128 



this assumption the effect of the addition of vanillin to 

 this soil on the number of microorganisms in it was 

 determined. 



Effect of the Addition of Vanillin to the Arlington 



Soil on the Number of Microorganisms 



Developing in It 



As was pointed out in a previous publication (6) the 

 addition of vanillin in suitable concentration to a soil 

 in which the vanillin-destroying bacteria are present 

 and are under conditions which allow them to act pro- 

 duces an initial decrease in the number of microorgan- 

 isms present which wdll develop on Brown's albumen 

 agar (1). This decrease is followed by a marked tempo- 

 rary increase in the number as the vanillin-destroying 

 bacteria feed on the vanillin and multiply. With the ex- 

 haustion of the vanillin and its decomposition products 

 the number of microorganisms returns to normal. By 

 studying, therefore, the effect of vanillin on the number 

 of microorganisms in the Arlington soil it was hoped 

 that an indication might be found as to whether the 

 conditions in that soil are suitable for their action on 

 vanillin. 



Dr.Oswald Schreiner was kind enough to furnish us 

 with a quantity of the Arlington soil. The soil as re- 

 ceived was very acid having a lime requirement by the 

 Veitch method of 4740 pounds per acre. 



Nine kilograms of the air dry soil were placed in two- 

 gallon pots and the pots were brought to the optimum 

 water content with distilled water. At the same time 

 nine kilograms of air dry Norfolk sandy loam from the 

 station farm were ])laced in two-gallon pots. This soil 

 was practically neutral, having a lime requirement of 

 600 pounds per acre. It was also brought to optimum 

 water content with distilled water. After standing 30 

 days the soil from two pots of the xVrlingion soil was 

 removed, mixed with a sterile spatula on sterile paper 

 and repotted. These served as checks. The soil from 

 two other pots was similarly treated but 9 gms. of va- 

 nillin was added to each jjot. The soil from two addi- 

 tional pots was removed, 9 gms. of vanillin added to 

 each pot and the soil well inoculated with a suspension 

 of a pure culture of a vanillin-destroying bacterium 

 isolated from Alabama soil. Two pots of the Norfolk 

 sandy loam were prepared as checks and two pots of 

 the same soil were prepared to each of which 9 gms. of 



