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Order Ceramiales

Family Rhodomelaceae

Pterosiphonia Falkenberg

Plants comprising prostrate and erect indeterminate axes, both polysiphonous; oriented dorsiventrally; erect axes bilaterally symmetrical, compressed to flattened, branching distichous and alternate; proximal segments of laterals in both systems of axes confluent with main axes, more strongly so in erect axes. Segments with five or more pericentral cells, uncorticated or corticated to varying degrees. Prostrate axes attached by rhizoids cut off from pericentral cells, with multicellular attachment pads. Tetrasporangia in distal parts of thallus, one per segment. Antheridial stands cylindro-conical, subterminal. Cystocarps ovoid to spheroid, subterminal. Twelve species are recognized worldwide (Guiry & Guiry 2016), of which four are present on the south coast, as well as one other entity that remains undescribed.

Key to species

1a. Axes terete, uncorticated, segments with 8-12 pericentral cells

P. spinifera

1b. Axes compressed, segments with 5 (-6) pericentral cells, cortication present or absent


2a. Cortication in main axes 3-4 layers thick, thallus apices overtopped by young laterals

P. cloiophylla

2b. Cortication in main axes about one layer thick or incomplete; thallus apices not overtopped by young laterals


3a. Cortication complete; laterals confluent with main axes for basal 6-8 segments

P. stegengae

3b. Cortication either absent or incomplete; laterals confluent with main axis for basal 2-3 or 3-4 segments


4a. Cortication incomplete; laterals confluent with main axis for basal 3-4 segments

P. stangerii

4b. Cortication absent; laterals confluent with main axis for basal 2-3 segments

P. sp. indet.

References Pterosiphonia

M.D. Guiry in Guiry, M.D. & Guiry, G.M. 2016. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.; searched on 13 October 2016.


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 19 April 2024.