Cystophora gracilis Womersley

Scientific Description

Habit and structure. Thallus dark brown, 20–50(–70) cm long, with a slender, fairly straight, primary axis bearing densely branched laterals and secondary axes. Holdfast discoid-conical, 3–10 mm across; epilithic. Primary axes in transverse section ovoid to compressed with rounded edges, 2–3(–4) mm broad and 1–2 mm thick, tapering only slightly from base to apex, alternately distichously branched from the face of the axis at intervals of 0.5–1.5 cm, usually denuded below with inconspicuous branch residues to 1 mm long and the remaining secondary axes 2–6 cm apart; secondary axes usually inclined upwards and not retroflex, 5–10(–15) cm long, 0.5–1 mm broad, closely branched. Laterals 0.5–6(–10) cm long, alternately and fairly irregularly branched with irregularly subdichotomous, terete, ramuli, with broad but not rounded axils and not lying in one plane; ramuli 0.2–1 cm long, 0.2–1 mm in diameter. Vesicles absent.

Reproduction. Thalli monoecious. Receptacles developed from ends of ramuli, simple, torulose, 2–8(–10) mm long and 0.5–1 mm in diameter, with relatively few (4–10) closely adjacent conceptacles, with a sterile apical awn; occasional old receptacles with a conceptacle in the awn, the fertile region then 1.5–2 cm long. Conceptacles bisexual, ostioles more or less in two rows, with simple paraphyses; oogonia ovoid, sessile, 95–130 µmlong and 60–80µmin diameter; antheridia mainly near ostiole, sessile or on branched paraphyses, elongate-ovoid, 14–20 µmlong and 10–14 µmin diameter.

Distribution.From Cowaramup Bay, W. Aust., to Wanna, S. Aust. and Seal Beach, Kangaroo I., S. Aust.

Habitat. C. gracilis occurs in the uppermost sublittoral and deep pools.

[After Womersley, Mar. Benthic Fl. Southern Australia II: 388 (1987)]