310 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



[Vol. 10 



A. niger, making qualitative tests for the presence of sugar and 

 noting the effects on N excretion of replacing the medium 

 weekly by water or by a 2 per cent sucrose solution. The 

 determinations showed that autolysis of this fungus is largely 

 due to the exhaustion of carbohydrate from the medium, because 

 a removal of the autolytic products and substitution of distilled 

 H ,0 increased the rate of autolysis, and replacement of the culture 

 solution by sugar solution lessened the rate to one-half that of 

 undisturbed cultures and to one-third that of the cultures in 

 which distilled H,0 replaced the medium. 



Waterman ('13), by shaking for 2 hours, a dried, living mat of 

 Aspergillus niger with a nutrient solution containing 2 per cent 

 glucose, removing and washing the mat, then boiling for 10 

 minutes in H 2 and testing the extract with Fehling's, showed 

 that no glucose as such had entered the mold. This was inter- 

 preted as showing that the protoplasm of the mold behaved as 

 a semi-permeable membrane toward the glucose, and that ad- 

 sorption was of no consequence in the accumulation of nutrients. 

 His tables of data show that he determined qualitatively with 

 Nessler's reagent and diphenylamin-sulphuric acid the ammonia 

 present or developed in the culture solution; in some instances 

 this was determined quantitatively with the same reagents. The 

 total nitrogen fixed in the mold and the percentage of sugar 

 assimilated were determined quantitatively, but the methods 

 used were not described. It is assumed that Kjeldahlization, 

 for the N, and some method with Fehling's solution, for the glu- 

 cose, were employed. Waterman believed that his results showed 

 that "ammonia is a normal excretion product in the metabolism 

 of Aspergillus niger" and that this fungus "is able to reduce 

 nitrate to ammonia." A young culture, in which the N content 



was 2 to 2^2 times that of a mature mat, was thoroughly washed 

 and the fungous mat then boiled in water. The extract contained 

 no trace of the inorganic salts originally added to the nutrient, 

 showing that the N salt assimilated by the fungus was quickly 

 changed into another form, and adsorption has little influence 

 on the nutrition. Waterman's other results are given in his own 

 words. 



" 1. The nitrogen fixed in the mature mould is proportional to the 



