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Order Ceramiales

Family Spyridiaceae

Spyridia Harvey

Thalli erect, with a clear distinction between indeterminate and determinate branches. Axial cells of indeterminate branches each cutting off a ring of periaxial (=nodal) cells; periaxial cells each cutting off two (internodal) cells in basipetal direction, the latter making a connection with the periaxial cells of the segment below. Cortication of (young) segments thus consisting of two transverse bands of cells of slightly different size and shape. Further cortication in older segments by development of rhizoidal cells. Cells of the determinate laterals each with a ring of nodal cells, with or without further development of cortication, but never in the manner of the main axes. Tetrasporangia on the nodes of the determinate branches, exserted, tetrahedrally divided. Spermatangia covering several segments in the proximal part of determinate laterals. Procarps and carposporophytes on short determinate laterals.

A genus of warm temperate seas, with 15 species currently recognised (Guiry & Guiry 2015), of which five are found on the south coast.

Key to the species

1a. Segments usually with two determinate laterals

Spyridia plumosa

1b. Segments with one determinate lateral


2a. Plants rather lax, with a single straight terminal spine on the determinate laterals

Spyridia filamentosa

2b. Plants sturdy, with two or more spines on the determinate laterals, in part recurved


3a. Determinate laterals completely corticated

Spyridia cupressina

3b. Determinate laterals not completely corticated, or at least the separate cortical bands clearly visible


4a. Determinate laterals usually with four terminal recurved spines

Spyridia horridula

4b. Determinate laterals with a terminal straight and 1-4 subterminal recurved spines

Spyridia hypnoides

References Spyridia

Guiry, M.D. & Guiry, G.M. 2015. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.; searched on 11 December 2015.


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.