262 



no more is secreted, but this maximum amount, which is then pré- 

 sent, remams constant durlng the entire lifetime of the fungus. 

 This was found to be the case when cultivated on glucose, starch 

 and mahose. Neither the chemical composition, nor the quantity 

 of thèse substances seemed to hâve any influence. 



If the concentration of the culture solution is higher than 1%, it 

 may disturb the course of enzyme production temporarily, be- 

 cause certain substances are formed, which mhibit the action of 

 the enzyme. Thèse substances disappear during the course of 

 development and the normal maximal quantity of enzyme is even- 

 tually produced. 



The diastase of Aspergillus niger is secreted into the culture 

 solution immediately after it is formed, 



The diastase may be kept for a long time without loosing its 

 strength. 



Saccharose has a deletenous influence on the action of diastase. 

 For some reason or other, the normal amount of diastase appears, 

 after ail the cane sugar and its split products hâve disappeared from 

 the culture solution. 



When Aspergillus niger was grov^n on 5% glycérine, no diastase 

 production could be proved at ail. 



Aspergillus niger has no lactase, even if it is grown on lactose. 

 There is therefore practically no development of the fungus on this 

 substance. 



Before I close I hâve pleasure to thank prof. Dr. F. A. F. C. We n t , 

 not only for his very valuable help, but also for his kindly allowing 

 me to proceed with his ow^n experiment and for puttmg at my dis- 

 posai ail the facilities of the Botanical Laboratory m Utrecht. 

 Without this very material help, I should hâve been unable to 

 carry out this research. I therefore wish to express my heartfelt 

 thanks at this point. 



Utrecht, Botanical Laboratory 1920—1922. PresentedApril 1922. 



