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Electronic Flora of South Australia Species Fact Sheet

Polysiphonia isogona Harvey 1855b: 231.

Phylum Rhodophyta – Family Rhodomelaceae – Tribe Polysiphonieae

Selected citations: Adams 1994: 320, pl. 110 centre left. De Toni 1903: 932. Lewis 1983: 262; 1984: 64. Millar & Kraft 1993: 58. Womersley 1979: 505, fig. 14.


Polysiphonia comoides Harvey 1855b: 231. De Toni 1903: 932.

Polysiphonia amoena Sonder 1855: 525; 1880: 35. De Toni 1903: 959. Harvey 1863, synop.: xxii. Lucas 1909: 41. Tisdall 1898: 514. [NON P. amoena sensu Kützing 1864: 13, pl. 40a-d. Lucas & Perrin 1947: 272, and Segi 1966: 504, pl. 2A; see Womersley 1979: 507.]

Polysiphonia neglecta Harvey ex J. Agardh 1863: 942. Harvey 1855a: 541; 1863, synop.: xxii (nomen nudum). Kützing 1864: 13, pl. 39d-g. Sonder 1880: 35.

Lophosiphonia neglecta (Harvey) De Toni 1903: 1071. Lucas 1909: 45. Lucas & Perrin 1947: 294.

Polysiphonia compacta Lucas 1913: 56. De Toni 1924: 399. Lucas & Perrin 1947: 276.

Thallus (Fig. 90A, B) medium to dark red-brown, (1–) 3–15 (–20) cm high, forming densely and irregularly branched, lax, often fastigiate tufts with numerous axes (often partly denuded below) arising from prostrate, entangled filaments. Attachment by rhizoids from prostrate filaments; usually epilithic. Structure. Prostrate filaments (100–) 140–250 µm in diameter with segments L/D 0.5–1.2 (–3), with scattered unicellular rhizoids cut off from the proximal ends of pericentral cells; erect branches 125–250 (–300) µm in diameter with segments L/D (0.8–) 2–4, extending to L/D 6 in mid parts of long axes, decreasing gradually to 30–80 µm in diameter with segments L/D 0.7–1 near the straight apices with moderately prominent trichoblasts which are lost below the upper few segments; lateral branches arising from the side of the basal cell of trichoblasts, the latter usually soon lost; cicatrigenous branches usually absent. Pericentral cells (8–) 9–10, rarely 7 (see below), elongate throughout the thallus, ecorticate; trichoblasts or scar cells variable in position, from occasional on lower branches to every 2–4 segments above or sometimes on every segment with a divergence of 1/4 or 1/5, trichoblasts relatively slender and short, 1–3 times furcate, basal cells 12–20 µm in diameter. Rhodoplasts discoid, usually densely aggregated, occasionally in chains.

Reproduction: Gametophytes dioecious. Carposporophytes with a slight basal fusion cell and short gonimoblast bearing clavate terminal carposporangia 25–45 µm in diameter. Cystocarps (Fig. 90C) stalked, subspherical or slightly conical to ovoid, (200–) 250–400 (–600) µm in diameter; pericarp ostiolate, 2 cells thick, outer cells angular, isodiametric, ostiolar cells not enlarged. Spermatangial branches (Fig. 90D) developing as one branch of a trichoblast, cylindrical, 150–220 (–310) µm long and 25–60 µm in diameter, commonly with 1–3 (–5) sterile apical cells when mature.

Tetrasporangia (Fig. 90E) forming long, gently spiralling series in upper branches with a divergence of 1/9, often extending below 1–3 laterals, slightly and evenly swelling the segments, occupying 0.5–0.8 the segment diameter when mature, subspherical to ovoid, 55–90 µm in diameter.

Type from Blind Bay, Cook Straits, New Zealand (Lyall); lectotype in BM, collected Aug. 1849; a similar specimen in TCD but dated Sept. 1850.

