Melanothamnus harveyi (Polysiphonia harveyi), Harvey's siphon weed,Bunker, F.StP. D., Brodie, J.A., Maggs, C. and Bunker, A.R. 2017. Seaweeds of Britain and Ireland. Second Edition, Wild Nature Press, Plymouth, UK is a small marine red alga in the division of Rhodophyta.
Description Melanothamnus harveyi is a small marine alga which grows in tufts no more than high. The erect branches are formed by a central axis surrounded by four perecentral cells of the same length. A cortex may develop by cells growing downwards in the grooves between the perecentrals. Latteral branches are usually dense. The holdfast is a disk of downgrowing filaments from which further erect branches develop. The general appearance is very variable.Maggs, C.A. and Hommersand, M.H. 1993. Seaweeds of the British Isles Volume 1 Rhodophyta Part 3A Ceramiales The Natural History Museum, London
Reproduction This species is dioecious, meaning that individuals either have male or female reproductive systems. Spermatangial axes develop on trichoblasts. The cystocarps are globular borne on wide stalks. Tetrasporangia occur in series near the tips of the branches.
Habitat Melanothamnus harveyi grows epiphytically on other algae as well as on artificial material.
Distribution This species can be found in England, Scotland, Ireland, Norway, France, Denmark and the east coast of North America.Morton, O. 2003. The marine macroalgae of County Donegal, Ireland. Bulletin of the Irish biogeographicaln Society no. 27: pp3 - 164
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