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Electronic Flora of South Australia Species Fact Sheet

Plocamium costatum (C. Agardh) Hooker & Harvey 1847: 404.

Phylum Rhodophyta – Class Florideophyceae – Order Gigartinales – Family Plocamiaceae

Selected citations: J. Agardh 1852: 403; 1876: 344. Guiler 1952: 89. Harvey 1849a: 122; 1859b: 318; 1863, synop.: xxxix. Kützing 1849: 886; 1866: 18, pl. 52d, e. Lucas 1909: 34; 1929a: 19; 1929b: 50. Lucas & Perrin 1947: 212, fig. 77. May 1965: 372. Reinbold 1897: 52; 1899: 45. Sonder 1855: 519. South & Adams 1979: 126, figs 4, 16–22. Womersley 1950: 170; 1966: 147; 1971a: 13, figs 7–11.


Delesseria plocamium var. costata C. Agardh 1822: 181; 1824: 251.

Thamnophora costata (C. Agardh) J. Agardh 1841: 10. Harvey 1844: 447.

Thallus (Fig. 126A) erect, fairly slender, 10 to 30 cm high from the prostrate base. Erect axes 1–1.5 (–2.5) mm broad, often with a lighter coloured central part and thus appearing costate in mid and lower parts of the axes. Ramuli in pairs, strongly and evenly serrate with short blunt teeth on the convex abaxial side, adaxial side straight to slightly concave; ramuli 1–2 (–3) mm long with lower ramulus usually about 0.5 mm broad at the base.

Reproduction: Sexual thalli dioecious. Cystocarps (Fig. 126B) sessile, globular, about 0.8 mm in diameter, smooth, sometimes slightly verrucose when dry, variously placed in the axil, on the adaxial edge of the ramulus, or more frequently on the abaxial edge of the lower ramulus. Spermatangia covering ends of branches and proliferous branchlets in axils of upper ramuli.

Stichidia in densely branched clusters (Fig. 126C) in the axils of ramuli, closely branched several times at wide angles especially in their upper parts (Fig. 126D); clusters 1–1.5 mm high with branches fairly uniform in width and 80–120 µm in diameter; in some cases the stichidial clusters extend in a series along the adaxial margin of the lower ramulus and up the axis to the base of the abaxial surface of the upper ramulus. Tetrasporangia densely arranged in apices of stichidial branches, 50–65 µm long by 35–45 µm in diameter, zonately divided.

Type from Novae Hollandiae (Desfontaines); holotype in Herb. Agardh, LD, 28056.

Selected specimens: Elliston, S. Aust., 10–12 m deep outside bar (Shepherd, 25.x.1971; AD, A42666). Victor Harbor, S. Aust., drift (Womersley, 24.vii.1949; AD, A11163). Sou'West R., Kangaroo I., S. Aust., 6 m deep (Mitchell, 24.viii.1963; AD, A26809). Robe, S. Aust., 3–6 m deep (Baldock, 15.v.1967; AD, A31491). 1.3 km off Cape Northumberland, S. Aust., 13 m deep (Shepherd, 19.iii.1974; AD, A44902). Lady Julia Percy I., Vic., 3–6 m deep (Shepherd, 4.i.1968; AD, A32348). Walkerville, Vic., drift (Sinkora A2098, 27.ii.1975; AD, A48400). Gabo I., Vic., 13 m deep (Shepherd, 14.ii.1973; AD, A43329). Low Head, Tas. (Perrin, June 1948; AD, A8969). S of Surveyors Cove, Port Arthur, Tas., 13–19 m deep (McGeary-Brown, 29.x.1986; AD, A57424). Green Cape, N.S.W., 16 m deep (Shepherd, 13.ii.1973; AD, A43030). Point Dromedary, N.S.W. (Bate; MEL, 1006161).

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

Distribution: From Elliston, Eyre Peninsula, S. Aust., to Point Dromedary, N.S.W., and around Tasmania. Found on coasts of rough to moderate wave action, and known from depths of 3 to 20 m.

New Zealand.

