58 



OSWALD SCHREINER AND J. J. SKINNER 



solutions is considered, it is found that in the presence of hypo- 

 xanthine the nitrate is greatly conserved ; that is, much less nitrate 

 is consumed by the plant in the presence of hypoxanthine. 



The amount of phosphate removed from the solutions of the 

 normal set was 330.1 mgms. and from the hypoxanthine set 361.2, 

 indicating a slightly greater phosphate requirement by the larger 

 plants. 



The amount of potash removed from the solutions of the nor- 

 mal set was 603.1 mgms. and from the hypoxanthine set 521.1 

 mgms., indicating a somewhat decreased potash absorption 

 amounting to 82 mgms. 



•The amount of nitrate consumed in the normal cultures was 

 450.1 mgms. and in the hypoxanthine cultures 247.6 mgms. This 

 shows a decreased consumption of nitrates amounting to 202.5 

 mgms. by the cultures growing in the presence of hypoxanthine, 

 although as shown above, an increased growth took place. Ni- 

 trate, nitrite, and ammonia were tested for in the hypoxanthine 

 cultures, similar to that in the nucleic acid experiments, and 

 there was no decomposition of the compound. It is obvious that 

 the hypoxanthine is able to replace the effect of nitrate in pro- 

 ducing growth. 



XANTHINE 



Xanthine, closely related to hypoxanthine, has likewise been 

 isolated and identified as a soil constituent.^ While it has not 

 been found as frequently as hypoxanthine, it appears neverthe- 

 less to be a frequent constituent of soils and in several cases has 

 been identified in the same soils in which hypoxanthine occurred. 



Xanthine occurs as such in a number of plants, as well as in 

 animal substances. It has been found in yellow lupines, sprouts 

 of tea leaves and no doubt further investigation will disclose its 

 presence in many other plants. While it may get into the soil 

 from these sources, it is more probable that the most constant 

 source of this soil constituent, like the other purine bases, is in 

 the decomposition of nucleic acids and nucleo-proteins in the soil. 



' Schreiner, 0. and Shorey, E. C, Pyrimidine Deriviitivcs and Purine Bases 

 in Soils. Jour. Biol. Chem. 8: 385. 1910. 



