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Order Ralfsiales

Family Ralfsiaceae

Ralfsia verrucosa (Areschoug) Areschoug in Fries 1845: 124

Plants crustose, to several cm or more across, yellow-brown to olive green, becoming dark brown or blackish when dry; often with concentric growth rings, but may be fragmented by grazing or develop overlapping lobes. Vegetative crust of closely-packed, upward-curving filaments arising from a horizontal layer that is basal or central in the crust. Crust often attached by multicellular rhizoids. Horizontal filaments ca. 5-8 µm in diameter with cells 10-15 (-30) µm long. Vertical filaments 6-8 cells long, tightly adherent, with similar diameter to horizontal filaments but cells slightly shorter, almost isodiametric except in surface layer, where cells are 12-15 µm long. Cells with one chloroplast. Phaeophycean hairs present in scattered bundles.

Unilocular sporangia in raised sori composed of tightly packed uniseriate paraphyses that are very narrow at the base and widen to ca. 5 µm at the apex, 10-15 cells long. Unilocular sporangia clavate, 60-120 µm long x 20-30 µm wide. Plurilocular sporangia in large sori, scarcely raised above thallus surface; sporangia tightly packed, without interspersed vegetative cells or paraphyses; sporangia uniseriate, up to 40 µm (10 cells) long, 3-4 µm in diameter, each with a slightly larger sterile terminal cell.

Collections, ecology and regional distribution

Common on west and south coast shores throughout the eulittoral zone and in pools, also often epizoic on limpets and snails. Recorded along the entire west coast to at least the northern Transkei region (1-47), but superficially very similar to Neoralfsia expansa, and where they overlap in distribution these taxa are probably often confused.

World distribution: Probably cosmopolitan on cold and warm-temperate coasts (Guiry & Guiry 2011).

Type locality: Western Götland, Sweden (Guiry & Guiry 2011).


Ralfsia verrucosa, Tsitsikamma.

Ralfsia verrucosa, xs of crust (stained slide).

Ralfsia verrucosa, xs of Tsitsikamma specimen showing structure of upper layer and unilocular sporangia.

Ralfsia verrucosa, xs of Tsitsikamma specimen showing structure and unilocular sporangia.

Ralfsia verrucosa. 1. Radial vertical section of thallus with several superimposed lobes and raised unilocular sporangial sori. 2. Radial section of thallus showing terminal plurilocular sporangia. 3. Unilocular sporangia and associated paraphyses. 4. Radial section showing median primary cell rows and hair bundles. Drawings from Stegenga et al. (1997).


References Ralfsia verrucosa

Fries, E.M. (1845). Summa vegetabilium Scandinaviae, seu enumeratio, systematica et critica, plantarum tum cotyledonearum, quum nemearum inter mare occidentale et album, inter Eidoram et Nordkap, hactenus lectarum, una cum singulae distributione geographica. pp. Sectio prior: [i], [iii], [i]-258, signatures 1-16 in fours. Holmiae & Lipsiae [Stockholm & Leipzig]: A. Bonnier.

Guiry, M.D. & Guiry, G.M. 2011. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.; searched November 2011.

Stegenga, H., Bolton, J.J. and R. J. Anderson. 1997. Seaweeds of the South African west coast. Contributions from the Bolus Herbarium 18: 655 pp.


Cite this record as:

Anderson RJ, Stegenga H, Bolton JJ. 2016. Seaweeds of the South African South Coast.
World Wide Web electronic publication, University of Cape Town,; Accessed on 26 February 2024.