Abrothallus usneae
Mycelium not staining blue in iodine.
Anamorph: not known.
Teleomorph: ascomata apothecia, 250-330 µm diam., sessile to substipitate, pulvinate, dark brown to black, with an inconspicuous pale greenish grey pruina. Hymenium brownish, K-. Epithecium composed of a reddish brown to dark olivaceous crystalline layer, dissolving in K. Hypothecium dark reddish brown, K-. Excipular tissue composed of brown isodiametric or elongate, sometimes branched cells. Interascal tissue composed of paraphyses 1.5-2.5 µm diam., hyaline, branched , not thickened at the apex. Asci 60-67 x 9.5-11 µm, narrowly clavate with a very strongly thickened apex when young, not blueing in iodine, 8-spored. Ascospores (12-) 14-16 (-17) x 4.5-5.5 µm, 1-septate with slightly unequal cells, hardly constricted at the septum, not splitting into part-spores, at first olivaceous, then dark yellow-brown, strongly verrucose.
On moribund thalli of Usnea species, especially U. cornuta and U. subfloridana, sometimes associated with Biatoropsis usnearum.
Western Scotland from Kintyre to Sutherland, Cairngorms, also Devon.