Diploicia canescens from Mayenne

In the upper left of this fragment of corroded, uncoloured glass is a roughly circular thallus of Diploicia canescens, with a missing central area. The thallus is 4 centimetres in diameter. This piece of glass came from a church in Mayenne, France and dates from the end of the 16th century.

Source: From plate 1 of Mellor, E. & Davy de Virville, A. (1922). La Détérioration des Vitraux d'église de la Mayenne par les Lichens. Bulletin de Mayenne-Sciences, 1921, 1-15.