Cystophora tenuis Womersley

Scientific Description

Habit and structure. Thallus dark brown, usually 30–60 cm long, with relatively slender primary (and secondary) axes bearing slender, lax, densely branched, laterals. Holdfast discoid-conical, 3–12 mm across; epilithic. Primary axes compressed, 2–4 mm broad below, 1–2 mm thick, oblong in transverse section, distichously branched at intervals of 3–10 mm with prominent (retroflex near the base) branch residues on lower parts of primary and older secondary axes; all branches from the face of the axes, attached for most of the width of the axis. Laterals 2–6 cm long, lax and slender, alternately distichous, with terete ramuli 5–10(–15) mm long and 250–500(–600) µm in diameter, lying largely in the one plane and tapering only slightly from base to apex, with moderately acute axils. Vesicles absent.

Reproduction. Thalli monoecious. Receptacles simple or branched, 2–6(–8) mm long and 500–700 µm in diameter, terete to slightly compressed, smooth to slightly verrucose but drying moniliform. Conceptacles essentially in two rows, bisexual; oogonia ovoid, sessile, 100–160 µm long and 55–80 µm in diameter; antheridia sessile or on branched paraphyses, elongate-ovoid, 20–25 µm long and 7–10 µm in diameter.

Distribution. C. tenuis appears to be restricted to south-west Western Australia.

[After Womersley, Mar. Benthic Fl. Southern Australia II: 390–392 (1987)]