Common on horizontal branches of broad leaved trees in moist habitats. It forms small circular patches of bright-green to olive-brown warted and often sorediate granules. Flat, brownish black apothecia, about 1 mm diameter

References: 
Wirth, V. et al. (2013) Die Flechten Deutchlands, Band 1
Smith, C.W. et al. editors (2009) The Lichens of Great Britain and Ireland
Dobson, F.S. (2018) Lichens: an Illustrated Guide to the British and Irish Species