Jan. 2S, 1918 



Nitrogen- A ssimilating Bacteria 



21 



28° C. for three weeks and those in Experiment II for two weeks. The 

 moisture lost by evaporation in both inoculated and uninoculated flasks 

 was replaced from time to time by the addition of sterile distilled water. 

 At the expiration of the incubation period the total nitrogen was deter- 

 mined as given under "Methods used in experiments." The results of 

 the experiments are given in Table XXVII. 



An inspection of the data reveals the fact that B. radicicola in pure 

 culture fixed a small amount of nitrogen when growing in a nonsymbiotic 

 state with no nitrate present. In the presence of nitrates there was an 

 increased fixation. Although the increase in total nitrogen is small, 

 because of the number of determinations made, it may be considered 

 as positive. The potassium and sodium salts seemed to be more effective 

 than the calcium nitrate, with one exception (Table XXVII, Experiment 

 I). It will be remembered that the latter salt appeared to depress nitro- 

 gen fixation by Azotobacter and the two former somewhat to favor it (p. 

 194-195). 



Table XXVII. — Influence of nitrates on the fixation of nitrogen by Bacillus radicicola, 

 giving the increase in nitrogen 



EXPERIMENT I 



Culture 

 No. 



Treatment (nitrate in 100 c. c. of medium.) 



None 



do 



do 



75 mgm. of NO3 as sodium nitrate . . . 



do 



do 



150 mgm. of NO3 as sodium nitrate . . 



do 



do 



75 mgm. of NO3 as calcium nitrate . . 



do 



do 



150 mgm. of NO^as calcium nitrate . . 



do 



do 



Nitrogen 

 increase. 



Mgm. 

 o. 15 



3-03 



2. 10 



3- 30 

 o. 90 



EXPERIMENT 11 



None 



do 



75 mgm. of NO3 as sodium nitrate . 



do 



150 mgm. of NO3 as sodium nitrate. . 



do 



75 mgm. of NO3 as calcium nitrate . 



do 



150 mgm. of NO3 as calcium nitrate . 

 do 



4.90 

 4.90 

 8. 70 

 8.50 



13-30 

 13.00 

 II. IS 

 II. 10 



14. 70 

 (a) 



}5-07S 

 I 9- 50 

 }u.35 

 }ii.65 



}i5-25 



o- 175 



0. 90 



1. 20 

 o- 525 

 o- 550 



a Lost by breakage during sterilization. 



