326 THE PARASITIC DISEASES OF PLANTS 
filled with bacteria in great numbers, that destroy the cell walls, 
finally causing the complete disintegration of these tissues. The 
isolation of the bacterium is easy and inoculation experiments 
show that it is capable of producing the same disease in various 
members of the potato family. The bacterlum appears to be 
carried from plant to plant by insects, and the potato beetle is 
an important agent in its distribution. 
The term potato rot is applied to any form of disease that is 
followed by the rotting of the potato. There are several different 
parasites that produce this phenomenon, some of them belonging 
to the higher fungi. It is thought that this bacterial disease is 
the cause of the larger part of the rots in our Northern States. A 
second bacterial rot of the potato is caused by a bacterium named 
B. solanisaprus (Har.). It is also a wilt rather than a rot, as we 
have used the terms, although after it affects the tuber itself it 
produces a general decay of the tissues. It is common in Canada, 
where it was first described. A third bacterial potato rot is caused 
by B. atrosepticus (Van Hall). 
It is important to note that the bacterium that causes the 
brown rot of the potato can also live as a parasite in the tobacco 
plant where it produces what is known as the Granville wilt. 
The Wilt Disease of the Gourd Family (B. tracheiphilus, Sm.) — 
This bacterium attacks various members of the gourd family, 
being best known in the cucumbers, muskmelons, pumpkins, and 
squashes. The bacterium that produces it will grow readily in 
laboratory media and invariably produces the disease when it is 
inoculated into healthy plants. It causes the wilting of the plant 
by clogging up its vascular ducts. The bacteria appear to be 
distributed by insects which inoculate the plant, chiefly on the 
leaves, by puncturing or by eating holes in them. The cucumber 
beetle and the squash bug are especial offenders in this respect, 
and anything that will keep these insects in check will help to 
reduce the troubles from the disease. 
The Corn Wilt (Pseudomonas stewarti)—This disease affects 
