Cystophora polycystidea J.Agardh

Scientific Description

Habit and structure. Thallus medium brown, bushy, 20–50(–100) cm long, with a robust, often branched, primary axis bearing dense, tufted, secondary axes and laterals. Holdfast discoidconical, 0.5–1.5 cm across; epilithic. Primary axes compressed, quadrangular in transverse section, 2–7 mm broad and 2–4 mm thick, alternately distichously branched from the axis face at intervals of 0.3–3 cm, with prominent scalariform residues 1–3 mm long below; secondary (and tertiary) axes not or slightly retroflex, similar to primary axes but slenderer. Laterals 2–10 cm long, lax, with irregularly radially and spirally arranged terete ramuli 0.5–1.5 cm long and 0.2–0.5 mm in diameter, simple or alternately branched largely in one plane. Vesicles numerous, clustered, replacing 5–20 of the basal ramuli of laterals (occasionally odd higher ones), petiolate and apiculate at least when young, elongate-ovoid and tapering at both ends, (2–)3–5(–7) mm long and (1–)2–3(–4) mm in diameter.

Reproduction. Thalli monoecious. Receptacles simple or occasionally branched, distantly moniliform, 0.5–2 cm long and 0.4–0.7(–1) mm in diameter at conceptacles. Conceptacles bisexual, ostioles scattered or tending to two rows, with simple paraphyses; oogonia sessile, ovoid, 80–120 µmlong and 45–65 µmin diameter; antheridia sessile or on branched paraphyses, elongate-ovoid, 16–24 µmlong and 7–10 µmin diameter.

Distribution.From Albany, W. Aust., to Long Bay, N.S.W. and the N coast of Tas.

Habitat. C. polycystidea is a common species in rock pools and moderately sheltered areas from low tide level down for 3–5 m.

[After Womersley, Mar. Benthic Fl. Southern Australia II: 380 (1987)]