1923] 



KLOTZ — NITROGEN METABOLISM IN FUNGI 



351 



amido compounds, if such are actual units in the protein structure 

 of the organism involved. In fact the conceptions of both 

 factions should be combined to help account for the various 

 degrees of utility of a particular nitrogenous compound for dif- 

 ferent fungi. Every genus of fungi and possibly every species 

 of a genus is an entity in itself as regards its physiology. For 

 example, Aspergillus niger makes a greater growth on (NH«)»SO< 



(NhQ, SO.- 



NtUNOi 



KNOj 



-% , 



ml** 



/s 



lt> 



17 



Fig. 11. Rates of carbohydrate consumption; amount of dextrose in 50 ml. media. 



Sphaeropsis malorum. 



than does A. glaucus, while the latter is superior in the ability 



assimilate 



Nitrogen distribution studies on fun 



mats to discover what amino acids are actually present in the 

 substance of the fungus, and subsequent cultural studies in which 

 different combinations and proportions of the units are used as 

 the sources of N would probably contribute much toward a 

 proper understanding of metabolism (van Slyke, '11). Such 

 work requires much time and the cooperative labor of several 

 associates, and could not for this reason be carried out during the 

 time of this investigation in this laboratory. 



A few determinations of the total N of dry fungous mats were 

 made and these showed the following : 



