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Electronic Flora of South Australia Genus Fact Sheet
Phylum Rhodophyta – Family Delesseriaceae
Thallus erect to decumbent, complanately branched with flat primary blades bearing lateral blades marginally, borne on slender pedicels, monostromatic apart from veins; all blades with a midrib and paired lateral veins (often faint); holdfast discoid, base often 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 which reach the thallus margin with their cells cutting off third-order cells or rows irregularly and mainly abaxially which fill up the spaces between the second-order rows; transverse intercalary divisions occur in the axial cells, then separating the second-order rows. Margin of blades with short dentations, those terminating second-order rows sometimes developing into lateral blades. Midrib becoming heavily corticated, second-order rows (and adjacent primary cells) becoming lightly corticated.
Reproduction: Gametophytes dioecious. Procarps scattered on monostromatic blades, on opposite sides or not, with a 4-celled carpogonial branch and 2 sterile groups; carposporophytes with a basal fusion cell and branched gonimoblast with terminal chains of carposporangia. Cystocarps swollen on one or both sides of blades, ostiolate, with a pericarp 3–8 cells thick of anticlinal cell rows. Spermatangial sod on both sides of blades between midrib and margins, with a layer of cortical cells on both sides and each cell producing 2–4 spermatangia.
Tetrasporangial sod on blades between midrib and lateral veins, with tetrasporangia in 2 layers, produced laterally from inner cortical cells and covered by a layer of outer cortical cells.
Type species: P. sinuosa (Goodenough & Woodward) Kützing (1843: 444) = P. rubens (Linnaeus) Batters. See Kylin 1923: 64, figs 43–51; Maggs & Hommersand 1993: 215, fig. 68.
Taxonomic notes: A genus of 6 or 7 species, of which P. australasica is the only Australian species.
References:
KÜTZING, F.T. (1843). Phycologia generalis. (Leipzig.)
KYLIN, H. (1923). Studien über die Entwicklungsgeschichte der Florideen. K. Svenska Vetensk Akad Handl. 63, 1–139.
MAGGS, C.A. & HOMMERSAND, M.H. (1993). Seaweeds of the British Isles. Vol. 1. Rhodophyta. Part 3A, Ceramiales. (HMSO: London.)
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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