[Vol. 10 



364 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



as shown by its growth on (NIDtSO*, is similar to that of the 

 Sphaeropsis. 



The general conclusion from these considerations is that there 

 is a distinctive physiology for each of these 3 organisms and that 

 this conditions the form of the inorganic nitrogen which is most 

 assimilable. There are no conclusive data in the literature to 

 show that nitrates must be reduced to nitrites or ammonia before 

 assimilation. Reasoning a priori, the form of nitrogen supplied 

 must be reduced (if an oxide) or oxidized (if NIL or NH,) to 

 form the amino group, and other conditions (as H-ion concen- 

 tration) being the same, organisms show a differential use of 

 these ions because of their different powers of reduction, oxida- 

 tion, and synthesis. As has been already pointed out, many 

 erroneous assumptions have been made in this regard because in- 

 vestigators failed to consider the NH, produced proteolytically. 

 For this reason also, the necessity for making dry- weight deter- 

 minations at frequent intervals is evident. 



The order of relative assimilability of nitrogenous compounds 

 for a specific fungus at one H-ion concentration may be entirely 

 different from the order at another P H value. Similarly the 

 effects of temperature, humidity, light, aeration, agitation, and 

 possibly other factors on assimilation must be so considered; 

 the problems are complex. 





Summary 



1. A review of the literature on the N metabolism of fungi 

 is given. 



2. The methods used are described and reasons are given for 

 the selections made. 



3. Autolysis is at first indicated by decrease in dry weight 

 of the fungous mat from a maximum and by the formation of 

 ammonia in the peptone and KNO« media; somewhat later, by 

 increase in total N of the culture solution from a minimum in all 

 the media, and by the appearance of a trace of amino N in the 3 

 inorganic nitrogenous media. 



4. Autolysis in a species is proportional to the rate and amount 

 of growth attained. 



