324 



Journal of Agricultural Research 



Vol. XVI, No. 12 



added to the flasks containing 150 gms. of sterile manured soil. These 

 flasks were then incubated at room temperature and plates and smears 

 made from them at regular intervals. In Experiment I, Table VII, the 

 ratio between the numbers of organisms of Ps. fluorescens, Ps. caudatus ,a.nd 

 B. cereus was i to i to i ; in Experiment II the ratio was i to 8 to 33; in 

 Experiment III the ratio was i to 7 to 33. Although B. cereus was as 

 abundant as the other organisms in Experiment' I and was much more 

 numerous than they in the later experiments, it failed to appear upon 

 any of the plates poured. The non-spore-forming organism.s multiplied 

 very rapidly, and in Experiment II, Ps. fluorescens developed from an 

 initial count of 30,000 to a maximum count of 560,000,000 on the third 

 day, an increase of over 18,500 times its count at the time of inoculation. 

 In the same experiment Ps. caudatus developed from an initial count of 

 180,000 to a maximum count of 1,190,000,000 on the seventh day, an 

 increase of 6,600 times its count at the time of inoculation. The micro- 

 scopic examination of the smears made during this series of experiments 

 showed that the vegetative cells of B. cereus rapidly decreased in numbers 

 and in a few days the organism could be identified only in the spore form, 

 while the non-spore formers, especially Ps. caudatus, showed a steady 

 increase in numbers for several days. 



Table Y I. —Multiplication of non-spore formers inoculated into sterile manured soil 

 [Count indicates numbers per gram of soil] 



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

 b No microscopic count made. 



