Ceramium tasmanicum (Kütz.) Womersley

Scientific Description

Habit and structure. Thallus dark red, 1–10 cm high, usually bushy and tufted with several erect axes from the base. Branching usually dense and irregular on all sides, the upper parts subdichotomous in varying planes, usually (especially in plants from rough-water coasts) with frequent small proliferous branchlets from the lower nodes; older branches often torulose due to swollen nodes. Attachment by a tuft of branched, uniseriate-celled rhizoids with occasional multicellular pads, originating from the periaxial and larger cortical cells of the lower 1–5 axial cells; epilithic or epiphytic (mainly on Codium fragile). Structure. Branches (300–)400–1000 µm in diameter below, 60–100 µm in diameter shortly below apices, tapering gradually (apart from the slender proliferous branchlets on broader older branches) to relatively slender, involute to moderately straight apices. Axial cells L/D 1–1.5 near apices with internodal spaces 0.3–1 times as long as the nodal cortication; cortication on older branches extending irregularly but usually not closing completely. Periaxial cells (5–)7–8, each cutting of 2–3 cells acropetally and basipetally, which each cut off a further 1–3 cells which continue to divide to form nodes 6–7 cells long near to the apices, usually slightly more developed acropetally than basipetally; cortex extending gradually until in larger branches where extension is more rapid and irregular (usually more so acropetally), with elongate cells, the nodal margins varying from relatively straight to most irregular, but usually maintaining an internodal space. Outer cortex of small cells formed in relatively young nodes, later covering the whole nodal cortex (except at the margins) as an irregular, loose (especially in prepared mounts and older nodes) layer of small, rounded, widely separated cells, without distinct rosettes except sometimes over the periaxial cells; long slender hairs are usually formed profusely from the terminal acropetal and outer cortical cells of young branches. Rhodoplasts discoid in cortical cells, ribbon shaped and more-or-less longitudinal in axial cells.

Reproduction. Gametophytes dioecious. Carposporophytes on upper branches, globular, 100–300 µm across, with 3–6 straight to slightly curved branchlets arising just below them; carposporangia ovoid, 25–35 µm in diameter. Spermatangia covering the nodal cortex of young branchlets, commencing adaxially but soon spreading around the node. Tetrasporangia in whorls of 2–6, arising from the periaxial cells (or immediate cortical derivatives), largely involucrate within the cortex, cruciately divided, subspherical to ovoid, 30–45 µm in diameter.

Distribution. W. Aust., and from Robe, S. Aust., to Western Port, Vic., and around Tas.

[After Womersley, Mar. Benthic Fl. Southern Australia IIIC: 400–402 (1998)]