310 Hie Wohurn Pot- Culture JUxperiments, 1914. 



whereas with the heaviest dressing of sulphate of copper no 

 crop at all was obtained in 1913, there was now somewhat less 

 than half a crop. With 05 per cent, of copper, which gave 

 only a small crop in 1913, the injurious action of sulphate of 

 copper was now not nearly so strongly marked, whereas with 

 quantities of '02 per cent, and less the result was neutral, or 

 possibly slightly stimulating, as found in 1913. 



With phosphate of copper there was no instance of injury, 

 and, on the whole, the ejffect of the applications was one of a 

 stimulating nature. It is noticeable, however, that though 

 these crops generally looked better than the untreated (see 

 Plates 5, 7, 9, 11), the produce when weighed showed no 

 actual increase. 



The results with carbonate of copper were in the same 

 direction, though hardly as marked as in 1913. The heaviest 

 dressing (-10 per cent.) gave under three-quai'ters of a crop, 

 but with quantities of "05 per cent, and under no harmful, but 

 possibly a somewhat stimulating, effect was produced. 



The results with nitrate of copper were very striking. They 

 are separately illustrated in Plates 1 and 2. The application of 

 •10 per cent, of copper almost entirely destroyed the crop, while 

 •05 per cent, reduced it to less than half a crop. When ^02 per 

 cent, of copi)er was used, no harm resulted, and lesser quantities 

 had decided stimulating influences, due, no doubt, to the 

 nitrogen supplied in the salt. It will be noticed from Plate 2 

 that the roots of the plants receiving ^02 per cent, of copper in 

 the form of nitrate had a distinctly feathery appearance, 

 whereas with •Ol per cent, this disappeared, and the roots 

 became of normal character. 



With arsenite of copper, all the first three (and heaviest) 

 dressings entirely destroyed the crop, while smaller amounts, 

 even down to •005 per cent, of copper, affected it adversely. 

 This was owing, no doubt, to the doubly toxic influence exer- 

 cised by the two bodies, copper and arsenic. The crops and 

 the corresponding roots are illustrated separately in Plates 3 

 and 4. It will be seen that even as little as •OOS per cent, of 

 copper in the form of arsenite produced some reduction on the 

 untreated crop. 



The appearances presented by the growing crops and the 

 corresponding roots as a result of using sulphate of copper and 

 and carbonate of copper respectivelj' have already been illus- 

 trated in last year's report (see Plates 3 and 4, 5 and 6, R.A.S.E. 

 Journal, 1913, pp. 416-17). The results of the experiments of 

 1914, as already mentioned, were in the same direction, though 

 injury — when done — was not so marked in amount as in 1913. 



In addition to illustrating the effect of a single salt of 

 copper used in different amounts, it has been thought desirable to 



