Polysiphonia denudata (Polysiphonia variegate (C.Agardh) Zanardini) is a small red alga, Rhodophyta, growing as tufts up to 20 cm long without a main branch axis.Maggs, C.A. and Hommersand, M.H. Seaweeds of the British Isles. Volume 1 Rhodophyta Part 3A Ceramiales The Natural History Museum, London
Description Polysiphonia denudata is erect with repeatedly branched axes. Each branch consists of a central axis with 5 to 7 elongated pericentral cells all of the same length. Cortication occurs lower down, these corticating cells grow down in the grooves between the pericentral cells. The holdfast is discoid.
Reproduction The plants are dioecious. They bear spermatangia towards the tips of branches. Cystocarps are barrel-shaped when mature borne on a wide short stalk. Tetrasporangia occur in a spiral series in the branches near the tips.
Habitat The alga is very rare, grows on rock, stones or other large algae in the low-littoral or below in sheltered sites.Newton, L. 1931. A Handbook of the British Seaweeds. British Museum, London
Distribution Reported from the north of Ireland in 1847, the specimen is in store in the Ulster Museum, BelfastMorton, O. 1994. Marine Algae of Northern Ireland. Ulster Museum in England from the south coast,Batters, E.A.L. 1902. A Catalogue of the British Marine Algae. supplement to the Journal of Botany 40:1 - 107 Scottish records considered misidentifications,Hardy, F.G.and Guiry, M.D. 2003. A Check-list and Atlas of the Seaweeds of Britain and Ireland. British Phycological Society. Netherlands to Portugal and West Africa. The Mediterranean and west Atlantic.
References
Further References Bunker, F.StP.D., Maggs, C.A., Brodie, J.A., Bunker, A.R. 2017. Seaweeds of Britain and Ireland. Second Edition. Wild Nature Press, Plymouth. UK.