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Genus RHODYMENIOCOLAX Setchell 1923: 394

Phylum Rhodophyta – Class Florideophyceae – Order Rhodymeniales – Family Rhodymeniaceae

Thallus 1–4 mm high, forming verrucose or stellate pustules usually with a basal stalk, on species of Rhodymenia. Structure multiaxial, developing a cortex 1–3 (–6) cells thick and a pseudoparenchymatous medulla of ovoid to elongate cells of varying sizes, with basal filaments penetrating the host medulla.

Reproduction: Gametangial thalli dioecious. Carpogonial branches 4-celled, borne on a multinucleate inner cortical (supporting) cell together with a 2-celled auxiliary cell branch. Carposporophyte developing outwardly, with a basal fusion cell and lobes of carposporangia. Basal nutritive tissue present, erect filaments largely disintegrating. Cystocarps protruding, hemispherical, with a pericarp, ostiolate. Spermatangia in extensive surface sori, cut off from elongate initials on cortical cells.

Tetrasporangia scattered in the unmodified cortex or in extensive nemathecia, decussately or cruciately divided.

Life history triphasic with isomorphic gametophytes and tetrasporophytes.

Type species: R. botryoidea Setchell 1923: 394.

Taxonomic notes: Previous to this, Rhodymeniocolax included only the type species from California, U.S.A., though L. Irvine & Guiry (1983, p. 97), suggest that a second species occurs in the British Isles and France. A third species occurs on Rhodymenia on southern Australian coasts. Comparisons with the type species are limited by lack of information on it.


IRVINE, L.M. & GUIRY, M.D. (1983). Rhodyméniales. In Irvine, L.M. (1983). Seaweeds of the British Isles. Vol. 1 Rhodophyta Part 2A Cryptonemiales (sensu stricto), Palmariales, Rhodyméniales. (British Museum (N.H.): London).

SETCHELL, W.A. (1923). Parasitic Florideae II. Univ. Calif Pubis Bot. 10, 393–396,

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

Author: H.B.S. Womersley

Publication: Womersley, H.B.S. (28 June, 1996)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIIB. Gracilarialse, Rhodymeniales, Corallinales and Bonnemaisoniales
Reproduced with permission from The Marine Benthic Flora of Southern Australia Part IIIB 1996, by H.B.S. Womersley. Australian Biological Resources Study, Canberra. Copyright Commonwealth of Australia.

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