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Electronic Flora of South Australia Genus Fact Sheet

Genus ERYTHROCLONIUM Sonder 1853: 691

Phylum Rhodophyta – Class Florideophyceae – Order Gigartinales – Family Areschougiaceae

Thallus erect, segmented, irregularly branched from the apices of the elongate-ovoid, clavate or slender segments, lower branches often becoming terete by cortical thickening; holdfast discoid or branched. Structure uniaxial, with each axial cell bearing pairs of periaxial cells (forming branched filaments) diverging at about 90° and alternating on successive axial cells, thus with periaxial filaments on four radii; axial filament distinct throughout the thallus, usually surrounded by slender, often twisted, rhizoids; medulla lax, becoming filled with rhizoids in old branches, bearing the pseudoparenchymatous cortex 2–4 cells thick, thickened by meristematic activity in older parts.

Reproduction: Sexual thalli usually dioecious; non-procarpic. Carpogonial branches 3 (–4)-celled, borne on outer medullary cells adjacent to the inner cortex, directed inwards with reflexed trichogynes, usually with sterile cell(s) on the basal cell. Connecting filaments usually single and unbranched, non-septate. Auxiliary cell an outer medullary cell with adjacent cells producing a small-celled nutritive tissue in the outer medulla. Gonimoblast initial first inwardly, developing a fusion cell with a stalk from the periaxial filament, with radial gonimoblasts and chains of carposporangia, terminally mature. Cystocarps lying within the medulla, with lax filamentous enveloping tissue, ostiolate. Spermatangia scattered, cut off from outer cortical cells.

Tetrasporangia scattered, formed from inner cortical cells usually with lateral pit-connections, usually protruding into the medulla.

Life history triphasic with isomorphic gametophytes and tetrasporophytes.

Lectotype species: E. muelleri Sonder 1853: 692.

Taxonomic notes: Erythroclonium includes four species from southern and western Australia, monographed by Min-Thein & Womersley (1976), characterised by the pairs of periaxial filaments on four radii on any two successive axial cells and an axial filament conspicuous throughout the thallus. One further species, E. corallinum (Suhr) Holmes, is recorded from South Africa (Norris 1988, p. 105, figs 9–15).


MIN-THEIN, U. & WOMERSLEY, H.B.S. (1976). Studies on southern Australian taxa of Solieriaceae, Rhabdoniaceae and Rhodophyllidaceae (Rhodophyta). Aust. J. Bot. 24, 1–166.

NORRIS, R.E. (1988). A review of Natalian Solieriaceae (Gigartinales, Rhodophyta), including the first South African records of Solieria and Meristotheca, and an investigation of Erythroclonium corallinum. S. Afr. J. Bot. 54, 103–108.

SONDER, O.W. (1853). Plantae Muellerianae. Algae. Linnaea 25, 657–709.

The Marine Benthic Flora of Southern Australia Part IIIA complete list of references.

Author: H.B.S. Womersley

Publication: Womersley, H.B.S. (14 January, 1994)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIIA, Bangiophyceae and Florideophyceae (to Gigartinales)
Reproduced with permission from The Marine Benthic Flora of Southern Australia Part IIIA 1994, by H.B.S. Womersley. Australian Biological Resources Study, Canberra. Copyright Commonwealth of Australia.


1. Thallus segments mostly 2–5 mm long, lower branches heavily thickened, with or without short adventitious segments


1. Thallus segments (3–) 4–10 (–20) mm long, lower branches not or only slightly thickened, without short adventitious segments


2. Lower branches usually denuded or with odd laterals of a few segments remaining

E. muelleri

2. Lower branches with conspicuous nodal clusters of adventitious, single, segments

E. sedoides

3. Segments slender, elongate, 0.25–0.8 mm in diameter

E. angustatum

3. Segments elongate ovoid to clavate, (1.5–) 2–4 mm in diameter

E. sonderi

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