CHAPTER XXVI. 

 BACTERIAL DISEASES OF PLANTS. 



Bacteria, as a rule, grow best in food substances that 

 are alkaline in reaction, while other fungus plants, molds, 

 rusts, apd mildews, find most favorable conditions in an= 

 acid medium. The juices of the animal body are alka- 

 line, those of plants are usually acid. These facts have 

 been usually regarded as the explanation of the greater 

 susceptibility of plants to diseases caused by fungi other 

 than the bacteria. Very few important diseases of ani- 

 mals are produced by molds, and, conversely, few bac- 

 terial diseases of plants are of great economic importance. 

 Another reason for the greater prevalence of bacterial 

 diseases in animals is that the invasion of the animal body 

 by bacteria is made possible through the natural openings 

 of the body. The invasion of the plant tissue is more dif- 

 ficult since there are no natural openings comparable to 

 those of the animal body. 



The diseases of plants caused by rusts, mildews, smuts, 

 etc., are of the most varied nature and affect all kinds of 

 plants. Methods of prevention through the use of solu- 

 tions applied to the seed as in the treatment of oats and 

 barley with formaldehyde or hot water in order to de- 

 stroy the smut spores on the grain, or the spraying of 

 fruit trees to destroy the fungi thereon, are widely and 

 successfully used. 



A number of bacterial diseases of plants have been 

 studied. The knowledge concerning many of them is 



