56 



produces a decided increase in the growth of wheat. 

 Explanations for this effect based on increased plant 

 food produced by bacterial action might be offered. 

 The appearance of the roots of the plants, however, 

 make it evident that the steam heating of the soil had 

 produced toxic material and that the inoculation had 

 caused its disappearance, or nullified its effect. 



Inoculation has also markedly improved the growth 

 ■of the plants in pyridine, quinoline, vanillin, and cu- 

 marin treated soils. The production of toxic condi- 

 tions in the steamed soil makes it more difficult to de- 

 termme whether the improved growth in these cases 

 is caused by the action of the microorganisms on the 

 toxic material produced by steaming or b}^ their action 

 on the compounds. The fact, however, that the toxic 

 effect of the compounds is evident on the germination 

 (cumarin and pja^dinc) and on the growth (cumarin, 

 pyridine and vanillin) in the sterile soil while in the 

 inoculated soils this effect has disappeared almost com- 

 pletely in the case of pyridine and vanillin, and very 

 largely in the case of cumarin would lead us to believe 

 /that microorganisms had acted on the cumarin, va- 

 nillin and pyridine. This is also substantiated by the 

 fact that no odor of pyridine, cumarin nor vanillin 

 remained in the soil removed from those bottles which 

 Avere inoculated while it was still present strongly in 

 the sterile bottles. The case of quinoline may be con- 

 sidered doubtful. The odor of quinoline still clung to 

 the soil in both sterile and inoculated bottles. 



That microorganisms have neutralized the toxicity 

 of the vanillin, cumarin and pjTidine and also acted 

 on the quinoline is shown more clearly by the follow- 

 ing: 



The soil removed from the bottles was dried for four 

 days. It was then placed in tumblers and brought to 

 a uniform water content. The soil from each bottle 

 filled two tumblers. Ten wheat seeds were planted in 

 each tumbler and allowed to grow for 11 days. Of 

 course, the soil from all the bottles, both sterile and 

 inoculated, was inoculated by the handling. The re- 

 sults are given in table IV; in Plate I, figures 2 and 3, 

 .and in Plate II, figures 4, 5 and 6. 



