Lecanora sinuosa Herk & Aptroot

       Thallus crustose, 3-5 cm in diameter, strongly verrucous with warts 0.1-0.4 mm in diameter resembling emerging apothecia which are barely open, whitish-grey, pale grayish. Apothecia sessile, flat or concave disc, brownish, light brown, 0.4-1 mm in diameter, margin thick, sinuous, concolorous to the thallus. Hymenium and cortex of the margin containing large crystals which diffuse between the paraphyses, soluble in KOH, insoluble in N and yellow in polarized light. Ascospores colorless, broadly elliptical, 13-17 x 7.5-9 µm. No pycnidia. Thallus: C-, K+ yellow, KC +/- yellow, P-, UV- (atranorin). Species found on the bark of deciduous trees (especially Quercus) in forests.

N.B. Species from the Lecanora subfusca group, very close to Lecanora chlarotera and Lecanora hybocarpa which have a smoother thallus not invaded by emerging apothecia, but there seem to be intermediate forms.