THE FUNGOID DISEASES OF PLANTS. 295 



plenty of moisture within so that it is no longer dependent upon the 

 weather. 



The effects produced by these fungi growing in the plant tissues 

 are extremely varied. Any part of the plant may be affected, some 

 diseases showing in one place and others elsewhere. The leaf may 

 become covered with spots of various colors, or it may wilt, or 

 roll up or drop off. Scabs may grow on the plant or its fruit, or the 

 whole may show signs of rotting. Plant diseases have received 

 various popular names that are loosely applied and not very clear 

 in their meaning. The more common descriptive names are the 

 following : 



Wilts are characterized by the wilting and withering of the plant. 



Rots are characterized by a tendency of the plant tissue to 

 soften and decay. 



Smuts show a mass of black or blackish spores. 



Mildews show a whitish, powdery growth over the surface of the 

 host. 



Rusts show spots of a reddish color, due to reddish-yellow 

 spores. 



Anthracnose is a name frequently applied to diseases causing 

 spots on the leaves or elsewhere. 



Blight is a term with no definite meaning, but is generally ap- 

 plied to almost anything that causes a general wilting and destruc- 

 tion of the plant. 



These terms are all in a measure descriptive terms of the effects 

 produced by the parasites on the host. None of them are specific 

 diseases, but all are produced by many different parasites on many 

 different hosts, and in some cases the same parasite may produce 

 different types of disease at different stages of its life. 



Methods of Combating Fungoid Diseases. There are 

 several general methods by which these diseases may be kept in 

 check: i. By the selection of resistant varieties of the /cultivated 

 plants. Experience has shown that some varieties yield readily to 

 the parasites while others are highly resistant. A careful selection 

 of the varieties, guided by experience, is sometimes of value in 

 checking disease. 2. By regulating the conditions of the cultivated 



