Bacterial Test for Plant Food Accessories {Auximones). 103 



three series of six flasks each. The first series served to test the growth of 

 the organism in normal culture. To each of the flasks of the second series 

 was added the phosphotungstic fraction from 1 grm. of bacterised peat, and 

 to the flasks of the third series the silver fraction from a similar quantity. 

 The amount of dry substance thus added to each flask was - 00017 grm. in 

 the case of the phosphotungstic fraction, and - 000035 grm. in the case of the 

 silver fraction. Each flask was then inoculated with 1 c.c. of a uniform 

 suspension of Azotobacter in distilled water, and two flasks from each series 

 were sterilised to serve as controls. After incubation for 10 days at a 

 temperature of 26° C, the contents of each flask were analysed by the 

 Kjeldahl process for its nitrogen content. The results obtained are as 

 follows : — 



Table I. 



Series. 



Nitrogen-content. 



Nitrogen fixation. 



Mean nitrogen 

 fixation. 



I. Normal mannite solu- 

 tion 



II. Normal mannite solu- 

 tion + phosphotungs- 

 tic fraction from 

 1 grm. bacterised 

 peat 



III. Normal mannite solu- 

 tion + silver fraction 

 from 1 grm. bacte- 

 rised peat 



1. Control 



2. „ 



3. Culture 



4. „ 

 5. 



1. Control 

 2. 



3. Culture 



1. Control 



2. „ 



3. Culture 



4. „ 

 5. 



mgrm. 



mgrm 



o-i 





o-i 





4-0 



3-9 



3-8 



3-7 



4-0 



3-9 



4-1 



4-0 



0-2 





0-2 





9-7 



9-5 



10 -1 



9-9 



10 -o 



9-8 



9-9 



9-7 



0-2 





0-2 





10 -3 



10-1 



10 -5 



10 3 



10 -9 



10 -7 



10 -7 



10 -5 



mgrm. 



3-9 



10 -4 



Although these results were promising, the use of this method as a test for 

 plant auximones was found to be unsuitable owing to the variability of the 

 organism and the length of time required for incubation, and a shorter and 

 more reliable method was desirable. 



Preliminary experiments had already shown that the application of 

 bacterised peat to the soil resulted in an increased production of nitrates, and 

 an examination of the effect of these auximones on nitrification in the soil 

 yielded further interesting results. Two equal quantities of soil weighing 

 2 lb. each .vere taken, and to one was added, in solution in distilled water, 

 the phosphotungstic fraction of that weight of bacterised peat (30 grm.) 



