166 University of California Publication* in Agricultural Sciences [Vol.3 



of potassium, iron and copper in certain series. With these facts in 

 mind the results of the investigation may be briefly stated as follows : 



The composition of the plants grown in different solutions varied 

 widely. 



Normal growth, i.e., approximately that of the controls, was always 

 accompanied by approximately equal percentages of calcium and 

 magnesium in the plants. 



In nearly all cases in which the growth of the plants was decreased 

 to a marked extent, the amounts of the two elements referred to above 

 were increased greatly. 



The degree of absorption of any salt seems to be independent of 

 the concentration present in the solution over a wide range. 



Certain relationships are pointed out between calcium and mag- 

 nesium absorption and the presence of iron and zinc salts in the 

 solution. 



Antagonism as evidenced by growth is correlated with absorption 

 of the ions, which were determined, in every instance. 



Stimulation of growth was recorded when ferric sulphate M<as 

 present in the nutrient solution in certain concentrations and with 

 ferric sulphate and zinc sulphate together. 



The amounts of the two ions uniformly determined were not neces- 

 sarily found in the same proportions in roots and tops. 



The possible effects of changes in concentrations of the various 

 solutions are considered, and the conclusion reached that the changes 

 in concentration were of secondary importance over the range of con- 

 centrations of the various salts used. 



Data are presented showing that growth is the same with widely 

 varying ratios of calcium to magnesium in the nutrient solution. 



The results in general confirm those of Loeb, Osterhout, and 

 Brooks in finding that antagonistic salt action tends toward the 

 preservation of normal permeability of the plasma membrane in living 

 tissue. 



This problem was suggested by Dr. C. B. Lipman. The writer 

 wishes to express his thanks for this and for many other valuable 

 suggestions offered while the work was in progress. The writer is also 

 indebted to Prof. L. T. Sharp for helpful advice. 



