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Distromium flabellatum Womersley 1967: 218, fig. 3.

Phylum Phaeophyta – Order Dictyotales – Family Dictyotaceae – Tribe Zonarieae

Thallus (Fig. 80B) medium to dark brown, more or less erect, usually 3–6 (–8) cm long and across, flabellate when young (Fig. 81E) and becoming split into few to numerous flabellate segments, attached by a matted rhizoidal holdfast 0.2–1.2 cm across and 0.2–0.8 cm long, with descending multicellular rhizoids from the lower side of the mid to lower thallus; epilithic or epiphytic on Amphibolis. Growth from a row of many apical cells (Fig. 8IE,F), becoming distromatic in subapical cells (Fig. 8IG). Fronds complanate, 1–3 (–6) mm broad below, 5–20(35) mm broad at their apices. Structure (Fig. 81H,I) two cells and 70–90 gm thick throughout; cells in surface view 20–35 (–40) µm across, L/B 2–5 (–7). Hairs (Fig. 81E,H) in prominent concentric bands on lower surface of thallus, 30–40 (–50) µm in diameter, simple or with a lateral branch 2–5 cells from their base, arising from cells cut off from one end of the lower thallus cells, without a basal meristem but with apical growth.

Reproduction: Sporangia (Fig. 81F,H) in concentric, often interrupted, sori or patches on the upper surface, external to the thallus, with the parent thallus cell subdividing usually after the sporangium is cut off, with a membranous indusium, sporangia ovoid to subspherical or pyriform, 150–250 µm in diameter, dividing tetrahedrally.

Type from Port Willunga, S. Aust., drift (Womersley, 5.ix. I 954); in ADU, A19784.

Selected specimens: 7 mile Beach, N. of Dongara, W. Aust., drift (Womersley. 17.ix.1979; ADU, A51349). N. of Point Clune, Rottnest I., W. Aust., 13 m deep (Kraft & Millar, 6.xii.1984; ADU, A57062 and MELU). Hopetoun, W. Aust., drift (Gordon, 20.xi.1968; ADU, A34131). Nuyts Reef, Great Australian Bight, S. Aust., 30 m deep (Shepherd, 27.iii.1980; ADU, A52330). Pearson I., S. Aust., 36 m deep (Shepherd, 10.i.1969; ADU, A34103). Henley Beach, S. Aust., drift on Amphibolis (Macbeth, 30.vii.1943; ADU, A10239). Aldinga, S. Aust., drift (Womersley, 17.ix.1966; ADU, A30711-"Marine Algae of southern Australia" No. 40). Pennington Bay, Kangaroo I., S. Aust., drift ( Womersley, 28.x.1966; ADU, A30850). Balcombe Bay, Port Phillip, Vic. (Macpherson, 26.ii.1961; ADU, A28564). Deal I., Bass Str., 30 m deep (Shepherd & Lewis, 3.v.1974; ADU, A45225).

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

Distribution: From 7 mile Beach (N. of Dongara), W. Aust., around southern Australia to Port Phillip, Vic. and Deal I., Bass Strait.

Taxonomic notes: Distromium flabellaturn occurs from 1 m to 36 m deep. It differs from D. skottsbergii Levring from Juan Fernandez I. and New Zealand, in that in the latter the sporangia apparently replace thallus cells (Levring 1940, fig. 3C–E), and from the Japanese D. decumbens (Okamura) Levring in habit and hairs (see Womersley 1967, p. 219). Further detailed comparisons with D. skottsbergii in particular are needed, since Levring states that paraphyses are absent and D. flabellatum has prominent, often branched, apically meristematic hairs; these contrast markedly to the phaeophycean hairs of D. multifidum, but appear similar to those of D. didymothrix Allender & Kraft (1983, p. 89, figs 8, 9A–D).


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.

LEVRING, T. (1940). Die Phaeophyceengattungen Chlanidophora, Distromium und Svringoderma. K. fysiogr. sällsk. Lund. Forh. 10(20), 1–11.

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 80B, 81 E–I.

Figure 80 image

Figure 80   enlarge

Fig. 80. A. Chlanidophora microphylla (ADU, A54821). B. Distromium flabellatum (ADU, A19784, holotype). C. Distromium multilidum (ADU, A29525, holotype).

Figure 81 image

Figure 81   enlarge

Fig. 81. A–D. Chlanidophora microphylla (A,C, ADU, A28962; B,D, ADU, A31097). A. Actively growing apices and two hair tufts. B. Older branches with tapering inactive apices and scattered tetrasporangia. C. Longitudinal section of apical cell and segmentation. D. Transverse section of thallus with sporangia and phaeophycean hairs. E–I. Distromium flahellatum (ADU, A19784, holotype). E. Thallus lower surface, with concentric lines of hairs. F. Thallus upper surface with sorus of sporangia. G. Longitudinal section of apical cell and segmentation. H. Longitudinal section of thallus through a sporangial sorus, with hairs from lower surface. I. Transverse section of thallus with base of a hair.

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