Coeloclonium tasmanicum (Harv.) Womersley

Scientific Description

Habit and structure. Thallus medium to dark red brown, fading to grey-red, 10–30 cm high, much branched irregularly with axes and main branches bearing lesser branchlets for 2–4 orders, these branchlets appearing as basally constricted segments with rounded apices, often in clusters of 2–4. Axes and main branches 2–4(–10) mm in diameter, lesser branches clavate to elongate-ovoid, (0.5–)1–2 mm in diameter and 2–8 mm long. Holdfast discoid or divided; epilithic, occasionally epiphytic. Structure. Apical filaments 8–15 cells long, projecting above the broad rounded apices (due to rapid enlargement of the pericentral cells and their derivatives), apical cells hemispherical, 12–18 µm in diameter. Pericentral cells 5, rapidly elongating at right angles to axial cells thus separated by spaces, becoming 90–130 µm in diameter and L/D (1.5–)4–10, when older bearing short, ovoid cells laterally; pericentral cells apically branched tri- or quadrichotomously for 2–3 orders, cells elongate, with an outer cortex 1–2 cells thick, outer cells mostly ovoid and 10–20 µm in diameter, in longitudinal rows; older branches with an extensive inner cortex of rhizoids cut off from the subcortical cells. Trichoblasts abundant at apices, 0.5–2 mm long. Cells uninucleate; rhodoplasts discoid, chained in larger cells.

Reproduction. Gametophytes dioecious. Procarps not observed. Carposporophytes with a basal cluster of filaments and slight fusion of lower, branched gonimoblast cells, with clavate terminal carposporangia 60–90 µm in diameter. Cystocarps ovoid, sessile, 1–1.5 mm in diameter, lateral on upper branches; pericarp several cells thick, with the erect filaments producing branched derivatives within the cellular cortex. Spermatangial plates not observed. Tetrasporangia borne on the pericentral cells or their derivatives, few to several per whorl, 120–220 µm in diameter.

Distribution. N of Dongara, W. Aust., to Walkerville, Vic., and around Tas.

[After Womersley, Mar. Benthic Fl. Southern Australia IIID: 410–413 (2003)]