Fig. 4. Photograph showing the action of copper sulphate on pea plants in the 

 presence of nutrient salts. (Oct. 3rd Dec. 20th, 1912.) 



1. 



2. 



3. 

 4. 

 5. 



6. 

 7. 

 8. 

 9. 

 10. 



Control. 



1/50,000 



1/100,000 



1/250,000 



1/500,000 



1/1,000,000 



1/2,500,000 



1/5,000,000 



1/10,000,000 



1/20,000,000 



copper sulphate. 



