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Dictyota furcellata (C. Agardh) J. Agardh 1848: 90; 1894a: 80.

Phylum Phaeophyta – Order Dictyotales – Family Dictyotaceae – Tribe Dictyoteae

Selected citations: Womersley 1967: 209.

Thallus (Fig. 65C) medium to dark brown, usually 5–20 cm long with branches 0.3–1.0 (–1.5) mm broad, mostly strictly dichotomously branched 2–10(45) mm apart, with no or few proliferations (if present, then small and from lower parts), with acute to broad and often rounded axils, branches tapering only slightly. Holdfast of rhizoids from the basal, often entangled, branches; epiphytic or epilithic. Apical cell (Fig. 66A) hemispherical and surmounting the narrow branch apex. Cortical cells 10–16 (–18) µm across, L/B (1–) 2–4. Hair tufts scattered, sparse but conspicuous, hairs 8–14 µm in diameter.

Reproduction: Tetrasporangia (Fig. 66B,C) 80–120 µm in diameter, scattered singly or in small groups, usually sparse. Oogonial sori irregularly ovate, scattered, 200–400 µm long and 150–350 µm across; oogonia 80–100/2m long and 40–60 µm in diameter. Antheridial sori elongate-ovate, scattered, 300–700 µm long and 100–200 /.an across.

Type from Shark Bay, W. Aust. (Gaudichaud); in Herb. Agardh, LD, 49414 (the type sheet is without a locality but is the only C. Agardh specimen in LD).

Selected specimens: Carbla Beach, Shark Bay, W. Aust. (Cambridge, 24.vii.1976; ADU, A51716). Egg I., Isles of St Francis, S. Aust., 35 m deep (Shepherd, 7.i.1971; ADU, A38089). Mangrove Point, upper Spencer Gulf, S. Aust., drift ( Womersley, 31.xii.1950; ADU, A13686, male and female). Investigator Strait, S. Aust., 23 m deep, 35°17'S, 137°17'E (Watson, 15.i.1971; ADU, A41024). Port Willunga, S. Aust., lower eulittoral pools (Womersley, 24.iv.1948; ADU, A8384). Rocky Point, Kangaroo I., S. Aust., upper sublittoral (Womersley, 18.i.1948; ADU, A6976). Crawfish Rock, Westernport Bay, Vic., 6 m deep (Watson & Womersley, 16.i.1974; ADU, A44850). Greens Beach, N. Tas., rock pool ( Wollaston & Mitchell, 4.iii.1964; ADU, A27576).

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

Distribution: From Shark Bay, W. Aust. around southern Australia to Westernport Bay, Vic., and the N. coast of Tasmania.

Taxonomic notes: Dictyota furcellata occurs from rock pools on sheltered coasts to deep water (e.g. 35 m deep for A38089). It is distinguished essentially by the very narrow and regularly dichotomous branches, each with a hemispherical apical cell, though some specimens are broader than the filiform type and most other specimens, with their lower parts becoming 254 about 1.5 mm broad in contrast to the typical 1 mm broad. The Greens Beach, Tas., specimen shows thick wall inclusions at each end of many medullary cells, similar to those in a specimen of D. dichotoma var. intricata (see above).


AGARDH, J.G. (1848). Species, Genera et Ordines Algarum. Vol. 1. (Gleerup: Lund.)

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

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 65C, 66 A–C.

Figure 65 image

Figure 65   enlarge

Fig. 65. A. Dictyota dichotoma (ADU, A52740). B. Dictyota dichotoma var. intricata (ADU, A10431). C. Dictyota furcellata (ADU, A8384). D. Dictyota alternifida (ADU, A56812). E. Dictyota fenestrata (ADU, A35640).

Figure 66 image

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.

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