Electronic Flora of South Australia Species Fact Sheet

Dilophus angustus J. Agardh I894a: 91. Womersley 1967: 211.

Phylum Phaeophyta – Order Dictyotales – Family Dictyotaceae – Tribe Dictyoteae

Thallus (Fig. 67C) light to medium brown, 2–9 cm long, fairly densely branched dichotomously or becoming somewhat laterally branched at intervals of 0.5–1.2 cm, branches (0.5–) 1–2 mm broad, linear or increasing slightly in width above the axils, axils acute to rounded, apices rounded. Apical cell not to slightly protruding; proliferations slight to absent. Holdfast rhizoidal, possibly with stolons; probably epilithic. Cortical cells 10–20 µm across, L/B 1.5–3. Medulla one cell thick centrally throughout the thallus, 2 (–3) cells thick near the margins (Fig. 68C); thickness centrally 80–130 µm, marginally 150–200µm. Hair tufts scattered, sparse.

Reproduction: Tetrasporangia (Fig. 68D) 40–65 µm in diameter, scattered. Sexual thalli unknown.

Type from Port Phillip, Vic. (Wilson); lectotype in Herb. Agardh, LD, 49599.

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

Distribution: Apart from the type, probable specimens are known from Pearson I., S. Aust., upper sublittoral (Specht, 17.ii.1960; ADU, A24519, sporangial); West Cape, Yorke Pen., S. Aust., lower eulittoral pool (Womersley, 24.iv.1955; ADU, A19885); and Point Roadknight, Vic., upper sublittoral pools (Womersley, 6.vi.1953; ADU, A18779).

Taxonomic notes: Dilophus angustus is a little known, slender, species, with only the margins becoming 2 (–3) medullary cells thick. It is superficially similar to small plants of Dictyota alternifida and is apparently a shallow water species.


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 67C, 68C,D.

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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