Electronic Flora of South Australia Genus Fact Sheet
Phylum Rhodophyta – Class Florideophyceae – Order Gigartinales – Family Gigartinaceae
Thallus erect, 5–60 cm high, foliose, simple or lobed or with flat lanceolate branches with narrow to broad marginal proliferations, relatively thin, usually membranous, usually not mucilaginous. Structure multiaxial, with a compact cortex of anticlinal, subdichotomous filaments of small cells, larger inwardly, and a medulla of slender anastomosing filaments.
Reproduction: Sexual thalli monoecious. Carpogonial branches 3-celled, borne on inner cortical (supporting) cells which also bear a sterile cortical branch. Procarpial, with the supporting cell acting as auxiliary cell following fertilization, and producing numerous gonimoblast initials of which only the inwardly orientated ones produce further gonimoblast cells; gonimoblast filament cells producing laterally 1–2 carposporangial initials, which divide and enlarge to form 1–2 ovoid carposporangia. Mature cystocarps embedded in the medulla, only slightly protruding, with compact enveloping tissue surrounding the carposporophyte, absorbing filaments present and traversing the enveloping tissue, and the enlarged auxiliary cell remaining only in young carposporophytes. Spermatangia in inconspicuous sori, cut off from outer cortical cells.
Tetrasporangial sori small, maculate, with rows of cruciately divided tetrasporangia derived from divisions of the surface cortical cells, radiating inwardly from the subsurface region.
Life history triphasic with isomorphic gametophytes and tetrasporophytes.
Type species: R. lanceolatum (Harvey) J. Agardh 1876: 186 [= R. gigartinoides (Sonder) Edyvane & Womersley].
Taxonomic notes: Edyvane & Womersley (1993) have shown that Rhodoglossum is characterised by tetrasporangial sori with rows of sporangia resulting from apical divisions of the surface cortical cells. The type species is very variable in frond morphology and is probably the only species of Rhodoglossum.
AGARDH, J.G. (1876). Species Genera et Ordines Algarum. Vol. 3, Part 1 - Epicrisis systematis Floridearum, pp. i-vii, 1–724. (Weigel: Leipzig.)
EDYVANE, K.S. & WOMERSLEY, H.B.S. (1993). Morphology and taxonomy of Rhodoglossum gigartinoides (Sonder) comb. nov. (Gigartinaceae, Rhodophyta) from Australia and New Zealand. Phycologia 32, 237–250.
The Marine Benthic Flora of Southern Australia Part IIIA complete list of references.
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.
State Herbarium of South Australia