414 BOTANICAL GAZETTE [JUNE 
of copper. It is especially interesting here to mention the rapid 
and rank growth made by the vetch plants in the highest concen- 
tration of copper. All the seeds germinated and the vetch plants 
seemed to grow erect to a height of 6 inches or more before they 
began to bend downward by their own weight. The plants in the 
normal soil and in those with low concentrations of copper made but 
very little upright growth. One further point is of great interest in 
regard to the vetch plants, and that is that even at the highest 
concentrations of copper, the root development appeared to be 
normal and showed a marked and vigorous development of nodules 
(the soils were all inoculated). In general the effects of the copper 
sulphate as given in table I stand out in sharp contrast with the 
results above reviewed. They exhibit, on the one hand, a very 
much greater resistance to the effects of copper on the part of both 
wheat and the vetch plants than Haywoop observed in the case of 
wheat and rye as above noted; and on the other hand, our observa- 
tions on the plants growing in the highest concentrations of copper 
given in table I lead us to believe that they will not withstand 
amounts of copper at all to be compared with those tolerated by the 
plants with which the experiments at the New York Experiment 
Station were carried out. From our results it would appear that 
the use of irrigation water containing a few parts of copper per 
million would not for many years react deleteriously to plant 
growth, while the very reverse is believed by Haywoop on the 
basis of his results. Further results were promised by Haywoop 
in 1908 based on his experiments with soils, but none have as yet 
appeared. 
With reference to the cause of the injurious action of copper 
there are two explanations. One shows that there is direct injury 
due to absorption of copper as manifested by analysis, and fre- 
quently showing a large quantity of copper in plants sprayed with 
fungicides or in those growing in soils with a high copper content. 
HAsELHOFF, however, whose work is cited above, claims that his 
investigations indicate an increased solution of lime and potash 
and subsequent leaching away of these materials through the action 
of copper sulphate, and that injury can be averted by applications 
of CaCO, to replace the losses taking place as indicated. 
