274 BOTANICAL GAZETTE [September 



KC1. In the same way G represents a solution in which the 

 molecular proportions are NaCl 25 per cent+KCl 75 per cent; / 

 represents NaCl 75 per cent+KCl 25 per cent; E represents KC1 

 50 per cent+CaCl 2 50 per cent; K represents NaCl 50 per cent+ 

 CaCl 2 50 per cent- 

 All points in the interior of the triangle represent mixtures of 

 the three equally toxic solutions NaCl 0.12 M, KC1 0.13 M, and 

 CaCl 2 0.164M. Along the line FJ are represented mixtures in 

 which the dissolved molecules are 25 per cent CaCl 2 ; the line 

 EK represents mixtures in which the dissolved molecules are 50 per 

 cent CaCl 2 ; the line DL mixtures in which the dissolved molecules 

 are 75 per cent CaCl 2 . In the same way FG means 75 per cent 

 KC1; EH, 50 per cent KC1; DI, 25 per cent KC1; GL, 25 per cent 

 NaCl; HK, 50 per cent NaCl; and //, 75 per cent NaCl. 



The point M is on the line FJ, meaning 25 per cent CaCl 2 ; 

 it is also on the line EH, meaning 50 per cent KC1; and likewise 

 on the line GL, meaning 25 per cent NaCl. It therefore represents 

 a mixture of the three equally toxic solutions, NaCl 0.12M, 

 KC1 0.13M, and CaCl 2 0.164M, in which the dissolved mole- 

 cules are 25 per cent CaCl 2 +5o per cent KCl+25 per cent NaCl. 

 In the same way the point represents a mixture in which the 

 dissolved molecules are 50 per cent CaCl 2 +25 per cent KCl+25 



per cent NaCl. 



omposition 



ram 



At any such 



may be erected expressing 



plant in that solution. When this has been done for a sufficient 

 number of points, a solid model may be constructed which gives 

 a complete description of the growth of the plant in all the solu- 

 tions. Such a model is shown in fig. 2. The ordinates represent 

 the aggregate length of roots per plant of wheat at the end of 30 

 days. The ordinates in the pure solutions are all equal (55 mm.), 



ine 



in part determined directly by experiment and in part calculated 

 from data obtained by growing plants in solutions of approximately 

 the same composition as those represented. 4 



* The data from which this model was constructed will appear in a subsequent 

 publication. 



