BULLETIN 
OF THE 
TORREY BOTANICAL CLUB 
JANUARY, 1919 
A study of some factors influencing the stimulative action of zinc 
sulphate on the growth of Aspergillus niger. Il. A com- 
parison of two strains of the fungus. 
R. A. STEINBERG 
(WITH PLATE I AND FOUR TEXT FIGURES) 
It will be apparent to those concerning themselves with the 
“stimulative” action of zinc sulphate on the growth of Asper- 
gillus niger that marked discrepancies exist between the results 
reported by different investigators. These variations are most 
apparent in the yields (dry-weight per 50 c.c. of nutrient solution) 
obtained in the apparent absence of zinc, the maximum yield in 
the presence of the optimum concentration of zinc, and the mini- 
mum concentration of zinc necessary for the maximum yield. 
Discussion of the variations apparent in the results reported 
will be confined to the following tabulation of the minimum con- 
centration of zinc for maximum growth, as given by various auth- 
ors: 
Wee a a i er hg ee ee 10.61 mg. Zn/L 
Weibel 9.10 ~ 
(9) 8 Sones eee ae aS hs a tag ght rahe al he 9 14 oe 8.41 = 
Weick ce ne ee er ee 0.09 us 
Poitier (NF 6 ec os es cree ee eee S ea 0.10 “ 
The differences are evidently too large to be laid to experimental 
errors. 
The experiments taken up in this paper are concerned with 
observations made on two strains of Aspergillus niger over a 

[The BULLETIN for December (45: 477-519) was issued December 23, 1918.} 
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