330 



Journal of Agricultural Research 



Vol. XVI, No. 12 



SOIL INOCULATED WITH A MIXTURE OF THE THREE ORGANISMS 



Table XIII contains the data obtained as the result of inoculating 

 sterilized manured soil with a mixture of the three organisms. In 

 Experiment I all of the organisms were inoculated , in approximately 

 equal numbers. It is a noteworthy fact that while Ps. fluorescens and 

 Ps. caudatus showed rapid development and were always present in 

 large numbers, B. cereus never developed upon the plates and showed 

 a very rapid decrease in the number of vegetative cells present in the 

 smears examined under the microscope. 



Table XIII. — Ammonia produced by a mixture of B. cereus and the two non-spore 

 formers inoculated into sterile manured soil 



o Computed from the number of organisms in the infusion used for inoculation. 



Despite the very evident fact that B. cereus was not active in the sam- 

 ples tested, the amount of ammonia produced was quite m.arked. This 

 was a strong indication that the ammonia produced was due to the 

 activity of the only other organisms present, Ps. fluorescens and Ps. 

 caudatus. In Experiment II the organisms were inoculated in the 

 proportion of i individual of Ps. fluorescens to 8 of Ps. caudatus to 33 of 

 B. cereus. Even with such a favorable start as this, B. cereus again failed 

 to develop on the plates and showed a rapid decrease in the number of 

 vegetative cells present. The degree of ammonification was marked 

 also in this series. 



Throughout the entire series of ammonification experiments a cor- 

 relation seemed to exist between the time that had elapsed since the 



