200 Wisconsin State Horticultural Society. 



are about as extensive in variety as the higher order. The 

 mildew seen on old bread is one kind, the fibrous roots covering 

 and permeating old logs is another, and the rust on wheat with 

 its roots spreading over the stalk is yet another. They all must 

 have the food prepared for them, and can flourish only where 

 they thus find it accompanied with a high temperature and con- 

 siderable moisture. 



Some regard blight as the result of severe cold weather in the 

 winter. If so, our hardiest plants and trees should be affected 

 the least, and tender ones the most, which is not always the case; 

 and again blio^ht occurs where thev have no extreme cold 

 weather, and is often the lightest where and when the weather 

 has been the most severe. Still further, where the trees are in- 

 jured by the winter, their growth is feeble, while blight is always 

 connected with rapid growth. Blight is never very severe except 

 in remarkably warm and damp weather, and it is at such times 

 that grain is attacked with rust and grapes with mildew. Rust 

 and potato rot are also forms of blight, but they cannot be 

 caused by cold weather. 



Botanists and niicrosco])i6ts generally believe that these dis- 

 eases are produced by fungi, but they disagree as to whether they 

 are the primary or secondary cause and as to the method by 

 which they make their attack and get into the plant or tree. He 

 had arrived at the conclusion that the spores of the fungi germi- 

 nate in sap that has been forced through either the stomata of 

 the vegetable growth, or through wounds made in the trees, 

 whether by accident, insects or the pressure of sap circulation. 

 If the spores can germinate in a drop of water on the leaf, and 

 thus gain power to force its roots through the stomata of leaves 

 or through the bark to the sap within, it should have the power 

 to do it in all cases, but we see vines, plants and trees of the same 

 variety standing in the same row or bed, surrounded by the same 

 atmospheric conditions, that are free from mildew, rust or blight, 

 ■while others by their side are badly affected. We little under- 

 stand the power with which plants force sap from their roots to 

 their leaves. When we do we may better understand this ques- 

 tion, how blight, rust and mildew force their way into and 



