78 Report OF THE BACTERIOLOGIST. 
exceptional cases many of the plants in a seed bed are infected 
with P. campestris. In the absence of more direct observation, a 
discussion of the method of entrance of the germs to the plants 
in the seed bed has little value. 
A second danger which probably is more important lies in the 
infection of the soil. By the act of transplanting, many of the 
plant roots are broken, exposing the cut ends of the fibro-vascu- 
lar bundles. Some growers regularly break the ends from the tap 
roots when they are not accidentally removed. At this time if 
P. campestris is in the soil either of the seed bed or the field it has 
an opportunity to enter these broken bundles. Field observa- 
tions have shown that infection through the roots is not infre- 
quent. If the conditions are such as to favor an outbreak these 
root-infected plants quickly become a total loss and act as cen- 
ters for spreading the disease in the field. 
The disinfection of cabbage seed, like the treatment of seed 
potatoes, is intended to prevent the spread of the disease organ- 
isms. When such treated seed is planted or the plants set in 
infected soil the treatment will have little value. 
It is not expected that seed disinfection will give complete pro- 
tection against black rot. In many cases the benefit may be very 
small. But as the treatment costs nothing except a little bother, 
and no other remedy is known, it is certainly advisable to disin- 
fect the seed and thereby avoid unnecessary risk. 
