3i6 
RODNEY H. TRUE AND HARLEY HARRIS BARTLETT 
From the solution containing 1/4 Ca(N03)2 + 3/4 KNO3 there was 
somewhat less absorption than from the 4/4 Ca(N03)2 solution. 
In the group of strongest solutions, with a total salt concentration 
of 480 N X io~^, a further general increase in the rate of absorption 
was seen. Absorption in the mixtures increased as the calcium con- 
tent increased, all being more favorable for absorption than the check 
in 4/4 Ca(N03)2 solution. A clearly marked absorption phase was 
seen for the first time in the solution of KNO3. This was probably 
due to the concentration factor, as has been indicated in a former 
study^ of absorption in KNO3 solutions. 
The most striking results of this experiment may be summarized 
briefly as follows: 
I. Root absorption from dilute solutions of Ca(N03)2, of KNO3, 
and of mixtures of these in a graded series increased in general with 
the increase of concentration from 120 to 480 N X io~^. Except in 
the highest concentration tested the plants lost more electrolytes in 
KNO3 solutions than they absorbed and in the highest concentration 
the net gain of ions was small.' Calcium nitrate in all concentrations 
supported an active absorption. It seems clear that in the series of 
concentrations here studied the ratio of Ca ions to K ions most favor- 
able to the process of absorption is 3 Ca++ to 2 K+ (3/4 Ca(N03)2 + 
1/4KNO3). In every group except that having the lowest total con- 
centration there was greater absorption from mixtures in all propor- 
tions than from solutions of either of the component salts in a pure 
state. 
In the solutions having the lowest concentration, it is likely that 
the small quantity of salts present was the limiting factor, it being 
perhaps insufficient to satisfy the necessary demands of the plant. 
Calcium Nitrate and Magnesium Nitrate. Experiment 2 
It was next desired to test the activity of root absorption in solu- 
tions of calcium and magnesium nitrates. Accordingly four groups 
of solutions were prepared having a total salt content of 120, 240, , 
360, and 480 N X io~^, respectively, each group consisting of the 
following numbers: 4/4 Ca(N03)2, 2/4 Ca(N03)2 + 2/4 Mg(N03)2, 
1/4 Ca(N03)2 + 3/4 Mg(N03)2, i/io Ca(N03)2 + 9/10 Mg(N03)2, and 
4/4 Mg(N03)2. As before, each solution received four seedlings and 
concentration changes were followed by means of a daily reading of 
6 Amer. Joiirn. Bot. 2: 1915. 
