FUNGICIDES 53 



(4) Persist for some time in an effective condition on the 

 plant. 



(5) Non-poisonous. 



Various fungicides have been boomed from time to 

 time, but Bordeaux mixture, discovered by Millardet in 

 18S5, is undoubtedly the best for use on an extensive 

 scale. In addition to its acknowledged value as a fungi- 

 cide, it is said in some instances, more especially in the 

 case of potatoes, to prolong the life of the foliage, and thus 

 favour the production of a heavier crop. 



Bordeaux Mixture. The essentials for the formation of 

 this fungicide are, copper sulphate (blue vitriol), and milk 

 of lime. Those two substances have from time to time been 

 used in very different proportions in the preparation of the 

 mixture. The general tendency during late years has been 

 to reduce the quantity of lime, and the following proportions, 

 known in America as the 'normal,' or i - 6 mixture, con- 

 sists of: 



Copper sulphate, . . . . 16 lbs. 



Quicklime, . . . . . n lbs. 



Water, 100 galls. 



Place the copper sulphate in a coarse sack and suspend it 

 until the sulphate is melted, just below the surface of a 

 few gallons of water in a cask. In another vessel slake 

 the lime gradually until it is reduced to a creamy con- 

 sistency. When both are thoroughly dissolved, each should 

 be made up to fifty gallons with water, then pour the milk 

 of lime and the copper sulphate solution slowly together 

 into one vessel, after which the liquid should be thoroughly 

 stirred for five minutes. The usual test recommended for 

 determining whether the solution is safe to use, is to place 

 the blade of a knife in the liquid for a minute. If the 

 blade becomes coated with copper, more milk of lime must 

 be added, whereas if the blade remains unchanged, the 

 solution is safe to use. 



Although Bordeaux mixture has been in use for so long a 

 period, the various modifications of its composition have been 

 the result of rule-of-thumb methods, and it is only quite 

 recently that the chemical side of the subject has been in- 

 vestigated by Mr. Spencer V. Pickering, F.R.S., of the Woburn 

 Experimental Fruit Farm. 



The result of this investigation has for the first time 



