STEINBERG: GROWTH OF ASPERGILLUS NIGER 3 
ally overlooked will not as yet have had time, even if it did de- 
velop, to have resulted in spore formation at the time of the sec- 
ond transfer. 
The two strains thus isolated were kept on agar slants, of the 
composition given above, in the thermostat, at 30-31° C. Sub- 
cultures for the inoculation of the flasks (containing Pfeffer solu- 
tion) were made on bread and were also kept in the thermostat 
at 30-31° C. The agar stock cultures were carried in duplicate, 
transfers being at irregular intervals. A duplicate stock culture 
once having been used either for the preparation of new stock 
cultures or of a bread culture was placed aside as unfit for further 
use. The practice was also made of preserving a single dupli- 
cate stock culture, unused, from each transfer. 
The methods used in the experiments described below have 
already been given in detail in a previous publication (6). I may 
note briefly that all cultures were kept at 30-31° C., and that 
150 c.c. pyrex Erlenmeyers were used. The Pfeffer nutrient solu- 
tion was made up with water redistilled through glass, “Crystal 
Domino” cane-sugar, and Merck’s ‘‘Reagent” NH«NO; and 
MgSO,.-7H20; the other compounds being the Baker ‘‘ Analyzed.” 
In one or two instances, in which Kahlbaum’s ‘Zur Anal.” 
MgSO,.-7H,0 was used, this fact is noted. Each culture in the 
pyrex flasks contained 50 c.c. of Pfeffer solution, the dry-weight 
or yield representing therefore the amount of tissue formed by 
the organism in such a culture. Ingculations at all times were 
from bread cultures. The period of growth of the cultures was 
a each case seven days. 
The existence of quantitative differences between the eo 
strains was quite clearly indicated in the very first experiment 
(Exp. I 
Ww eg 
f Nl ei ee es a ee owe + o> 0.237 gram 0.546 gram 
Ob Mg. ZNfls 2 eae O08 2": Bd d, OR a 
The yield of the W strain is less than half that of the Y strain in 
the apparent absence of zinc, whereas it is slightly greater than 
that of the Y strain in the presence of 0.1 mg. Zn/L. 

2 ee a er 
* The detailed data for each experiment are given in the Appendix. 
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