Opegraphaceae Opegrapha vermicellifera Growth type crustose Chemical results and UV negative Occurs in shaded, dry recesses of basic-barked trees, rare on rock. Smooth greyish thallus, usually sterile with small, prominent pycnidia with white or pale grey pruina. Pycnidia semi-immersed when young, chestnut brown with pale ostiole. When fertile lirellae 0.6 to 1.2mm, slender, exciple sometimes furrowed or pruinose. Spores 4-7 septate, 16-25 x 3-4 µm, the ends +/- pointed. Microscope photograph below. Similar: Lecanactis abietina. Pycnidial pruina C+ red, medulla UV+ yellow or grey. L. subabietina. Pruina K+ yellow, thallus negative, UV+ bluish white

Microscope photograph

Opegrapha vermicellifera
On Oak and Yew. Holton Lee, Corfe Mullen and Lytchett Minster, Dorset. October 2012, January 2014, December 2016