154 
AMERICAN JOURNAL OF BOTANY 
[Vol. 8 
son between the yields from series i and series 2 indicates that series 2, with 
a total concentration value four times that of series i , gave yields throughout 
which were approximately three times as great as the corresponding yields 
from series i . The exact ratios of the yields from series 2 to the correspond- 
ing ones from series i are given in table 3, as are also similar ratios between 
Series 
Series 
Series 
Se ries 
Series 
I 
2 
3 
4 
5 
— — ^ 
— X 
\ 
\ 
\ 
\ 
^■ 
X- 
\ 
\ 
\^ 
R- II2I2 3I2432I3 4546352I6I5324 7 8473652I 
C- 87 7 666555 5 4 4 4 44 3 5 3333 2222 2 2 21 IIII II I 
Fig. 2. Graphs showing the absolute yields from the cultures of series i to 5. 
the yields from series 2 and 3, and between those from series 4 and 5. 
A relation similar to the one here pointed out between total salt concen- 
tration and yield exists throughout all the series, as is clearly shown by the 
graphs of figure 2, and by the columns of ratios in table 3. This relation 
disappears, however, in the high-yielding cultures of series 3. It was found 
that in these cultures the sugar supply was sufficiently exhausted to become 
a limiting factor for grow^th, thus preventing changes in the total salt 
concentration from showing their true effects. If these high-yielding cul- 
tures are omitted from the comparison and only the 21 cultures of series 3 
which have low or medium yields are compared with the corresponding 
cultures of series 2, it will be found that the yields from series 3 are approxi- 
mately twice as great as are the corresponding yields from series 2, while 
the total salt concentration in series 3 is double that in series 2. A similar 
comparison of the corresponding 21 cultures of series 4 and 5 shows a similar 
correlation between concentration and yield. The ratio of the total salt 
concentration between series 4 and 5 is i : 2, while the ratios between the 
yields of the corresponding cultures is also approximately 1:2, which 
indicates that by doubling the total osmotic concentration of the solutions 
without altering the salt proportions, the yields are also approximately 
