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Electronic Flora of South Australia Genus Fact Sheet

Genus HALICNIDE J. Agardh 1898: 201

Phylum Rhodophyta – Family Delesseriaceae

Thallus complanately and marginally branched, with flat primary blades bearing ovate to elongate lateral blades with slender basal stipes, all blades with marginal, simple or branched, multicellular spines, older blades also with surface spines; blades with well-developed vein systems of a midrib and paired, opposite, lateral veins; holdfast becoming stoloniferous. Structure. Apical cell segmenting to give an axial filament and 2 lateral and 2 transverse pericentral cells, the lateral cells forming second-order rows the cells of which cut off occasional third-order cells both abaxially and adaxially, forming a blade of compact, irregularly arranged cells. Original second-order rows become separated by 2–4 axial cells due to intercalary divisions near the apex, then becoming corticated to form the opposite lateral veins, and terminating at the margin in the multicellular spines, which arise also from any marginal cell. The blade between the veins remains monostromatic when young but becomes tristromatic with cortical cells on both sides, and surface cells of older blades also form spines (mostly simple).

Reproduction: Gametophytes dioecious. Procarps scattered on blades, detailed structure not observed; carposporophytes with a basal fusion cell and terminal chains of ovoid carposporangia. Cystocarps swollen on both sides of blades, ostiolate, with a thick pericarp of anticlinal rows of cells, bearing short surface spines. Spermatangial sori on both sides of blades, with cortical cells subdividing and producing an outer layer of spermatangia.

Tetrasporangial sori on small, compressed, marginal leaflets also with surface spines, cut off from inner cortical cells on both surfaces, covered by small outer cortical cells.

Type species: H. similans (J. Agardh) J. Agardh 1898: 206.

Taxonomic notes: Halicnide is a distinctive genus with the prominent midrib bearing well-developed opposite lateral veins and marginal and surface spines over the blades. However, only the young blade areas between the veins remain monostromatic and the tetrasporangial blades are distinctly compressed and not "spherical" (c.f. Wynne 1996, p. 176).


AGARDH, J.G. (1898). Species Genera et Ordines Algarum. Vol. 3, Part 3 - De dispositione Delesseriearum. (Gleerup: Lund.)

WYNNE, M.J. (1996). A revised key to genera of the red algal family Delesseriaceae. Nova Hedwigia 112, 171–190.

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

Author: H. B. S. Womersley

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.

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