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Electronic Flora of South Australia Species Fact Sheet

Polysiphonia mollis Hooker & Harvey ex Harvey 1847: 43; 1855a: 539; 1859b: 299; 1863, synop.: xx.

Phylum Rhodophyta – Family Rhodomelaceae – Tribe Polysiphonieae

Selected citations: J. Agardh 1863: 968. De Toni 1903: 877; 1924: 394. Guiler 1952: 103. Hooker & Harvey 1847: 399. Huisman & Walker 1990: 440. Kützing 1849: 823; 1863: 27, pl. 88a-c. Lucas 1909: 41; 1929a: 21; 1929b: 51. Lucas & Perrin 1947: 267. Mazza 1909: No. 284. Meñez 1964: 213, fig. 3? Reinbold 1897: 57. Silva et al. 1996: 543. Sonder 1853: 701; 1855: 524; 1880: 34. Tisdall 1898: 514. Wilson 1892: 167. Womersley 1956: 82, 83; 1979: 476, fig. 4D–G.


Polysiphonia flavescens Zanardini 1874: 490. De Toni 1903: 955; 1924: 402. Guiler 1952: 103. Lucas 1909: 41; 1929a: 21. Lucas & Perrin 1947: 270.

Thallus (Fig. 80D) red-brown, usually 4–20 cm high, with a single, erect, basal axis (occasionally a slight prostrate part) and profusely branched above (often denuded below in older plants) subdichotomously to laterally to form dense, fastigiate to spreading, soft tufts. Holdfast discoid, small; commonly epiphytic on Posidonia, Heterozostera, Halophila or larger algae. Structure. Basal axis 300–700 µm in diameter with segments L/D 0.3–1, attached by unicellular rhizoids cut off from the lower pericentral cells; branches above the basal axis 250–500 µm in diameter with segments L/D 1–4 (–8), decreasing in lesser branches to 100–150 µm in diameter with segments L/D 0.7–3 and to 30–50 µm in diameter with segments L/D about 1 close to the apices; apices straight, apical cell and trichoblasts prominent; lateral branches arising close to apices from the basal cell of trichoblasts, with the trichoblast usually remaining lateral to the new branch rather than outside it; cicatrigenous branches often present below. Pericentral cells 4, elongate throughout the thallus except within a few segments of apices; ecorticate except for slight cortication in older parts near the base of the erect axis by filaments of relatively short cells originating from the corners of the pericentral cells and lying lengthwise over the junction; trichoblasts (or scar cells) formed on every segment, with a divergence of 1/4, relatively slender, basal cells 8–12 µm in diameter. Rhodoplasts discoid to angular; scattered or commonly in irregular chains.

Reproduction: Gametophytes dioecious. Carposporophytes with a slight basal fusion cell and short, branched, gonimoblast with shortly clavate terminal carposporangia 25–50 µm in diameter. Cystocarps (Fig. 80E) short-stalked, globular to ovoid, not or slightly urceolate, 250–400 µm in diameter; pericarp ostiolate, 2 cells thick, outer cells isodiametric, angular. Spermatangial branches (Fig. 80F) developing as one branch of a trichoblast, elongate-ovoid to cylindrical, (80–) 120–200 µm long and 35–50 µm in diameter, without a sterile apical cell, or with an inconspicuous one.

Tetrasporangia (Fig. 80G) forming gently spiral series in upper branches (often extending below one to several laterals), slightly to prominently swelling and distorting the branch, subspherical to ovoid, 50–70 µm in diameter.

Type from Tasmania, on larger algae (Gunn); lectotype in BM.

Selected specimens: Salmon Bay, Rottnest I., W. Aust., on Sargassum, drift (Parsons, 12.xi.1968; AD, A33387). Muston, American R. inlet, Kangaroo I., S. Aust., 2–3 m deep (Womersley, 21.xi.1968; AD, A32929) and 4–5 m deep (Shepherd, 29.xii.1977; AD, A48954). Taroona, Tas., 1–3 m deep (Shepherd, 19.iii.1975; AD, A46226).

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

Distribution: Rottnest I., W. Aust., around southern Australia and Tasmania to Port Phillip, Victoria.

Indian Ocean (see Silva et al. 1996: 543); Pacific Ocean? (Abbott & Hollenberg 1976: 688).

Taxonomic notes: The type material of P. mollis in BM consists of a sheet with two specimens, both 'Gunn 1316'. The lower is selected as lectotype; the upper isolectotype is attached to a Eucalyptus leaf. Another specimen from V.D.L. is labelled 'Polysip. mollis var'. Two features that are not convincingly shown in the type are the single erect base and the origin of the lateral branches. However, Harvey in his original description referred to 'Root scutate. Fronds erect, solitary, or approximating' and in the recent material examined the erect basal axis attached by a cluster of rhizoids is a general feature. The origin of branches from trichoblasts is a difficult feature to discern in herbarium specimens, but a careful examination of the type shows that almost certainly branches do originate from the basal cell of trichoblasts, as they clearly do in fresh collections which in other features agree well with the type.

P. mollis is characterised by the erect base and branches which taper from 300 µm or more near the base to 30–50 µm in diameter close to the apices, the branching associated with the trichoblasts, and the soft, readily disintegrating nature of the thallus. It is a common epiphyte in relatively calm situations or where a current flows.

P. mollis has been recorded (often doubtfully) from many parts of the tropical Indian and Pacific Oceans, e.g. from Japan by Yendo (1916b, p. 261), now placed under P. japonica Harvey by Yoshida (1998, p. 1067); from Sri Lanka by Durairatnam (1961, p. 70) on the basis of a sterile specimen ; from Mauritius by Børgesen (1945, p. 30) but see Silva et al. (1996, p. 543); from Bangladesh by Islam (1976, p. 64); from the central Pacific and from Mexico by Hollenberg (1961, p. 359, pl. 4 fig. 2; 1968a, p. 69, fig. 43) but referred by Abbott (1999, p. 432) to P. tongatensis Harvey ex Kützing; and from Queensland by Askenasy (1894, p. 13, pl. 3 fig. 13, pl. 4 figs 20–22) and by Cribb (1956b, p. 131, pl. 4 figs 1–4, p1.5). However, it appears unlikely that P. mollis occurs outside southern Australia.

An isotype of P. flavescens Zanardini from Georgetown, Tas. (Goodwin), in Herb. Zanardini, Venice, is identical with P. mollis and comes from the same type locality.


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ABBOTT, I.A. (1999). Marine Red Algae of the Hawaiian Islands. (Bishop Museum Press: Honolulu, Hawai'i.)

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WOMERSLEY, H.B.S. (1956). The marine algae of Kangaroo Island 1V. The algal ecology of American River inlet. Aust. J. Mar. Freshw. Res. 7, 64–87, Plates 1–7.

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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. 80 D–G.

Figure 80 image

Figure 80   enlarge

Fig. 80. A–C. Polysiphonia amphibolis (AD, A32838). A. Branches with cystocarps. B. Spermatangial branches. C. Tetrasporangial branches. D–G. Polysiphonia mollis (AD, A32929). D. Habit. E. Branches with cystocarps. F. Spermatangial branches. G. Tetrasporangial branches. (All as in Womersley 1979, courtesy of Aust. J. Bot.)

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