Diplotomma alboatrum forme saxicole des rochers acides
Diplotomma ambiguum (Ach.) Flagey ?
Diplotomma alboatrum (Hoff.) Flot. éco ambiguum
Buellia alboatra var. ambigua (Ach.) Th. Fr.
Differs from Diplotomma alboatrum type by its habitat: acid rocks. Thallus thick, markedly areolate and sometimes fragmented, margin undefined, whitish, lace-like. Apothecia immersed at first then prominent, disc plane becoming convex, black, but often whitish owing to dense pruine. Ascospores blackish, submuriform, broadly ellipsoid to ovoid, (14) 15-20 x 7-12 (14) µm according to our measures. On acid rocks or acid stoneworks. Very similar to the type that grows on calcareous rocks or concrete but rare in our prospection area compared to Diplotomma alboatrum forme saxicole calcicole.