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Electronic Flora of South Australia Species Fact Sheet

Acrocarpia robusta (J. Agardh) Womersley 1964: 99.

Phylum Phaeophyta – Order Fucales – Family Cystoseiraceae


Cystoseira robusta J. Agardh 1896: 41.

Thallus (Fig. 130B) dark brown, 10–35 (–45) cm long, with one to several primary branches from the holdfast, bushy above. Holdfast 0.5–2.5 cm across, conical, lacerate with short subdichotomous haptera in older plants; epilithic. Primary branches 10–25 cm long, 1–3 mm thick until near the apices, terete, straight, with tristichously arranged laterals and occasional secondary axes arising adaxially from young laterals, denuded below,with pointed branch residues 0.5–2 mm long. Laterals dense, 1–2 mm apart, 1–4 (–6) cm long, with tristichously and spirally arranged ramuli 0.5–1 mm apart (Fig. 132E); ramuli once bifurcate near their base, 1–3 (–4) mm long, 200–350 µm in diameter. Structure of a central medulla of elongate cells with abundant hyphae and a cortex of isodiametric cells with a surface meristoderm.

Reproduction: Receptacles (Fig. 132F) developed from ends of upper ramuli, 2–5 mm long, 400–600 µm in diameter, pedicellate, torulose (especially when dried). Conceptacles (Fig. 132G) crowded, bisexual, with a prominent basal columella bearing phaeophycean hairs, ostioles scattered; oogonia sessile, ovoid, 100–200 µm long and 80–150 µm in diameter; antheridia sessile or on branched paraphyses, elongate-ovoid, 25–40 µm long and 7–10 µm in diameter.

Type from Israelite Bay, W. Aust. (Brooke); in Herb. Agardh, LD, 00708.

Selected specimens: Cape Naturaliste, W. Aust., uppermost sublittoral ( Womersley, Clarke & Engler, 2.ix.1979; ADU, A50622). Sarge Bay, Cape Leeuwin, W. Aust., drift (Woelkerling, 16.xi.1968; ADU, A34210). Flinders Bay, Augusta, W. Aust., drift (Royce 815, 28.x.1950; PERTH and ADU, A26473). Nanarup, Albany, W. Aust., upper sublittoral (Parsons, 19.xi.1968; ADU, A33990-"Marine Algae of southern Australia" No. 53). Point Valliant, Two People Bay, W. Aust., sublittoral fringe ( Womersley, 30.viii.1979; ADU, A50547-"Marine Algae of southern Australia" No. 53b). Hopetoun, W. Aust., upper sublittoral (Gordon, 20.xi.1968; ADU, A34175). Cave Islet, Recherche Arch., W. Aust., in pool (Willis, 20.xi.1950; ADU, A15877). Israelite Bay, W. Aust., drift (Wells, 10.xii.1974; ADU, A46091).

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

Distribution: From Cape Naturaliste to Israelite Bay, W. Aust.

Taxonomic notes: A. robusta is often common in the uppermost sublittoral on granite rocks. It differs from A. paniculata in habit and in the shorter, basally bifurcate ramuli fringing the laterals.


AGARDH, J.G. (1896). Analecta Algologica. Cont. III. Ada Univ. lund. 32, 1–140, Plate 1.

WOMERSLEY, H.B.S. (1964). The morphology and taxonomy of Cystophora and related genera (Phaeophyta). Aust. J. Bot. 12, 53–110, Plates 1–16.

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

Illustrations in Womersley Part II, 1997: FIGS 130B, 132 E–G.

Figure 130 image

Figure 130   enlarge

Fig. 130. A. Acrocarpia paniculata (ADU, Al 1002). B. Acrocarpia robusta (ADU, A50622).

Figure 132 image

Figure 132   enlarge

Fig. 132. A,B. Caulocystis cephalornithos (A, ADU, A26881; B, ADU, A57286). A. Terminal branches and receptacles. B. Cross section of receptacle with bisexual conceptacles. C,D. Acrocarpia paniculata ( C, ADU, A26801; D, ADU, A57342). C. Terminal branch with receptacles. D. Cross section of receptacle with bisexual conceptacles. E–G. Acrocarpia robusta (E,F, ADU, A26473; G, ADU, A50547). E. Branch with bifurcate ramuli. F. Branch with receptacles. G. Cross section of receptacle with bisexual conceptacles each with a central columella. H. Cystophora platylobium (ADU, A57321). Cross section of receptacle with elongate, bisexual, conceptacles. I. Cystophora retroflexa (ADU, A57386). Cross section of receptacle with bisexual conceptacles.

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