OTHER BACTERIAL DISEASES OF PLANTS. 301 



Cruciferae, it is a natural suggestion that a change of crop to some 

 kind of plant not in this family should be made when any particular 

 plot of ground becomes infested with the disease. The destruction of 

 all weeds of the mustard family in the vacinity of cabbage plots is 

 also to be recommended.. 



OTHER BACTERIAL DISEASES OF PLANTS. 



The illustration given will serve to show the kind of evidence 

 that is sought for in the study of plant diseases. In the list that 

 follows, demonstrative evidence has been obtained in practically all 

 cases, so that all of the diseases in this list may be accepted as caused 

 by bacteria. The list given is a long one, and if it be compared wi'h 

 the list of animal diseases given in the last chapter it will be seen to 

 surpass that list. These plant diseases have not the importance nor 

 have they developed the interest that attains to some of the animal 

 diseases, but nevertheless they are of great significance in farming 

 operations, sometimes causing very large losses. As in the case of 

 animal diseases the bacteria causing them are not confined to one 

 plant host. The black rot, for example, attacks the cabbage, the 

 cauliflower, the turnip, kale, Brussels sprouts, collards, rutabagas, 

 radish, as well as some other plants, all of the family Crucifem. So, 

 as with the other diseases, the same parasite may attack several 

 hosts. 



Classification of Bacterial Diseases. Plant diseases are less 

 clearly defined and classified than animal diseases. Popular names 

 have been applied to them without careful discrimination till the 

 popular names have ceased to have any sharp meaning. The 

 bacterial diseases may, however, be fairly well divided into three 

 types, distinguished by the kind of effect they have upon the host. 

 These are: i. The Wilts. In these the bacteria attack chiefly the 

 vascular bundles, either destroying their cells or clogging them. 

 This shuts off the ordinary water-supply to the plants and causes 

 them to wilt and wither. 2. The Bacterioses and Rots. In these 

 diseases the bacteria invade the tissues generally, not being confined to 

 the bundles, and destroy the plant cells at once. They may cause the 



