Jan. 2S, igis Nitroge7i- Assimilating Bacteria 227 



(4) Pigmentation occurred when potassium and sodium nitrates, 

 and especially calcium nitrate, were used with Azotobacter, the colora- 

 tion increasing with the concentration of the salt. This effect was more 

 marked in Azotobacter strains which produce little or no pigment in the 

 absence of nitrates. 



(5) All three nitrates studied caused an increase in the number and 

 size of volutin bodies in Azotobacter cells. From all appearances 

 these salts also tended to hasten the development of these bodies. 



(6) The number of Bacillus radicicola in sterilized soil was increased 

 by the addition of small quantities of potassium, sodium, ammonium, 

 and calcium nitrates. This increase was not so marked as in the Azoto- 

 bacter cultures. B. radicicola appeared to be much more resistant to 

 higher concentrations of nitrates than Azotobacter. 



(7) B. radicicola under aerobic conditions did not reduce nitrates 

 in solution to nitrite, ammonia, or elemental nitrogen. The presence 

 of nitrates did not materially influence the small amount of atmos- 

 pheric nitrogen fixed under these conditions. 



(8) When grown on agar films, B. radicicola fixed a small amount 

 of nitrogen, varying from 0.15 to 0.43 mgm. of nitrogen in 100 c. c. of 

 the medium. The addition of various amounts of potassium, sodium, 

 and calcium nitrates increased to a slight extent the amount of nitrogen 

 assimilated. 



(9) In liquid cultures all three nitrates caused a large increase in the 

 amount of gum obtained by precipitation with acetone. 



(10) The presence of large amounts of potassium, sodium, and cal- 

 cium nitrates proved detrimental to the formation of nodules on alfalfa. 

 B. radicicola did not appear to lose its infecting power when grown on 

 media containing varying amounts of sodium and calcium nitrates. 

 Alfalfa seedlings grown in the presence of large amounts of nitrate did 

 not produce nodules when inoculated wdth a viable culture of B. radicicola. 

 Nitrates in soil cultures prevented the re-formation of nodules once 

 removed and also caused a decrease in the number of nodules already 

 present. 



LITERATURE CITED 

 (i) Bassler, p. 



1895. SANDKULTURVERSUCHE UBER DIE STICKSTOFFASSIMILATION DER GELBEN 

 LUPINE IM STERIUSIERTEN UND GEIMPFTEN BODE.V BEX DARGEBOT 



WECHSELNDER MENGEN VON SALPETERSAUREN SALZEN. In Jahresbef. 

 Agr. Chein., n. F., Bd. 18 fjahrg. 38), p. 131. 



(2) BEIJERINCK, M. W. 



1888. DIE BACTERIEN DER PAPILIONACEEN-KNOLIXHEN. In Bot. Ztg., Jahfg. 



46, No. 48, p. 758-771. (Continued article.) 



(3) 



1891. OVER OPHOOPING VAN ATMOSPHERISCHE STICKSTOP IN CULTUREN VAN 



BACILLUS RADICICOLA. In Verslag. en Meded. K. Akad. Weteiisch. 

 [Amsterdam], r. 3, deel 8, p. 460-475. 



