i6o 
AMERICAN JOURNAL OF BOTANY 
[Vol. 8 
solution of culture R1C8 in series 3 was used in this test. This solution 
has a total salt-concentration value of 4.2 atmospheres, and the three salts 
KH2PO4, Ca(N03)2, and MgS04 are present in the proportions of 0.0710 m., 
0.0063 itIm and 0.0108 m., respectively. 
The results of this test are shown in the graph of figure 6 in which the 
ordinates represent dr}^ weights in grams and the abscissas represent 
concentrations of sugar in atmospheres. This graph brings out the fact 
that as the sugar concentration is increased (and therefore the amount of 
sugar per culture, since the amount of solution was the same in all the 
cultures, namely 50 cc), the dry- weight yields were proportionately higher, 
thus showing a linear relation between the amounts of sugar employed and 
the yield values. 
Gms. 
2.20 
2.00 
1. 80 
1. 60 
1.40 
1.20 
1.00 
. 80 
.60 
.40 
.20 
Atm. 12345678 
Fig. 6. Graph showing relation between dry- weight yields of Aspergillus niger and the 
sugar content of the nutrient solutions. 
It is to be observed that the culture with a sugar content of 3 atmospheres 
gave an average yield of 0.974 gram, which is nearly the same as the yield 
from culture R1C8 of series 3 having the same composition, the yield ob- 
tained from this latter culture being 0.977 gram. However, the yields 
continued to increase proportionately with increase in sugar concentration 
up to a concentration of 8 atmospheres, at which concentration the dry 
