PROCEEDINGS, 1918 53 



ary mixture, it is to be expected that such mixtures would act 

 differently when applied to foliage. 



Other investigators corroborate the findings of Pickering 

 and Sicard and agree with them regarding the greater fungicidal 

 value of such barely alkaline mixtures as Woburn Bordeaux. 

 On the other hand, there are not wanting those who take ex- 

 ception to this view and favor compounds in which an excess 

 of lime has been employed. Vermorel and. Dantony (10) for 

 example, contend that alkaline Bordeaux mixtures, contrary to 

 general opinion,contain copper in a soluble state 2000 to 4000 

 times more concentrated than is necessary to stop the growth 

 of mildew and that objections raised against (alkaline) Bor- 

 deaux are not justified. 



Lutman (11) states the case as follows: 



"The importance of the fungicidal properties of lime and 

 the slow solubility of the copper salts formed in Bordeaux mix- 

 ture cannot be too strongly emphasized, for it is upon these 

 facts that the long continued efficacy of the ordinary mixture 

 depends. The copper salts becoming slowly soluble over the 

 larger part of the sprayed area serve to protect the larger parts 

 of the foliage, but dotted throughout these dried films are small 

 particles of lime, the double function of which is to prevent too 

 much of the copper salts in their immediate region from becom- 

 ing too promptly soluble, and to prevent germination of the 

 spores and the growth of the fungi over the region ir which 

 they lie. The claim is made for the Pickering Bordeaux that 

 since it contains no superfluous lime particles, it is fungicidal 

 as soon as it is applied. It should be pointed out, however, as 

 a corollary of this claim that this mixture must be,if valid, in- 

 herently defective in that it necessarily cannot remain fungici- 

 dal for nearly so long a time as the ordinary Bordeaux, because 

 its copper will have passed into a soluble condition and have 

 been washed away by the rain at a time when the ordinary mix- 

 ture with its excess of lime has some copper still entering into 

 solution to protect the plant. The question seems to resolve 

 itself as follows: the relative desirability of copper salts in con- 

 siderable quantities immediately available for use and for a 

 relatively short period of time, and of lesser quantities of these 

 salts available at once but distributed over a longer time. Since 

 the ordinary mixtures furnish enough free copper to exercise 

 a fungicidal effect, there would seem to be no reason for short- 

 ening the life of an application of the mixture by spraying 

 with a neutral Bordeaux. If lasting fungicidal properties are 

 desired, the ordinary Bordeaux is better than the neutral Bor- 



