57 



Table IV. Growlh of Wheat in Soil From Sterile 

 Bottles (Uid Inoeiilated Bottles. 



From the growth of the wheat phints in the untreated 

 soil from the sterile and inoculated bottles it is evident 

 that the difference between the two has largely disap- 

 peared. This is perhaps due to bacterial action in the 

 soil which came from the sterile bottle. Less marked 

 differences than are given in Table III are also noted 

 between the soil from the sterile and inoculated bottles 

 in the case of all the compounds. This is particularly 

 true of pja'idine. Comparing the growth of the wheat 

 in the treated and untreated soils it is evident, how^ever, 

 that the toxic effect of cumarin, vanillin and quinoline 

 is still present in the soil from the sterile bottles. In 

 the soil from the inoculated bottles the growth in the 

 vanillin and cumarin treated soils is as great if not 

 greater than that in the untreated. The toxic effect of 

 the quinoline has also largel}^ disappeared. It would 

 seem clear then that the microorganisms have in some 

 way neutralized the toxicity of vanillin, cumarin, pyri- 

 dine and quinoline. 



Discussion. The development of material toxic to 

 higher plants in soil which has been steam heated has 

 been observed by others. Pickering (13, 14, 15, 16) 

 observed that the germination and the growth of 

 plants is retarded in heated soils. He believes that 

 the toxic substances formed are organic in nature. 

 Pickering also found that the toxic qualities of heated 

 soils are reduced on storing them under moist aerated 

 conditions. This he believes is not due to bacterial ac- 

 tion but to chemical changes in which the action of 

 water is particularly concerned. Russel and Pether- 

 bridge (19) state that there is no evidence that the 

 active substances in steam heated soils are necessarilv 



