ASCOMYCOTA | LECANOROMYCETES > LECANORALES > Lecanoracea

Genus formally Lecanora, meaning 'beautiful small bowl' - from the shape of the apothecia

Common name:            Members of the genus collectively known as a 'rim lichens'

Synonyms:                     Lecanora carpinea

Primary habitat:            Woodland, wayside trees

Usual substrata:            Bark

Growth form:                Corticolous

Thallus:                  Crustose

Apothecia:                    Lecanorine

BLS identity rating:        Graded 2/5 (relatively straightforward, but see note regarding spot-testing)

Thallus forming discrete patches, generally continuous and smooth, thin, white to pale grey, or pale white-greenish, often becoming darker and somewhat cracked in the centre with age; surrounded by a white prothallus.

Apothecia can be numerous, sometimes clustered and possibly distorted or angular if crowded and compressed; sessile, constricted at the base; initially flat, becoming slightly convex with age; typically, 0.5-1.5mm dia., with a smooth, well- developed thalline margin, which may become excluded in older specimens; disc cream to pale brown-orange, although the true colour is usually difficult to see due to the presence of thick white-grey pruinose.

This species occurs mainly on smooth-barked, smaller and/or young deciduous trees, both on the trunk as well as small branches and twigs; widespread throughout Britain and Ireland, but with local distribution.

Formerly Lecanora carpinea, a species within the Lecanora rupicola group, which were moved to the Glaucomaria genus a few years back; the other two species affected being Lecanora rupicola and Lecanora swartzii.  

Whilst the species is quite distinctive it could easily be confused with the similarly paleLecanora albella, hence the need to spot-test, but testing requires the use of a Pd (para-phenylenediamine) solution, which is beyond the scope of what I want to do. Part-testing could be done with C on the apothecia as Glaucomaria carpinea reacts C+ yellow, whereas Lecanora albella has no reaction. Both species can be found locally, but with Lecanora albella more likely to be found on small branches and twigs rather than on the trunk as the specimen featured below. It also favours more acid trees, such as oak, in less nutrient- rich habitats.