: 
RECORD OF THE EXPERIMENTS. 33 
The series of results of experiment 6 is in striking contrast to 
those of experiment 5. In experiment 5 the concentration of the 
equivalent solutions was so low that even the absorption from a 
solution containing only magnesium was sufficient to reduce it to 
equilibrium concentration. In experiment 6, on the other hand, 
tripling the concentration of the equivalent solutions resulted in 
showing the marked influence of successive increments of calcium 
on absorption. In culture 2 (magnesium alone) there were no 
lateral roots, and the nonfunctioning primary root did not alter the 
concentration of the solution. In culture 3, however, the substi- 
tution of one seventy-fifth of the magnesium by calcium resulted in 
the growth of laterals 1 to 4 mm. long, accompanied by appreciable 
absorption. The equivalent cultures from No. 6 on showed more 
perfect root systems, correlated with increasingly greater absorption. 
EXPERIMENT 7. 
A series of solutions containing magnesium and calcium in the 
. 9 . . . . e 
molecular ratio 7 were used in experiment 7; i. e., solutions con- 
taining enough calcium to insure perfect root development, but not 
enough to bring about maximum salt absorption. The duration of 
cultures was 7 days; temperature at beginning and at end of experi- 
ment 22.3°. 
TaBLE VII.—Statement of results, experiment 7. 
es 
Number of culture........------------- 1 ad Sa S00 bos 6 7 
Concentration: 
Distilled| M 2M 4M 6M 8M 10M 
Before growth. ....---------------- water. | 500,000 | 500,000 | 500,000 | 500,000 | 500,000 | 500,000 
122M | 12M | 10M 8M 8M 8M 9M 
After growth....-.---------------- 500, 000 | 500,000 | 500,000 | 500,000 | 500,000 | 500,000 | 500,000 
| | 
Number of culture ........------------ 8 9 10 i Ne Poms > ee 14 
Concentration: 
12M | 14M | 16M | 18M | 20M | 22M | 24M 
cipok tl s  a 500,000 | 500,000 | 500,006 | 500, 000 | 500,000 | 500,006 | 500, 000 
9M um | iM | wM | wM | 16M | isM 
3 i: ei) b | Bs | bh BM | | 
These results (graphically represented in fig. 20) are directly 
comparable with those of experiments 1 and 2. As would have 
8M 
500,000 
and that of calcium alone 
been expected, the equilibrium concentration lies between 
12M 
500,000 
With regard to the amounts of salt excreted into cul- 
that of magnesium alone 
7M 
500,000" 
231 
