68 PAUL J. ANDERSON 



The principle apparently is the same in these cases as in that 

 of the blossoms covered with cement dust, i.e., lime is the toxic 

 ingredient. About the only difference between spraying the 

 flowers with these mixtures and dusting them with cement dust 

 is that in one the lime is in water while in the other it is dry. 



SUMMARY 



We may briefly summarize the results of the investigation : 



1. Dust from the cement kiln stacks settles on the vegetation 

 within a radius of two miles from the mills. 



2. This dust contains a large amount of alkaline, soluble cal- 

 cium salts. 



3. When the dust falls on the fruit blossoms some of it goes 

 into solution in the stigmatic secretions and pollen falling on the 

 stigma will not germinate. Thus the flowers will not be fertilized. 



4. Artificial germination tests show that pollen will not germi- 

 nate even in very weak solution of the dust. 



5. When the blossoms are dusted as fast as they open, only a 

 very small percentage sets fruit. 



