314 RODNEY H. TRUE AND HARLEY HARRIS BARTLETT 
on the part of the plants was probably due in a large measure to the 
gradual saturation of the solution with CO2 from the living roots 
rather than to the loss of salts. ^ The plants in the KNO3 solution lost 
electrolytes at a rather regular rate until the nth day when probably 
through exhaustion or injury the roots began to give up ions rapidly, 
a course continued during the five remaining days of the experimental 
period. This course was closely paralleled by the plants grown in the 
control culture in distilled water. The plants in the Ca(N03)2 solution 
began to absorb fairly rapidly on the third day and continued to do 
so at a relatively uniform rate for the next ten days. At that turning 
point, the plants began to give up ions more rapidly than they absorbed 
them and continued to do so at a relative uniform rate until the close 
of the experiment. All mixtures in this group were more favorable 
for absorption than KNO3 alone. When the solution contained 
3/4 Ca(N03)2 + 1/4 KNO3 the result differed but little from that 
seen in the pure Ca(N03)2 solution. In the solution containing 
2/4 Ca(N03)2 + 2/4 KNO3 a clear decrease in absorption took place. 
When 1/4 Ca(N03)2 + 3/4 KNO3 was offered the favorable action of 
the small quantity of Ca salt so geatly outweighed in its influence 
the larger quantity of KNO3 present that a marked net absorption 
was seen although it was less than in all other mixtures of this total 
concentration. The most favorable mixture was that containing 
3/4 Ca(N03)2 + 1/4 KNO3. 
In the group having a total concentration of 240 N X I0"~^ a very 
similar situation was found in the solutions of the pure salts. In KNO3 
the plants lost electrolytes at all stages of the experiment, rather 
slowly and regularly for the first week, more rapidly in the immediately 
succeeding days and very rapidly after the nth day. In respect to 
absorption the KNO3 solution was obviously again in the same class 
as distilled water. In the Ca(N03)2 solution, after the usual pre- 
liminary period of stand-still, absorption set in and continued to the 
end of the experiment, a somewhat greater total absorption being seen 
than in the weaker solution of the same salt in the 120 N X io~^ group. 
In the mixed solutions the favorable influence of combining calcium 
with potassium was strikingly seen. In all proportions of these 
kations the excess of absorption over loss was greater after the 9th 
day than in the pure calcium nitrate solution, although potassium 
nitrate in a pure condition was itself detrimental to the absorption 
^ For a full discussion of this point see Amer. Jour. Bot. 2: 259. 1915- 
