302 THE PARASITIC DISEASES OF PLANTS. 
tissues to become much softened, thus producing the soft rots, or thi 
may fail to cause this softening but injure them in other ways, so th 
the plant does not rot but becomes filled with bacteria and the tissu 
are much injured. These are sometimes called Bacterioses. 
The Tumor Diseases. In these cases the bacteria cause the form 
tion of unusual growths, tubercles, or tumors, on the various parts 
the plants. 
The Wilts. The black rot of cabbage belongs to this class ai 
is really not a "rot," but a wilt. In addition, three others will 1 
briefly described. 
Brown Rot of Potato, Egg Plant and Tomato (B. solanacearum) .- 
Although frequently called a rot, this disease is really a wilt. It is 
widely distributed disease of the potato, especially in the northe 
part of United States and Canada. The leaves of the attacked pla 
first wilt and shrivel and then the stem turns brown or black. T 
affection extends down the vascular bundles and may reach t 
tuber. In this it spreads through the vascular bundles, causing 
time a destruction of the potato that has given to it the name 
brown rot. The bundles are found to be filled with bacteria 
great numbers, that destroy the cell walls, finally causing the coi 
plete disintegration of these tissues. The isolation of the bacteriu 
is easy and inoculation experiments show that it is capable of pr 
ducing the same disease in various members of the potato fami] 
The bacterium appears to be carried from plant to plant by insec 
and the potato beetle is an important agent in its distribution. 
The term potato rot is applied to any form of disease that 
followed by the rotting of the potato. There are several differe 
parasites that produce this phenomenon, some of them belongi] 
to the higher fungoid types. It is thought that this bacterial disea 
is the cause of the larger part of the rots in our Northern States, 
second bacterial rot of the potato is caused by a bacterium nam< 
B. solanisaprus (Har.). It is also a wilt rather than a rot, as ^ 
have used the terms, although after it affects the tuber itself it pr 
duces a general decay of the tissues. It is common in Canad 
where it was first described. A third bacterial potato rot is causi 
by B. atrosepticus (VanHall). 
