1920] 
DUGGAR—H-ION CONCENTRATION AND NUTRIENT SOLUTIONS 47 
grown under the conditions described,—related in part, pre- 
sumably, to adsorption and buffer action. 
In general, it would seem that there may be no single “best” 
solution for the growth of any of the 3 plants employed in this 
work. In all probability a “best” solution, like the “optimum” 
temperature, is represented within the “optimum” concen- 
tration rather by considerable range of salt or ion proportions, 
influenced to a greater or less degree by environmental factors. 
If the initial Pa of the culture solution is considerably less 
than neutrality there is generally a tendency for this to be 
shifted toward the neutral point, although this depends in part 
upon the composition of the solution and in part upon the plant 
grown. 
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