191 1.] Identification and Eradication of Weeds. 465 



so escaping permanent injury ; the young leaves of charlock, 

 on the other hand, are broad, rough, and more or less hori- 

 zontal, and retain the spray fluid, to their destruction. The 

 solution used should be a 2, 3, or 4 per cent, solution of copper 

 sulphate* (8, 12, or 16 lb. in 40 gallons of water), or a 15 per 

 cent, solution of iron sulphate* (60 lb. in 40 gallons of water), 

 40 gallons in either case being sufficient for an acre. Where a 

 2 per cent, solution of copper sulphate is used, it may be 

 useful to spray a second time, after an interval of ten days or 

 a fortnight. In wet climates the stronger solution should be 

 employed. Soft water should be used when possible, and the 

 spraying machine should generate a fine spray under air 

 pressure. Spraying should take place during calm, settled 

 weather, about the time the charlock enters the "rough leaf" 

 stage, about May or June, when it is not more than 3m. high, 

 and the corn crop is still rather short. f Wooden buckets and 

 tubs must be used to prepare the solution. 



Experimental results show that spraying as recommended 

 above does no permanent injury to the corn crop, nor to 

 "seeds " sown in such a crop, while, in some cases at least, 

 mangolds, beans, peas, tares, and sainfoin have been sprayed 

 for the purpose of destroying charlock without injury to the 

 crops concerned. 



Poisonous Properties. — The whole charlock plant is irritant 

 in character when in bloom, but the seeds are considered 

 dangerous if eaten. It is stated by Cornevin J that when used 

 in admixture in the manufacture of a poor quality oil-cake, 

 and fed to cattle, the cake caused intestinal inflammation, 

 severe diarrhoea, and great thirst, probably due to oil of 

 mustard. Percival says that the seeds "are sold by many 

 farmers to oil-cake manufacturers, finally appearing as im- 

 purities in rape and other ' cakes.' " § 



Wild Radish. 

 The Wild Radish (Raphanus Raphanistrum, L.), known 

 also as Runch, Jointed Charlock, or White Charlock, is a weed 

 closely allied to Sinapis arvensis, which it resembles in habit, 



* Ninety-eight per cent. pure. 



t Charlock may also be sprayed when in flower ; though spraying at this time is 

 to be avoided when it is possible to spray the seedlings, yet it results in the destruc- 

 tion of many of the flowers and so largely prevents the formation of seed. 



X Ch. Cornevin, Bes Plantes Vendnetises. 



§ John Percival, Agricultural Botany, 4th ed., 19 10, p. 385. 



