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Petrospongium rugosum (Okamura) Setchell & Gardner 1924: 12; 1925: 509, pl. 39 figs 42,43.

Phylum Phaeophyta – Order Chordariales – Family Leathesiaceae

Selected citations: Inagaki 1958: 97, figs 1–3. Lindauer et al. 1961: 222, fig. 46. McLennan 1956: 1, fig. 1. Womersley 1967: 231.


Cylindrocarpus rugosa Okamura 1907: 20, pl. 5 figs 1–6. Abbott & Hollenberg 1976: 177, fig. 144.

Thallus (Fig. 29A) red-brown to dark brown, spreading with broad marginal lobes and a rugose surface, usually 5–50 mm across and 1–3 mm thick, firm but somewhat mucoid, epilithic and tightly adherent except for old parts. Basal layer of branched, entwined filaments, partly rhizoidal from lower medullary cells, cells cylindrical, (8–) 10–15 (–20) µm in diameter and L/B 5–10. Medulla 300–1500 (–2000) µm high, of erect, branched, fairly closely appressed filaments with cells ovoid, 20–70 in diameter and L/B 1.5–2.5 but larger and longer below with occasional intercalary divisions and producing numerous, irregularly growing rhizoids. Determinate cortical filaments forming a dense, compact layer of even height overlying the medulla, grading from upper medullary cells, 120–200 µm and (5–) 8–10 (–12) cells high, each filament with 1–3 branches; cells elongate-ovoid below, cylindrical to slightly inflated above, 8–10 (–12) µm in diameter and L/B 1–2, terminal cell rounded but not enlarged. Phaeoplasts (Fig. 29C) one to a few per cell, discoid to laminate or elongate, each with a pyrenoid; physodes abundant. Phaeophycean hairs scattered or clustered, arising from outer medullary cells, 5–8 Aim in diameter.

Reproduction: Unilocular sporangia (Fig. 29B) sessile or on a 1–2 celled pedicel, arising from inner cortical cells, basally attached or becoming laterally attached by further upward growth of the pedicel and downward extension of the sporangium, elongate-ovoid to slightly reniform, 60–100 (–120) µm long and 15–25 (–30) µm in diameter.

Type from Japan (lectotype should be selected); in SAP.

Selected specimens: Cape Marengo, Vic., mid eulittoral ( Womersley, 13.x.1985; ADU, A56878). Apollo Bay, Vic., lower eulittoral ( Womersley, 23.i.1967; ADU, A31188). Point Roadknight, Vic., lower eulittoral (Skinner, 6.i.1978; ADU, A49080). Point Lonsdale, Vic., mid eulittoral (Skinner, 17.i.1979; ADU, A50231). Mallacoota Point, Vic., mid eulittoral (Womersley, 12.xi.1982; ADU, A55347-"Marine Algae of southern Australia" No. 245). Kurnell Point, N.S.W., mid eulittoral (Womersley, 14.xi.1982; ADU, A55348). Bilgola, N.S.W., on surf-sprayed rock (May 921, 3.xi.1945; NSW).

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

Distribution: Japan, Pacific coast of N. America, New Zealand.

In southern Australia, from Cape Marengo, Vic., to Bilgola, N.S.W.

Taxonomic notes: Petrospongium rugosum is readily distinguished by its cylindrical, branched, cortical filaments and sporangia which are often laterally attached when mature.


ABBOTT, I.A. & HOLLENBERG, G.J. (1976). Marine Algae of California. (Stanford Univ. Press: Stanford.)

INAGAKI, K. (1958). A systematic study of the order Chordariales from Japan and its vicinity. Sci. Pap. Inst. Algol. Res. Hokkaido Univ. 4, 87–197, Plates I-XI.

LINDAUER, V.W., CHAPMAN, V.J. & AIKEN, M. (1961). The marine algae of New Zealand. II. Phaeophyceae. Nova Hedwigia 3, 129–350, Plates 57–97.

OKAMURA, K. (1907). 'cones of Japanese Algae. Vol. 1, pt. 1, pp. 1–22, Plates 1–5.

SETCHELL, W.A. & GARDNER, N.L. (1924). Phycological Contributions VII. Univ. Calif. Publ. Bot. 13(8), 1–13.

SETCHELL, W.A. & GARDNER, N.L. (1925). The marine algae of the Pacific coast of North America. Part III. Melanophyceae. Univ. Calif Publ. Bot. 8, 383–898, Plates 34–107.

WOMERSLEY, H.B.S. (1967). A critical survey of the marine algae of southern Australia. II. Phaeophyta. Aust. J. Bot. 15, 189–270.

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

Author: H.B.S. Womersley & S. Skinner

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: FIG. 29 A–C.

Figure 29 image

Figure 29   enlarge

Fig. 29. A–C. Petrospongium rugosum (A, ADU, A49080; B,C, ADU, A50231). A. Habit. B. Thallus section showing medulla (with hyphae), cortex of branched filaments, phaeophycean hairs and unilocular sporangia. C. Cells of a determinate cortical filament with phaeoplasts and physodes. D–F. Leathesia difformis (D,E, ADU, A44619; F, ADU, A48248). D. Thallus section showing large, anastomosing medullary cells, determinate cortical filaments, plurilocular sporangia and phaeophycean hairs. E. Determinate cortical filament with phaeoplasts. F. Upper medulla and cortex with unilocular sporangia and a phaeophycean hair. G–I. Leathesia intermedia (G,H, ADU, A49179; I, ADU, A29943). G. Thallus section showing large medullary cells, determinate cortical filaments with large terminal cells, plurilocular sporangia and phaeophycean hairs. H. Determinate cortical filament with phaeoplasts and physodes. I. Outer medulla and cortex with unilocular sporangia and a phaeophycean hair.

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