58 



organic, but suggest that ammonia and otlicr inorganic 

 substances may be responsible for the toxicity. They 

 also state that they could obtain no definite proof that 

 the harmful effect on germinating seeds passes off 

 after a time. Seaver and Clark (20, 21) emphasize 

 the fact that the decomposition products found in 

 heated soil may be toxic to higher plants but favorable 

 for the development of Pyronema or other moulds. 

 Schreiner and Lathrop (27) found that in steam heated 

 soils there was an increase in water soluble constituents 

 and in acidity. They seem inclined to believe that 

 the toxicity of the heated soils to plant growth is due 

 to the development of organic harmful material. John- 

 son (11) states that ammonium compounds develop in 

 heated soils and are responsible for the harmfulness 

 of the soil to green plants. The writers results do 

 not indicate whether the toxic material formed in the 

 soil used in the experiment noted above is organic or 

 inorganic. They do show, however, that the toxicity 

 has been largely destroyed by the action of micro- 

 organisms. 



The results also show that under the conditions of 

 the experiment and in the soil used microorganisms 

 have largely neutralized or destroyed the toxicity of 

 vanillin, cumarin, pyridine and quinoline. The prob- 

 able method by which this neutralization is accom- 

 plished is indicated in the following section. 



Bacteria Feeding on Vanillin, Cumarin, Pyridine and 



Quinoline. 



As there seemed no doubt but that microorganisms 

 were instrumental in destroying the toxicity of the four 

 compounds used attempts were made to isolate the 

 organisms responsible. 



Vanillin. A nutrient solution was prepared contain- 

 ing vanillin as the only source of carbon." 



To 50 cc. of this solution, after sterilization, were 

 added a few grains of soil from a vanillin treated pot 

 used in the experiments reported above. In a few days 

 the cloudy appearance of the medium showed a heavy 



This solution contained: 



NaN03 0.1 gm. 



K.HPOj 0.1 gm. 



MgSOi 0.05 gm. 



NH4CI 0.1 gm. 



KCI 0.05 gm. 



Vanillin 0.1 gm. 



H2O distilled 200 cc. 