Taxonomic notes: P. costatum is distinguished by the clustered stichidia which are branched in their upper parts (often near their apices), and sessile cystocarps. The thallus branches are broader than in P. angustum and also have strongly serrate curved ramuli; in thallus characters P. costatum is close to P. dilatatum but the massive, unbranched stichidia and pedicellate cystocarps distinguish the latter.

In some specimens of P. costatum, the cystocarps in young branches appear pedicellate. This, however, is due to their occurrence on short proliferous branches arising in the axils of older branches and the cystocarps are actually sessile on very slender ramuli; older parts of such plants show typical sessile cystocarps on mature ramuli.


AGARDH, C.A. (1822). Species Algarum. Vol. 1, Part 2, pp. 169–398. (Berling: Lund.)

AGARDH, C.A. (1824). Systema Algarum. (Berling: Lund.)

AGARDH, J.G. (1841). In historiam algarum symbolae. Linnaea 15, 1–50, 443–457.

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

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

GUILER, E.R. (1952). The marine algae of Tasmania. Check-list with localities. Pap. Proc. R. Soc. Tasm. 86, 71–106.

HARVEY, W.H. (1844). Algae of Tasmania. Lond. J. Bot. 3, 428–454.

HARVEY, W.H. (1849a). Nereis Australis, pp. 65–124, Plates 26–50. (Reeve: London.)

HARVEY, W.H. (1859b). Algae. In Hooker, J.D., The Botany of the Antarctic Voyage. Flora Tasmaniae. Vol. II, pp. 282–320.

HARVEY, W.H. (1863). Phycologia Australica. Vol. 5, Plates 241–300, synop., pp. i-lxxiii. (Reeve: London.)

HOOKER, J.D. & HARVEY, W.H. (1847). Algae Tasmanicae. Lond. J. Bot. 6, 397–417.

KÜTZING, F.T. (1849). Species Algarum. (Leipzig.)

KÜTZING, F.T. (1866). Tabulae Phycologicae. Vol. 16. (Nordhausen.)

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

LUCAS, A.H.S. (1909). Revised list of the Fucoideae and Florideae of Australia. Proc. Linn. Soc. N.S.W. 34, 9–60.

LUCAS, A.H.S. (1929a). The marine algae of Tasmania. Pap. Proc. R. Soc. Tasm. 1928, 6–27.

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 naherer Umgebung (Siid Australien), gesammelt von Dr. A. Engelhart-Kingston. Nuova Notarisia 8, 41–62.

REINBOLD, T. (1899). Meeresalgen von Investigator Street (Süd Australien), gesammelt von Miss Nellie Davey (Waltham, Honiton). Hedwigia 38, 39–51.

SONDER, O.W. (1855). Algae annis 1852 et 1853 collectae. Linnaea 26, 506–528.

SOUTH, G.R. & ADAMS, N.M. (1979). A revision of the genus Plocamium Lamouroux (Rhodophyta, Gigartinales) in New Zealand. Phycologia 18, 120–132.

WOMERSLEY, H.B.S. (1950). The marine algae of Kangaroo Island. III. List of Species 1. Trans. R. Soc. S. Aust. 73, 137–197.

WOMERSLEY, H.B.S. (1966). Port Phillip survey, 1957–1963: Algae. Mem. natn. Mus., Vict. No. 27, 133–156.

WOMERSLEY, H.B.S. (1971a). The genus Plocamium (Rhodophyta) in southern Australia. Trans. R. Soc. S. Aust. 95, 9–27.

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

Author: H.B.S. Womersley

Publication: Womersley, H.B.S. (14 January, 1994)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIIA, Bangiophyceae and Florideophyceae (to Gigartinales)
Reproduced with permission from The Marine Benthic Flora of Southern Australia Part IIIA 1994, by H.B.S. Womersley. Australian Biological Resources Study, Canberra. Copyright Commonwealth of Australia.

Illustration in Womersley Part IIIA, 1994: FIG. 126.

Figure 126 image

Figure 126   enlarge

Fig. 126. Plocamium costatum (A, AD, A11163; B–D, AD, A31491). A. Habit. B. Branch with cystocarps in axils of ramuli. C. Branch with axillary clusters of stichidia. D. Branched stichidia. [A–D as in Womersley 1971.]

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