53 



ninxiimiiii minibers first, followed by those in the va- 

 nillin and quinoline treated soils, Qninoline depresses 

 the nnmher of microorganisms for the longest period, 

 a period of 17 days. Its odor also persisted longest, 

 being still evident 55 days after the treatment. 



The Flora of the Plates. No complete data on the 

 tlora of the jjlates was recorded. It was noted, however, 

 that the increase in the numbers of microorganisms 

 was due chiefly to the development of bacteria and 

 not to an increase in the numbers of Actinomyces. As 

 far as the medium would allow differentiation, the 

 number of Actinomyces colonies previous to treating 

 the soil was 30-40 per plate at a dilution of 1 to 20,000 

 or about 20-30 percent of the total number of micro- 

 organisms. The number of Actinomyces colonies per 

 plate at the 1-20,000 dilution after the soil had been 

 treated with the compounds is given in Table II. Each 

 figure is the average of a count of two plates from each 

 of two duplicate pots. 



Table II. Number of Actinonujces Colonies Appearing 

 on the 1 to 20,000 Dilution Plates. 



From the data given in Table II it is evident that 

 the number of Actinomyces, both actual and relative 

 to the total number of organisms, decreased markedly 

 in the pots treated with vanillin, cumarin and quino- 

 line. In the pyridine treated pots the actual number of 

 Actinomyces increased. The bacteria, however, in the 

 pyridine treated pots increased in proportion, as is 

 indicated by the fact that the percent of Actinomyces 

 colonies did not increase decidedly. 



By comparing the figures in Table I and Table II 

 we find a more or less close correlation between the 

 lowest percentage of Actinomyces and the greatest 

 number of microorganisms. In fact, at the time of 



