126 THE NEW HORTICULTURE. 



that there is a most marked similarity between the diseases of 

 man and trees. We have the quick and fatal work of the 

 cholera germs duplicated in the blight; the slow, insidious 

 method of consumption in the yellows, while the black-knot 

 and root-rot furnish an excellent counterpart to the various 

 forms of scrofula. 



Now, then, admitting that the germs are already in the 

 human blood, if we can show how a like condition probably 

 exists in the sap of all trees, the problem of blight, yellows, 

 black-knot and root-rot will be solved, provided we can show 

 how the conditions for their development can be prevented. 

 However, I do not mean to say that, while the bacteria are 

 already in the sap, they may not also be in the atmosphere, 

 and in epidemics of blight or yellows, for instance, very 

 greatly aggravate the attack. 



Now, then, for the proof that all pear trees, for instance, 

 are probably infected with the bacteria of blight. It will be 

 no valid objection to say that if so, the microscope would 

 show it, for the quantity of sap exposed beneath a powerful 

 instrument is so exceedingly small that while the bacteria in 

 the sap of a badly diseased tree might be seen, they could 

 easily exist in that of an apparently healthy tree in numbers 

 that would escape detection. 



Remember, then, that when the first outbreaks of blight 

 occurred at several points in New England and the eastern 

 states, and admitting, for argument's sake, that the attacks 

 were strictly external, fruit culture there, as a science, was far 

 in advance of the balance of the country, nurseries much 

 larger, as well as more numerous, and orchards more exten- 

 sive, we see how easily and rapidly the bacteria of blight must 

 have spread. Every breeze bore them by millions, not only 

 in the air, but in the pollen of infected trees, to other trees in 

 bloom, or dropped them on surfaces cut or wounded by the 

 hoe or plow. Every insect and bee carried them for miles 

 around. The busy woodpecker and sapsucker took them on 

 their bills from diseased trees and drilled them into healthy 

 ones, whence buds and cuttings carried them to the nurseries. 

 Once there, dissemination, of course, took a wider range, until 



