Strictly speaking, a fungicide is a material to kill a fungus - from the Latin fungus, and the Latin caedo - to kill. The object of this book is to discuss materials and techniques of delivering a killing dose to the locus of toxicity in the light of the chemistry and physiology of toxic action and\' of mechanics of application. It attempts to develop the underlying theory on which the practice is based and by which the practice may be improved. The problem of dissecting fungicidal action has been simplified by the introduction of 3 fairly new tool, t he dosage-response curve which has the property of distinguishing mechanism of action from size of dose - quality from quantity. The volume brings together the discoveries in the realm of fungicides without which the horticulture would never have become what it now is.