A key to common lichens on trees in England

Pier Luigi Nimis, Pat Wolseley, Stefano Martellos
This key to common species of lichens on trees was prepared in collaboration between two partners of the European project KeyToNature (www.keytonature.eu), the Natural History Museum of London and the University of Trieste, as a further aid to the Open Air Laboratories (OPAL) Air Survey which looks at lichens as indicators of air quality (www.opalexplorenature.org/?q=AirSurvey).