Cystophora expansa Womersley

Scientific Description

Habit and structure. Thallus dark brown, 20–60 cm long, densely branched from a coarse primary axis. Holdfast discoid-conical, 1–2(–3) cm across; epilithic. Primary axes 2–5(–10) mm broad and 1–2(–4) mm thick, with narrower edges, relatively straight with alternately distichous laterals from the axis face and prominent, reflexed, branch residues usually 0.5–1 cm apart; secondary axes 2–10 cm long, distichously and closely branched, usually basally denuded with close and prominent branch residues, not or slightly flexuous. Laterals 3–8 cm long, tristichously (occasionally subdistichously) branched from a 3-sided rhachis, bearing slender, alternately distichous ramuli 0.5–2(–3) cm long and 0.2–0.6(–l) mm thick. Vesicles usually present, scattered on laterals and replacing one to several of the lower branches of the ramuli, elongate-ellipsoid, 3–5(–7) mm long and 1–2 mm broad, petiolate, with an apiculate (when young) or rounded apex.

Reproduction. Thalli monoecious. Receptacles usually simple, developed from ends of ultimate branches of ramuli, 0.5–1(–1.5) cm long and 0.5–1(–1.5) mm in diameter, terete to slightly compressed, becoming closely torulose, apiculate. Conceptacles bisexual, closely adjacent but with relatively few per receptacle, with ostioles more or less in two rows, with simple paraphyses; oogonia sessile, ovoid, 90–150 long µm and 55–80 µmin diameter; antheridia sessile or on branched paraphyses, elongate-ovoid, 20–25 µmlong and 8–10 µmin diameter.

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

Habitat. C. expansa is a common species in shallow water and deeper pools on coasts of moderate wave action.

[After Womersley, Mar. Benthic Fl. Southern Australia II: 382–384 (1987)]