552 University of California Publications in Agricultural Sciences [Vol. 1 



Pfeffer,"' ^Miiller/^" Lehmann,"" and Brenchley.^-" In our 

 analyses both grain and straw were examined, and copper and 

 zinc onl.y were determined. These were both determined electro- 

 lytically. Unlike Yedrodi/-^ we could find nothing more than 

 traces of copper or zinc in the grain, but succeeded easily in 

 obtaining definite quantities of those metals in the straw from 

 some of the pots. In the first crop, from thirtj^-six to forty-three 

 grams of straw were taken for analysis for copper, and, after 

 ashing, the mineral residue was prepared for analysis for copper 

 by the metliod above mentioned, straw from the pots receiving 

 100, 800, 1100, and 1200 p. p. m. CuSO, being employed. In the 

 first case, the percentage of copper in the straw varied from 

 nothing to 0.0006 per cent. In the second case, the percentage 

 of copper was 0.0002. In the third case, it was 0.0033 per cent, 

 and in the fourth case, 0.0044 per cent. 



In the pots receiving ZnS04, there were chosen for analysis 

 the straw produced in those receiving 100, 300, 500, 1000, 1100, 

 1200, 1300, and 1600 p. p. m. In the first case, the analysis 

 showed the presence of zinc to the extent of 0.00036 per cent; 

 in the second, 0.0008 per cent; in the third, 0.003 per cent; 

 in the fourth, 0.017 per cent; in the fifth, 0.013 per cent; in 

 the sixth, 0.013 per cent ; in the seventh, 0.01 per cent ; and 

 in the eighth, 0.012 per cent. In the cases of both zinc and 

 copper the percentage of the metals absorbed by the barley 

 plant was smaller than that reported as being absorbed by 

 the plants studied by other investigators whose w^ork is re- 

 ferred to in the literature last cited. In general, it Seems that 

 up to a certain point increasing quantities of the metals added 

 to the soil induce larger absorptions of metal by the plant, but 

 beyond that point the addition of metals to the soil appears to 

 be without effect in inducing further absorption. This seems to 

 be particularly true in the case of the zinc. We do not desire, 

 however, to draw" any conclusions from the relatively meager 

 data which we have gathered on the subject in question under 



11" Pflanzenphysiologie, Leipzig, 1897 and 1901. 



118 Ztsclir. Pflanzenkrank., 4, p. 142. 



119 Arch. Hyg., 27, p. 1. 



120 Inorganic plant poisons and stimulants, Cambridge, 1914. 



121 diem. Ztg., 20, p. 399. 



