Cladonia firma (Nyl.) Nyl.

   Primary thallus persistent forming a small tuft of squamules 0.4-2 cm high with a crenate to lobed apex often appearing "snowy" with white, strongly upturned as a whole to form in dry weather a tuft similar to a chrysanthemum flower, upper surface gray-green, glaucous gray, olive green in humid weather, lower surface felty, whitish (more brownish towards the base) with purplish-gray tones over the entire surface, particularly on old, dry individuals. Podetions rare, small, more or less deformed and scyphus-shaped, 1-8 mm in height, corticate and slightly warty surface. Apothecia very rare, nodular, dark brown. Very rare, subglobose pycnidia, at the margin of the scypha. Photobiont: trebouxioid. C-, K+ yellow, KC-, P+ red, UV-. A fairly common thermophilic species in our prospecting area because it has coastal and oceanic tendencies, growing in decalcified dunes or on the slightly acidic soils of shale cliffs. A fairly close species to Cladonia foliacea which has larger lobes with a greener upper surface and a whiter lower surface and which is K- and Cladonia cervicornis subsp. cervicornis also K+ yellow whose lobes are larger and thicker and only incised at the top and whose underside is dirty whitish soiled with blackish at the base, frequently fertile and which grows on more acidic soils.