Psoromidium aleuroides

Detailed description

Thallus small-squamulose, to 10 cm diam. Squamules small, rounded, 0.5-2.0 mm diam., crowded, imbricate to ± suberect, margins shallowly to deeply crenate, bright lettuce-green to pale greenish-grey, turning brownish-buff on storage, matt, with paler margins, forming an areolate crust on a thick, black, byssoid prothallus, discrete and scattered near margins. Cephalodia rosette- shaped, placodioid, flattened, pale blue-grey, 1-3 mm diam., at margins of squamules or on prothallus. Apothecia numerous, sessile, often aggregated and ± confluent, 0.4-1.0 mm diam., dark red-brown, matt, with a thin, pale margin, at first, soon becoming convex and immarginate. Asci clavate to ellipsoid, 70-75 µm long. Paraphyses slender, apices not thickened, simple, sometimes dichotomously branching above asci. Ascospores ellipsoid or elongate-ellipsoid to broadly fusiform, rounded or bluntly apiculate at ends, 10-13.5(-15) × 4-6 µm, wall slightly scabrid, c. 1 µm thick.