Water is the solvent for metabolic processes, it participates directly in many biochemical reactions and has a vital skeletal function. It also plays a key role in the behaviour and spread of fungi. The chapters of this book, which was originally published in 1986, give a broad perspective on this vast subject. The contributions were all written by acknowledged experts in their field, and subjects of great practical importance are discussed. The bio-deterioration of plant products, such as foodstuffs, grain and timber, the relationship between weather patterns and the likelihood of disease epidemics and the characteristics of pathogenic and mycorrhizal fungi, are described. Overall the book provides a physiological basis that unites the different aspects of the subject area, which had previously been studied in isolation from each other.