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



addition of potassium chloride to the solution are much more evident 

 in the tops than in the roots with respect to the increasing concen- 

 trations of potassium chloride. 



Using a constant concentration of potassium chloride of .18 M., 

 which is an increase of .02 M. over the highest concentration of that 

 salt reported in table 8, against varying concentrations of magnesium 

 sulphate, the results reported in table 9 were obtained. There is a 

 marked increase in total ash as the concentration of the nutrient solu- 

 tion with respect to magnesium sulphate increases. Parallel with this 

 increase is the higher percentage of potassium. The growth decreases 

 inversely. Antagonism between the two salts is evident where the 

 lower concentrations of magnesium sulphate were used. In cultures 2 

 and 4 of this series, we have a marked increase in growth over that of 

 culture 3. Absorption is markedly lower at the two high points than 

 at the intermediate concentration, where the solution is evidently 

 more toxic. The least growth obtained in the series was recorded in 

 culture 7. which shows the highest absorption of all the elements 

 determined. In the two higher concentrations of magnesium sulphate 

 used the growth was increased somewhat while the percentage of cal- 

 cium, magnesium, and potassium in the plants decreased markedly. 

 It seems worthy of note that the amount of iron in the ash was not 

 sufficient to allow of titration at any concentration employed in the 

 series. This series very well illustrates the point which has been 

 brought out a number of times before of the relationship between 

 absorption and growth. Here we have five cultures in the one series 

 of which this relationship is evident. The relations are not absolute 

 in every instance, but there can be no doubt whatever of the tendency 

 toward decreased absorption as growth increases, or that antagonism 

 between ions results in decreased absorption of at least some of the 

 ions present in the nutrient solution. 



We turn now to a consideration of the effects of a few of the salts 

 of the heavy metals upon growth and absorption. In table 10 the 

 effects of adding various concentrations of aluminum chloride are 

 shown. Growth is decreased in every concentration of the salt used. 

 The high percentage. of magnesium is marked in both roots and tops. 

 On the other hand, the percentage of calcium is increased relatively 

 little. The percentage of iron found was practically constant and in 

 total quantity is in marked contrast to the last series considered in 

 which the amount was so small that it could not be determined. 



In a solution of .20 M. calcium chloride, the results with the varv- 



