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Electronic Flora of South Australia Genus Fact Sheet

Genus POLYSIPHONIA Greville 1823: lxvii, 308, nom. cons.

Phylum Rhodophyta – Family Rhodomelaceae – Tribe Polysiphonieae

Thallus erect, radially branched with progressively slenderer branches towards the apices but without differentiation into indeterminate and determinate branches, with basal rhizoidal holdfasts or prostrate axes attached by unicellular or multicellular rhizoids cut off or not from the pericentral cells. Structure. Growth apical, monopodial, with trichoblasts usually present and arising exogenously from every or many subapical cells; trichoblasts colourless (non-rhodoplastic), spirally arranged, usually caducous leaving a basal scar cell. Pericentral cells 4–24 (rarely 5), the same length as the central cell, relatively constant in number within a species, the first cut off below the trichoblast, the others in alternating sequence, ecorticate or corticated by descending filaments. Lateral branches borne on basal cell of trichoblasts or replacing them, or adventitious (cicatrigenous) from the central cell of older branches. Cells mostly uninucleate.

Reproduction: Gametophytes usually dioecious, rarely monoecious, occasionally with mixed phases.

Procarps on the fifth pericentral cell arising on the supra-basal segment of a trichoblast, with a 2-celled lateral sterile group, a (3–) 4-celled carpogonial branch and a 1-celled basal sterile group. Fertilization is followed by diploidization of the auxiliary cell via a connecting cell, with formation of a single gonimoblast initial, then a basal fusion cell and a branched carposporophyte with clavate terminal carposporangia, replaced from subapical cells. Cystocarps globular to urceolate, with or without a neck; pericarp arising pre-fertilization, from pericentral cells adjacent to the procarp, developing 12–14 axial filaments each with 2 outer pericentral cells and often corticated. Spermatangia borne on modified trichoblasts, as a single or several terete branches, usually with a basal sterile and often apical cells; axial cells with 4 pericentral cells, dividing anticlinally and periclinally to form 2 (–3) layers, with a surface layer of spermatangia.

Tetrasporangia produced in lateral branchlets, one per segment, usually spirally arranged (occasionally in linear series), tetrahedrally divided, covered by 2 pre-sporangial cover cells and sometimes a third, basal, post-sporangial cover cell.

Type species: P. urceolata (Dillwyn) Greville (1824, p. 309), type cons. [= P. stricta (Dillwyn) Greville 1824, p. 309].

Taxonomic notes: A genus of very many species, common on most coasts of the world, with some 26 species on southern Australian coasts. The type species has been redescribed in detail by Kim et al. 2000, and Kim & Lee (1999) have described a related genus, Neosiphonia, from Korea; several species of Polysiphonia are transferred to Neosiphonia.


GREVILLE, R.K. (1823). Scottish Cryptog. Fl. Vol. 2 (Edinburgh & London.)

GREVILLE, R.K. (1824). Flora edinensis. (Edinburgh.)

KIM, M.S. & LEE, I.K. (1999). Neosiphonia flavimarina gen. et sp. nov. with a taxonomic reassessment of the genus Polysiphonia (Rhodomelaceae, Rhodophyta). Phycol. Research 47, 271–281.

KIM, M.-S., MAGGS, C.A., McIVOR, I. & GUIRY, M.D. (2000). Reappraisal of the type species of Polysiphonia (Rhodomelaceae, Rhodophyta). Eur. J. Phycol. 35, 83–92.

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.


1. Pericentral cells 4


1. Pericentral cells 5–12


2. Thallus ecorticate throughout or with only slight cortication near the base of older axes


2. Thallus corticate at least over most of the main branches


3. Thallus epiphytic on Haplodasya urceolata, less than 2 mm high, attached by a cellular disc

P. haplodasyae

3. Thallus usually well over 2 mm high, not epiphytic on Haplodasya urceolata, with normal attachment rhizoids


4. Rhizoids not cut off from (ie. protoplast in open connection with) the parent pericentral cells


4. Rhizoids cut off by a pit connection from the parent pericentral cells


5. Trichoblasts or scar cells normally on every segment, attachment tendrils present

P. shepherdii

5. Trichoblasts or scar cells only occasionally present, tendril branches absent


6. Thallus usually less than 2 cm high (rarely to 4 cm), prostrate system well developed, forming spreading mats on low intertidal rock, occasionally epiphytic; branches of similar diameter (80–120 µm) throughout; male branches without sterile tip cells

