Vahliella leucophaea  

Thallus crustose-squamulose, of indented, unevenly crenulate, ± rounded, appressed, turgid squamules to 2 mm diam., forming a rather thick cracked-areolate crust. Upper cortex distinct, of 2-3 layers of short, thick-walled cells. Medulla loose, containing clusters of Nostoc, individual cells 4-5 μm diam., gradually merging into rhizohyphae below. Lower cortex lacking. Hypothallus usually obvious, black. squamules grey, grey-brown to black, discrete at margin, often becoming ± imbricate at centre, not enlarged at margins. Soredia and isidia absent.
Anamorph: not known.
Teleomorph: ascomata apothecia, to 1 mm diam., frequent, often clustered. Disc brown-black, rarely brownish in shade, ± convex. Thalline exciple often indistinct, sometimes unevenly developed on one side of an apothecium. Hymenium 100-120 μm high, faintly brownish, composed of compacted, intricately interwoven hyphae, reacting I+ blue-green rapidly changing to red-brown (hemiamyloid). Subhymenial layers to 150 μm high, sometimes brownish, of intricately interwoven hyphae. Interascal tissue of unbranched septate paraphyses ca 2 μm diam. with clavate, pigmented apices. Asci to 100 × 15 μm, clavate to  ± cylindrical, with a ± flat amyloid layer below the apex and a hardly thickened cap, 8-spored. Ascospores 15-17 × 5-6 μm,  ellipsoidal, hyaline, aseptate, smooth-walled, the inner side of spore wall uneven, without a perispore, gelatinous sheath or appendages, often with internal oil droplets which tend to adhere forming plasma-bridges which may appear as incipient septa, but which dissolve in K.
Chemistry: no lichen substances detected by TLC.