574 Bulletin i6y 



13. Nitrogen. — A nitrogen free medium was made as fol- 

 lows (27:198) : 



Water 500. cc. 



Cane sugar 2.5 gr. 



Mono-potassium phosphate 1. 



Magnesium sulphate 0.5 



Sodium chlorid 0.2 



This was heated until dissolved, and divided into two equal 

 portions. To one was added 2 grams of ammonium tartrate, to 

 the other 2 grams of Bausch and Lomb's peptone. 



The results upon these media are tabulated as follows : 



TABLE 65. NITROGEN REQUIREMENTS 



Tartrate solution Peptone solution 



Strain Growth Time Growth Time 



/•.v. alba, + ' ,L 



Ps. fluorescens, + Id. Id. 



Ps. longa, — + 1 d. 



Ps. mesenterica, + Id. Id. 



Ps. tenuis. + Id. Id. 



Ps. jmtrida: + 1 d. 3 d. 



CXII, + 3d. + Id. 



CXV, + 3 <1. + 1 d. 



CXL, + 3d. + Id. 



CXLV, + Ld. + Id. 



CXLVIII, + 3 d. 1 d. 



XXXVI, + Id. + 1 d. 



LI, + Id. + Id. 



1 Ps. putrida showed the hest growth of any at three days, with 

 beautiful green fluorescence. 



In order further to test the nitrogen requirements, the Fol- 

 lowing medium was made, considerable care being taken to make 



it nitrogen free. 



Twice distilled water 3000. cc. 



Sucrose 15. gr. 



Mono-potassium phosphate (tested purity, no 



nitrogen ) 6. 



Magnesium sulphate (tested purity, no nitro- 

 gen) 0.3 



Sodium chlorid (tested purity) 1.5 



After being thoroughly mixed this solution was divided into 



ten equal portions. One of these was reserved for a control, to 



another was added 2'/, of peptone, while to each of the other 



eight portions was added respectively o.S'r of the following 





