NITROGENOUS SOIL CONSTITUENTS 



53 



special effort was made to maintain absolutely sterile conditions, 

 inasmuch as this would have been a practical impossibility in 

 experiments on so large a scale involving over a thousand plants 

 in a single test. Moreover, it may even appear questionable 

 whether absolute sterility, as being too artificial a condition for 

 the determination of the effect of soil constituents on plants, 

 would be desirable. 



It would seem that chemical control under as normal conditions 

 as a cultural experiment will allow, is better than conducting 

 the experiment under the artificial condition of sterility, which, 

 after all, is made only so that biochemical changes be excluded. 

 In these experiments the bottles were sterilized before being used 

 in making culture solutions for the various changes, the pans and 

 other apparatus used in germinating the seed were sterilized 

 from time to time, and corks used for the cultures were always 

 clean and sterilized before use. Although all of these precautions 

 were taken, it was of course not possible to exclude some micro- 

 organisms in such work, as the solutions were exposed from time 

 to time to the air. There was no excessive microorganic life 

 noticeable. While bacteria and other microorganisms were pres- 

 ent in the solutions to a slight extent, it can hardly be said that 

 their influence could have been large; that is, such influence as 

 they had was probably so slight as to be negligible so far as the 

 general and larger tendencies which are shown to exist are con- 

 cerned. 



HYPOXANTHINE 



Hypoxanthine has been isolated from a number of soils, having 

 been found in 9 out of 24 soils examined for it.* It appears, 

 therefore, to be a soil constituent which will be frequently encoun- 

 tered in soil investigations. Hypoxanthine exists in some plants 

 as such, but probably arises principally in the soil as a result of 

 the changes of nucleic acids and nucleo-proteins. Its occurrence 

 among the splitting products of nucleic acid has been mentioned 

 in connection with the latter compound. In the light of the 



^ Schreiner, O. and Lathrop, E. C, The Distribution of Organic Constituents 

 in Soils, Jour. Franklin Inst. 171: 145. 1911.' 



