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Dilophus marginatus J. Agardh 1894a: "91.

Phylum Phaeophyta – Order Dictyotales – Family Dictyotaceae – Tribe Dictyoteae

Selected citations: Allender & Kraft 1983: 118, figs 26F–H, 27. Womersley 1967: 212.

Thallus (Fig. 67D) light to medium brown, usually densely clumped from a stoloniferous base, 3–12 cm long, dichotomously branched at intervals of (0.5–) 1–4 cm, branches (1–) 2–4 (–5) mm broad, linear or increasing slightly in width above the axils, usually becoming undulate by concavities on alternating sides (later associated with sporangia), axils rounded, apices broad with the apical cell not or slightly protruding; proliferations usually absent or rate, in some populations profuse from the surface of branches. Holdfast rhizoidal, together with stolons producing further erect branches; epilithic or with stolons entangled with other algae. Cortical cells 10–20 (–25) µm across, L/B (1–) 2–3 (–4). Medulla (Fig. 68E,F) one cell thick centrally throughout most of the thallus, 2–3 (–4) cells thick near the margins, becoming 4–5 cells thick at very base (Fig. 68G); thickness centrally 100–150 µm, marginally 200–250 µm; stolons slightly compressed, with a medulla usually 4 cells thick. Hair tufts scattered, hairs 10–18 µm in diameter.

Reproduction: Tetrasporangia (Fig. 68F) 80–100(420) µm in diameter, scattered or clustered within more or less square patches in concavities on alternate sides of the branches. Sexual thalli unknown.

Type from Port Phillip, Vic. (Mueller); in Herb. Agardh, LD, 49606.

Selected specimens: Boat ramp, Port Stanvac, S. Aust., 0.5 m deep (Clarke, 3.vi.1982; ADU, A53910). Cape Northumberland, S. Aust., shaded reef pool (Womersley, 15.x.1985; ADU, A56810-"Marine Algae of southern Australia" No.255, densely proliferous). Bridgewater Bay, Vic., lower eulittoral (Beauglehole, 13.i.1950; ADU, A15600). Brighton beach, Port Phillip, Vic., drift (Womersley, 29.v.1948; ADU, A8333). Bridport, N. Tas., upper sublittoral pools (Wollaston & Mitchell, 4.iii.1964; ADU, A27960). Long Reef, N.S.W., low eulittoral pools (Womersley, 19.iii.1949; ADU, A10199). Newport, N.S.W., reef pools ( Womersley, 30.v.1950; ADU, A13060). Noosa, Qld. (Cribb 16.22, 24.v.1949; ADU, A11940).

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

Distribution: From Port Stanvac, S. Aust. around south-eastern Australia and the N. coast of Tasmania to Noosa, Qld. Lord Howe I.

Taxonomic notes: Dilophus marginatus usually occurs as well developed plants on eastern Australian coasts and to Cape Northumberland in South Australia and at Lord Howe I. Further west, the few plants known are smaller with branches only 1–3 mm broad.


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

ALLENDER, B.M. & KRAFT, G.T. (1983). The marine algae of Lord Howe Island (New South Wales): The Dictyotales and Cutleriales (Phaeophyta). Brunonia 6, 73–130.

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 67D, 68 E–G.

Figure 67 image

Figure 67   enlarge

Fig. 67. A. Glossophora nigricans (ADU, A33254). B. Dilophus robustus (ADU, A28590). C. Dilophus angustus (ADU, A19885). D. Dilophus marginatus (ADU, A56810).

Figure 68 image

Figure 68   enlarge

Fig. 68. A,B. Dilophus robustus (ADU, A28590). A. Transverse section of upper thallus. B. Transverse section of lower thallus. C,D. Dilophus angustus ( C, ADU, A18573; D, ADU, A24519). C. Transverse section of mid thallus. D. Surface view of tetrasporangial thallus. E–G. Dilophus marginatus (ADU, A56810). E. Transverse section of upper thallus. F. Transverse section of mid thallus with tetrasporangia. G. Transverse section of thallus close to holdfast, with rhizoids. H–K. Dilophus tener (H,I, ADU, A30323; J, ADU, A38154; K, ADU, A34095). H. Upper branches with tetrasporangia and hair tufts. I. Transverse section of young thallus with undivided sporangia. J. Transverse section of mid thallus. K. Transverse section of thallus close to the base.

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