Bifurcaria bifurcata R. Ross
Also known as Bifurcaria rotunda (Hudson) Papenfuss and B. tuberculata Stackhouse.
Description: Cylindrical, rich yellow-brown, 300-500 mm long. Fronds tough, cylindrical, smooth, narrowly forked from about half way up the thallus. Holdfast composed of intertwined rhizoidal growths. Receptacles (below) cylindrical elongated at apices with many conceptacles. Ostioles usually very prominent. Antheridial conceptacles usually above and oggonial conceptacles below. Inconspicuous, simple air vesicles occasionally found at the base of the receptacles.
Habitat: In Britain and Ireland mostly found in pools at about MTL, occasionally at low water on wave-washed ledges.
Distribution: SW Britain and W Ireland N to Donegal. Unaccountably ± absent from the south coast of Ireland. Most common in limestone areas, and associated with the Black Sea Urchin, Paracentrotus lividus and the coralline alga Lithophyllum incrustans. Bifurcaria is a particular feature of the Burren in Co. Clare, particularly around Black Head, Kilkee and Spanish Point. Populations persisting for many years.
Key characteristics: Cylindrical thallus, rhizoidal holdfast, regular narrow forking.
Similar species: Halidrys siliquosa also occurs in similar pools but is profusely alternately branched, and commonly has compartmented floation structures with the shape of pea pods.
Photographs © M.D. Guiry