1917] Lipman-Gericke : Smelter Wastes and Barley Growth 519 



but that much of the salt remaining is adsorbed by the soil and 

 becomes inactive so far as the barley roots are concerned. 



Third Gkop 

 In table Vic, which sets forth the yields of dry matter 

 obtained in the third crop of the FeSO^ series, we find some 

 data of unusual interest. Despite discrepancies in the weights 

 of dry matter obtained in duplicate pots, there can be little 

 question that the higher concentrations of FeS04, beginning 

 with 1.4 per cent, definitely stimulate straw production, while 

 the lower concentrations employed, less definitely but probably 

 without doubt, depress it. Grain production, on the other hand, 

 seems to have been stimulated in the third crop by all concentra- 

 tions of FeSO^ employed, and the yields are high enough and 

 agree well enough in the duplicates to justify that conclusion. 

 In the case of the roots, still another effect was probably induced 

 by FeS04. No stimulation can be definitely noted, yet the 

 toxic effect, if any, is small and apparent in very few instances. 

 In the case of the total dry matter produced, marked stimulation 

 seems to have been obtained at concentrations of FeSO^ respec- 

 tively of 1.4 per cent, 1.6 per cent, and 2 per cent. "When com- 

 pared with the third crop of the CuSO^ and ZnSO^ series, the 

 third crop of the FeSO^ series stands out sharply. It gives 

 stimulation only at the higher concentrations, the ZnS04 gives 

 no stimulation and almost positive toxicity throughout, and the 

 CuSO^ gives stimulation almost throughout the whole series in 

 the third crop. While all three of the salts may be quite harm- 

 less and even stimulating in relatively small quantities, they 

 manifest very definite and specific characters when employed in 

 higher concentrations and when results are obtained on the same 

 soil for more than one season. 



Lead Sulfate — Greenhouse Soil 



Entirely unlike the three salts thus far discussed, PbS04 

 exercises what appears to us to be a definitely toxic effect 

 throughout the first crop. This observation must be considered 

 separately for every crop. It should be noted that unlike the 



