This well known book deals with a number of diseases chosen from different fields of plant pathology which are of importance in the U.S.A. It provides the reader with basic facts, the scientific foundation for a further discussion on general principles, such as found in the second part of the book in the chapters on the relation of environment to disease development and host-parasite interactions. In the introduction the author explains how difficult it is to define between a normal and a diseased plant in its physiological development, thus emphasizing the dynamic character of a disease.