1913] LIPMAN & WILSON—TOXIC SALTS AND -ACIDS 415 
The next series deals with the effects of ZnSO, on plants. The 
experiment was arranged similarly to the preceding, but the con- 
centrations are slightly different, as shown in table II. 
TABLE II 
EFFEcts oF ZNSO, ON PLANTS 
DRY WEIGHT OF VETCH a sg 
ZnSO, ppm. 
Roots gm. Tops gm. Tops gm. 
FPR Re urge Hee Se FR Acs 2.0 18.5 
IOs Suc eee ee eg £5 12.5 $9.5 
BOs es 8s ee ee eee re 20.0 18.5 
TOO go ai oe oe 4.5 22.0 18.5 
ROO a Sc ee eee 45 20.0 14.6 
3008 5 iS eee er rere 2.0 20.0 10.8 
BOO a les ec ga 1.8 18.0 19.8 
BOO er eee 1.5 15-5 13.7 
These results do not show any marked toxicity of ZnSO, either 
for the vetch or the wheat. In the case of the vetch, there would 
even seem to be an appreciable degree of stimulation up to rather 
large concentrations of zinc. We can certainly not confirm any 
toxic effects of zinc salts on plants observed by others, at any rate 
so far as the concentrations employed above are concerned. The 
seeds germinated in the zinc-treated soils in a normal manner, and 
the plants in all the concentrations of the ZnSO, seemed to make a 
normal growth. Whatever differences may be noted in table II 
between the growths made in the pots of the different concentra- 
tions of salt employed must be attributed to insect or fungus injury 
rather than to any effect of the ZnSO,. A comparison of our results 
with the effects of zinc noted by EHRENBERG, whose work is above 
cited, would seem to indicate that the later investigations® attribute 
both favorable and unfavorable effects to the zinc dissolved out from 
the galvanized iron cylinders used in the vegetation experiments. 
EHRENBERG Claims that zinc acts favorably in that it displaces the 
bases from their insoluble combinations, and because of its harmful 
effect on soil organisms makes less competition for the plant in 
the latter’s search for soil nitrogen. On the other hand, the same 
author points out that zinc sets free hydroxyl ions which exercise 
§ Landw. Versuchs. 72:15. 1910. 
