1917] Lipvian-Gericke : Smelter Wastes and Barley Growth 509 



since there is no regularity in the inhibiting power of CuSO^ 

 referred to ; but small as well as large concentrations at isolated 

 points in the series depressed the yields as above pointed out, 

 whereas the rest of the concentrations, also small and large, 

 stimulated the yields. 



While the total dry matter produced in the third crop, as 

 shown above, is greater than that yielded in the second crop, 

 the yield of grain in the latter is far superior to that in the 

 third crop. Thus the highest grain yield in the third crop is 

 scarcely more than one-third that of the second crop, and the 

 lowest yield of the third crop is about one-sixth that of the 

 second crop. Nevertheless these facts are of no significance in 

 connection with the effects of CuSO^, since the control pots 

 manifest the same depression in grain yields which is character- 

 istic of the treated pots in the third crop. Likewise, in most 

 cases the treated pots produced more grain than the untreated 

 pots. 



The point of maximum stimulation of CuSO^ to the produc- 

 tion of dry matter by the barley plant on the greenhouse soil is 

 very difficult to discern. While apparently it occurs at the 

 concentration of from 0.18' per cent to 0.2 per cent CuSO^ of 

 the dry weight of the soil, the irregularity and non-agreement 

 of many of the duplicate pots render decisions in such matters 

 unsafe, if not valueless. In general, however, the figures in table 

 lie leave little room to doubt the non-injurious nature and 

 perhaps the stimulating effect of CUSO4, at considerable con- 

 centrations, for barley in the greenhouse soil under the 

 conditions described. 



Copper Sulfate — Adobe Soil 



Tables Ilia and b give the results obtained with CUSO4 

 treatment in the case of the adobe soil in the first and second 

 crops respectively. It will be noted at the outset that the yields 

 on the adobe soil are much lighter than those on the greenhouse 

 soil. The reasons for this circumstance are of course not far 

 to seek, in the light of the origin and descriptions of the soils 

 used in these experiments which are given above. Only two 

 crops were grown on the adobe soil, because we did not decide 



