Dr. John W. Thomson is one of the world's leading authorities on temperate and arctic lichens of the New World. He has completed the second volume of his monographic series "American Arctic Lichens", in which he provides the most comprehensive treatment to date on microlichens. The monograph provides illustrations, descriptions, diagnoses, distributional data, and identification keys for 624 species in 104 genera. The proposed monograph will be an invaluable tool for research, training, and environmental study of arctic lichens. Ecologists, botanists, and ecosystem scientists will depend on this volume for accurate field identifications. New and fruitful research projects will be stimulated by its publication.