Electronic Flora of South Australia Species Fact Sheet
Phylum Phaeophyta – Order Dictyotales – Family Dictyotaceae – Tribe Dictyoteae
Selected citations: Womersley 1967: 210.
D. radicans Harvey 1855c: 536: 1859a: pl. 119.
Thallus (Fig. 63A) medium to dark brown, 5–20 cm long, irregularly alternately branched at intervals of (0.5–) 1–3 cm, branches usually broadening from their base upwards, occasionally tapering near apices, 2–4 (–7) mm broad, with the apical cell usually in a truncate apex or slight depression. Branches with occasional to numerous, irregular, surface proliferations, some developing into branchlets, with a terete base several cells in diameter. Attachment of thallus by numerous long, terete, fibres (Fig. 63A), 200–500 µm and 8–12 cells in diameter, issuing from the thallus surface near the base; epiphytic or epilithic. Cortical cells 15–20 µm across, L/B (1.5–) 2–3 (–4).
Reproduction: Tetrasporangia (Fig. 64A,B) 100–180 µm in diameter, in more or less square, block-like patches on alternating sides of the thallus with the branch centrally concave to each patch and thus undulate; tetrasporangia sparsely to densely grouped in each patch. Oogonia unknown. Antheridial sori (Fig. 64C,D) in similar concave, alternating patches to the tetrasporangia, sori irregular to slightly elongate in shape, 200–400 µm across, with individual antheridia (Fig. 64D) 60–100 µm long and 15–30 µm in diameter.
Type from "Nova Hollandia" (Peron); in Herb. Lamouroux, CN.
Selected specimens: Point Peron, W. Aust; drift (Royce 948, 22.ii.1951; ADU, A14150). Point Sinclair, S. Aust., drift (Womersley, 7.ii.1954; ADU, A19576). Egg I., Isles of St Francis, S. Aust., 32–38 m deep (Shepherd, 11.i.1971; ADU, A38036). Marion Bay, Yorke Pen., S. Aust., drift (Womersley, 9.iv.1950; ADU, A13163). Seal Beach, Kangaroo I., S. Aust., drift (Womersley, 21.i.1965; ADU, A28588, male). Walkerville, Vic., drift (Sinkora A2181, 9.iii.1975; ADU, A48553). Guyton Point, Robbins I., Tas., drift ( Wollaston & Mitchell, 23.ii.1964; ADU, A27720).
Distribution: From Rottnest 1., W. Aust. around southern Australia to Walkerville, Vic., and the N. coast of Tasmania. Records from outside southern Australia are doubtful (Womersley 1967, p. 210).
Taxonomic notes: D. prolifera is a deep-water species, known largely from the drift but also collected from 7 to 38 m deep in South Australian Waters. It is characterised by the terete attachment fibres and the block-like, often sparse, patches of tetrasporangia or antheridial sori on alternating, concave, surfaces of the branches.
HARVEY, W.H. (1855c). Some account of the marine botany of the colony of Western Australia. Trans. R. Ir. Acad. 22, 525–566.
HARVEY, W.H. (1859a). Phycologia Australica. Vol. 2, Plates 61–120. (Reeve: London.)
LAMOUROUX, J.V.F. (1809b). Exposition des caractêres du genre Dictyota (1) et tableau des espèces qu'il renferme. J. de Bot. 2, 38–44.
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 63A, 64 A–D.
Figure 63 enlarge
Fig. 63. A. Dictyota prolifera (ADU, A28588). B. Dictyota naevosa (ADU, A19176). C. Dictyota dietnensis, broad form (ADU, A35639). D. Dictyota diemensis, narrow form (ADU, A56304).
Figure 64 enlarge
Fig. 64. A–D. Dictyota prolifera (A,B, ADU, A19576; C,D, ADU, A28588). A. Thallus with sporangial sori on opposite sides in concave undulations, with small proliferations. B. Transverse section of thallus with undivided sporangia. C. Thallus with male sori on opposite sides. D. Transverse section of male sorus with antheridia and paraphyses, and a young hair tuft from opposite surface. E. Dictyota naevosa (ADU, A13602). Transverse section of thallus with undivided sporangia. F. Dictyota diemensis, broad form (ADU, A35622). Transverse section of thallus with undivided sporangia. G. Dictyota diemensis, narrow form (ADU, A56304). Transverse section of thallus with undivided sporangia. H–M. Dictyota dichotoma (ADU, A26409). H. Surface view of branch with scattered sporangia and hair groups. I. Transverse section of thallus with sporangia. J. Surface view of branch with oogonial sori. K. Transverse section of thallus with an oogonial sorus. L. Surface view of an antheridial sorus with sterile peripheral paraphyses. M. Transverse section of thallus with an antheridial sorus.
State Herbarium of South Australia