DISEASES DUE TO BACTERIA 131 
the seed-bed suggests that the seed from infected fruit 
may also be infected or carry the causal organism 
externally, though so far, no actual proof of this has been 
obtained. Observations in nurseries and large scale 
experiments have shown that the disease may sometimes 
spread downwards; successful ‘“ prick” inoculations 
have been made on the upper parts of plants and indicate 
that insects may produce infection of these parts. It is 
also fairly certain that the pruning knife is a potent 
factor in spreading the disease. In one house it was 
observed that this disease had spread from one end on both 
sides of the house, while in another it had spread a certain 
distance down one side only. In the former case it was 
found that the pruning had been across the house from 
left to right, while in the latter the pruning had been 
down one side and up the other. 
Symptoms of the Disease.-—The stem of an attacked 
plant shows the earliest symptoms of disease as light or 
dark brown to black, sunken patches of irregular shape, 
varying from small spots to long furrows and “ blazes.” 
The blazes are often three or more inches long, and 
frequently extend over the entire length of an internode, 
In slight cases these markings occur intermittently along 
the stem, while in bad cases the typical furrows can be 
found throughout the whole length of the stem and on 
the leaf and truss stalks. 
On the leaf the disease first appears as yellow blotches 
near the mid-rib and the main veins. Later, these turn 
brown and extend so that finally the greater part of the 
surface becomes browned and much distorted by the 
shrivelling of the diseased areas. 
The fruits show light or dark brown sunken patches 
with round or irregular outline. They vary from a 
few spots developed near the calyx to many scattered 
promiscuously over the surface of the fruit. They 
greatly reduce the market value, and in bad cases the 
fruit is rendered quite unsaleable, being almost covered 
with these pock-like depressions. 
