160 University of California Publications in Agricultural Sciences [Vol.3 



Possible Effects of Variations in the Concentrations of 

 the Solutions on the Plants 



No attempt was made to maintain the total concentration of the 

 nutrient solution constant. This would be exceedingly difficult to do 

 in work of this character, since it would be necessary to vary the 

 concentration of the nutrient solution to maintain the balance of the 

 solution as regards total concentration. The conclusion seems justi- 

 fied that within the range employed the concentration of the nutrient 

 solution is of minor importance as far as growth is concerned. For 

 instance, in table 1, the variation in the concentration of the solution 

 was .279 M. in terms of calcium chloride, yet the total growth varied 

 but little from .001 M. to .28 M. Again in table 2 the growth is very 

 nearly the same at a concentration of .25 M.. with calcium and mag- 

 nesium chlorides, and a total concentration of .54 M. of the same salts. 

 In table 3 the greatest growth occurred in a concentration of .46 M. 

 in terms of the salts above mentioned, while at the lower concentra- 

 tions of .304 M., growth was but a third that obtained in the higher 

 concentrations. These examples make clear the point above men- 

 tioned, namely, that the concentration over the range used was of 

 but minor importance. It is obvious that the above discussion does 

 not apply to the series in which salts of the heavy metals were used, 

 since the variations in concentration in those series were but slight. 



Consideration of a Possible Calcium-Magnesium Ratio 



Since Loew 44 first advanced the hypothesis of the lime-magnesia 

 ratio, much experimental evidence has been collected by various inves- 

 tigators both for and against the existence of an optimum ratio be- 

 tween these two elements as regards the growth of plants. The 

 literature bearing upon the subject has been very fully reviewed by 

 Lipman, 45 so that detailed references are not necessary here. 



Since the ratios of calcium to magnesium in the solution used by 

 the writer were known and also because of the fact that the analytical 

 data allowed of the calculation of such a ratio for the plants, it 

 seemed of interest to present some of these data here. 



The following two tables give the results obtained from two series 

 in which widely varying proportions of calcium and magnesium were 

 used. 



« Flora, vol. 75 (1892), p. 368. 



« Plant world, vol. 19 (1916), p. 83. 



