383 
In the two experiments, the latex was coagulated to form sheet 
rubber by the employment of 3 per cent, of its volume of ‘formol’. 
le lubber was kept for a quarter of an hour in water at 8o°C., then 
.passed through the press and well washed with water. The report of 
the experts to which the samples were submitted showed that the 
lubber had exactly the same appearance as that shown by Hevea 
rubber fenn the Far East It was valued at 2*. per lb., with Para 
The wounds from tapping healed normally in the case of most of 
the trees With some, however, the bark dried up, and cracks were 
pioduced in it, the wounds thus formed being attacked by insects. 
FUNGUS NOTES. 
Recent Work on Bordeaux Mixture. 
In considering the poisonous action of copper salts on plant organ- 
isms when they are used in the form of sprays, it must be borne in 
mind that no substance in the solid form is capable of penetrating 
the walls by which the living protoplasm of practically all plants is 
piotected, and that, consequently, in order to bring about the death of 
the organism, the copper salt must be soluble in water. Such a soluble 
salt is copper sulphate, or blue stone, and it might at first seem 
that the application of a solution of this substance to diseased plants 
would be all that is required to kill the fungi causing the disease, 
1 h,s course has several drawbacks. In the first place, it is often found 
that such a solution, when strong enough to kill the fungi, damages 
the host plant as well ; secondly, it is easily washed off by rain. 
In order, therefore, to diminish its harmful effect on the host 
plant, and at the same time to increase its adhesiveness, it is mixed, 
m the preparation of Bordeaux mixture, with lime-water, or \Vater 
containing slaked lime partly in solution and partly in suspension. 
As a result of this mixing, an insoluble compound of copper is 
formed, which may often be mixed with excess of lime. The Bordeaux 
mixture must contain no copper in the form of the soluble sulphate, 
if injury to the leaves of the sprayed plant is to be avoided. Conse- 
quently, enough lime is always added to turn all the copper into the 
solid form. The liquid containing the insoluble copper precipitate 
suspended in the form of fine particles is then sprayed on the plant, 
and covers the parts to be protected with a fine film of insoluble cop- 
per compounds. The question now naturally arises as to how this 
insoluble substance is again rendered soluble, as it must be, if it is to 
bring about the death of germinating fungus spores, which would 
otherwise infect the sprayed plant. 
There are three theories which have been put forward to account 
for the manner in which the insoluble copper compounds are rendered 
soluble ; these are: (I) that the copper is brought into solution by the 
