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Electronic Flora of South Australia Genus Fact Sheet

Genus DASYCLONIUM J. Agardh 1894: 80.

Phylum Rhodophyta – Family Rhodomelaceae – Tribe Polyzonieae

Thallus prostrate or largely erect, with indeterminate axes bearing distichously determinate laterals from each second segment; determinate laterals exogenous, with exogenous branches pectinately or digitately arranged, simple or themselves branched, free or basally united to varying degrees. Lateral indeterminate axes arise endogenously, separated by 3 determinate laterals. Attachment by paired rhizoids from adjacent pericentral cells, not cut off and with digitate haptera. Structure. Indeterminate axes with 6 pericentral cells, determinate laterals with 3 pericentral cells, upper parts 3 cells broad, polysiphonous to near the mucronate apical cell or with monosiphonous ends. Trichoblasts absent. Cells uni- or multinucleate.

Reproduction: Gametophytes dioecious. Procarps borne on a lower segment of the basal branch of determinate laterals; carposporophytes with a short gonimoblast and terminal carposporangia; cystocarps ovoid, pericarp ostiolate, ecorticate. Spermatangial organs usually triradiate, developed from the lower part of branches of the determinate laterals, the flanges with marginal sterile cells.

Tetrasporangial branches arising endogenously from the segment above the determinate laterals, developing short outgrowths, with tetrasporangia in straight series of 2–25, each with 3 cover cells which usually subdivide.

Type species: D. incisum (J. Agardh) Kylin 1956: 534.

Taxonomic notes: Scagel (1953 as Euzoniella; 1962) recognised 2 groups in Dasyclonium, the Incisate group (7 species) with branches of the determinate laterals free, and the Cuneifoliate group (3 species) with them united laterally into a foliose structure.

The 3 southern Australian species are in the Incisate group. While D. harveyanum appears to be distinct, relationships between D. incisum and D. flaccidum are less clear and warrant further study.


AGARDH, J.G. (1894). Analecta Algologica. Cont. II. Acta Univ. lund. 30, 1–98, Plate 1.

KYLIN, H. (1956). Die Gattungen der Rhodophyceen. (Gleerups: Lund.)

SCAGEL, R.F. (1953). A morphological study of some dorsiventral Rhodomelaceae. Univ. Calif. Pubis Bot. 27, 1–108.

SCAGEL, R.F. (1962). The genus Dasyclonium J. Agardh. Canadian J. Bot. 40, 1017–1040, Plates i-iv.

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

Publication: Womersley, H.B.S. (24 February, 2003)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIID. Ceramiales – Delesseriaceae, Sarcomeniaceae, Rhodomelaceae
Reproduced with permission from The Marine Benthic Flora of Southern Australia Part IIID 2003, by H.B.S. Womersley. Australian Biological Resources Study, Canberra. Copyright Commonwealth of Australia.


1. Basal branch of determinate laterals itself branched

D. harveyanum

1. Basal branch of determinate laterals simple


2. Determinate laterals 0.5–1.2 (–1.6) mm long, polysiphonous to the terminal mucronate cell, determinate laterals less than 120 µm in diameter, segments L/D 0.1–1, with pericentral cells usually isodiametric (L/D usually 1–1.5); indeterminate axes (110–) 150–200 in diameter

D. incisum

2. Determinate laterals usually 1–2 mm long, branch ends often monosiphonous for several segments to the terminal mucro, determinate laterals often over 120 µm in diameter with pericentral cells elongate and L/D (1.5–) 2–3; indeterminate axes (130–) 250–400 µm in diameter

D. flaccidum

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