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Electronic Flora of South Australia Species Fact Sheet

Hymenocladia divaricata Harvey 1855a: 553; 1858, pl. 20.

Phylum Rhodophyta – Class Florideophyceae – Order Rhodymeniales – Family Rhodymeniaceae

Selected citations: J. Agardh 1871: 455; 1876: 314. De Toni 1900b: 502. De Toni & Forti 1923: 28. Kylin 1931: 24. Lucas 1929b: 49. Lucas & Perrin 1947: 198. May 1965: 388. Reinbold 1897: 52. Sonder 1881: 17. Sparling 1957: 367.


Fucus divaricatus R. Brown ex Turner 1811: 110, pl. 181, nom. illegit.

Chylocladia divaricata (R. Brown ex Turner)J. Agardh 1852: 367.

Thallus (Fig. 44A) yellow-red to red-brown, 5–18 cm high, much branched with compressed branch axes 2–3 (–5) mm broad centrally, bearing marginally and irregularly compressed laterals 2–10 cm long, and 1–2 (–3) mm broad, often with lesser laterals, and all branches densely covered with slender, simple or irregularly branched, subterete ramuli (0.5–) 1–2 (–3) mm long and (100–) 150–250 µm in diameter; ramuli mostly distichously arranged but flexed out of the plane, with some irregularly placed or from the branch surfaces, apices relatively acute. Holdfast discoid, 1–3 mm across; epiphytic on Amphibolis, or epilithic? Structure probably multiaxial but apices narrow, developing a cortex (Fig. 44E) 1–2 cells thick, outer cells ovoid and 4–5 µm in diameter, grading over 2–4 cells to the medulla 4–6 cells across, the large inner cells ovoid and 70–140 µm in diameter with walls thin (to 10 µm thick), with intermixed filaments of smaller elongate cells 5–12 µm in diameter; secondary pit-connections frequent. Rhodoplasts elongate, ribbon like in inner cells.

Reproduction: Gametangial thalli monoecious (Fig. 44B). Carpogonial and auxiliary cell branches unknown. Carposporophytes (Fig. 44C) with a basal, branched, fusion complex with the upper cells all forming carposporangia, with secondary lobes developing later; carposporangia ovoid, 45–90 µm in diameter. Basal nutritive tissue prominent (Fig. 44C), with cells of the erect filaments largely disintegrating but some lower thick-walled cells remaining. Cystocarps scattered on lesser branches on the surface or edges, hemispherical and broad based, 1–2 mm in basal diameter, pericarp 130–220 µm and 8–14 cells thick, inner cells ovoid, with a prominent ostiole. Spermatangia in small sori (Fig. 44B), cut off from elongate initials (Fig. 44D), ovoid, 1.5–2 µm in diameter.

Tetrasporangia (Fig. 44E) scattered, transformed from intercalary outer medullary cells, subspherical, 70–100 µm in diameter, tetrahedrally divided.

Type from King George Sound, W. Aust. (Harvey, Tray. Set 68); lectotype in Herb. Harvey, TCD.

Selected specimens: Albany, W. Aust., drift (Kraft 4173, 14.xii.1971; AD, A41826). Middleton Beach, Albany, W. Aust., drift (Wood, 10.x.1960; AD, A24571). Tiparra Reef, Spencer Gulf, S. Aust., 11 m deep on Amphibolis (Shepherd, 5.xi.1971; AD, A38341). Stenhouse Bay, S. Aust., drift (Womersley, 9.iv.1950; AD, A13203). Sturt Bay, S. Aust. (Davey 387; AD, A893). Tapley Shoal, Gulf St Vincent, S. Aust., 10 in deep (Shepherd, 2.ii.1969; AD, A33471). D'Estrees Bay, Kangaroo I., S. Aust., drift (Womersley, 11.i.1950; AD, Al2715). Cape Jaffa, S. Aust., drift on Amphibolis (Womersley, 25.xi.1992; AD, A61793).

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

Distribution: King George Sound, W. Aust., to Cape Jaffa, S. Aust.

