Electronic Flora of South Australia Species Fact Sheet
Phylum Phaeophyta – Order Dictyotales – Family Dictyotaceae – Tribe Dictyoteae
Dictyota nigricans J. Agardh 1882: 94.
Dictyota latifolia sensu J. Agardh 1894a: 65. Womersley 1950: 151.
Thallus (Fig. 67A) light brown (when young) to dark brown, (5–) 15–50 cm long, sparingly subdichotomously to laterally branched (usually more so near the base) at intervals of (3–) 5–25 cm with rounded axils, often proliferous from damaged parts, branches (1–) 2–4 (–7) cm broad, 150–200 µm thick, with the apical cell transversely lenticular and not or slightly protruding on a broad apex. Surface of the thallus, at least on most mature parts, becoming densely covered with short, upwardly directed ramelli. Attachment of thallus by rhizoids from lower cells and by short, multicellular fibres from the basal 1–3 cm; epilithic. Ramelli (Fig. 66H–K) 0.3–1.5 (–3) mm long, terete and 120–250 µm in diameter to compressed and 300–500 (–1000) µm broad, when terete with a core of medullary cells at least near their base, when compressed with a single layer of medullary cells; young parts of actively growing branches usually bare of ramelli, as are basal parts of some thalli. Structure of single layers of cortical and medullary cells, with the medulla at the margins of older parts becoming 2–3 cells thick, or 2 cells thick throughout close to the base. Cortical cells 12–20 (–25) µm across, L/B 1–2 (–3).
Reproduction: Tetrasporangia (Fig. 66H,I) (60–) 80–100 µm in diameter, scattered over the thallus (apart from close to the margins) and occasionally on the compressed ramelli. Oogonial sori (Fig. 66J) similarly scattered, irregularly ovate, 200–300 µm long and 100–150 µm across; oogonia 60–80 nm long and 40–50 µm in diameter. Antheridial sori (Fig. 66K) similarly scattered, irregularly ovate, 300–500 µ long and 150–400 µm across; antheridia 70–90 µm long and 25–35 µm in diameter.
Lectotype from Orford, Tas. (Meredith); in Herb. Agardh, LD, 48774.
Selected specimens: Dongara, W. Aust., drift (Smith, 14.ii.1944; ADU, A2028). Bickley Bay, Rottnest I., W. Aust., drift (Baird, Nov. 1945; ADU, A2090). Masillon I., Isles of St Francis, S. Aust., 22 m deep (Shepherd, 5.i.1971; ADU, A37884). Elliston Bay, S. Aust., 10–11 m deep (Shepherd, 20.x.1969; ADU, A34979). West Bay, Kangaroo I., S. Aust., drift (Womersley, 6.i.1946; ADU, A3299). Point Tinline, Kangaroo I., S. Aust., drift (Womersley, 2.ii.1956; ADU, A20346). Amphitheatre Rock, West I., S. Aust., 12–22 m deep (Shepherd, 1.i.1969; ADU, A33254-"Marine Algae of southern Australia" No. 37). Walkerville, Vic., drift (Sinkora A2105, 28.ii.1975; ADU, A48410).
Distribution: From Dongara, W. Aust. to Walkerville, Vic. and around Tasmania, usually from deeper water or shaded deep pools on rough-water coasts.
Taxonomic notes: The structure of Glossophora nigricans was discussed by Womersley (1950, p. 151, as Dictyota latifolia) and the synonymy by Womersley (1967, p. 214). This southern Australian species differs from the type species (G. kunthii, from South America and New Zealand) in attaining a broader thallus, with generally shorter ramelli, and having duplication of medullary cells only in old parts and the margins (c.f. Levring 1941, p. 621, fig. 6).
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.
LEVRING, T. (1941). Die Meeresalgen der Juan Fernandez-Inseln. Nat. Hist. Juan Fernandez & Easter Is., Vol. 2, 601–670, Plates 49–53.
WOMERSLEY, H.B.S. (1950). The Marine Algae of Kangaroo Island. III. List of Species, 1. Trans. R. Soc. S. Aust. 73, 137–197.
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.
Womersley, H.B.S. (14 December, 1987)
The Marine Benthic Flora of Southern Australia
©Board of the Botanic Gardens and State Herbarium, Government of South Australia
Illustrations in Womersley Part II, 1997: FIGS 66 H–K, 67A.
Figure 66 enlarge
Fig. 66. A–C. Dictyota furcellata (ADU, A8384). A. Apex of a branch. B. Surface view with sporangia and a hair tuft. C. Transverse section with sporangia and phaeophycean hairs. D,E. Dictyota alternifida (ADU, A56812). D. Surface view with sporangia and a hair tuft. E. Transverse section with sporangia. F,G. Dictyota fenestrata ( F, ADU, A8537; G, ADU, A35640). F. Upper branches with sporangia. G. Upper branches with male sori. H–K. Glossophora nigricans (ADU, A33254). H. Surface view with ramelli and sporangia. I. Transverse section with undivided sporangia and a ramellus. J. Surface view with ramelli and oogonial sori. K. Surface view with ramelli and male sori.
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).
State Herbarium of South Australia