[E FORMS OF ANTAGONISM CURVES AS AFFECTED 



BY CONCENTRATION 



W. J. V. OSTERHOUT 



(with three figures) 



A study of the literature shows that the effect of concentration 



form of the antagonism 



The 



marked 



are diluted to one-half strength. The writer has found this to be 

 the case with antagonism curves of different types obtained by 

 using a great variety of solutions. The purpose of this paper is 

 not to give the results of these experiments, but merely to state 

 some general principles in the hope that they may be of use to those 



make 



diagram 



matic composit 

 of salts; these 



com 



For the sake 



sim 



one pair of salts, which are designate* 

 CDE, therefore, reDresents diasrramma 



The 



mixtures 



The ordi- 



The abscissas represent molecular proportions; thus the point G 

 represents a mixture in which the dissolved molecules are 75 per 

 cent A and 25 per cent B; the point H a mixture in which the dis- 

 solved molecules are 50 per cent A and 50 per cent B. 

 nates represent the growth of roots in the various mixtures. 



The antagonism at any point is the total growth minus the 

 growth which would have taken place if no antagonism existed. 1 

 This antagonism is best expressed as percentage of the growth 

 which would have taken place in the absence of antagonism. Hence 



m 



FD-FG 

 FG Xl °°- 







1 This latter amount of growth is called the additive effect and is expressed by the 



horizontal dotted line CE. Cf. Bot. Gaz. 58:178. 1914. 

 367] 



[Botanical Gazette, vol. 58 



