STEINBERG: GROWTH OF ASPERGILLUS NIGER 9 
W when grown in the absence of zinc resulted initially in a 
yield of 0.237 gram, and the Y culture of 0.546 gram, the final 
yields were 0.177 gram and 0.222 gram. Similarly for the cul- 
tures grown in the presence of 0.01 mg. Zn/L, the initial yields 
were 0.565 gram and 0.781 gram and at the time of interruption of 




















































































































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the research but 0.287 gram and 0.440 gram for W and Y strains 
‘respectively. Other zinc concentrations display an analogous 
modification. _ 
The progressive modification of the growth capacity hardly 
manifests itself, it can be observed, in the higher zinc concentra- 
tions. That is, by adding sufficient zinc the characteristic maxi- 
mum yield of about 1 gram is obtained. A progressive change 
in the strains with respect to their sensitiveness to zinc would ex- 
hibit itself, it is rather likely, with higher zine concentrations only 
after a considerable modification. The extent of the modifica- 
tion necessary would depend on the readiness with which the effects 
of slight fluctuation in zinc content at these concentrations could 
be perceived. 
The same fact is presented to us from another angle if we con- 
