Polysiphonia stricta (Dillwyn) Greville
Also known as Polysiphonia urceolata and Polysiphonia spiralis.
Description: Soft, slender cylindrical, usually densely tufted, deep red fronds, to 200 mm long, arising from a creeping rhizoidal base. Branching pseudodichotomous to distally alternate. Minute central siphon with 4 pericentral siphons, ecorticate. Articulations 3-5 times as long as broad in main branches, rather shorter than broad in ramuli. Cystocarps visble to the unaided eye, forming urceolate pericarps (below).
Habitat: On rocks, shells and epiphytic (especially on Laminaria hyperborea stipes), intertidal at all levels and subtidal, generally distributed, abundant, particularly on wave-exposed shores and in pool overflows. Particularly common in spring.
Photographs © M.D. Guiry