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_ Solution of the copper of the Bordeaux mixture by atmospheric _ 
Conditions, for all experiments go to show that the Bordeaux | : 
mixture is effective from the day it is applied. So much in 
brief review of some of the experiments that have led me to the — 
following conclusions regarding the ee of this a pias oe 
) fungicide : aot 
bs chiefly accomplished by the solvent action of the fungus spores them- 
= for es have _— to dissolve sufficient a to yell 
- “the Spores of parasitic fungi is probably not more than one pari 
) he Soluble metallic eoppet to = 000, apes water r (dew Se 
1902 ] TOXIC PROPERTIES OF COPPER COMPOUNDS 43 
the union of the epidermal cells.%* When the dew is on the leaf 
we have two solutions—the dew drop without and the cell sap 
within—separated by a more or less permeable membrane. 
The result of these conditions must result in the exosmosis of at 
least some of the contents of the cell sap, which coming in con- 
tact with the copper hydroxid adhering to the leaf surface causes 
more or less of it to pass into solution. An important point in 
this connection is that the solution of the copper, whether 
effected by the host or the fungus spore itself, is possible in the 
presence of an excess of lime. This excess is apparently some- 
what detrimental to the solvent action on the copper, and in this 
way doubtless serves a very valuable purpose in preventing a too 
rapid solution. It also protects the Cu(OH), from the solvent 
action of the ammonia, nitrites, and nitrates of the atmosphere. 
According to Millardet and Gayon’s” experiments, the amount 
of lime ordinarily used in Bordeaux mixture is sufficient to pro- 
tect the copper absolutely from solution for eighteen days under 
ordinary atmospheric conditions. This ought to have been suf- 
ficient to have set aside the hypothesis which accounted for the 
I. The solution of that part of the Cu(OH), of Bordeaux, oo 
mixture which under orchard conditions is of fungicide value, - 
emselves oe ee 
ae The ; amount ot copper necessar aay for ioe jestr iction_ n of 
a 
