MILDEW (O. Eng. meledéaw or mildeaw, explained as “mealdew,” cf. Ger. Mehlthau, with more probability, as “honeydew,” Goth, melith, honey, cf. Lat. mel, Gr. μέλι), a popular name given to various minute fungi from their appearance, and from the sudden, dew-like manner of their occurrence. Like many other popular names of plants, it is used to denote different species which possess very small botanical affinity. The term is applied, not only to species belonging to various systematic groups, but also to such as follow different modes of life. The corn-mildew, the hop-mildew and the vine-mildew are, for example, parasitic upon living plants, and the mildews of damp linen and of paper are saprophytes (Gr. σαπρός, rotten), that is, they subsist on matter which is already dead. As regards mildews in general, the conditions of life and growth are mainly suitable nutrition and dampness accompanied by a high temperature. The life history of the same species of mildew frequently covers two or more generations, and these are often passed on hosts of different kinds. In some cases again the same generation confines its attack to the same kind of host, while in others the same generation grows on various hosts (see Fungi; Hop; and Wheat).