Polysiphonia, known as red hair algae,[1] is a genus of filamentous red algae with about 19 species on the coasts of the British Isles[2] and about 200 species worldwide,[3] including Crete in Greece, Antarctica and Greenland.

[6] Polysiphonia is a red alga, polysiphonous[2] and usually well branched, with some plants reaching a length of about 30 cm.

[4] The species are entirely marine, found growing on rock, other algae, mussels or limpets and artificial substrata etc.

A complex series of fusions and developments follow as the diploid zygote develops to become the carposporophyte, this is a separate phase of the life-cycle and is entirely parasitic on the female, it is surrounded by the haploid pericarp of the parent female plant.

These spores settle and grow to become the male and female plants thus completing the cycle.