1923] 



KLOTZ — NITROGEN METABOLISM IN FUNGI 



333 



the "humin" N filtered off, and the filtrate and washings then 

 neutralized with saturated NaOH solution and made to volume 

 (100 ml.) . A portion of this solution was made distinctly alkaline 

 to phenolphthalein, aerated to rid it of amide and ammonium N, 

 and the "peptid" N estimated by the van Slyke "micro" 

 method, as in the amino N determinations. The results for 

 amino N theoretically should be subtracted from the results 

 obtained here to give the N that was bound in the peptid linkings 

 and freed by hydrolysis, but this was not done owing to the 

 questionable accuracy of the former. Hydrolysis of culture fluid 

 from the 3 mineral N media (numbers 3, 4, and 5) was not found 

 to increase the NH«.N content, so it was reasoned that higher 

 peptids, or proteins, are not excretion products of the 3 fungi 



cultured on these media . 



From the NH, obtained by the aeration of the hydrolyzed 

 material was subtracted that of the ammonia determination and 

 the result called " amide" nitrogen. 



Data and Discussion 



A preliminary experiment was carried out to obtain an indi- 

 cation of the capacity or inability of Sphaeropsis malorwn and 

 Diplodia natalensis to utilize elementary N t . These fungi are 

 sphaeropsidaceous forms, as is the Phoma Betae which was shown 

 to have the capacity for fixing free N«. The Ascomycete, 

 Nectria Ipomoeae, was also used in this experiment. The tech- 

 nique described by Duggar and Davis ('16) was followed exactly 

 except that 1-liter, round-bottom Jena flasks were used as the 

 culture, digestion, and distillation flasks. The cultures were 

 incubated in darkness at a temperature of 28° C. Duggar's 

 solution for fungi was used as the culture medium, the carbon 

 source being common cane sugar instead of glucose, and the N 

 source 2 different concentrations of peptone solution. The 

 results here given show the total incapacity of these 3 forms to 

 fix the N i of the air under the conditions of the experiment. 



