30^ The Wohurn Pot- Culture Experiments, 1914, 



('10 per cent.i) dressing with sulphate of copper, the two 

 heaviest ("10 and '05 per cent.) with nitrate of copper, and the 

 heaviest ('lO per cent.) with arsenite of copper. 



With sulphate of copper in the heaviest dressing the first 

 plant did not appear until January 29, 1914 ; with nitrate of 

 copper ('10 and "Oo per cent.) the first appeared on February 2, 

 1914, and only two or three plants came up in all ; while with 

 arsenite of copper ("10 per cent.) only two plants came up, 

 though the germination in the case of the smaller applications 

 was quite satisfactory. 



The twelve plants were thinned to six plants on March 16, 

 except where these had been already materially affected, 

 when all the plants were left. Observations taken at diflt'erent 

 periods during the period of growth led to the following 

 general conclusions : — 



The untreated plants throughout were healthy and vigorous. 



With sulphate of copper the plants receiving the heaviest 

 application ('10 per cent.) did not make much growth, and 

 showed but little tillering. With the dressing of "05 per cent, 

 better growth was obtained, but both this and the heavier 

 application clearly showed toxic indications. 



With phosphate of copper the plants were decidedly good, 

 and seemed to have been to some extent stimulated throughout 

 the whole series. There was no indication of toxic influence 

 in any of these pots. With carbonate of copper the indica- 

 tions, though in the same direction as with the sulphate, were 

 not 80 marked. 



Nitrate of copper gave more marked signs of injury than 

 any of the foregoing. With '10 per cent, of copper there was 

 no growth whatever, and with •05 per cent, the indications 

 were very similar to those with the heavy dressing (•10 per 

 cent.) of sulphate of copper. Towards the later period of 

 growth the lighter applications of nitrate of copper seemed to 

 show the benefit of the nitrogen in the darker foliage produced. 



Lastly, with arsenite of copper, all the plants were killed 

 off by the heaviest dressing (•lO per cent.). With •OS per cent, 

 though the germination had been good, the plants were very 

 weak, and nearly all eventually died. Much the same effect 

 was produced with the application of '02 per cent., and the 

 still smaller dressings also affected the plants injuriously. 



The wheat came into ear on June 12. Photographs of the 

 growing crops were taken on August 10, and the crops them- 

 selves were cut on August 18. The results are given in 

 comparative form in Table I. 



1 Note. — The figures wherever given in this experiment refer to the 

 amount of metal (copper) contained in the various salts as actually applied and 

 not to the amounts of the salts themselves. 



