Cetraria aculeata (Schreb.) Fr. morpho aculeata

   Thallus as a tiny bush with a thorny appearance (in dry weather) which can reach 5 cm in height, spread out loosely and without order and does not seem well fixed to the ground (in wet weather), very branched, more or less flattened branches of irregular section, hollow, up to 1 mm in diameter with pointed ends like thorns, surface shiny and as if varnished, chestnut-brown, brown, reddish-brown in dry weather and in summer, greenish-brown, yellowish-brown, olive in humid weather and in winter (if the color is blackish or blackish brown, see Cetraria muricata), with pseudocyphellae in hollows and at the level of the branches, concave, elongated and oval, whitish and sometimes small spinules over the entire surface (see in this case Cetraria aculeata forma). Very rare apothecia, 2-4 mm in diameter, concave then flat and finally convex disc, concolorous to the thallus, very fine margin with small spinules. Spores simple, colorless, elliptical, 5-8 x 2.5-4 µm. Photobiont: Trebouxia. No characteristic colored chemical reactions. Probably a common species but often going unnoticed, occurring on the sandy soil of acid dunes with heather or in dry heather moors, often with Cladonia portentosa s. l.. Coastal trends in Brittany.

N.B. In dry weather the species shrivels and becomes very barely visible among plant debris.

N.B. Cetraria aculeata morpho sorediata has been described which, as its name indicates, has small soredia; for some authors it is in fact Cetraria aculeata parasitized by Taeniolella rolfii.