170 The Philippine Journal of Science 1921 
haustive experiments have been carried on with a planting 
exclusively of such a slightly susceptible host. 
6. In a district or region in which the extremely suscep- 
tible varieties such as the limes and grapefruits constitute the 
important, commercial orchards, either complete eradication of 
the affected host plants or substitution of less susceptible hosts 
is apparently the only means of preventing severe losses from 
this disease. From the results presented in this paper such 
is not the case, however, with the less susceptible species. 
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