Caliciaceae Diplotomma alboatrum Growth type crustose. Chemical results negative On calcareous rocks and mortar, also recorded from nutrient-enriched, basic-barked trees. Very variable. White, pale or dark grey thallus, apothecia often pruinose with thin grey margins. Spores brown, 1-3 septate becoming submuriform, (11-)15-20(-30) x (6-)8-10(-17) µm. Microscope photographs below. Sometimes host to Arthonia punctella and Verrucaria latericola Similar: D. chlorophaeum. K+ yellow>red, P+ orange. Discs not pruinose. Diplotomma hedinii, spores without longitudinal septa, frequently curved. D. pharcidium. Corticolous, often not pruinose, spores +/- slightly curved. Diplotomma murorum occurs on the thallus of Caloplaca teicholyta.

Microscope photographs

Diplotomma alboatrum
Dorset. September 2012, February 2013, March 2014