184 



BOTANICAL GAZETTE 



[august 



having almost the same composition as the solutions given in the 



table mentioned. 



may be menti 



exam 



maxima 



If instead of mixing two equally toxic solutions we keep the 

 concentration of one salt constant while varying that of the other, 

 it becomes very difficult to determine the additive curve, especially 



TABLE II 



Mixtures of unequally toxic solutions 

 Wheat (growth during 30 days) (NaCl o. 12 M + CaCl 2 0.12 M) 



Culture solution 



Aggregate length of 

 roots per plant 



m mm. 



Additive effect 



Antagonism 



CaCL 



75 per cent CaCl 2 



u 



25 

 50 



5° 



75 



i5 

 S5 



5 

 95 



u 



.. 



u 



.. 



u 



.. 



NaCl. 



CaCU 

 NaCl. 



CaCl 2 



NaCl. 



CaCl, 

 NaCl 



8^ 



125 



19s 



310 



85 



75 



12 



73 



66.=; 



60 



99 



NaCl 



.. 



4* 



U 



CaCl 2 

 NaCl 



CaCl 2 

 NaCl 



380 



438 



300 



55 



75 

 195-66.5 



0.67 



66.5 



1 93 



310 



60 



58 



56 



55 

 55 



60 



380-58 

 58 



438-56 

 56 



3°°-55 

 55 



4-17 



OOJ 



6.82 



4-45 



The percentages refer to molecular proportions; that is, 75 per cent CaCL+25 F*r cent NaCl 

 means a solution in which 75 per cent of the dissolved molecules are CaCL and 25 P« cent are NaCl. 



when variations in osmotic pressure influence the result. It is 

 therefore difficult to obtain an accurate quantitative expression of 

 antagonism by this method, and in critical cases it may be impos- 



nism 



Emphasis should be laid on the fact that the growth of parts 

 not in immediate contact with the solution does not furnish a trust- 

 worthy criterion of antagonism. Thus the leaves of wheat (which 

 are not in contact with the solution) often grow well at the start in 



