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Electronic Flora of South Australia Family Fact Sheet

Tribe SPYRIDIEAE Schmitz 1889: 451

Phylum Rhodophyta – Order Ceramiales – Family Ceramiaceae

Thallus erect, radially branched, with uniaxial branches and apical cells which cut off a row of short axial cells which develop into an indeterminate branch, from each cell of which one or more determinate branchlets (ramelli) develop laterally or in whorls. The ramelli are of limited growth, developing rapidly by apical divisions to 10–30 cells long and expanding by cell elongation to their mature length of generally 1–3 mm. The axial cells of indeterminate branches also cut off in alternating sequence a ring of periaxial cells, which form a band around the node between two axial cells. Each of these periaxial (nodal) cells cuts off two cells from its lower end, and these elongate and become pit-connected to the nodal cells of the next lower segment to give complete cortication, showing bands of shorter and broader nodal cells alternating with the bands of internodal cells, which are longer, narrower, and approximately twice as many as the nodal cells. Further outer cortication occurs some distance from the branch apices, from descending rhizoids developed from the nodal cells, and this obscures the regular pattern of nodal and internodal cell bands, especially in certain species (e.g. S. squalida). The cells of the determinate ramelli each cut off a ring of 6–8 cells from their upper end, and these develop into a nodal band 1–3 cells broad; gland cells absent. Cells uninucleate.

Reproduction: Gametophytes dioecious. Procarps (3–6) produced on small lateral branchlets of restricted growth, with normally three periaxial cells in each fertile segment, one of which (the supporting cell) bears the carpogonial branch, and each periaxial forms an auxiliary cell; two (or rarely three) gonimoblasts are initiated and the mature carposporophyte is commonly bilobed. Carposporophytes become surrounded by pericarpic filaments developed from the segments above and below the one bearing the procarp, giving the appearance of a cystocarp with a well developed pericarp wall held together by a mucilaginous sheath and some lateral pit-connections; these filaments disintegrate fairly readily in preserved material. Spermatangia cover several cells in the lower part of the ramelli, usually excluding the basal cell. They are derived from filaments originating from the nodal cells, which grow over the two adjacent cells, then cut off spermatangial initials before forming the continuous surface layer of spermatangia.

Tetrasporangia occur on the lower cells of the ramelli, sessile and mostly on the upper (adaxial) side, tetrahedrally divided.

Life History triphasic with isomorphic gametophytes and tetrasporophytes.

Taxonomic notes: The tribe contains the single genus Spyridia.

References:

SCHMITZ, F. (1889). Systematische Ubersicht der bisher bekannten Gattungen der Florideen. Flora, Jena 72, 435–456, Plate 21.

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

Author: H.B.S. Womersley

Publication: Womersley, H.B.S. (24 December, 1998)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIIC. Ceramiales – Ceramiaceae, Dasyaceae
©State Herbarium of South Australia, Government of South Australia


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