Electronic Flora of South Australia Genus Fact Sheet

Genus COELOCLONIUM J. Agardh 1876: 639

Phylum Rhodophyta – Family Rhodomelaceae – Tribe Chondrieae

Thallus erect, usually much branched with lesser branches basally constricted and in some cases segmented, branches terete, with broad rounded apices, sometimes depressed, surmounted by a short apical filament bearing trichoblasts and cutting off 5 pericentral cells. Holdfast discoid or divided. Structure. Pericentral cells rapidly elongating at right angles to axial cells, becoming separated by spaces, branching apically tri- or quadrichotomously for 2–3 orders, then with an outer cortex of small, compact cells, 1–2 cells thick. Older branches usually with a rhizoidal inner cortex and in some species with rhizoids filling the spaces between the pericentral cells. Cells usually uninucleate.

Reproduction: Gametophytes dioecious. Carposporophytes with a basal cluster of filaments or slight fusion of lower cells and a branched gonimoblast with clavate terminal carposporangia. Cystocarps ovoid, sessile or short-stalked; pericarp with a broad ostiole, ecorticate to lightly corticate. Spermatangial organs (where known) flat, ovate discs, with a sterile margin.

Tetrasporangia borne on the pericentral cells or their derivatives, from none to few per whorl.

Lectotype species: C. opuntioides (Harvey) J. Agardh C. tasmanicum (Harvey) Womersley]

Taxonomic notes: A genus of some 5 species, mainly southern Australian, distinguished from Chondria by the elongation of the pericentral cells at right angles to the axial cells. This is comparable to the term "periaxial cells" as applied by Min-Thein & Womersley (1976, p. 38) and contrasts with the usual orientation of pericentral cells in the Rhodomelaceae. However, they are here referred to as pericentral cells since they are rhodomelaceous.

References:

AGARDH, J.G. (1876). Species Genera et Ordines Algarum. Vol. 3, Part 1 - Epicrisis systematis Floridearum, pp. i-vii, 1–724. (Weigel: Leipzig.)

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.

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

Publication: Womersley, H.B.S. (24 February, 2003)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIID. Ceramiales – Delesseriaceae, Sarcomeniaceae, Rhodomelaceae
Reproduced with permission from The Marine Benthic Flora of Southern Australia Part IIID 2003, by H.B.S. Womersley. Australian Biological Resources Study, Canberra. Copyright Commonwealth of Australia.

KEY TO SPECIES OF COELOCLONIUM

1. Thallus usually 10–30 cm high, much branched irregularly with clavate segments which readily disintegrate; usually epilithic	C. tasmanicum
1. Thallus usually less than 10 (–15) cm high, branched verticillately, umbellately or only slightly, segments not readily disintegrating; epiphytic, usually on Posidonia or Amphibolis	2
2. Thallus slender, 2–4 cm high, branches 0.5–1 mm in diameter, branching slight	C. debile
2. Thallus usually 2–10 (–15) high, relatively robust, branching umbellate or mostly verticillate, branches 1–3 mm in diameter	3
3. Thallus 1–3 cm high with 2–3 successive umbells of synchronous branches; usually epiphytic on Posidonia (or Amphibolis)	C. umbellula
3. Thallus 5–15 cm high, much branched, verticillate or clustered, or singly and not synchronous; usually epiphytic on Amphibolis or algae	C. verticillatum

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