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Electronic Flora of South Australia
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Electronic Flora of South Australia Family Fact Sheet


Phylum Rhodophyta – Class Florideophyceae – Order Gigartinales

Thallus prostrate, completely to partly adherent, usually epilithic, often with hypobasal calcification between the attachment rhizoids; growth marginal on thallus and terminal on erect filaments. Structure of radiating filaments, either forming a basal layer of branched rows producing erect to assurgent filaments above, or a central (nearer the lower side) region of few to numerous filaments with assurgent filaments both upwards and downwards. Assurgent to erect filaments simple to branched, tightly coherent laterally or somewhat loose in a gelatinous matrix; internal calcification of aragonite present or absent; pit-plugs without cap layers; rhodoplasts numerous, discoid.

Reproduction: Sexual plants (where known) monoecious or dioecious, with superficial nemathecia (with paraphyses); carpogonial branches and auxiliary cell branches 3–6 cells long, non-procarpic, carposporophytes consisting of short, simple or branched, chains of carposporangia; male nemathecia with clustered spermatangial filaments.

Tetrasporangia in superficial nemathecia, cruciately divided, with slender multicellular paraphyses.

Taxonomic notes: A family of probably four or five genera (see Denizot 1968 and Irvine & Maggs 1983, p. 52), of which two occur in southern Australia.


DENIZOT, M. (1968). Les Algues Floridées encroûtantes (a l'exclusion des Corallinacées). (Paris.)

IRVINE, L.M. & MAGGS, C.A. (1983). Peyssonneliaceae. In Irvine, L.M., Seaweeds of the British Isles. Part 2A. Cryptonemiales (sensu stricto), Palmariales, Rhodymeniales. [British Museum (N.H.): London.]

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

Author: H.B.S. Womersley

Publication: Womersley, H.B.S. (14 January, 1994)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIIA, Bangiophyceae and Florideophyceae (to Gigartinales)
Reproduced with permission from The Marine Benthic Flora of Southern Australia Part IIIA 1994, by H.B.S. Womersley. Australian Biological Resources Study, Canberra. Copyright Commonwealth of Australia.


1. Thallus robust, orbicular, largely free from the substratum; RVS showing filaments assurgent from an ill-defined layer in the lower thallus, with shorter filaments assurgent to the lower side and producing rhizoids; tetrasporangial nemathecia without paraphyses, the whole nemathecium readily lost


1. Thallus totally to partially adherent to the substratum, orbicular or becoming irregularly divided or lobed; RVS showing a distinct basal layer of radiating or polyflabellate filaments next to the substrate, producing rhizoids below and above producing assurgent to erect filaments a few to many cells long, closely adjacent or relatively separate and in a gelatinous matrix; tetrasporangia usually formed within superficial nemathecia of slender filaments on the thallus surface, cruciately divided


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