Megalospora tuberculosa (Fée) Sipman

    Thallus inconspicuous, restricted to a membranous film covering the bark below, pulverulent to powdery, granulose, pale dull grey-greenish, pale greenish, covered with pale yellow to whitish granules potentially clustered and then forming tubercules, whitish, to 2-5 mm across, and with white-yellowish soralia, the combination of granules, tubercules and soredia giving a leprose aspect to some sections of the thallus. Apothecia very rare, rounded, 1-2 mm diam., disc flat, dark brown, exciple paler, persistent. Asci 1-spored. Ascospores 7-11-septate, 70-160 x 25-35 µm. Thallus: C-, K+ pale yellow, KC+ yellow, Pd-, UV-. Rare, mostly on bark of old trees (Quercus), notably towards their base in humid woodlands. N.B. The fertile form is easy to identify notably because of its very large ascospores, but the usual sterile form is far less easy to distinguish. Host of Skyttea megalosporae which seems to be the case in the specimens presented in photograph.