Cetraria aculeata (Schreb.) Fr.
Thallus forming small shrubby and thorny-like tufts (during dry weather), to 5 cm high, spreading loosely without apparent order, seemingly little attached to the substratum (when moist), highly ramified, branches irregular in section, main branches to 1 mm diam., sharp tips prickle-like, surface glossy shine, chestnut, dark-brown, brown-redish, brown-greenish, pitted with pseudocyphellae, concave, and elongate, whitish, usually present in pits and at ramification levels, and sometimes small spinules (see in this case Cetraria muricata variously interpreted according to the authors: from a simple morphotype in the plain to an independent species in the mountains). Apothecia scarce, 2-5 mm diam., disc concave, then convex, concolourous with the thallus, exciple with small spinules. Photobiont : Trebouxia. Chemical spot tests negative. Probably rather common but unnoticed, on coastal acidic sand-dunes amongst Calluna or dry heathlands, often together with Cladonia portentosa s. l.. Coastal trends in Brittany. N.B. This species shrivels up when dry and becomes hardly visible amongst plant debris. N.B. Cetraria aculeata morpho sorediata has been described which, as its name suggests, has small soredia, for some authors it would in fact be Cetraria aculeata parasitized by Taeoniella rolfii, see below the photographs of fertile Cetraria aculeata.