Taxonomic notes: Harvey (1855a, p. 553, followed by 1858, pl. 20), described H. divaricata as a new species, independently of Fucus divaricatus R. Brown ex Turner, which J. Agardh (1852, p. 367) considered was probably a Chylocladia; while it is more likely that F. divaricatus is the same as Harvey's species, the latter name cannot be transferred to Hymenocladia and Harvey must be considered the author of H. divaricata. The holotype of F. divaricatus is in the BM; it was recorded only from "the coast of New Holland" (R. Brown). There is also an earlier Fucus divaricatus Linnaeus (1763, p. 1627) which Turner notes is Fucus vesiculosus.


AGARDH, J.G. (1852). Species Genera et Ordines Algarum. Vol. 2, Part 2, pp. 337–720. (Gleerup: Lund.)

AGARDH, J.G. (1871). Om Chatham-Oarnes Alger. K. Vetensk Akad. Forschandl. 5, 435–456.

AGARDH, J.G. (1876). Species Genera et Ordines Algarum. Vol. 3, Part 1 — Epicrisis systematis Floridearum, pp. i-vii, 1–724. (Weigel: Leipzig.)

DE TONI, G.B. & FORTI, A. (1923). Alghe di Australia, Tasmania e Nouva Zelanda. Mem. R. Inst. Veneto Sci., Lett. Arti 29, 1–183, Plates 1–10.

DE TONI, G.B. (1900b). Sylloge Algarum omnium hucusque Cognitarum. Vol. 4. Florideae. Sect. 2, pp. 387–776. (Padua.)

HARVEY, W.H. (1855a). Some account of the marine botany of the colony of Western Australia. Trans. R. Ir. Acad. 22, 525–566.

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

KYLIN, H. (1931). Die Florideenordnung Rhodyméniales. Lunds Univ. Årsskr. N.F. Avd. 2, 27 (11), 1–48, Plates 1–20.

LINNAEUS, C. (1763). Species plantarum. Edn 2, 2, 785–1684. (Stockholm.)

LUCAS, A.H.S. & PERRIN, F. (1947). The Seaweeds of South Australia. Part 2. The Red Seaweeds. (Govt Printer: Adelaide.)

LUCAS, A.H.S. (1929b). A census of the marine algae of South Australia. Trans. R. Soc. S. Aust. 53, 45–53.

MAY, V. (1965). A census and key to the species of Rhodophyceae (red algae) recorded from Australia. Contr. N.S.W. natn. Herb. 3, 349–429.

REINBOLD, T. (1897). Die Algen der Lacepede und Guichen Bay und deren näherer Umgebung (Süd Australien), gesammelt von Dr. A. Engelhart-Kingston. Nuova Notarisia 8, 41–62.

SONDER, O.W. (1881). In Mueller, F., Fragmenta Phytographiae Australiae. Supplementum ad volumen undecinum: Algae Australianae hactenus cognitae, pp. 1–42, 105–107. (Melbourne.)

SPARLING, S.R. (1957). The structure and reproduction of some members of the Rhodymeniaceae. Univ. Calif Pubis Bot. 29, 319–396.

TURNER, D. (1811). Fuci sive Plantarum Fucorum Generi a Botanicis Ascriptarum Icones Descriptiones et Historia. Vol. 3, pp. 1–148, Plates 135–196. (London.)

The Marine Benthic Flora of Southern Australia Part IIIB complete list of references.

Author: H.B.S. Womersley

Publication: Womersley, H.B.S. (28 June, 1996)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIIB. Gracilarialse, Rhodymeniales, Corallinales and Bonnemaisoniales
Reproduced with permission from The Marine Benthic Flora of Southern Australia Part IIIB 1996, by H.B.S. Womersley. Australian Biological Resources Study, Canberra. Copyright Commonwealth of Australia.

Illustration in Womersley Part IIIA, 1996: FIG. 44.

Figure 44 image

Figure 44   enlarge

Fig. 44. Hymenocladia divaricata (A, B, D, E, AD, A61793; C, AD, A33471). A. Habit. B. Transverse section of monoecious branch with a young cystocarp and spermatangial sorus (upper right). C. Section of mature cystocarp. D. Section of spermatangial sorus. E. Transverse section of branch with tetrasporangia in medullary cells.

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