376 BOTANICAL GAZETTE [may 



benefit to oxidation in the residue. Judging from the growth of the 

 plants, the first portion of the distillate contained a larger proportion 

 of this deleterious substance than the second, although this smaller 

 amount appears to be just as deleterious to the oxidizing powers of 

 the roots as the larger amount present in the first portion. The 

 oxidizing power of the plants in the residue was much greater than in 

 the distillates or in the original soil extract. 



Evidently the oxidizing powers of the roots are affected by certain 

 external conditions, since an improvement in the physiological 

 properties of the soil extract results in increased oxidation, and the 

 presence of deleterious bodies results in decreased oxidation. 



From the experimental results thus far presented, it appears that 

 the oxidizing power of the soil extracts themselves can be regarded 



in the experiments. In one of the preliminary experiments reported 

 in Table I, it was shown that the soil extract after filtration through 

 a Pasteur- Chamberland filter tube exhibited some oxidation, even 

 when no plants were growing. It was likewise shown by the results 

 in Table II that certain nutrient salts dissolved in distilled water were 

 able to accomplish a material amount of oxidation without the pres- 

 ence of growing plants. It seems unlikely, therefore, that any con- 

 siderable amount of oxidation was performed by microorganisms, 

 we consider the result in this last experiment, where oxidation was 

 increased in the residue from distillation after continued bolhng ^ 

 seems that any extensive action, not only of microorganisms, but a s 

 of enzymes, must be precluded. In the soil, however, it is quite pro^ 

 able that both of these oxidizing factors would come into play, 

 it is quite certain that the oxidizing power of the roots would acco 

 plish a considerable portion of the oxidation observed. 



ENZYMES 



« _ ucc _ . preceding pages of the enzootic 



nature of the oxidizing action of the roots and consideration wi 



Mentio 



about 



be given to the nature of the enzyme or enzymes which bring^ ^^ 

 the oxidation. So far as known, "the oxidation effects obser ^ tivities 

 entirely due to the action of enzymes and not to the other a 

 connected with the growth of the roots themselves. 



