100 Wisconsin State Horticultural Society. 



poisonous fluid that oozes out of the diseased part, so deadly that, 

 as it runs down the tree, it turns bark and Wood as black as a 

 coal, completely destroying the cellular structure of every part it 

 touches. This virus is found in the fluid containing the bacteria 

 which is used to inoculate with. It cannot be separated from 

 them, and though diluted in its form, it must retain more or less 

 of its deadly power. It seems much more reasonable to suppose 

 that the result produced comes from the poison thus brought into 

 contact with the starch germs of the inoculated tree, developing 

 the same acid fermentation as in the tree from which it was taken, 

 and thus the bacteria have the conditions favoring their rapid 

 development. 



To adjust the magnitude and rapidity of the results often seen 

 to the cause, the Professor attributes it to the gradual weaken- 

 ing of the vigor of the trees by the slow but long continued 

 destruction of the starch germs by the bacteria. The disease is 

 there, but the effect is not seen, until a trying climatic change 

 occurs, when it is suddenly produced. Then it would seem that 

 trees weakened from other causes would be the most subject to 

 blight, instead of trees of the greatest constitutional vigor (as our 

 crabs), and at a time too, when their growth is the most rapid 

 and vigorous. On the other hand, if it is a disease of the circu- 

 lation, induced mainly by climatic conditions, as some think, it 

 would seem most natural and most reasonable that this class of 

 trees would be most affected, and at this very time, for in no other 

 trees and at no other time is there so great a disturbance or dis- 

 arrangement of natural conditions. Blight is sometimes seen un- 

 der other circumstances, but is much the most prevalent when the 

 wood-growth is very rapid, where the heat and moisture are op- 

 pressive. The cells are then crowded with sap, the excessive 

 moisture in the atmosphere checks evaporation, the diluted sap 

 remains stagnant in leaf and limb, and fermentation sets in, which 

 soon destroys the starch getms in the cells — a condition of things 

 which is seen in other forms of vegetable and animal life to 

 attract and favor the development of parasites and minute forms 

 of lower organic life. 



It may be objected that this is simply a theory, lacking proof, 



