AGRICULTURAL EXPERIMENT STATION. 115 



to interfere with the experiments so far as is known. After 

 thirty-six hours the results were noted as follows : 



First row, one and one-half teaspooufuls to 2 gallons water, 

 nearly all the insects killed. 



Second row, one teaspoonful to 2 gallons water, same as first, 

 so far as one could perceive. 



Third row, one-half teaspoonful to 2 gallons water, perhaps 

 one-half the beetles dead. 



Fourth row, one-fourth teaspoonful to 2 gallons water, could 

 only find an occasional one dead. 



Tbe leaves were not scorched in any of the rows. 



From these experiments we see that one teaspoonful of Paris 

 Green to 2 gallons of water, or at the rate of 1 pound to 112 

 gallons, did as effectual work as the stronger mixture, while the 

 lesser amounts were not sufficient. This is perhaps as good a 

 rule as can be given, and the amount may be varied more or less, 

 if the strength of the Paris Green is found to vary. 



CAUSES OF POTATO SCAB. 



Since my last Report some very important investigations into 

 the cause of Potato Scab have been made at the Indiana Experi- 

 ment Station by Mr. H. L. Bolley and at the Connecticut Station 

 by Dr. Roland Thaxter. Though there were differences of opinion, 

 botanists had about concluded that this disease was due to chemi- 

 cal or mechanical conditions and not to a vegetable or animal par- 

 asite, but the investigations of these gentlemen have opened the 

 question anew. They claim to have discovered specific forms of 

 organisms that will when introduced into healthy potato tubers 

 produce the scab, and wherever the disease occurs these organ- 

 isms are present. It is exceedingly interesting to know that the 

 species of bacterium found by Mr. Bolley, and regarded by him as 

 the cause of the disease, is entirely different from the filamentous 

 fungus found by Dr. Thaxter. It is reasonable to conclude as is 

 done by Dr. Thaxter that there are two kinds of Potato Scab, 

 the organism studied by Mr. Bolley producing what is called 

 shallow or surface scab and the one found by Dr. Thaxter 

 causing the deep scab. The investigations of these gentlemen 

 seem so thorough it is hard to find any errors in their work and 

 the conclusions reached seem inevitable. Now that the parasitic 



