1922] GERICKE—MAGNESIA INJURY 113 
produce injury. It does, as has been shown in other experiments, 
prevent injury where magnesium ions are excessive. The harmful 
effect of some of the positive ions, however, can also be prevented 
or greatly mitigated by the presence of certain negative ions. The 
phosphate ion comes in this category in the cases of the MgHPO, 
and KH.PO, in this experiment, the former salt producing no 
injury and the latter salt only a little. Under certain conditions, 
therefore, it may be expected that additions of phosphate salts 
should prove beneficial to nutrient solutions that are toxic due to 
excessive concentrations of either magnesium or potassium. This 
the writer has found to be the case in other experiments. 
No reference has been made to the literature, as this is to be 
taken up later when the subject will be discussed in greater detail. 
UNIVERSITY OF CALIFORNIA 
