CHAPTER XXVII 

 BACTERIAL DISEASES OF PLANTS 



The most important transmissible diseases of animals are 

 those caused by bacteria rather than by the other groups 

 of microorganisms such as molds and yeasts, while in the 

 plant kingdom the reverse is true. The molds are by na- 

 ture better fitted to penetrate into the tissues of the plant 

 than are the bacteria. 



Just as the increased commerce in animals has hastened 

 and accentuated the spread of the transmissible diseases of 

 animals, the increased sale of seeds and plants of all kinds 

 and their shipment from one part of the country to another 

 has led to the rapid spread of both bacterial and fungus 

 plant diseases. At the present time about forty bacterial 

 diseases of plants have been described. A few are wide- 

 spread and are certain to come to the notice of every one 

 engaged in farming, and are of great economic importance. 



The bacterial diseases of plants may be divided into four 

 classes, depending on the manner in which they affect the 

 plant: the blights, the rots, the wilts, and the galls. In 

 the first the tissue is killed by the organism, but it is not 

 decomposed as in the rots, in which the tissue is not only 

 killed but decomposed; while in the wilts the passage of 

 water to some portion of the plant is interfered with, and 

 hence death of the affected tissues soon ensues. 



The complicated questions that arise in connection with 

 the immunity against bacterial diseases of animals do not 

 occur in the bacterial diseases of plants. There is a differ- 

 ence in the susceptibility of different plants to the same 



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