PEACH AND THE PEAR. 279 



their home in one or more branches and here cause a 

 very boiling- of the sap. Blight was absent, or very rare, 

 on the Peninsula until we commenced to crowd in Pear 

 trees, and then, just as with human beings, the minute 

 they were crowded, zymotic diseases (bacterial, or fer- 

 mentative diseases) appeared, and here is a decided proof 

 of its germ origin. If we starve trees we may get blight, 

 just as when we crowd and starve numbers of human 

 beings, we have typhus fever, measles, typhoid fever, 

 and other zymotic diseases, breaking out among them. 

 If we over-feed trees, we may get blight just as we get 

 cholera, or, cholera morbus, at least, in man. In seasons 

 of changing temperature, of thunder storms, of very 

 sudden changes from heat to cold, and vice versa, we 

 know pear-blight thrives, and under just such circum- 

 stances, we know bacteria increase and multiply, and all 

 this is an evidence to me of the bacterial origin of this 

 curse on the Pear tree. The peculiar bacterium which 

 causes blight has been claimed to have been found by 

 Prof T. J. Burrill of the Illinois Industrial University. 

 He calls it the ''Micrococcus Amylonovus" and gives 

 some description of it which I have not at hand. 

 Now given the peculiar germ that causes the trouble, 

 the next point is to experiment practically with it. 

 These germs can all be increased indefinitely in 

 number by artificial culture, in such menstrua as 

 beef-tea and gelatinized solutions and such, and they 



