daidala Watson. Structure 6 cells and 80–120(–150) µm thick throughout, with cells in regular rows in transverse section; cortical cells the same size as medullary cells (or becoming paired), 2–4 to each medullary cell lengthwise, 20–27 µm across (when not paired) in surface view, L/B (0.6–)1–1.5(–2). Hair tufts apparently absent.

Reproduction. Sori of sporangia scattered on upper branches, irregularly ovate, 0.5–2 mm long and 0.3–1 mm across, with paraphyses 5–9 cells and 150–250 µm long, with the terminal cell subspherical, 35–45 µm in diameter; sporangia clavate to ovoid, 120–160 µm long and 60–85 µm in diameter, with 8 spores, without a stalk cell. Sexual reproduction unknown.

Distribution.From Fremantle, W. Aust., to Southport, Qld.

[After Womersley, Mar. Benthic Fl. Southern Australia II: 250 (1987)]