Erythroclonium muelleri Sond.

Scientific Description

Habit and structure. Thallus medium to dark red, 5–22 cm high, profusely branched with main branches subdichotomous to alternate and above with whorls of branches from the apices of elongate-ovoid segments (2–)3–5 mm long and 0.5–1(–1.5) mm in diameter, usually with unbranched or once branched terminal segments 2–4 mm long; lower branches becoming thickened and terete, 1–2(–3) mm in diameter, usually denuded and without adventitious branchlets. Holdfast discoid, 2–5 mm across, with 1(–2) axis branched close to the base; epilithic. Structure uniaxial, with the axial filament remaining large and distinct throughout the thallus, each cell bearing two periaxial filaments more-or-less at right angles and alternating on successive cells, forming a lax medulla of branched filaments; rhizoids twisted around the axial filament from an early stage, and in thickened lower branches filling the medulla. Cortex pseudoparenchymatous, (1–)2–3 cells thick, inner cells ovoid and 10–20 µm in diameter, outer cells isodiametric and 8–12 µm across, becoming meristematic below to form a cortex 20–30 cells thick. Rhodoplasts discoid to elongate, many per cell.

Reproduction. Sexual thalli dioecious; non-procarpic. Carpogonial branches 3(–4)-celled, borne singly on elongate medullary cells adjacent to the cortex, directed inwards with reflexed trichogynes, with the basal cell(s) often bearing sterile cells. Connecting filaments single, unbranched. Auxiliary cell an outer medullary cell with adjacent cells producing branched chains of small nutritive cells. First gonimoblast initial inward, later radial from the large fusion cell connected to a fusion stalk from the medullary filament, with short chains (terminally mature) of ovoid carposporangia 12–18 µm in diameter. Cystocarps within the medulla, with enveloping tissue of laxly entangled filaments, ostiolate. Spermatangia scattered, with surface cortical cells cutting off 3–5 initials each of which forms 2–3 ovoid spermatangia 2–4 µm in diameter. Tetrasporangia scattered in the cortex, formed from inner cortical cells and pit-connected laterally to other cells, protruding into the medulla, ovoid, 80–130 µm long and 40–65 µm in diameter.

Distribution.Geographe Bay, W. Aust., to Port Phillip, Vic., and around Tas.

[After Womersley, Mar. Benthic Fl. Southern Australia IIIA: 351–353 (1994)]