Some Accessory Factors in Plant Growth and Nutrition. 239 



These accessory substances essential to animal nutrition are known to be 

 soluble in water and alcohol, and, in order to ascertain as rapidly as possible 

 whether there are present in the bacterised peat such water- and alcohol- 

 soluble substances which have a similar effect on plant growth, an experiment 

 was made to test the effect of an aqueous extract of the alcohol-soluble 

 material of the bacterised peat on the growth and fixation of nitrogen by 

 Azotobacter ehroococcum. 



The bacterised peat was extracted with absolute alcohol in a shaking 

 machine for three hours, and the extract evaporated to dryness in vacuo. 

 The residue was taken up in warm distilled water, the liquid filtered, and 

 the clear filtrate diluted until it contained the extract of 10 grm. of peat per 

 litre. Portions consisting of 100 c.c. of this liquid were then transferred to 

 each of 12 conical flasks, and the contents of six of the flasks boiled briskly 

 over a Bunsen burner for five minutes ; 100 c.c. portions of distilled water 

 were placed in each of six similar flasks ; to each of the 18 flasks of the 

 series were added 1 grm. mannite, - 2 grm. K2HPO4, 0*02 grm. MgSCt, and 

 - 2 grm. CaC03, and each was inoculated with 1 c.c. of a uniform suspension 

 of Azotobacter ehroococcum. The contents of two flasks from each of the 

 three series of six were analysed at once to serve as controls, while the 

 remaining four of each series were incubated for eight days at 26° C, at 

 the end of which period they were analysed by the Kjeldahl process for 

 their nitrogen content. The results are given in the following Table : — 



Table I. 



Series. 



Nitrogen content. 



Nitrogen 

 fixation. 



Mean nitrogen 

 fixation. 



I. Complete food 



II. Complete food + alcoholic 

 extract of bacterised peat 



III. Complete food + boiled 

 alcoholic extract of bacte- 

 rised peat 



1. Control 

 2. 



3. Culture 



4. 



5. 



6. 



1. Control 

 2. 



3. Culture 



4. 



5. 



1. Control 

 2. 



3. Culture 



4. 



5. 



4 1 Mean, 



4/0-4 mgrm. 



6 



4 



6 



4 



6 "I Mean, 

 3 J 2 "5 mgrm. 

 7 



5 



Mean, 

 2 - 4 mgrm. 



mgrm. 



4-2 

 4 -0 



3- 2 



4- 



18 -2 

 18 -0 



17 -4 



18 -4 



17 -2 



16 -6 



18 -2 



17 -0 



mgrm. 



3-8 



18 -0 



17 -2 



T 2 



