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Genus SPONGOCLONIUM Sonder 1855: 515

Phylum Rhodophyta – Order Ceramiales – Family Ceramiaceae – Tribe Spongoclonieae

Thallus erect, 5–30 cm high, much branched irregularly with or without prominent axes, densely corticated at least on mid and lower axes by branched, entwined, rhizoids produced from the basal cells of laterals, forming moderate to thick spongy axes, plus an outer cortex of lax, branched filaments variable in length; axial and branch cells each producing a single, radially or distichously branched, branchlet or ultimate ramulus. Cells multinucleate.

Reproduction: Gametophytes dioecious. Procarp systems enclosed in a gelatinous sheath, carpogonial branches borne on the subterminal cell of short, lateral, 3 (–5)-celled branches, with 2 periaxial cells on the third cell; the three sterile cells (terminal cell and 2 periaxial cells) enlarge and become rounded. Post-fertilization the auxiliary cell produces successive, rounded, gonimolobes and a loose involucre of filaments develops from axial cells below the carposporophyte, which is terminal on a lateral branch of 4–10 cells. Spermatangial heads are borne on branchlet cells, sessile or pedicellate and ovoid to elongate, with 4–8 axial cells bearing branched whorls with ultimate spermatangia.

Tetrasporangia occur on branchlet cells, sessile or pedicellate, subspherical to ovoid, tetrahedrally divided.

Type species: S. conspicuum Sonder 1855: 515.

Taxonomic notes: A genus of 10–15 species (including species placed in Mesothamnion), with 4 species on southern Australian coasts. The features of Spongoclonium conspicuum have been clarified by Wollaston (1990) and 2 other species (S. brownianum and S. fasciculatum) show the features of the type species, together with a newly described species.

Several other species were placed under Spongoclonium by J. Agardh (1892, pp. 39–42) and De Toni (1903, pp. 1357–1364). followed by Lucas (1927). These are now placed in other genera as follows:

S. wollastonianum is Dasythamniella wollastoniana [including S. wilsonianum]. S. dasyurum is Dasythamniella dasyura [incl. D. setosa].

S. latissimum is Dasythamniella latissima.

S. angustatum is Hirsutithallia angustata.

S. violaceum is Callithamnion violaceum [including S. paradoxum and S. scoparium].


AGARDH, J.G. (1892). Analecta Algologica. Acta Univ. lund. 28, 1–182, Plates 1–3.

DE TONI, G.B. (1903). Sylloge Algarum omnium hucusque Cognitarum. Vol. 4. Florideae. Sect. 3, pp. 775–1521 + 1523–1525. (Padua.)

LUCAS, A.H.S. (1927). Notes on Australian marine algae. IV. The Australian species of the genus Spongoclonium. Proc. Linn. Soc. N.S.W. 52, 460–470, Plates 27–35.

SONDER, O.W. (1855). Algae annis 1852 et 1853 collectae. Linnaea 26, 506–528.

WOLLASTON, E.M. (1990). Recognition of the genera Spongoclonium and Lasiothalia Harvey (Ceramiaceae, Rhodophyta) in southern Australia. Bot. Mar. 33, 19–30.

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

Author: H.B.S. Womersley and E.M. Wollaston

Publication: Womersley, H.B.S. (24 December, 1998)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIIC. Ceramiales – Ceramiaceae, Dasyaceae
©State Herbarium of South Australia, Government of South Australia


1. Thallus slender, corticated only slightly below.

S. australicum

1. Thallus robust, heavily corticated on axes and lateral branches


2. Axes densely corticated to near the apices, clothed with simple or basally branched; branchlets decreasing only slightly in diameter from 20–30 µm basally to (10–) 14–22 µm in diameter near their apices; tetrasporangia on 1–3-celled pedicels

S. conspicuum

2. Axes moderately to densely corticate in mid and lower parts, ecorticate over the upper 20–40 cells; tetrasporangia sessile or pedicellate


3. Branchlets in fascicles, basally branched, straight to slightly curved, basally 10–22 µm in diameter, apical cells 8–13 µm in diameter; tetrasporangia usually sessile

S. fasciculatum

3. Branchlets curved, basally 25–55 (–100) µm in diameter, apical cells 12–20 µm in diameter; tetrasporangia sessile or often pedicellate

S. brownianum

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