Joint Convention. 197 



and over again for the same purpose, life would soon be extinct 

 through exhaustion of material. Before organic matter can be 

 made again available for plant food, it must be reduced almost to 

 its primitive elements, and this reduction is mainly effected 

 through the process of fermentation or putrefaction, in which bac- 

 teria appear to be an active and important agent. Stupendous as 

 is its work, it is an agent so minute that twenty million individ- 

 uals of this class mav be enclosed within a a-lobe small enouorh 

 to be passed through the eye of a cambric needle." 



Professor Burrill deserves much credit for his observations 

 and careful experiments, but he cannot safely assume that they 

 prove bacteria to be the cause of blight in the pear and apple 

 or of the yellows in the peach, for when he applied the virus to 

 the bark without woundini; it, and even to the tender twiijs and 

 leaves, there was no evil result, but where the bark was first in- 

 jured the disease in some instances followed. Does not this go 

 to prove that bacteria are not the cause of the disease, that they 

 cannot enter the bud leaf or bark of themselves, but depend on 

 otiier causes to prepare the way. The saliva of a mad dog on 

 unbroken skin is harmless, but apply it where the skin has been 

 injured and death ensues. When the trees were inoculated the 

 bark was injured and the fluid containing the bacteria was in- 

 serted; a fluid so poisonous that it kills all it touches when it 

 flows down the blighted tree, not by causing bacteria to 

 develop, but by burning, poisoning the tissues of bark and wood. 

 What would be the effect of this deadly infection aside from the 

 bacteria on the tender tissues of the bark? 



I do not think it proves that the bacteria are the cause of 

 blight because he found them in connection with it, or even in 

 the limb below the part visibly affected, where the limb appeared 

 to be sound. A part of a leaf, tiie tender petals of the flower, 

 or a small patch of bark becomes aft'ected or injured, and decay 

 sets in, and then bacteria develop. There are several kinds of 

 blight, or blight produced by different causes, as tender trees or 

 tender growth, frozen sap, injuring the cellular structure of the 

 tree, so that when warm weather sets in fermentation commences. 

 This is sometimes seen before the leaves appear, but usually soon 



