-I ^ , , 
0 30 60 
MIN. 
Fig. I. Curves showing the effects of NaCl and CaCl2 on the respiration of Elodea 
canadensis. The horizontal Hne at the left of the point marked O on the abscissae repre- 
sents the normal rate of respiration before the addition of the salt. 
Curve A represents the rate of respiration in NaCl o.i M, curve B in CaCU 0.07 M; 
the other curves represent the rate in mixtures of these having the following molecular 
percentages: curve C in 99.65 percent NaCl+0.35 percent CaCU; curve D in 98.62 NaCl 
+ 1.38 CaCh; curve E in 98.85 NaCl+1.15 CaCU; curve F in 98.28 NaCl+1.72 CaCla. 
The broken line represents the control in distilled water. Each curve represents a typical 
experiment. 
The determination of antagonism should preferably be made at a period 
of the experiment when both solutions of pure salts give either an increase 
or a decrease in rate. Since the former was impossible, an exposure of one 
hour was chosen, at which period both gave a decrease and the time curves 
had become nearly horizontal. Figure 2 shows the rates of respiration in 
various mixtures and in the solutions of pure salts. The ordinates represent 
