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Electronic Flora of South Australia Species Fact Sheet

Sargassum tristichum Greville & C. Agardh ex Sonder 1845: 51; 1848: 163.

Phylum Phaeophyta – Order Fucales – Family Sargassaceae

Selected citations: J. Agardh 1848: 300; 1872: 71; 1889: 76, pl. 24 figs 1–7. Grunow 1915: 362.


Cystoseira tristicha Greville & C. Agardh in Greville 1830: synop. xxxiii (nomen nudum).

Carpacanthus tristichus (Greville & C. Agardh) Kützing 1849: 622.

Carpacanthus oligophyllus Kützing 1849: 421; 1862: 12, pl. 37.

Sargassum biforme Sonder 1848: 163. J. Agardh 1848: 301; 1872: 67; 1889: 75, pl. 23 figs 12–14? Grunow 1915: 362.

Carpacanthus biformis Kützing 1849: 625; 1861: 14, pl. 44.

Thallus (Fig. 163A) medium to dark brown, 10–60 cm long, with a short, simple or branched, stipe 1–2 cm long, terete, 2–4 mm in diameter, with few, stubby, branch residues, bearing apically 1–4 primary branches. Holdfast discoid-conical, 5–12 mm across, usually with a single stipe; epilithic. Primary branches 10–60 cm long, axes moderately robust, triquetrous, bearing tristichously arranged but irregularly twisted, slightly retroflex, simple, laterals, becoming denuded below. Laterals (lower) 3–7 (–10) cm long, 0.5–1.5 cm broad, smooth, margins entire; upper laterals distinctly smaller, 1–3 cm long, 1–5 (–8)mm broad, entire or with odd spines, often lost from older fertile fronds. Vesicles absent or usually only a few per plant, occasionally frequent, petiolate, subspherical, 3–6 mm in diameter, with a small (occasionally compressed) mucro.

Reproduction: Thalli monoecious. Receptacles (Fig. 164H) bisexual, in dense clusters on upper laterals, petiolate, simple, 2–5 (–8) mm long, 1–1.5 (–2) mm broad, strongly triquetrous with prominent spines along the ridges, with scattered ostioles on the receptacle surfaces. Conceptacles unisexual or bisexual; oogonia sessile, ovoid, 140–250 (–320) µ long and 90–150 (–200) µm in diameter; antheridia sessile or on branched paraphyses, ovoid, 12–16 µ long and 7–10 µm in diameter.

Type from W. Aust.; lectotype in MEL, 687695 (ex Herb. Greville).

Selected specimens: Mandurah, W. Aust. drift (Oberlander, 21.i.1961; ADU, A24715). Bunker Bay, Cape Naturaliste, W. Aust., uppermost sublittoral (Womersley, 2.ix.1979: ADU, A50549-"Marine Algae of southern Australia" No. 292). Cowaramup Bay, W. Aust., 2–3 m deep (Clarke & Engler, 1.ix.1979; ADU, A50662). Gnarabup Beach (20 km N. of Hamelin Bay), W. Aust., 1 m deep (Womersley, 1.ix.1979; ADU, A50673). Point Sinclair, S. Aust., upper sublittoral pools (Womersley, 8.ii.1954; ADU, A19551 and 9.ii.1954; ADU, A19552). Wittelbee Point, S. Aust., upper sublittoral (Womersley, 22.i.1951; ADU, A13630). Elliston, S. Aust., upper sublittoral pools (Womersley, 14.ii.1954; ADU, A 19404). Wanna, S. Aust., upper sub-littoral pools (Womersley, 19.ii.1959; ADU, A22427). Pondalowie Bay, S. Aust., 5–8 m deep (Shepherd, 14.iv.1963; ADU, A26606). Port Noarlunga, S. Aust., upper sublittoral ( Womersley, 25.i.1961; ADU, A24707).

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

Distribution: From Rottnest I., W. Aust. to Port Noarlunga, S. Aust.

Taxonomic notes: Sargassum tristichum is often common in rock pools and the upper sublittoral, usually extending to only a few metres deep. The triquetrous, spinous, receptacles are similar to those of S. lacerifolium, but S. tristichum is distinct in its flat and usually entire-margined laterals. De Toni & Forti (1923, p. 66) gave records from Geraldton, W. Aust., and Burnie, Tas.; both records are doubtful and need checking.

S. biforme Sonder [type from W. Aust. (Preiss), holotype in MEL, 687509] was described at the same time as S. tristichum and, while further studies of its seasonal variation in Western Australia are needed, it appears that the former is a young state of the latter, with receptacles that are just becoming tristichous and dentate. The type of the latter species has mature, distinctly tristichous, receptacles. S. biforme var. isophylla Sonder (1848, p. 163) [S. isophyllum (Sonder) J. Agardh 1848, p. 298] is based on MEL 30149, and appears to be a young, sterile, plant of S. tristichum.


AGARDH, J.G. (1848). Species, Genera et Ordines Algarum. Vol. 1. (Gleerup: Lund.)

AGARDH, J.G. (1872). Till algernes systematik. Ada Univ. lund. 9(8), 1–71.

AGARDH, J.G. (1889). Species Sargassorum Australiae. K. Svenska Vetenskapsakad. Handl. 23(3), 1–133, Plates 1–31.

DE TONI, G.B. & FORTI, A. (1923). Alghe di Australia, Tasmania e Nouva Zelanda. Memorie R. Inst. veneto Sci. 29, 1–183.

GREVILLE, R.K. (1830). Algae Britannicae. (Edinburgh.)

GRUNOW, A. (1915). Additamenta ad cognitionem Sargassorum. Verh. Zool. -Bot. Wien 65, 329–448.

KÜTZING, F.T. (1849). Species Algarum. (Leipzig.)

KÜTZING, F.T. (1861). Tabulae Phycologicae. Vol. 11. (Nordhausen.)

KÜTZING, F.T. (1862). Tabulae Phycologicae. Vol. 12. (Nordhausen.)

SONDER, O.W. (1845). Nova Algarum genera et species, quas in itinere ad oras occidentales Novae Hollandiae, collegit L. Preiss. Bot. Ztg 3, 49–57.

SONDER, O.W. (1848). Algae. In Lehmann, C., Plantae Preissianae. Vol. 2, pp. 161–195. (Hamburg.)

The Marine Benthic Flora of Southern Australia Part II complete list of references.

Author: H.B.S. Womersley

Publication: Womersley, H.B.S. (14 December, 1987)
The Marine Benthic Flora of Southern Australia
Part II
©Board of the Botanic Gardens and State Herbarium, Government of South Australia

Illustration in Womersley Part II, 1997: FIGS 163A, 16411.

Figure 163 image

Figure 163   enlarge

Fig. 163. A. Sargassum tristichum (ADU, A19551). B. Sargassum lacerilbhum (ADU, A55356).

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