TRUE & HARVEY: ABSORPTION OF CALCIUM SALTS 503 
maintained at 18° C. by automatic control so accurate that the range 
of variation was seldom above four tenths of a degree Centigrade 
during the course of an experiment running a fortnight. The con- 
tainers remained in darkness except during the short time required 
for the determination of the conductivity which took place in rather 
faint diffused light. Since it is obviously unsafe to draw conclusions 
from a comparison of ohms, results were always calculated to concen- 
trations expressed as gram-normals of the salt in question dissolved 
in a million liters of water (grm. norm. X 107-*). The water was 
obtained by twice distilling Potomac River water from glass with 
electric heat in a laboratory from which gas was excluded. Each 
experiment was usually continued until signs of deterioration began to 
appear in the seedlings. 
CaLcium NITRATE 
Several experiments were carried out with squash seedlings in 
calcium nitrate solutions. Since they were in close agreement but 
one is presented here, that running from May first to May fifteenth, 
last, inclusive. The distilled water used in making up the solutions 
had an initial conductivity equal to that of a solution containing 11.7 
grm. norm. X 10-6 Ca(NOs3)o. Nine cultures each containing 5 seed- 
lings and 500 cc. of solution were set up in a series ranging in con- 
centration from 18.2 to 867.0 grm. norm. X I10-®. Daily observations 
were made until signs of exhaustion began to appear. Since in the 
cultures containing less than 50 grm. norm. the behavior of the seed- 
lings varied so little in the different members of the series only a part 
of the record is shown here in order not to confuse the table with 
several nearly coinciding curves. In the curve representing the 
record of the culture in distilled water a dashed line is employed 
(Fig. 1). 
It will be observed that in both distilled water and in cultures 
containing calcium nitrate up to a concentration of 100 grm. norm. 
< 10-* the solutions gain in concentration for two or three days, a 
course which in the distilled water is followed by a very slight ab- 
sorption until near the close of the experimental period. At no time, 
however, were the plants able to regain any considerable proportion 
of the electrolytes lost to the medium during the first few days. 
With the dilute solutions of the salt (under 100 grm. norm.) this 
period of leach gradually passes over into one of active absorption 
as a result of which these solutions are reduced to a lower ion content 
than the distilled water. 
As the initial salt content of the solution is increased to approxi- 
mately 500 grm. norm. the slight leach seen in the weaker solutions 
