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Electronic Flora of South Australia Species Fact Sheet

Callithamnion caulescens (J. Agardh) Womersley, comb. nov.

Phylum Rhodophyta – Order Ceramiales – Family Ceramiaceae – Tribe Callithamnieae


Callithamnion byssoides var. caulescens J. Agardh 1876: 39. Sonder 1881: 10.

Seirospora byssoides var. caulescens (J. Agardh) De Toni 1903: 1351. Lucas 1909: 49; 1929a: 24.

Thallus (Figs 113A) erect, flaccid and spreading, medium red-brown, 2–6 cm high, densely tufted with several orders of branching grading gradually from lower corticated axes (Fig. 113C) to slender ultimate branchlets (Fig. 113B) in flat-topped clusters, radially branched throughout. Lesser branches irregularly branched from every cell, ecorticate, lower main branches and axes corticate by descending rhizoids, often spirally twisted around the axial cells, lying within the axial cell wall. Attachment by rhizoids; epilithic or epiphytic. Structure. Apical cells 5–8 µm in diameter and L/D 1.5–2.5, often with a terminal hair, 2–4 subapical cells of similar dimensions. Lower and mid axes, including cortication, 150–500 µm in diameter, cells L/D 8–12 (decreasing to 0.5–2 near the base), corticating rhizoids (8–) 15–25 µm in diameter with cells L/D 6–12. Lower ecorticate branch cells 50–80 µm in diameter and L/D (2–) 3–6, decreasing gradually to 10–20 µm in diameter and L/D 2–3 (–8) at 3–4 cells from apices. Cells multinucleate; rhodoplasts discoid to elongate in small cells, ribbon like and longitudinally aligned in larger cells.

Reproduction: Gametophytes dioecious. Procarps borne on axial cells of the lesser branches, with two periaxial cells, one (the supporting cell) bearing a 4-celled horizontal carpogonial branch; post-fertilization each cuts off an auxiliary cell and rounded lobes (Fig. 113E) 180–250 µm across of carposporangia 25–35 µm in diameter; involucral branchlets absent. Spermatangia (Fig. 113D) borne on short branched filaments or clusters, often in series on successive cells.

Tetrasporangia (Fig. 113E, F) sessile on upper branchlets, scattered, ovoid to subspherical, 25–45 µm in diameter, tetrahedrally to decussately divided.

Type from Tasmania (Gunn); lectotype in Herb. Agardh, LD, 18430.

Selected specimens: Ardrossan, S. Aust., low eulittoral (Womersley, 8.xi.1980; AD, A51865). American R. inlet, Kangaroo I., S. Aust., drift (Womersley, 25.viii.1963; AD, A26747). Apollo Bay, Vic., drift on Heterozostera in harbour (Womersley, 31.viii.1971; AD, A39532 -"Marine Algae of southern Australia" No. 394) and on pipeline in harbour, 0–0.5 m deep (Owen, 1.ix.1971; AD, A39501). St Leonards, Port Phillip, Vic., 1–3 m deep on Ecklonia (Womersley, 9.viii.1959; AD, A23085). Hebe Reef, N of Georgetown, Tas., 6 m deep (Edgar, 22.x.1995; AD, A64793).

Distribution map based
on current data relating to
specimens held in the
State Herbarium of SA

Distribution: Ardrossan, S. Aust., to Port Phillip, Vic., and N Tasmania.

Taxonomic notes: The type of var. caulescens J. Agardh is densely epiphytic on a filiform alga (a Gracilaria?); it was distinguished by Agardh by the decurrent corticating filaments within the wall sheath of axial cells, and differs from A. byssoides in having coarser axial cells and rounded carposporophyte lobes. Records of C. byssoides from Tasmania (eg. Dixon & Price 1981, p. 117) are probably based on var. caulescens, here recognised as a species.


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

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

DIXON, P.S. & PRICE, J.H. (1981). The genus Callithamnion (Rhodophyta, Ceramiaceae) in the British Isles. Bull. Br. Mus. nat. Hist. (Bot.) 9(2), 99–141.

LUCAS, A.H.S. (1909). Revised list of the Fucoideae and Florideae of Australia. Proc. Linn. Soc. N.S.W. 34, 9–60.

LUCAS, A.H.S. (1929a). The marine algae of Tasmania. Pap. Proc. R. Soc. Tasm. 1928, 6–27.

SONDER, O.W. (1881). In Mueller, F., Fragmenta Phytographiae Australiae. Supplementum ad volumen undecinum: Algae Australianae hactenus cognitae, pp. 1–42, 105–107. (Melbourne.)

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

Author: H.B.S. Womersley & 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

Illustration in Womersley Part IIIA, 1998: FIG. 113.

Figure 113 image

Figure 113   enlarge

Fig. 113. Callithamnion caulescens (A39532). A. Habit. B. Branches. C. Cortication of lower axial cells. D. Branch with a procarp with twinned auxiliary cells. E. Twinned carposporophytes.

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