312 
RODNEY H. TRUE AND HARLEY HARRIS BARTLETT 
Washington, D. C. This paper therefore deals primarily with the 
physiological interactions sometimes called antagonisms,^ as these 
come to expression in modifying root absorption. It was intended 
by the use of mixtures of the same salt of several bases to get a com- 
parative expression of the effect of the different combinations of 
kations concerned. 
Methods 
The methods used have been described elsewhere,^' ^ and the 
reader is referred to the details there given. The sole change involved 
in the investigation reported in the present paper lies in the fact that 
the solutions contained mixtures of salts in pairs. 
Experimental Results 
Calcium Nitrate and Potassium Nitrate. Experiment i 
It was proposed in this experiment to ascertain the effect of 
calcium and potassium ions in the presence of the common anion, 
NOs", on the absorption or excretion of electrolytes. 
Four groups of solutions were prepared, each of which consisted of 
five chemically equivalent solutions, grading by fourths from pure 
Ca(N03)2 to pure KNO3, as follows: 
1. 4/4 Ca(N03)2. Ratio of kations to anions, 4 Ca++ : 8 NO3- 
2. 3/4 Ca(N03)2 + 1/4 KNO3. Ratio of kations to anions, 3 Ca++ 
+ 2K+ : 8 NO3-. 
3. 2/4 Ca(N03)2 + 2/4 KNO3. Ratio of kations to anions, 2 Ca++ 
+ 4 K+ : 8*N03-. 
4. 1/4 Ca(N03)2 + 3/4 KNO3. Ratio of kations to anions, iCa++ 
+ 6 K+ : 8 NO3-. 
5. 4/4 KNO3. Ratio of kations to anions, 8 K+ : 8 NO3-. 
Thus, each member of a group had the same N03~ concentration 
and approximately the same electrical conductivity. Disregarding 
valence, the ratios of kations to anions in the five solutions of each 
group formed the series 4 : 8, 5 : 8, 6 : 8, 7 : 8, and 8 : 8. The four 
3 True, R. H. Antagonism and Balanced Solutions. Science, n. s. 41: 653- 
656. 1915. 
4 True, R. H., and Bartlett, H. H. Absorption and Excretion of Salts by Roots, 
as Influenced by Concentration and Composition of Culture Solutions. I. Concen- 
tration Relations of Dilute Solutions of Calcium and Magnesium Nitrates to Pea 
Roots. U. S. Department of Agriculture, Bureau of Plant Industry, Bull. 231, 1912. 
