INUL\SE FORMATION IN ASPERGILLUS 125 



since too many uncontrolled factors are introduced. It is very 

 difficult to estimate the amount of mycelium used in experiments, 

 if the fresh mycelium is used directly, but, if it is dehydrated by 

 means of such substances as alcohol, acetone, or ether, the dry 

 weight of the fungus is a fairly accurate index of the actual com- 

 parative number of cells present in different amounts of mycelium. 

 This allows a comparative study of different cultures. The use 

 of ether, acetone, etc., in this method removes many substances 

 such as certain lipoids, etc., which would be present as foreign 

 substances in a fresh mycelial extract. There are many other 

 advantages, which make this method more convenient to use, 

 but which need not be discussed here. With regard to the use 

 of enzymes, which have been excreted into the culture medium, 

 it seems apparent that it is impossible to control the nature of 

 the substances with which the enzyme is in contact and, for this 

 reason it is impossible to compare the activity of various enzyme 

 solutions under such conditions. Furthermore, if only the origi- 

 nal salts and carbohydrates of the culture medium were present 

 in their original concentrations, which is manifestly not the 

 case, it would be very difficult to compare the activity of enzymes 

 acting under such conditions with the activity of enzymes de- 

 rived directly from the mycelium. It, therefore, seemed more 

 desirable to employ methods similar to those of Dox rather than 

 those of Boselli, whose results are quite at variance with those 

 usually obtained in experiments of this nature. For similar 

 reasons, no attempt was made to estimate the amount of enzyme 

 produced based on the rate of disappearance of the carbohydrate 

 from the culture medium, as has been done by certain other 

 investigators. 



It has been shown from the work of previous investigators that 

 in general the period of greatest enzyme content in the fungi is 

 just at the beginning of sporulation, and these experiments show 

 that this is also true with regard to the inulase content of A sper- 

 gillus niger. For this reason the enzyme preparations used 

 have been prepared from the mycelium at this stage of its life 

 cycle. 



