Lichenology in Britain is going through a buoyant phase, no doubt stimulated by the increasingly useful and high quality websites, plus increased communication enabled by yahoo-sites dedicated to lichens. Data are now widely available on the National Biodiversity Network (NBN) Gateway, and there are local groups flourishing throughout Britain, and seemingly regular work for field surveyors. But in no small way, and not just in Britain, lichenology has been boosted by the number and quality of the lichen identification books that have become available over the last 10 years: Purvis et al., (Reference Purvis, Coppins, Hawksworth, James and Moore1992) was greeted as the comprehensive volume of the day, the ‘big red Flora’. This was followed 17 years later by Smith et al. in 2009, an updated and expanded flora of 1,873 species, 1,046 pages, weighing in at 2kg. But complimentary to these tomes has been the regular production of Frank Dobson's Lichens An Illustrated Guide to the British and Irish Species. The first ‘Dobson’ came out in 1979 with 450 British lichens and black and white photos. Subsequent editions now arrive at the 6th edition, which is revised and enlarged and has full colour pictures throughout.

The latest edition has over 900 species, subspecies and varieties, and includes some of the more recent changes and additions that have been accepted subsequent to Smith et al. Reference Smith, Aptroot, Coppins, Fletcher, Gilbert, James and Wolseley2009. The book is laid out in a user-friendly way, with genera set out in alphabetical order. Each genus has a small dichotomous key to species, and often drawings to illustrate pertinent microscopic features, such as ascus tip, ascospores or paraphyses. Each species has a short description of macro- and microscopic features, and each entry has a small colour photograph and a map, showing the distribution in the British Isles. These distribution maps are more detailed than in previous editions and are a real bonus to this 6th edition; the dots on the maps are colour coded, to show three recording periods: green dots 1650–1959, black 1960–1999 and red 2000–2011. The red dots over-lie any previous records, so it is not possible to say what are new recent records, or which are re-finds from previous periods. However, the red dots do show the current state of play with the distribution of species. You will need a hand lens in order to see the detail, but no lichenologist should be without this essential tool anyway! The data are provided from the British Lichen Society, and mention is made of the NBN Gateway to access the full Lichen Database.

As well as comprehensive keys, and succinct species descriptions, there is a small selected Bibliography and a good Glossary. The diagrammatic representation of lichen zonation on rocky seashores is nicely done, but is somewhat cramped into the same page as diagrams of isidia and soralia. The Introduction section covers most of the background and supportive information necessary for beginners to get a grasp of what looking at lichens is all about: What is a lichen? Reproductive strategies, Ecology of lichens, How to study lichens, etc.

In the section under Air pollution, there is a summary relating the effects on the lichen flora resulting from recent reduction of atmospheric pollution from sulphur dioxide. This is brought up to date by describing the effects of atmospheric pollution from excessive nutrient enrichment derived from modern farming practices. A welcome new section in the 6th edition is a brief summary about lichen communities, although reference to James et al. (Reference James, Hawksworth, Rose and Seaward1977) is perhaps a bit wishful, as this volume is long out of print and very difficult to access.

To cover all the species included in this expanded edition, space is at a premium, and to some extent, clarity of the pictures is somewhat diminished by their small size. Undoubtedly, pictures are a prime source of usefulness for the book – everyone needs to “see a picture” if only to get the ‘jizz’ of what the species may look like. Some comments have been made about the quality of the pictures in edition 6, and undoubtedly, some are better than others. The main problem, however, is that the scale information (×2, ×4, etc.,) appears incorrect in some photos. For small crustose species it evidently means what one would expect, but for larger lichens such as Lobaria amplissima and L. virens, this interpretation would lead one to believe that the lichen is much smaller than it really is. Somehow, the wrong figures have been given for some photos. In Peltigera membranacea, for example, the photo states ×4, whereas the picture as printed is easily life-size. However, today, there are several sources of lichen photos easily accessible on websites, and when identifying a lichen, most people do search around for another picture, as lichens can be notoriously variable in shape and colour, such as wet and dry states, so no single picture will necessarily capture the full features.

There are a couple of lines mentioning the British Lichen Society at the end of the Selected Bibliography section, but I was perhaps looking for more enthusiastic mention of the BLS; how the Society's website would be a source of support and encouragement, and that joining the BLS would be beneficial in opening up contact with other lichenologists, especially encouraging to those just starting out in discovering lichens.

There is no question that the Dobson guides remain popular and are an invaluable aid to identifying British and Irish species. It is the book not only for beginners, but also for those with more experience. It is amazing what is tucked away in this volume which is handy enough to be used in the field; indeed, when asked if it is worth getting Dobson 6 if you already have Dobson 5, the answer from most field lichenologists would surely be “yes” as their older version will be showing drastic signs of wear and tear from being in and out of rucksacks in all weathers. That is not to say the books (paperback and hardback) are not well made and on good paper.

Dobson (or “Dobbo” as Frank's book is fondly referred to), is indispensable in so many respects and it fills a niche that is not met by any other British publication. This latest edition is compact – perhaps as compact as it is possible to be without splitting into two volumes to retain clarity – and is welcomed as an old familiar friend with added accoutrements to tempt our interest.