[Vol. 10 



312 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



the autolysate it was found that yeast consumes only about 20 

 per cent of the amide group, whereas 80 per cent of the amino 

 acid part was used in the synthesis. The description of the 

 methods employed is very indefinite. The fermenting fluid was 

 shaken to obtain a homogeneous mixture and then pipetted off. 

 Protein N was estimated by Stutzer's method and by precipitation 

 with iron acetate. In experiments 5 to 10 total and NH 4 .N were 

 determined and in experiment 11 the N of the amide group, but 

 the methods are not given. The work of Ehrlich was criticized 

 on the basis of the absence of NH, in the medium. 



In an interesting investigation with Aspergillus niger in which 

 (NHi)jSOi was used in conjunction with various amino acids, 

 peptone, autolysate, and amino acid mixtures, Zaleski and 

 Pjukow ('14), by determining the total and NH,.N of the culture 

 fluid, obtained satisfactory results. Knowing the original N 

 they computed from these determinations the kind and amount 

 of N consumed. (NH 4 ) 2 S0 4 was utilized to a greater extent than 

 single amino acids in mixtures of the two, but the NH 4 salt, as 

 shown by consumption, was not so good as mixtures of the amino 

 acids or the fungous autolysate, when mixed with these organic 

 sources of N. The order of the serviceability of single amino 

 acids used with (NH 4 ) 2 S0 4 was phenylamine, leucine, glycine, 

 alanine, aspartic acid; histidine was not utilized. The fact that 

 (NH 4 ) 2 S0 4 was used even in the amino acid mixtures showed 

 that the fungus synthesized other amino acids. The decom- 

 position of the various amino acids proceeded at different rates 

 which were proportional to their utility for this organism. The 

 relative usefulness of the NH 4 salts and amino acids could be 

 varied in several ways: (1) by varying the acid radical to which 

 the (NH 4 ) was joined, (2) by changing the carbon source; with a 

 less available carbon source the amino acid was more utilized, 

 (3) by the addition of a stimulant, as ZnSOi, which lessened the 

 consumption of the amino acid by promoting a more economic 

 consumption of the sugar. Glycine in the presence of OH,. 

 COONH* was not used. The addition of CaC0 3 to the nutrient 

 containing (NHO1SO4 and alanine decreased the use of the ala- 

 nine, and this was explained by saying that the carbonate neu- 

 tralized the acid produced in growth and produced an alkaline 



