REPORT OF THE ENTOMOLOGIST AND BOTANIST. 249 



SESSIONAL PAPER No. 16 



the Eoyal Agricultural Society, on some of the experiments referred to, is of particular 

 interest to Canadian experimenters, who have been disappointed at the results some- 

 times obtained when spraying has been tried for the destruction of mustard in districts 

 where the Bird Rape (also called Kale, or Smooth-leaved Charlock) is abundant. This 

 is particularly the case in Manitoba, where by far the greater proportion of the plants 

 called Wild Mustard are really Bird Rape (Brassica caw,pestrls, L.) ' I have not been 

 able to detect anything in the structure of the Charlock that should make it so readily 

 a prey to the copper sulphate. This is still more remarkable when we find that it does 

 not in the least injure another species in the same genus, which in Cumberland is 

 known as the " Smooth-leaved Charlock." This plant, the Brassica campestris of 

 Linnaeus, is very common in some districts. A correspondent in Cornwall writes that 

 it is very common in his county. He has observed that while the common Charlock 

 is easily destroyed by copper sulphate, the smooth-leaved plant is quite uninjured by 

 it. This is probably the explanation of the difference in the testimonies as to the 

 influence of copper sulphate on Charlock. The two plants so closely resemble each 

 other that only a careful observer can distinguish that they differ. The true Charlock 

 (Brassica Sinapistrum, Boiss.) is destroyed by treatment, while the smooth-leaved 

 Charlock {Brassica campestris, L.) is not affected. 



'As the general outcome of Mr. Hornsby's experiments, it would seem that for Char- 

 lock when still young, 40 gallons per acre of 2 per cent solution of sulphate of copper 

 would be found effectual, but that, if the Charlock were already in flower, as much as 

 OO gallons of a 4 per cent solution would be required.' 



