10 



The same method was also followed in regard to the blight 

 of quince and apple trees, and also with the conifera, and in 

 all cases the inoculated leaves took the disease. 



I then tried to determine, if possible, whether or not the 

 bacteria causing the blight in the pear tree would, if inocu- 

 lated into the quince or apple tree, give the blight to those 

 trees ; and whether or not the bacterium of the quince tree 

 blight would cause the blight in the pear or apple tree; and 

 also the bacteria of the apple tree blight cause the disease in 

 the pear or quince trees. To determine this I cross inocu- 

 lated many leaves of the different fruit trees with the blight 

 bacteria from the other kinds of fruit trees, and in no case 

 was I able to produce the blight, except by the inoculation 

 of the bacteria obtained from the blight of the particular 

 kind of tree inoculated. It thus appears that each kind of 

 fruit tree, at least so far as pear, quince and apple are con- 

 cerned, has its special species of bacteria that produce the 

 blight in that tree, and that this species of bacteria will not 

 produce blight in the other kinds of fruit trees. 



It should be mentioned, here, however, that I was able to 

 produce blight in three different species of conifereus trees 

 by the inoculation of the blight bacteria obtained from but 

 one species of tree. 



REMEDIES, 



From the above it is readily seen that, since the cause of 

 the blight is a minute plant — bacterium — that feeds upon and 

 lives, grows and multiplies within the tissues of its host 

 plant, that we can not reach the micro-organisms that are 

 thus internal parasites, and kill them by the application of 

 any substances to the tree in the form of a spray, as we can 

 do for many fungoid diseases. We would kill the tree before 

 the bacteria could be reached and affected. Hence the only 

 means of combatting this disease blight at present known, is 

 the cutting off of the affected portion far below the external 



