1922] GERICKE—MAGNESIA INJURY Iil 
cultures were allowed to grow four weeks. Table I gives the 
experimental data. 
The injury sustained by the seedlings grown in the solutions of 
potassium salts differed with the salts used, being least in the 
KH,PO, set and most marked in that of K,SO,. Considerable 
abscission of the leaf tips occurred in the seedlings grown in the 
solutions of KNO,, although these cultures made by far the best 
growth (total dry matter production) of any of the nine different 
salt solutions employed. In marked contrast to these are the 
results obtained from the cultures grown in the solutions of different 
calcium salts, none of which gave any symptoms of the character- 
istic injury. Of the cultures grown in the solutions of magnesium 
TABLE I 
RELATIVE EFFECTS OF SALTS IN PRODUCING ABSCISSION OF LEAF TIPS OF WHEAT 
SEEDLINGS 
Salts goncentrty | Pu Value Injury 
ey ie cae a 0.01 6.3 Decided 
re i eae 0.01 5.2 Slight (some plants showing none) 
poe Pea oe eee ha 0.01 7.4 Excessive 
CeO as ey 0.01 eee N 
CaHPO, and Ca(H,PO,),.. .|Saturated 5.0 None 
0.002 
Mb cla a eles Gk sa 0.01 6.7 None 
WAMUING ee i es 0.01 ‘3 Excessive 
rd 6 i 8 pee Ie Ea bie 0-01 eB None 
Bi a eis Gs cee 0.01 6.0 Excessive 
salts, those grown in Mg(NO,),. and MgSO, were severely injured, 
but those grown in MgHPO, were not, being perfectly normal in 
this respect. While the P,, values of solutions were not the same, 
nevertheless it is not evident that this was an important factor to 
account for the results. 
The injury of abscission to the leaf tips of the cultures grown 
in the solutions of potassium salts appeared to be similar in every 
respect to that of the cultures grown in solutions of Mg(NO,), 
tr MgSO,. Whether it was physiologically the same cannot be 
stated at this time. If the injury to these seedlings was physio- 
logically the same, it appears that there are at least two factors 
apparent in the data that are related to this injury of abscission 
of leaf tips, as follows: 
