14 MAY 1983, Page 23

Lichen lore

Sir: It is pleasing to read townsman Roy Kerridge being observant of the countryside on his trip to the Hebrides (7 May). He should be informed, however, that the lichens he saw on the trees are not 'unhealthy strands'; on the contrary, they flourish in Scotland because the air is clean. As well as clothing the trees, they are also responsible for the colours of the 'grey- green boulders' he mentions. Lichens do not harm the trees they grow on, and they show us that there are still some parts of Britain where the fumes of our cities have not yet reached.

Frank Brightman

59 Rosendale Road, West Dulwich, London SE21