Electronic Flora of South Australia Family Fact Sheet

ORDER RHODYMENIALES Schmitz in Engler 1892: 19

Phylum Rhodophyta – Class Florideophyceae

Thallus usually erect, foliose to complanately or radially branched, branches terete to compressed or flat, solid or hollow and often segmented; some genera parasitic, minute, pulvinate or lobed. Structure multiaxial, pseudoparenchymatous, developing a small-celled cortex and larger-celled medulla, often with secretory cells on inner cells; hollow genera often with longitudinal filaments within the medulla, in some families with transverse diaphragms or partitions. Pit-plugs without cap layers.

Reproduction: Gametangial thalli usually dioecious, procarpic. Carpogonial branches 3- or 4-celled, borne on inner cortical cells together with 2- (or 3-) celled auxiliary cell branches, with the auxiliary initial often being a cortical cell; auxiliary cells produced before fertilization but usually maturing afterwards, often containing a spherical proteinaceous globule; diploid nucleus transferred to auxiliary cell directly or via a connecting cell. Carposporophyte developing outwards, with a basal, erect, fusion cell(s) and with most gonimoblast cells, or only the terminal ones, becoming carposporangia; basal nutritive tissue present or not, with numerous connections to the auxiliary initial cell or supporting cell, with erect filaments of cells from the nutritive tissue to the pericarp remaining as the "tela arachnoidea" of slender elongate cells, or as more or less separated stellate cells around the developing carposporophyte, or in many genera disintegrating. Cystocarps protuberant or largely immersed, with a well-developed pericarp, usually ostiolate. Spermatangia cut off from surface cortical cells via initials.

Tetrasporangia cut off laterally or terminally from mid cortical cells, or transformed from cortical cells, cruciately, decussately or tetrahedrally divided (polysporangia in Coeloseira).

Life history triphasic, with isomorphic gametophytes and tetrasporophytes.

Taxonomic notes: The order is usually recognised to include three families and some 38 genera (Kraft 1981), of which 17 genera occur on southern Australian coasts. The families and genera of the Rhodymeniales have been reviewed by Guiry & Irvine (1981) and Irvine & Guiry (1986), and Hawkes & Scagel (1986) monograph and discuss this order on the coast of British Columbia and northern Washington, U.S.A.

References:

ENGLER, A. (1892). Syllabus der Vorlesungen über specielle und medicinisch-pharmaceutische Botanik ... Grosse Ausgabe. (Borntraeger: Berlin.)

GUIRY, M.D. & IRVINE, D.E.G. (1981). A critical reassessment of infraordinal classification in the Rhodyméniales. Proc. Eight hunt Seaweed Symp., 106–111.

HAWKES, M.W. & SCAGEL, R.F. (1986). The marine algae of British Columbia and northern Washington: division Rhodophyta (red algae), class Rhodophyceae, order Rhodyméniales. Can. J. Bot. 64, 1549–1580.

IRVINE, D.E.G. & GUIRY, M.D. (1986). Taxonomy of the Rhodyméniales. In T.V. Desikachary (Ed.). Taxonomy of Algae, pp. 287–303, Plates 1, 2. (Univ. Madras: Madras.)

KRAFT, G.T. (1981). Rhodophyta: morphology and classification. In Lobban, C.S. & Wynne, M.J. (Eds), The Biology of Seaweeds, Ch. 1, pp. 6–51. (Bot. Monogr. Vol. 17, Blackwell: Oxford.)

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.

KEY TO FAMILIES OF RHODYMENIALES

Email Contact: State Herbarium of South Australia