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Myriodesma serrulatum (Lamouroux) Decaisne 1841: 148.

Phylum Phaeophyta – Order Fucales – Family Cystoseiraceae

Selected citations: Harvey 1862: pl. 219. Nizamuddin & Womersley 1967: 376, pls 69B, 73 fig. 2.


Dictyopteris serrulata Lamouroux 1813: 271, pl. 11 fig. 6.

Thallus (Fig. 151B) medium to dark brown, 15–30 cm long, with usually two complanately branched fronds from the branched stipe. Holdfast discoid-conical; probably epilithic. Stipe 2–18 cm long, with 1–4 di- or trichotomies at intervals of 1–6 cm, each (1–) 2–3 mm in diameter. Fronds 10–25 cm long, irregularly pinnate with long, alternate, laterals (2–) 3–6 (–10) cm long, 2–4 (–5) mm broad, linear but tapering above, coarsely and regularly serrate (Fig. 155D) along their length with teeth 1–1.5 mm long; denuded below; midrib present, inconspicuous near apices. Structure of fronds 0.4–0.6 mm and 10–20 cells thick, with a medulla of elongate cells in older parts and a cortex of isodiametric cells with a surface phaeoplastic meristoderm.

Reproduction: Thalli monoecious. Conceptacles prominent, conspicuously raised above the surface, forming an irregular line on each side of midrib (Fig. 155D), bisexual, with a basal group of phaeophycean hairs and also sterile, simple or once-branched paraphyses; oogonia sessile, ovoid, 90–140 µm long and 60–80 µm in diameter; antheridia sessile or on branched paraphyses, elongate, 22–36 µm long and 8–15 µm in diameter.

Type from "Nouv. Holl"; in Herb. Lamouroux, CN.

Selected specimens: Port Denison, W. Aust., drift (Parsons, 8.xi.1968; ADU, A33157). Cliff Head, W. Aust., drift (Womersley, 18.ix.1979; ADU, A51221-"Marine Algae of southern Australia" No. 197). Flinders Bay, W. Aust., drift (Womersley, 1.ix.1979; ADU, A50636). Point Valliant, Two People Bay, W. Aust., 1–4 m deep (Clarke & Engler, 30.viii.1979; ADU, A50966).

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

Distribution: From Port Denison to Cape Riche (Harvey), W. Aust.

Taxonomic notes: M. serrulatum is characterised by the regularly serrate fronds with an irregular line of prominent, raised, conceptacles on each side of the slight midrib.


DECAISNE, J. (1841). Plantes de l'Arabie heureuse. Archs Mus. natn. Hist. nat., Paris 2, 89–199.

HARVEY, W.H. (1862). Phycologia Australica. Vol. 4, Plates 181–240. (Reeve: London.)

LAMOUROUX, J.V.F. (1813). Essai sur les genres de la famille des thalassiophytes non articulées. Ann. Mus. Hist. Nat., Paris 20, 21–47, 115–139, 267–293, Plates 7–13(1–7).

NIZAMUDDIN, M. & WOMERSLEY, H.B.S. (1967) The morphology and taxonomy of Myriodesma (Fucales). Nova Hedwigia 12, 373–383, Plates 69–73.

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 151B, 155D.

Figure 151 image

Figure 151   enlarge

Fig. 151. A. Myriodesma leptophyllum (ADU, A57326). B. Myriodesma serrulatum (ADU, A51221).

Figure 155 image

Figure 155   enlarge

Fig. 155. A. Platythalia quercifolia (ADU, A30788). End of a lateral branch with scattered conceptacles. B. Platythalia angustifolia (ADU, A30988). Apex of a branch with laterals containing submarginal conceptacles. C. Myriodesma leptophyllum (ADU, A57326). Upper branches with conceptacles. D. Myriodesma serrulatum (ADU, A51221). Upper branches with raised conceptacles. E. Myriodesma integrifolium (ADU, A57457). Upper branches with conceptacles.

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