Verrucaria squamulosa, section through thallus showing the dark basal layer, the hyphae with brown (rather than black) walls close to the edge of the thallus.
Scratchpads developed and conceived by (alphabetical):
Ed Baker,
Katherine Bouton
Alice Heaton
Dimitris Koureas,
Laurence Livermore,
Dave Roberts,
Simon Rycroft,
Ben Scott,
Vince Smith
