conspectus: period of greatest susceptibility 9 



tissues in late summer and autumn, the disease is checked and 

 disappears, or remains as a slow canker to appear again on other 

 parts the following spring. It is a very instructive experiment 

 to see, for example, inoculations of Bacillus amylovorus on ripen- 



Fig. 3. — Mango leaves show- Fig. 4. — West Indian coconut bud- 



ing bacterial spots. Specimens rot. The reflexed persistent dead fronds are 



received from South Africa. typical. {After John R. Johnston.) 

 {Courtesy of Miss Doidge.) 



ing fruits and shoots of the pear wholly fail toward the end 

 of summer, which were eminently successful on the same trees 

 at its beginning. The difference in this case is not due to 

 lessened virulence on the part of the organism, but to changes 

 in the host-plant, making it non-susceptible. Similar changes 



