This is the latest book from the legendary author who has produced so many publications for amateurs and ecologists. He has done much to widen the appeal of lichenology in Britain. Covering about 500 species of the more common lichens to be found on trees and bare wood this key aims to provide a useful tool for ecologists and the less experienced lichenologist. The book deals with characteristics which are observable in the field through the use of a hand lens and the simple chemical spot tests of C (sodium hypochlorite) and K (potassium hydroxide). Microscopical details are left to the very end when they are needed (e.g. for Caloplaca cerinella and C. cerinelloides). Thumb-nail marginal illustrations of structural features and British distribution maps are provided throughout and both are useful aids.
To help the less experienced lichenologist the book offers a sound introduction to the biology and ecology of lichens and a good explanation of the structural features, an understanding of which is necessary for identification. A short glossary is also provided. It offers three alternative methods of identification: 128 photographs, species characteristics set out in tabular form and the main key which seems very workable.
For the more experienced ecologist the key has the advantage of going directly to species level without having to determine the genus first. Thus species in different genera which have similar field characteristics are grouped in the same area of the key. This proved most useful to me for identifying sorediate crusts.
Any user should be aware of the major weaknesses of this key which are ones shared with all books of this type. The user finds a species name but has no description to confirm the determination. Although there are some photographs, errors will be expected and users are encouraged to use other sources to check identifications. With only the commoner species being dealt with, such confirmation could help to avoid rarer species, and those appearing similar, being misidentified. This book is also recommended as an example to any lichenologist planning to prepare their own identification guides for their country or region to help amateurs and ecologists.