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Electronic Flora of South Australia Genus Fact Sheet

Genus CYSTOSEIRA C. Agardh 1820: 50, nom. cons.

Phylum Phaeophyta – Order Fucales – Family Cystoseiraceae

Thallus 10–50 cm(-2 m) long, with a short stipe from a discoid-conical holdfast, with the axis bearing radially or subdistichously few to numerous primary branches which are usually formed and lost seasonally; axis usually erect, monopodially or sympodially branched. Primary branches long, radially to bilaterally and alternately branched, with the laterals progressively shorter above, and in many species with flattened, simple or branched, basal laterals and slender, terete upper laterals and ramuli; rhachis often with small muricate processes or spines. Vesicles present in most species, often developed seasonally, situated within the laterals or the ultimate ramuli, often in chains of 2–5. Growth from a single, three-sided apical cell in an apical depression. Structure of a compact, central, medulla of elongate cells, without or with few hyphae, and a cortex of isodiametric cells with a surface phaeoplastic meristoderm; cryptostomata scattered over the whole frond, sometimes absent.

Reproduction: Receptacles developed seasonally from ultimate ramuli, terete to lanceolate and verrucose, often distal to a vesicle, simple or branched, in some species with appendages. Conceptacles usually bisexual, ostioles scattered, basal columella with phaeophycean hairs present or absent, tongue cell in juvenile stages unicellular or as a filament of 3–5 cells; oogonia basal in the conceptacle, sessile, partly embedded or not, with a single egg and the supernumerary nuclei extruded, with the eggs freed from the conceptacle or held near the ostiole by mucilage; antheridia usually on the upper conceptacle wall, sessile or on branched paraphyses.

Lectotype species: C. concatenata (Linnaeus) C. Agardh [ = C. foeniculacea (Linnaeus) C. Agardh].

Taxonomic notes: A genus of about 55 species (Roberts 1978, p. 399) found throughout the tropical and warmer temperate regions, with most of the species on Mediterranean and adjoining Atlantic coasts. Cystophyllum is included within Cystoseira (Papenfuss & Jensen 1967, p. 21; Roberts 1978, p. 401), and the southern Australian plants, previously referred (Womersley 1967, p. 254) to Cystophyllum onustum (Mertens) J. Agardh, are considered a form of the Indo-Pacific tropical-subtropical Cystoseira trinodis.

The morphology, structure and reproduction of Cystoseira have been discussed by Roberts (1967).


AGARDH, C.A. (1820). Species Algarum. Vol. 1, Part 1, Fucoideae, pp. 1–168. (Lund.)

PAPENFUSS, G.F. & JENSEN, J.B. (1967). The morphology, taxonomy and nomenclature of Cystophyllum trinode (Forsskål) J. Agardh and Cystoseira myrica (S.G. Gmelin) C. Agardh (Fucales: Cystoseiraceae). Blumea 15, 17–24, Figs 1–4.

ROBERTS, M. (1967). Studies on marine algae of the British Isles. 3. The genus Cystoseira. Br. phycol. Bull. 3, 345–366.

ROBERTS, M. (1978). Active speciation in the taxonomy of the genus Cystoseira C. Ag. In Irvine, D.E.G. & Price, J.H. (Eds) Modern approaches to the taxonomy of red and brown algae. Systematics Association Special Vol. 10, pp. 399–422. (Academic Press: London.)

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
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