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Homoeostrichus sinclairii (Hooker & Harvey) J. Agardh 1894a: 15.

Phylum Phaeophyta – Order Dictyotales – Family Dictyotaceae – Tribe Zonarieae


Zonaria sinclairii Hooker & Harvey 1845: 530. Harvey 1858: pl. 49. Womersley 1967: 226.

Zonaria stuposa R. Brown ex J. Agardh 1848: 110,

Thallus (Fig. 85B) medium brown, 5–15 cm long, much branched with numerous long, slender, stupose axes 0.3–1 mm thick, bearing flabellate laterals above, arising from a matted, rhizoidal holdfast 5–25 mm across and 3–10(1 5) mm long; epilithic. Fronds with complanate terminal and lateral branches, flabellate to spathulate (Fig. 86A), usually lacerate and often with spinous lateral projections, becoming denuded below with the central region becoming stupose and forming the slender pedicel; upper parts usually 2–6 (–10) mm broad near their apices. Structure (Fig. 86C–G) 6 cells (rarely 7 in old parts) and 120–160 µm thick throughout, with cells in regular rows in transverse section (Fig. 86F) and in longitudinal section with the primary transverse walls concave to the branch apices (Fig. 86C–E); inactive margins with the apical cells often paired and/or segmenting on both lateral faces; cortical cells single (rarely paired) over each medullary cell (Fig. 86B,F) in transverse section, 2–4 (–7) over each medullary cell in longitudinal section, (10–) 16–24 µm across, L/B 1–2 (–3). Hair tufts absent.

Reproduction: Sporangia scattered amongst dense masses of paraphyses centrally on upper branches (Fig. 86A), subspherical to ovoid, 90–180 (–200) pm long and 80–180 µm in diameter, producing four spores (Fig. 86F,G) irregularly tetrahedrally, with a multicellular stalk (Fig. 86F,G) when mature, 2–4 cells long and 3–6 cells broad adjacent to the sporangium. Paraphyses (Fig. 86G) clavate, usually slightly curved (4–) 6–12 cells and (250–) 300–500 µm long with upper cells (35–) 40–50 µm in diameter and L/B 1–1.5 (–2.5); cell divisions apical. Sexual reproduction unknown.

Type . Recorded as from the Bay of Islands, New Zealand (Sinclair), but probably from south eastern Australia (see Womersley 1967, p. 227); type material in TCD and K.

Selected specimens: Head of Great Australian Bight, S. Aust., drift (Womersley, 4.ii.1954; ADU, A19171). D'Entrecasteaux Reef, S. Aust., 15–20 m deep (Shepherd, 27.iii.1980: ADU, A52152). Elliston, S. Aust., upper sublittoral pools (Womersley, 15.i.1951; ADU, A13664). Pennington Bay, Kangaroo I., S. Aust., drift (Womersley, 14.i.1947; ADU, A4310). West I., S. Aust., 3–5 m deep on jetty (Shepherd, 27.xii.1965; ADU, A30374). Cape Northumberland, S. Aust., shaded reef pools (Womersley, 15.x.1985; ADU, A56811). 5 km off Surry R. mouth, Portland, Vic., 20 m deep (Watson, 28.xi.1981; ADU, A52810). West Point, Erith I., Kent Group, Bass Str., 10 m deep (Shepherd & Lewis, 10.v.1974; ADU, A45194). Newport, N.S.W., reef pools (Womersley, 30.v.1950; ADU, Al 3057). Newcastle, N.S.W. (Harvey, AIg. Aust. Exsicc. 82; MEL 16907).

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

Distribution: From the Head of the Great Australian Bight, S. Aust. to Newcastle, N.S.W., including Bass Strait Islands.

Taxonomic notes: H. sinclairii occurs from low tide level (usually in shaded pools) to 38 m deep, and probably extends further west than the Head of the Great Australian Bight.

It is distinctive in habit, in the concave cross walls, in the multicellular pedicels to the tetrasporangia, and resembles H. olsenii in the structure of inactive margins.


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.

HARVEY, W.H. (1858). Phycologia Australica. Vol. I, Plates 1–60. (Reeve: London.)

HOOKER, J.D. & HARVEY, W.H. (1845). Algae Novae Zelandiae. Lond. J. Bot. 4, 521–551.

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 85B, 86.

Figure 85 image

Figure 85   enlarge

Fig. 85. A. Honweostrichus canaliculatus (ADU, A 18976). B. Homoeostrichus sinclairii (ADU, A19171). C. Homoeostrichus olscnii (ADU, A55409, holotype).

Figure 86 image

Figure 86   enlarge

Fig. 86. Homoeostrichus sinclaira (A,B,E–G, ADU, A13664; C,D, ADU, A5681 I). A. Terminal branch with sporangia and paraphyses. B. Surface view of cortical cell rows. C. Longitudinal section of an active apex showing segmentation. D. Longitudinal section of mature segments. E. Longitudinal section of an inactive apex showing segmentation of apical cell region. F. Transverse section with paraphyses and tetrasporangium. G. Longitudinal section with paraphyses and tetrasporangia with multicellular stalks.

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