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Electronic Flora of South Australia Species Fact Sheet

Polysiphonia forfex Harvey 1859a: pl. 96; 1863, synop.: xxii.

Phylum Rhodophyta – Family Rhodomelaceae – Tribe Polysiphonieae

Selected citations: Huisman & Walker 1990: 439. Womersley 1979: 495, fig. 10D–G.


Polysiphonia forcipata Harvey 1855a: 541. J. Agardh 1863: 1024. De Toni 1903: 920. Kützing 1864: 15, pl. 44a-d. Lucas 1909: 41. Lucas & Perrin 1947: 272. Segi 1966: 508, pl. 12A. Sonder 1880: 35. [NON P. .forcipata J. Agardh 1842: 127 from the Adriatic = P. furcellata (C. Agardh) Harvey].

Thallus (Fig. 86D) red-brown, 1–5 cm high, with an erect basal axis, subdichotomously to laterally branched with usually patent branches, sometimes fastigiate and unilateral above, usually with somewhat forcipate or involute apices. Holdfast 1–3 mm across, of clumped rhizoids; epiphytic on Posidonia or larger algae. Structure. Basal axis 300–700 µm in diameter with segments L/D 0.3–0.5, with rhizoids cut off from the pericentral cells or cortical cells of the basal segments; mid branches 300–500 µm in diameter with segments L/D 0.3–0.5, tapering to 100–150 µm in diameter with segments L/D 0.2–0.3 shortly behind the apices, then tapering abruptly to the involute apices (Fig. 86G), with relatively inconspicuous trichoblasts; lateral branches several to many segments apart, arising in place of trichoblasts; cicatrigenous branches occasional. Pericentral cells 6 occasionally 5 or 7, isodiametric to slightly broader than long in face view (Fig. 86G), and commonly in longitudinal rows but sometimes irregular, lightly corticate near the base of main axes with relatively large cells cut off from the sides of the pericentral cells; trichoblasts or scar cells on every segment, trichoblasts slender (basal cells 15–20 µm in diameter), 3–5 times furcate. Rhodoplasts elongate-ovoid to ribbon-like.

Reproduction: Gametophytes dioecious. Carposporophytes with a small basal fusion cell and short gonimoblast bearing clavate terminal carposporangia 35–50 µm in diameter. Cystocarps (Fig. 86E) short-stalked, subspherical to ovoid, 250–400 µm in diameter; pericarp ostiolate, 2 cells thick, outer cells angular, isodiametric, with the apical ostiolar cells becoming enlarged. Spermatangial branches (Fig. 86F) replacing the whole trichoblast, elongate-ovoid, 120–270 µm long and 70–120 µm in diameter.

Tetrasporangia (Fig. 86G) forming spiral series in upper branches, with a divergence of about 1/5 owing to irregularly placed pericentral cells, often descending below 1–2 branchings, not or very slightly distorting the segments and occupying only 0.3–0.5 the branch diameter, 55–110 µm in diameter.

Type from Rottnest I., W. Aust., on Posidonia (Harvey, Trav. Set 186 as P. forcipata); holotype in Herb. Harvey, TCD; isotype in BM.

Selected specimens: Fremantle, W. Aust. [Harvey, (Alg. Aust. Exsicc. 171A); MEL, 1006731]. Whitford Beach, Perth, W. Aust., on Sargassum, 4 m deep (Cook, 20.viii.1979; AD, A50697). Rottnest I., W. Aust., drift on Laurencia brongniartii (Cribb 67.52, 9.viii.1950; AD, A13963) and on Sargassum, NW end (Gordon, 12.xi.1968; AD, A33132). Salmon Bay, Rottnest I., W. Aust., on Sargassum, drift (Parsons, 12.xi.1968; AD, A33385). Point Peron, W. Aust., upper sublittoral (Womersley, 24.ix.1979; AD, A51026).

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

Distribution: Coast near Fremantle, Rottnest I., Garden I. and King George Sound, W. Aust. Epiphytic on Posidonia and some robust algae.

Taxonomic notes: Harvey (1859a, pl. 96) changed the name of his P. forcipata to P. forfex, recognising J. Agardh's earlier use of the former name. He recorded the species on Zostera, a name used by Harvey for Posidonia australis.

P. forfex occurs mainly on or near Rottnest I., but Harvey recorded it also from King George Sound. It is distinguished by its habit, normally 6 pericentral cells, and the very short segments throughout the thallus. Comparisons with P. brevisegmenta are made under the latter species.

P. forcipata Harvey was recorded from Japan by Segi (1951, p. 251, fig. 31, Pl. 13 fig. 1) but this record is referred to P. fragilis Suringar by Yoshida (1998, p. 1066). Yoon (1986, p. 36), followed by Silva et al. 1996, p. 542, places P. forfex as P. japonica var. forfex, but his description (presumably of Korean plants) differs from the Australian plants in referring to 4–6 pericentral cells (usually 6 in the latter) and is inadequate for comparisons. It seems unwise to follow Yoon for the present.


AGARDH, J.G. (1842). Algae Maris Mediterranei et Adriatici, Observationes in Diagnosin Specierum et Dispositionem Generum. (Fortin, Masson: Paris.)

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.)

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. (1859a). Phycologia Australica. Vol. 2, Plates 61–120. (Reeve: London.)

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

HUISMAN, J.M. & WALKER, D.I. (1990). A catalogue of the marine plants of Rottnest Island, Western Australia, with notes on their distribution and biogeography. Kingia 1, 349–459.

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

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.

SEGI, T. (1951). Systematic study of the genus Polysiphonia from Japan and its vicinity. J Fac. Fish., Prefect. Univ. Mie 1, 169–272, Plates 1–16.

SEGI, T. (1966). The type or authentic specimens of Polysiphonia in Europe. Rep. Fac. Fish., Prefect. Univ. Mie 5, 503–516, Plates 1–25.

SILVA, P.C., BASSON, P.W. & MOE, R.L. (1996). Catalogue of the Benthic Marine Algae of the Indian Ocean. (Univ. California Press: Berkeley.)

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

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

YOON, H.-Y. (1986). A taxonomic study of genus Polysiphonia (Rhodophyta) from Korea. Korean J. Phycol. 1, 3–86.

YOSHIDA, T. (1998). Marine Algae of Japan. (Uchida Rokakuho Publ. Co.: Tokyo.)

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. 86 D–G.

Figure 86 image

Figure 86   enlarge

Fig. 86. A–C. Polysiphonia teges (AD, A49279). A. Habit. B. Prostrate axes with erect branches. C. Tetrasporangial branches. D–G. Polysiphonia forfex (D, MEL, 1006731, Alg. Aust. Exsicc. 171A; E–G, AD, A50697). D. Habit. E. Branches with cystocarps. F. Branch with spermatangial organs. G. Tetrasporangial branches. (A–D as in Womersley 1979, courtesy of Aust. J. Bot.)

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