REMEDY FOR MILDEW. 215 



produces such a change in its vital action as to excite a 

 distinct form of disease, as sudden changes of temperature, 

 or of the electrical condition of the atmosphere, hot and 

 damp weather at unusual periods of the season ; also, 

 sometimes, mechanical violence. 



[NOTE. Fungi and insects have, by some, been con 

 sidered as exciting causes of disease, while others regard 

 them as resulting from previously existing disease.] 



755. Among the diseases in which parasitic plants 

 appear, or which are caused by parasitic plants, may be 

 mentioned mildew, blight or red rust, smut and ergot. 



756. The term mildew, or meal dew, is most properly 

 applied to the mould or fungous growth on the leaves 

 of trees and some forage plants, in the shape of white 

 mealy patches. 



757. But it is most commonly applied to a disease in 

 wheat and barley, also called rust. It appears in the 

 shape of small spots of dingy white, oblong in shape, 

 showing itself first on the upper side of the leaf, but soon 

 on the lower side and the stem also. The white mildew 

 attacks many species of plants, especially roses, peaches, 

 hops, vines, pease, the maple tree, &c. 



758. It is first seen as round white or yellowish mealy 

 spots, composed of very delicate creeping threads. As the 

 disease develops, these spots throw off spores or cells, 

 which attach themselves to other plants and produce 

 similar fungi or spots on them. There is no other change 

 in the appearance of this disease, and no change in color. 

 The oidium of the vine is a kind of white mildew. 



759. The simplest and most effectual remedy for this 

 is to take a lump of stone lime of two or three pounds 

 weight, and about the same quantity of sulphur. Pour 

 hot water on them, which, by the slacking of the lime, 



19* 



