Fig. 16. Photograph showing the action of boric acid on pea plants in the presence 

 of nutrient salts. (Sept. 30th Dec. 20th, 1912.) 



Control. 



1/5,000 



1/10,000 



1/25,000 



1/50,000 



1/100,000 



1/250,000 



1/500,000 



1/1,000,000 



boric acid. 



