THE OBSERVER'S BOOK OF LICHENS K . A.
KERSHAW a n d
K.
L.
ALVIN
(.Published by F. Warne & Co. at 5/-) attractive book will be populär not only with those who find a passing interest in these most ancient plants and wish to know them by name but also with those who wish to study their curious structure and many methods of reproduction. THIS
An excellent introduction gives an account of these things without overburdening the beginner with too many scientific terms. Those that must be used are clearly defined as they occur and a brief glossary is added for reference. The numerous coloured and uncoloured illustrations enable beginners to recognise the genera and a few species of each by the naked eye or a small lens without the use of a microscope or chemical test, though these are necessary for more serious study. The Key to the Genera is easy to use, being based on visible features of the thallus and apothecium. For advanced study, not contemplated in this book, a high-powered microscope (say 400 magnification) is necessary when determination depends on the character of the spores— ranging from 0.01 mm. to 1 mm. It is also useful for small organic structures, but most readers will be content to see them in the magnified drawings that illustrate the Introduction. After all that has been written about Lichens with scientific thoroughness a simple readable book based on modern scientific knowledge was much needed, for these often tiny beautiful plants do arouse curiosity and are important since they occur in every climate and Situation throughout the world and are the soil foundation of all later Vegetation. The only thing I quarrel with is that these authors declare that this is the first attempt in this country to provide a populär introductory book on lichens. It is now 107 years since Dr. W. Lauder Lindsay said just that in his " Populär History of British Lichens " which he dedicated to the two Hookers, Sir William and Dr. Joseph. His fine lithographs are more delicately drawn than theirs and hand-coloured. He has a long and very interesting Introduction not only explaining the structure of these plants, but speaking of their distribution in time and place and their many uses ; he chose to ignore the problem of symbiosis while the Great Schwendenerian Controversy raged (see page 379). So a new populär book is needed. J.C.N.VV.