Selected specimens: Haslam, Streaky Bay, S. Aust., eulittoral (Skinner, 30.xi.1977; AD, A48875). Kellidie Bay entrance, Coffin Bay, S. Aust., lower eulittoral (Womersley, 22.viii.1962; AD, A31870). Sleaford Bay, S. Aust., low eulittoral (Robertson, 12.v.1968; AD, A32519). 4 km N of St Kilda, S. Aust., 1 m deep (Steffensen, 11.ix.1975; AD, A46529). Port Elliot, S. Aust., low eulittoral (Woelkerling, 1.iii.1968; AD, 32284). Pennington Bay, Kangaroo I., S. Aust., in shallow pools (Prudhomme van Reine, 26.ix.1988; AD, A59123). Robe, S. Aust., pools on slipway (Womersley, 9.ix.1968; AD, A32684-"Marine Algae of southern Australia" No. 124) and upper sublittoral pools (Womersley, 13.v.1972; AD, A42246). Bridgewater Bay, Vic., low eulittoral (Womersley, 25.i.1967; AD, A31783). Kirk Point, Port Phillip, Vic., drift (Womersley, 30.viii.1971; AD, A39520). Walkerville, Vic., lower eulittoral (Sinkora A2056, 23.ii.1975; MEL, 504904 and AD, A49496). Low Head, Tas. (Perrin, Aug. 1948; AD, A49963). Hope 1., Dover, Tas., 2–5 m deep (Sanderson, 17.x.1994; AD, A64182). Blackmans Bay, Tas., low eulittoral (Skinner, 20.ii.1978; AD, A49201).

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

Distribution: New Zealand (widely distributed).

In southern Australia from King George Sound, W. Aust. to Tasmania and Port Jackson, N.S.W.; doubtfully from Queensland (Lewis, 1984, p. 64).

Taxonomic notes: P. isogona is a widespread species on southern Australian and New Zealand coasts; synonymy and relationships were discussed by Womersley (1979, pp 506–508), who also commented on otherwise identical plants but with 7 pericentral cells; these were regarded as of uncertain relationships.

Usually growing as a turf, often amongst sand, at about low tide level under moderate to strong wave action, occasionally in calmer water.


ADAMS, N.M. (1994). Seaweeds of New Zealand. (Cant. Univ. Press: Christchurch.)

AGARDH, J.G. (1863). Species Genera et Ordines Algarum. Vol. 2, Part 3, pp. 787–1291. (Gleerup: Lund.)

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

DE TONI, G.B. (1924). Sylloge Algarum omnium hucusque Cognitarum. Vol. 6. Florideae. (Padua.)

HARVEY, W.H. (1855a). Some account of the marine botany of the colony of Western Australia. Trans. R. Jr. Acad. 22, 525–566.

HARVEY, W.H. (1855b). Algae. In Hooker, J.D., The Botany of the Antarctic Voyage. II. Flora Novae-Zelandiae. Part II, pp. 211–266, Plates 107–121. (Reeve: London.)

HARVEY, W.H. (1863). Phycologia Australica. Vol. 5, Plates 241–300, synop., pp. i-lxxiii. (Reeve: London.)

KÜTZING, F.T. (1864). Tabulae Phycologicae. Vol. 14. (Nordhausen.)

LEWIS, J.A. (1983). Floristic composition and periodicity of subtidal algae on an artifical structure in Port Phillip Bay (Victoria, Australia). Aquatic Bot. 15, 257–274.

LEWIS, J.A. (1984). Checklist and bibliography of benthic marine macroalgae recorded from northern Australia. I. Rhodophyta. Dept. Defence, Materials Res. Lab., Melbourne, Vic. Report MRL-R-912.

LUCAS, A.H.S. & PERRIN, F. (1947). The Seaweeds of South Australia. Part 2. The Red Seaweeds. (Govt Printer: Adelaide.)

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. (1913).—Notes on Australian marine algae. I. Proc. Linn. Soc. N.S.W. 38, 49–60, Plates 1–5.

MILLAR, A.J.K. & KRAFT, G.T. (1993). Catalogue of marine and freshwater Red Algae (Rhodophyta) of New South Wales, including Lord Howe Island, South-western Pacific. Aust. Syst. Bot. 6, 1–90.

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

SONDER, O.W. (1880). In Mueller, F., Fragmenta Phytographiae Australiae. Supplementum ad volumen undecinum: Algae Australianae hactenus cognitae, pp. 1–42, 105–107. (Melbourne.)

TISDALL, H.T. (1898). The algae of Victoria. Rep. 7th Meet. Aust. Ass. Adv. Sci., Sydney, 1898, pp. 493–516.

WOMERSLEY, H.B.S. (1979). Southern Australian species of Polysiphonia Greville (Rhodophyta). Aust. J. Bot. 27, 459–528.

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.

Illustration in Womersley Part IIIA, 2003: FIG. 90.

Figure 90 image

Figure 90   enlarge

Fig. 90. Polysiphonia isogona (A, lectotype in BM; B, D, AD, A32684; C, E, AD, A42246). A. Lectotype. B. Habit. C. Branches with cystocarps. D. Spermatangial branches. E. Tetrasporangial branches. (All as in Womersley 1979, courtesy of Aust. J. Bot.)

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