June a, 
Pseudo-Antagonism of Sodium and Calcium 
755 
experiment was concluded early in order to avoid the possible killing of 
root tips. Even by so doing many of the seedlings in the solution having 
a ratio of loo Na:o Ca had dead root tips and were, therefore, discarded. 
Table III.— Rough-lemon seedlings grovm 2j days in solution cultures 
Ratio of Na and Ca in solution. 
Number cl 
seedlings 
analyzed. 
Composition calculated to a basis of loo plants. 
Green 
weight. 
Dry 
weight. 
Ash. 
K. 
Na. 
Gm. 
Gm. 
Gm. 
Gm. 
Gm. 
100 Na;o Ca. 
28 
23- 47 
4.27 
0. 236 
0. 0414 
0. 0272 
98 Na;2 Ca. 
40 
26. 94 • 
4. 64 
•273 
•0532 
. 0225 
85 Na:i5 Ca. 
62 
24. 56 
4. 13 
. 263 
. 0446 
•0157 
The results of this experiment are quite at variance with those of the 
preceding experiments. Here the differences in green weight and dry 
weight are so small as to be attributable to the inherent variability of the 
plants rather than to differences in the composition of the solutions. 
Three experiments were conducted with the same mixtures as in 
experiment 2, using 60 seedlings for each ratio. African sour-orange 
{Citrus aurantium), grapefruit (C. grandis), and St. Michael orange 
(C. sinensis) seedlings were used, the solutions being renewed at the end 
of two weeks. After four weeks had elapsed the experiments were dis¬ 
carded because the root tips of the seedlings in the solution with the 
ratio 100 Na:o Ca were dead. 
On June 25 rough-lemon seedlings were placed in mixtures similar to 
those in experiment 3. On July 8 the solutions were renewed and on 
July 9 the experiment was discarded. In the solution having the ratio 
100 Na:o Ca the root of nearly every seedling had become slimy and 
gelatinous and was dead for a considerable distance back from the root tip. 
The roots of the seedlings in the solutions having the ratios 98 Na:2 Ca 
and 85 Na:i5 Ca, respectively, were bright in appearance and although 
small had begun to develop lateral rootlets. 
The above experiments indicate that citrus seedlings can not survive 
many days in a solution of 230 parts per million NaCl (0.004 M; 100 
Na:o Ca). One might be led to believe that antagonism has occurred 
with the ratio 98 Na: 2 Ca, since the seedlings are found to grow when a 
trace of calcium is present, whereas, in the solution with a 100 Na;o Ca 
ratio they are soon stunted and shortly afterward die. Experiment 4 
indicates, however, that this is an instance of calcium starvation rather 
than of NaCl toxicity. It was found by analyses of culture solutions 
that citrus seedlings do not require a large concentration of calcium 
provided the supply is maintained. The usual methods of chemical 
analysis are not sufficiently delicate to detect significant absorption 
differences in the brief periods required by the conductivity method of 
studying permeability. 
Experiment 4 was carried on with St. Michael orange seedlings, which 
were placed in the culture jars on September 4. Each set of cultures 
consisted of 12 jars with 3 seedlings per jar in the first set and 2 seedlings 
per jar in the remainder. 
The first culture solution was that employed by Hoagland (j). The 
cultures were still growing on November i. The second set of cultures 
