Electronic Flora of South Australia Species Fact Sheet

Dilophus fastigiatus (Sonder) J. Agardh 1882: 107; 1894a: 92.

Phylum Phaeophyta – Order Dictyotales – Family Dictyotaceae – Tribe Dictyoteae

Selected citations: Womersley 1967: 212.


Dictyota fastigiata Sonder 1845: 50; 1846: 155. Harvey 1859a: pl. 82.

Thallus (Fig. 69C) medium to dark brown, (5–) 10–30 cm long, regularly dichotomously branched at intervals of (1–) 2–8 cm, branches (2–) 3–7 mm broad, linear, sometimes faintly zoned, axils acute to rounded, apices rounded with the apical cell not or only slightly protruding; proliferations absent except following damage. Holdfast rhizoidal; epilithic. Cortical cells 12–20 µm across, L/B 1–2. Medulla near apices and sometimes in older parts 2 cells thick centrally (Fig. 70E,G), older parts normally 4 cells thick, 4 (–6) cells thick near the margins; thickness centrally 200–300 (–400) µm, marginally (300–) 400–500 µm thick. Hair tufts scattered, hairs 12–18 µm in diameter.

Reproduction: Tetrasporangia (Fig. 70D,E) 120–180 (–200) µm in diameter, scattered over the branches. Oogonial sori (Fig. 70F) scattered, round to ovate, 120–240 µm long and 100–160 µm across; oogonia (Fig. 70G) 60–100 µm long and 25–50 µ in diameter. Antheridial sori (Fig. 70H) scattered, irregularly ovate to elongate, 300–1000 (–2000) µm long and 200–300(500) µm across; antheridia (Fig. 701) 50–80 µm long and 20–25 µm in diameter.

Type from Western Australia (Preiss); in MEL, 17111.

Selected specimens: Port Denison, W. Aust., drift (Woelkerling, 8.xi.1968; ADU, A33160). Hamelin Bay, W. Aust., drift (Womersley, 1.ix.1979; ADU, A50607). Smooth I., Isles of St Francis, S. Aust., 21 m deep (Shepherd, 29.iii.1980; ADU, A52170). Tiparra reef, S. Aust., 12 m deep (Shepherd, 27.vii.1970; ADU, A35986). Seal Bay, Kangaroo I., S. Aust., drift (Womersley, 29.x.1966; ADU, A30974). Yilki, Victor Harbor, S. Aust., drift (Womersley, 30.ix.1985; ADU, A56795). Port MacDonnell, S. Aust., drift (Womersley, 19.viii.1953; ADU, A18978). Walkerville, Vic., drift (Sinkora A2286, 6.iii.1976; ADU, A48463).

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

Distribution: From Champion Bay, W. Aust., to Walkerville, Vic.

Taxonomic notes: Dilophus fastigiatus is characterised by its distant, dichotomous, branching (mostly 2–7 cm apart) and branches 3–6 mm broad, and contrasts with the narrower (usually 1–2 mm broad) branches of D. gunnianus which are also usually much branched above with some branches laterally placed. At Victor Harbor, where both species occur, they may be readily segregated, but further study is needed of the species on the west coast of Western Australia where narrow specimens with distant branching occur.


AGARDH, J.G. (1882). Till algernes systematik. Acta Univ. lund. 17, 1–136, Plates 1–3.

AGARDH, J.G. (1894a). Analecta Algologica. Cont. I. Acta Univ. lund. 29, 1–144, Plates 1, 2.

HARVEY, W.H. (1859a). Phycologia Australica. Vol. 2, Plates 61–120. (Reeve: London.)

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. (1846). Algae. In Lehmann, C., Plantae Preissianae. Vol. 2, pp. 148–160. (Hamburg.)

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

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 69C, 70 D–I.

Figure 69 image

Figure 69   enlarge

Fig. 69. A. Dilophus tener (ADU, A38154). B. Dilophus crinitus (Herb. Agardh, LD, 49509, holotype). C. Dilophus fastigiatus (ADU, A56795).

Figure 70 image

Figure 70   enlarge

Fig. 70. A–C. Dilophus crinitus (ADU, A18579). A. End of a branch with fibrils. B. Transverse section of upper thallus. C. Transverse section of lower thallus. D–I. Dilophus fastigiatus (ADU, A30974). D. Surface view of thallus with tetrasporangia. E. Transverse section of thallus with undivided tetrasporangia. F. Surface view of thallus with oogonial sori. G. Transverse section of thallus with oogonial sori and a phaeophycean hair tuft. H. Surface view of thallus with antheridial sori. I. Transverse section of thallus with antheridial sori. J–M. Dilophus gunnianus (ADU, A56796). J. Surface view of thallus with tetrasporangia. K. Transverse section of upper thallus with undivided tetrasporangia. L. Transverse section of mid thallus with undivided tetrasporangia. M. Transverse section of lower thallus.

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