THE EXCHANGE OF IONS 
In K2SO4 a small net absorption was seen in concentrations ranging 
from 140 to 204^ X 10-^ The similarity of the records of the more 
dilute solutions of K2SO4 to that of the distilled water check is seen at 
a glance. In the higher concentrations an equilibrium seemed to 
be immediately established between the roots and the solution, the 
result being seen in the slight change in ion concentration which 
took place until the leakage due to approaching collapse set in. 
The growth made by the roots of seedlings grown in these solutions 
was equal to or less than that seen in distilled water. 
Potassium Dihydrogen Phosphate. Experiments 9 and 10 
The range of concentration of solutions of potassium phosphate 
studied lay between 6 and 208M X I0~^ the fixed interval between 
members of the series being 6M X io~*^ in experiment 9 and 16M 
X io~^ in experiment 10. The experiment was continued fifteen 
days in the stronger solutions, sixteen or seventeen days in the weaker 
ones. The results are graphically shown in figures 9 and 10. 
The striking fact shown by these curves is an almost unrelieved 
loss of salts by the seedlings in all concentrations tested. During the 
■first four or five days a period of rapid gain in concentration by the 
medium was seen, followed by a period of slackened loss by the plants. 
Even in this second period, which corresponds in the salts previously 
studied to the time of most rapid absorption, the usual result seen is 
an interval in which a more or less well marked equilibrium was 
maintained. In 64, 96, 176, and i()2M X io~^ solutions, absorption 
predominated by a narrow margin for several days, but in the other 
members of the series the loss of ions by the roots was the rule. The 
final period of loss by the plants due to approaching breakdown was a 
very marked feature, at times an exaggerated one. 
In every solution of the series the result was a marked net 
loss of ions by the plants. In none was this net loss so great as in the 
distilled water check, but in the weaker solutions the leaching of the 
roots seemed to be almost as severe. 
The growth made by the roots in no case showed any considerable 
advance over that made in distilled water. Indeed, the whole picture 
presented by this salt in the concentrations here studied strikingly 
resembled that presented by distilled water. Further evidence, 
showing the harmful action of KH2PO4, was seen in the loss of about 
15 per cent, of the plants used in the cultures. In several cases entire 
cultures had to be abandoned. 
