128 SOME RECENT RESEARCHES IN PLANT PHYSIOLOGY 



obtained by diluting mixtures of isotoxic solutions, A and 

 B, Osterhout employs a solid model in which the ordinates 

 are lengths of growth and the base is a square, one side of 

 which, CD, represents pure water, and the other side, GH, 

 the solution. This can be diluted with water, the effect of 



FIG. 13. A SOLID MODEL WHICH GIVES A COMPLETE DESCRIPTION OF 

 THE CHANGES PRODUCED IN THE FORM OF THE ANTAGONISM CURVE 

 BY ALTERING THE CONCENTRATIONS OF THE SOLUTIONS. 



which is to shift the line representing it inwards halfway 

 towards the side CD. It then will occupy the position 

 EF, as shown in Fig. 12. 



By altering the composition of the isotoxic mixture also, 

 a number of lengths of growth may be obtained, and a 

 solid model may then be constructed, as in Fig. 13. 



