Rhodochorton purpureum

Description:
Plants forming matted purplish-red tufts or a thin turf of sparingly branched, erect filaments, 5-10 mm long. Cells 3-4 times as long as broad. Cells with a single reticulate plastid without pyrenoids, later fragmented. Reproducing by tetrasporangia, mostly in winter. Monosporangia absent.

Key characteristics:
Turf-forming habit and association with upper intertidal, shaded habitats or Laminaria hyperborea (espécie inexistente nos Açores) stipes. Absence of monosporangia.

Habitat:
On rock or epiphytic (especially on
Laminaria hyperborea stipes), upper infralittoral to subtidal, often in caves and shady crevices. Widely distributed, common.

Similar species:
Rhodothamniella floridula, which forms more extensive turfs. Microscopic examination (for the presence or absence of pyrenoids) is required to be certain of the identity of this species.

(In: Seaweed Site - ©Michael D. Guiry - http://seaweed.ucg.ie/descriptions/Audpur.html)