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 CruciJ era. 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 
