356 BOTANICAL GAZETTE [may 



ductivity in certain soils is due to the presence of toxic organic com- 

 pounds. 7 The beneficial effect of oxidation in such soils may be 

 inferred from the results of thorough tillage, involving sub-drainage 

 and cultivation, since these operations promote aeration of the soil 

 with subsequent increase in growth of roots and microorganisms. 

 Under such conditions experience has shown that the organic sub- 

 stances in the soil are most completely converted into substances 

 commonly known as humus. It is certain that the oxidizing activ- 

 ities of the soil and plant play a significant part in this important 

 process. 



PREVIOUS WORK 



The existence of an oxidation process in soils has long been 

 known. Without apparently understanding the precise cause of 

 this phenomenon, Liebig pointed out its importance for productive 

 soils, and, according to the same author, the phenomenon had been 

 earlier investigated by Ingenhouss and De Saussure. Among 

 the more modern investigations on the processes of oxidation in 

 soils the works of Deherain and Demoussy, 8 Wollny, 9 Russell, 10 

 and Darbishire and Russell 11 should be mentioned. These 

 investigations are all along the line of bacterial activities in the soils. 

 Recent studies by Konig, 12 however, furnish evidence of a catalytic 



me 



The literature dealing with the oxidizing power of plant jmce> 

 is already voluminous. Within recent years, our knowledge o 

 processes going on within the plant has been greatly extended by t e 



. , 1 ... c:„^ cpvcra 



studies which have been made upon oxidizing enzymes. Since se\ 

 comprehensive and instructive summaries of work on this su jec 

 have appeared, among which may be mentioned those of Bach a 

 of Czapek's Biochemie, it is unnecessary in the present paper toreut a 

 what has been done in this rapidly developing field. 



7 Jour. Amer. Chem. Soc. 30:1295, 1599. 1908. Bur. Soils, U. S. Dept - 

 Bulls. 36, 40, 53. 



1897. 



s Annales Agron. 22:305. 1896. 



9 Die Zersetzung der organischen Stoffe und die Humusbildung. 



Heidelberg 



10 Jour. Agr. Sci. 1 : 2 6i. 1905. 

 "Jour. Agr. Sci. 2:305. 1907. 

 13 Landw. Versuchsst. 63:471. 1906; 66:401. 1907 



