1917] Lipman-Gericke : Smelter Wastes and Barley Growth 513 



as a criterion to determine the effects of CUSO4 on the growth 

 of barley in the Oakley sand. Our data show very clearly the 

 stimulating effect of CUSO4 for barley in the first crop on the 

 Oakley sand. They also show, more clearly than any series 

 above described, the toxic effect exercised by CUSO4 at the higher 

 concentrations. The stimulating effects further do not occur at 

 such high concentrations of CuSO^ in the case of the Oakley 

 sand as in that of the greenhouse soil or even in that of the 

 adobe soil. To be specific, we find that at concentrations of 100, 

 200, and 300 p. p. m., CuSO^ is definitely stimulating to barley 

 production on the Oakley soil under the conditions of our ex- 

 periment. The most marked results of the stimulation in ques- 

 tion are not manifest in the production of straw or even in that 

 of roots when it is at all perceptible, but is very marked in nearly 

 all cases so far as grain production is concerned. It is a curious 

 fact that at a concentration of 600 p. p. m. CuSO^ in the Oakley 

 soil, we obtain the largest grain production of the whole series, 

 and yet the straw production is depressed through the CuSO^ 

 treatment at that concentration and the root development almost 

 entirelj^ inhibited. This fact is very difficult to explain, but 

 exhibits parallelism to similar facts observed by both Pammel 

 and Van Slyke in the experiments above cited. When the dry 

 matter produced is considered as a whole, and straw, grain, and 

 roots are considered together, stimulation is noted only in the 

 case of the first two concentrations of CuSO^ employed, and the 

 stimulation is not very marked. In other words, one is obliged 

 to state definitely the criterion employed when forming a judg- 

 ment as to the existence or non-existence of a stimulating effect 

 of CuSO^ on barley grown on the Oaklej^ sand. It will be 

 necessarj^ in the future, for a more decided judgment of the 

 question in hand, to grow several successive crops of barley on 

 the soil named, once treated with CuSO^, as shown in the table, 

 and possibly also to supply available nitrogen, which is a serious 

 limiting factor in the growth of barley on that soil. Without 

 making any final statements in the premises, however, the data 

 given by us in table IV seem to point strongly to the existence 

 of a stimulating action of CuSO^ to barley growth, even on the 

 Oakley sand. 



