A key to common lichens on trees in England

This key to common species of lichens on trees was prepared in collaboration between two partners of the European project KeyToNature (http://www.keytonature.eu) the Natural History Museum of London and the University of Trieste, as a further aid to the Open Air Laboratory (OPAL) survey of lichens as indicators of air quality.
Author(s): 
Pier Luigi Nimis, Pat Wolseley & Stefano Martellos
Free: 
Yes
Available as: 
PDF