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Electronic Flora of South Australia Genus Fact Sheet
Phylum Rhodophyta – Class Florideophyceae – Order Gigartinales – Family Halymeniaceae
Thallus foliose, lobed or divided above, relatively thick, mucilaginous, spreading more or less horizontally from just above the discoid holdfast and thus with only a very short stipe which appears submarginal. Structure multiaxial with broad apices, developing a cortex several to many cells thick, the outer cortex of anticlinal rows of elongate cells and the inner cortex of ovoid cells, in general not becoming stellate; medulla sparse to moderately dense, of irregular filaments of ovoid to elongate cells, without refractive ganglionic cells.
Reproduction: Sexual thalli dioecious. Carpogonial branch ampullae with a 5–8-celled primary filament and several secondary (with a few tertiary) filaments and a 2-celled carpogonial branch. Auxiliary cell ampullae with longer primary and secondary filaments, developing up to 5 orders of filaments of small ovoid cells, with a large, basal, auxiliary cell. Carposporophyte dense, lying largely within the medulla, with a basal fusion cell and a prominent involucre developed from the ampullary filaments and small cells derived from them. Spermatangia developed from surface cortical cells.
Tetrasporangia scattered, attached to mid cells of the cortex, cruciately divided.
Life history triphasic with isomorphic gametophytes and tetrasporophytes.
Type species: A. nitidissima J. Agardh 1876: 680.
Taxonomic notes: A genus of 4 species (see Chiang 1970, p. 6), characterised by the habit, with a broad thallus spreading laterally from the holdfast with very little stipe, a medulla with few slender rhizoids and a relatively thick but loose involucre. It is most closely related to Pachymenia which differs in the above features.
References:
AGARDH, J.G. (1876). Species Genera et Ordines Algarum. Vol. 3, Part 1 - Epicrisis systematis Floridearum, pp. i-vii, 1–724. (Weigel: Leipzig.)
CHIANG, Y.-M. (1970). Morphological studies of red algae of the family Cryptonemiaceae. Univ. Calif Pubis Bot. 58, 1–83, Plates 1–10.
The Marine Benthic Flora of Southern Australia Part IIIA complete list of references.
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.
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