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Electronic Flora of South Australia Genus Fact Sheet

Genus DITRIA Hollenberg 1967a: 206

Phylum Rhodophyta – Family Rhodomelaceae – Tribe Herposiphonieae

Thallus entirely prostrate, with dorsi-ventral indeterminate axes bearing in spiral sequence, singly or in pairs, simple determinate laterals flexed to alternate sides, separated usually by an unbranched segment which bears only a single dorsal cell cut off the axial cell. Structure. Pericentral cells 5, ecorticate, axes compressed, determinate laterals terete with trichoblasts on upper segments. Rhizoids cut off from ventral pericentral cells, unicellular with multicellular haptera. Cells uninucleate.

Reproduction: Gametophytes dioecious. Procarps borne on trichoblasts, with a 4-celled carpogonial branch and 2 sterile groups; carposporophyte with a basal fusion cell and gonimoblast with clavate terminal carposporangia; cystocarps terminal on determinate laterals, ovoid, ostiolate, pericarp ecorticate. Spermatangial organs replacing trichoblasts on determinate laterals, lanceoid, with sterile basal and terminal cells.

Tetrasporangia in ends of determinate laterals, single per segment.

Type species: D. reptans Hollenberg 1967a: 208, fig. 4.

Taxonomic notes: A genus of 3 species, the type, D. zonaricola (Okamura) Yoshida & Yoshida (1983) from Japan, and D. expleta Huisman. The type and D. zonaricola have dormant ventral lateral initials whereas in D. expleta these form one determinate lateral of each pair. This results in a striking difference between D. expleta and the other 2 species, which might be considered of generic status.


HOLLENBERG, G.J. (1967a). New genera in the Rhodomelaceae from the Central Pacific. Bull. S. Calif. Acad. Sci. 66, 201–221.

YOSHIDA, T. & YOSHIDA, M. (1983). Observations on Ditria zonaricola (Okamura) comb. nov. based on Herpopteros zonaricola Okamura (Rhodophyta, Rhodomelaceae). J. Fac. Sci., Hokkaido Univ. Ser. V (Bot.) 13, 39–48.

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.

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