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Alleynea bicornis Womersley, sp. nov.

Phylum Rhodophyta – Family Rhodomelaceae – Tribe Polysiphonieae

Thallus (Fig. 92A) dark brown-red, drying very dark, 10–30 cm high, with few to numerous erect, simple or branched, axes arising from an entangled, stoloniferous, base. Axes bear short determinate lateral branches (Fig. 92B) radially and spirally, 1–3 mm apart, 2–4 mm long, branched 3–5 times subdichotomously and more-or-less complanately, with prominent bicornate ends (Fig. 92H). Attachment by short branches and compound multicellular rhizoids with multicellular haptera (Fig. 92H) from stoloniferous branches; epilithic. Structure. Apical cells (Fig. 92D) of axes and laterals hemispherical to dome-shaped, 15–20 in diameter, segmenting transversely or obliquely to form a lateral and the ultimate bicornate ends (Fig. 92C, J) with pericentral cells cut off from the third to fifth axial cells. Pericentral cells 6 (Fig. 92F, G), clear in transverse section, developing from close to apices a large-celled inner cortex and small-celled outer cortex (Fig. 92G). Axes 700–1200 µm in diameter below, tapering gradually to 300–600 µm in diameter near apices. Determinate laterals 250–350 µm in diameter near their base, tapering gradually to 80–100 in diameter at base of bicornate ends, then abruptly to the apical cells. Trichoblasts (Fig. 92E) only seen on female plants, 300–600 µm long, coarse, basal cells 35–45 µm in diameter and L/D 1.5–2, upper cells 25–30 µm in diameter and L/D 2–3. Rhizoids cut off from pericentral cells. Cells uninucleate, larger cells multinucleate; rhodoplasts discoid, elongate and ribbon-like in larger cells.

Reproduction: Procarps (Fig. 921) on the suprabasal cell of trichoblasts, with a 4-celled carpogonial branch and 2–3 sterile cells. Carposporophyte with a small basal fusion cell and short, branched gonimoblast filaments with elongate-clavate terminal carposporangia 35–50 µm in diameter. Cystocarps (Fig. 92J, K) ovoid, 400–600 µm in diameter; pericarp ostiolate, 2 cells thick, ecorticate, outer cells isodiametric and irregularly arranged. Spermatangial plants unknown.

Stichidia in irregularly branched clusters (Fig. 92L) on the determinate laterals, ecorticate, usually curved, 0.5–1 mm long and 90–120 µm in diameter, with tetrasporangia in gently spiral or almost straight rows (Fig. 92M), 50–100 µm in diameter, with 2 cover cells.

Type from Chinamans Hat Island beach, Yorke Pen., S. Aust., drift (Womersley, 16.xii.1999); holotype in AD, A68425 (tetrasporangial), syntype (cystocarpic) and 2 isotypes (tetrasporangial).

Selected specimens: Hopetoun, W. Aust., drift (Wollaston, 20.ii.1957; AD, A22100). Twilight Cove, Eyre, W. Aust., 6 m deep (Kirkman, 16.xii.1981; AD, A56690). Head of Great Australian Bight, S. Aust., drift (Womersley, 4.ii.1954; AD, A19230). Point Sinclair, S. Aust., drift (Womersley, 25.i.1951; AD, A13905). Seamount off Cannan Reefs, S. Aust., 22–30 m deep (Branden, 22.i.1991; AD, A61206). The "hotspot", near Flinders I., S. Aust., 25 m deep (Branden, 23.i.1991; AD, A61215). Elliston, S. Aust., drift (Womersley, 13.i.1951; AD, A13583-"Marine Algae of southern Australia" No. 418) and 9 m deep in bay (Shepherd, 27.x.1971; AD, A42697). Pearson Is, S. Aust., 36 m deep (Shepherd, 10.i.1969; AD, A34108). Point Avoid, S. Aust., drift (Womersley, 2.xii.1975; AD, A46915). Pondalowie Bay, S. Aust., drift (Womersley, 9.xi.1980; AD, A51858). Cable Hut Bay, Yorke Pen., S. Aust., 2–3 m deep (Kald, 10.vi.1968; AD, A33067). South West R., Kangaroo I., S. Aust., 6 m deep (F.J. Mitchell, 24.viii.1963; AD, A26823). Vivonne Bay, Kangaroo I., S. Aust., drift (Womersley, 14.i.1948; AD, A6854). Pennington Bay, Kangaroo I., S. Aust., drift (Womersley, 27.i.1946; AD, A2877). Stanley Beach, Kangaroo I., S. Aust., drift (Womersley, 27.i.1956; AD, A20363).

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

Distribution: Hopetoun, W. Aust., to Yorke Pen. and Stanley Beach, Kangaroo I., S. Australia.

Taxonomic notes: Alleynea bicornis is a distinctive deep-water alga on the western coasts of South Australia. The epithet bicornis refers to the 2-horned branch apices, and was first used by Sonder as Rytiphloea bicornis on specimens from "between King George's Sound and Cape Lewin" now in MEL, 668479, on 2 sheets with Sonder's drawings. Sonder (1880, p. 35), also gave Polysiphonia bicornis as a nomen nudum and Shepherd & Womersley (1981, p. 368) listed it as Pterosiphonia bicornis.

Alleynea is characterised by the presence of radially and spirally arranged determinate laterals along the indeterminate axes, and 6 pericentral cells with cortication from close to the apices.


SHEPHERD, S.A. & WOMERSLEY, H.B.S. (1981). The algal and seagrass ecology of Waterloo Bay, South Australia. Aquat. Bot. 11, 305–371.

SONDER, O.W. (1880). 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 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. 92.

Figure 92 image

Figure 92   enlarge

Fig. 92. Alleynea bicornis (A, F, G, J–M, AD, A68425; B–E, AD, A42697; H, I, AD, A13583). A. Habit. B. Young axis with determinate laterals. C. Branch apices with apical cells. D. Segmentation of apices. E. Trichoblasts. F. Transverse section of young axis. G. Transverse section of older axis. H. Multicellular, clumped rhizoids. I. Procarps within early pericarps, trichogynes present. J. Young branches with juvenile cystocarps. K. Mature cystocarps. L. Branched cluster of stichidia. M. Stichidia with tetrasporangia.

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