STEINBERG: GROWTH OF ASPERGILLUS NIGER 7 
WwW Y 
0.06 mg. sl Bp he Ss ey ey accel 0.688 gram 0.793 gram 
0.07 BE Sret ia lalg woateraty cies “eels GOOF." O75 57° 
OCU Fhe Se ae aig Sie ee eek ce 0.758 0.734 
0.09 AAUP chaise Swans MECCA ere + O7OLs 7" 0.770°.;"' 
0,10 SP eee sat en ccan i g wee Uuite 0.800 “ 0.799.“ 
The minimum concentrations of zinc necessary for the forma- 
tion of maximum dry-weight is for the W strain probably greater, 
in this case, than 0.1 mg. Zn/L, and for the Y strain, approximately 
0.06 mg. Zn/L. The yields in the absence of zinc are a trifle higher 
than in Exps. VIII and IX. In the presence of 0.01 mg. Zn/L the 
yield of the W strain is identical in Exps. VIII and XVIII; whereas 
the yield of the Y strain, though 0.283 gram in the preceting: ex- 
periment, is in the present trial 0.440 gram. 
Many of the cultures in Exp. XVIII were photographed and 









































































































\ Y ; ee Oe | i TI a8 any 
‘asi Be BE DR Be 
PREECE 
tt 
Pi Po = 
wv rl ae es 
~~ acl br a ae oe 
Mo = 
o 
& S 
Ee 
© 
r 0.0! 0,02 0.03 0.04 0.05 0,06 0,07 0,08 0,09 0.10 
Milligrams Line per Liter 
Fic. 3. For explanation see text. 
are reproduced in PLrateE 1. In Text Fic. 3 the yields are shown 
plotted against the zinc concentrations. 
To facilitate a survey of the changes in the yields obtained 
under supposedly identical conditions as these experiments pro- 
gressed, the yields in ‘‘zinc-free’’ media for the entire period are 
summarized in the following table: 
Both strains, it will be noted, showed a rapid decrease in re- 
spect to their capacity for growth in the Pfeffer solution. The 
two strains, nevertheless, are distinct in that the W always forms 
a smaller amount of tissue than the Y strain. The fact that a 
decrease in the capacity for growth has indeed taken place will 
