251 



Fig. 13. Maltose 5%. Diastase in the culture solution, (d = days). 



10*^ or 12* day, but in this case a considérable quantity cf sugar 

 is left even on the 24* and 3P* day\ as can be seen from the 

 rotation of the culture solution in the polarimeter. This is in other 

 séries zéro on the days in which the maximum dry weight is reached, 

 i. e. the 10**^ or 12*^^ days; hère it is = r23'24" on the 24*^ day, 

 on which the dry weight only has diminished to 91 1 m.Gr. Dissi- 

 milation has hère gained the upperhand, yet assimilation is still 

 so active, that there is little decrease. So it is probable, that at the 

 same time substances are secreted, which prevent the diastase from 

 unfolding its full powers. The maltose itself must also retard the 

 action of the enzyme. If the séries had been longer proceeded 



^ The rotation of the culture solution shows, as might hâve been expected, 

 that Aspergillus niger changes maltose into glucose. This however takes such a 

 very long time, that we can not imagine glucose is the end product of the hydro- 

 lysis of starch. This hydrolysis in most cases is so rapid, that the end product can 

 not be but maltose. 



I am strengthened m this opinion by the follov.-ing fact: in the third séries, 

 grown on 5% starch, the reducing power of the culture solution was tested every 

 day. When on the 9 day ail the starch had disappeared, the reducing power of 

 the solution was found to be equal to that of a 0.4% maltose solution i. e. equal 

 volumes of 0.4% maltose solution and culture solution reduced the same amount 

 of Fehlings solution. This is not a positive proof that in this case maltose is the 

 end product, but it makes it very probable. 



3* 



