330 J. J. SKINNER 



in the field, 25% in the treated soil which grew garden peas in 

 the field, and 29% in the treated soil which grew string beans in 

 the field. 



Cowpeas growing in pots in the soil which grew cowpeas in 

 the field made 29% less growth in the soil treated with vanillin 

 than in the soil from the check plot. Garden peas in the soil 

 from the vanillin-garden pea field plot also made 29% less growth 

 than in soil from the check plot, and string means made 6% less 

 growth in the soil from the vanillin-string bean plot than in soil 

 from its check plot. 



The vanillin was still harmful to the respective crops six months 

 after its application, and after it had produced the same crop in 

 the field. These experiments show that vanillin persists in this 

 heavy silty clay loam soil and affects its fertility for a considerable 

 length of time. 



