Calicium salicinum
Thallus immersed, often staining the substratum grey, or thin, grey-green and minutely granular.
Anamorph: conidiomata pycnidia, 60-120 µm diam., semi-immersed, dark brown to black above. Conidia dimorphic, one type 2-2.5 x ca 1.5 µm, ellipsoidal and often inaequilateral, and the other 5-8 x ca 1 µm, filiform and curved.
Teleomorph: ascomata stalked mazaedial apothecia, 0.4-1.1 mm tall, 10-15 times as high as width of stalk, brown-black, with brown pruina on the lower side of the exciple and sometimes upper part of stalk, I–. Head 180-400 (-600) µm diam., lens-shaped. Stalk 50-120 µm diam., black. Asci cylindrical. Ascospores uniseriately arranged, 8-11 × 4-5 μm, ellipsoidal, with helically arranged ridges and occasional cracks.
Chemistry: thallus Pd+ yellow-orange, K+ yellow→red (norstictic acid).
Assessed by Woods & Coppins (2012) as of Least Concern.
Scattered throughout S England, Wales and Scotland. BLS map here.
On dry, acid bark and wood, especially on the dry sides of old Quercus trunks.