Relation to Deleterious Chemical Agents 449 



being directed toward a solution of the problems of in- 

 fertility. 



274. Relative toxicity of some organic compounds. 

 In the table below are given some of the interesting results 

 obtained by Schreiner and Reed respecting the effects of 

 various organic compounds upon wheat placed in water 

 cultures from 7 to 10 days ; the concentrations indicated 

 are in parts per million (p.p.m.) in distilled water : 



Among twenty-two nitrogen-containing compounds, two 

 were found which were injurious at the surprisingly low 

 concentration of less than 10 p.p.m. In the above ex- 

 periments water cultures were employed; but tests by 

 Bonns in my laboratory have shown that wheat in paraf- 

 fined pots containing rich garden loam is practically un- 

 affected by pyridine at the enormous rate of 8000 p.p.m., 

 this solution being used to moisten the soil to 60 per cent 

 of its water-holding capacity. If this relationship should 

 2o 