P. scopulorum

6. Thallus usually over 2 cm high, prostrate system slight compared with the much-branched erect systems; branches tapering to upper parts, usually over 120 µm in diameter below; male branches with a sterile tip of 5–7 cells


7. Thallus slender, upper branches 40–60 µm in diameter, lower branches 70–180 µm in diameter with segments L/D 1.5–2, all lateral branchlets non-spinous

P. subtilissima

7. Thallus moderately robust, upper branches 100–150 µm in diameter, lower branches 180–250 p in diameter with segments L/D 4–10, branchlets spinous-tipped and of relatively limited growth

P. senticulosa

8. Pericentral cells throughout thallus broader than long, thallus under 0.5 cm high (epiphytic on Codium)

P. brevisegmenta

8. Pericentral cells in most of thallus longer than broad, thallus usually over 2 cm high (except P. amphibolis)


9. Thallus rarely over 1 cm high, forming a tangled felt on the stems of Amphibolis; rhizoids with multicellular pads

P. amphibolis

9. Thallus normally over 2 cm high, epilithic or epiphytic; rhizoids unicellular with lobed, digitate pads


10. Branches originating from the basal cells of trichoblasts


10. Branches originating in place of trichoblasts


11. Thallus usually with a single erect basal axis, with slight basal cortication on older axes, 250–500 µm in diameter below; often epiphytic

P. mollis

11. Thallus with several to numerous axes from prostrate basal filaments, ecorticate, with either slender axes 70–150 µm in diameter below or long (20–30 cm) axes with segments becoming 250–400 µm in diameter and L/D 6–12 (–18); epilithic or epiphytic


12. Thallus with entangled, prostrate basal filaments producing numerous erect filaments 70–150 µm in diameter below; usually epilithic

P. sertularioides

12. Thallus with several robust erect axes from prostrate basal filaments, 250–400 µm in diameter below and becoming L/D 6–12 (–18); epiphytic or epilithic

P. perriniae

13. Lower branches usually under 300 µm in diameter, upper branchlets 50–80 µm in diameter, with numerous patent laterals often markedly slenderer than parent branches

P. infestans

13. Lower branches usually over 300 µm in diameter, upper branchlets over 100 µm in diameter, with few if any slender patent laterals


14. Thallus with fasciculate lateral branchlets, attachment tendrils, and ovoid, multicellular propagules, branch segments broader than long

P. propagulifera

14. Thallus subdichotomous with few laterals, without tendrils or propagules, segments often as long as or longer than broad


15. Base erect and becoming slightly corticated, usually epiphytic, apices involute

P. succulenta

15. Base prostrate, ecorticate, apices straight

P. blandii

16. Lesser branches basally constricted, mainly cicatrigenous

P. crassiuscula

16. Lesser branches not basally constricted, mainly apical with some cicatrigenous


17. Branches near apices arising from basal cell of trichoblasts; pericentral cells isodiametric; branches usually patent; basal axis single

P. daveyae

17. Branches near apices replacing trichoblasts; ecorticate pericentral cells usually longer than broad; branches fastigiate; basal axes usually several from a common holdfast

P. australiensis

18. Pericentral cells normally 5 or 6


18. Pericentral cells 7 or more


19. Pericentral cells normally 5; most segments, at least in mid parts of thallus, longer than broad

P. abscissoides

19. Pericentral cells usually 6; segments L/D usually less than 1


20. Thallus to 1 cm high, with prostrate filaments producing numerous erect branches with few laterals; pericentral cells elongate

P. teges

20. Thallus to 5 cm high, base erect, subdichotomously to laterally branched above; pericentral cells isodiametric

P. forfex

21. Pericentral cells 7 (–8), ecorticate or corticate


21. Pericentral cells 9–12 (rarely 7 or 8, see P. isogona), ecorticate


22. Thallus ecorticate


22. Thallus corticate except on upper branchlets

P. brodiei

23. Branching fastigiate, branches markedly basally constricted

P. constricta

23. Branching mostly patent, short laterals frequent, not basally constricted

P. decipiens

24. Thallus with prostrate entangled base and slender, erect, fastigiate branches less than 300 µm in diameter


24. Thallus with a single, erect, axis, and coarse patent branches usually over 300 µm in diameter

P. atricapilla

25. Pericentral cells usually 10–11 (–12); rhizoids not cut off from pericentral cells; spermatangial branches replacing whole trichoblast

P. adamsiae

25. Pericentral cells usually 9 (8–10); rhizoids cut off from pericentral cells; spermatangial branches developing as basal branch of trichoblast

P. isogona

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