226 
Methods of Preveniing and Checking 
Gayon, and Schloesing ' that the conidia (the minute spores) of 
the vine mildew cannot germinate in water containing the most 
infinitesimal quantity of sulphate of copper. This was proved by 
experiments of the following nature. The conidia of the fungus 
sown upon leaves that had been treated with weak sulphate of 
copper solution did not germinate, while conidia sown upon 
leaves untreated with sulphate of copper germinated perfectly in 
the rain-drops upon their upper surfaces. It was found that the 
vine leaves had great power of absorbing the sulphate of copper, 
as leaves treated upon their upper surfaces with sulphate of 
copper resisted inoculation by the fungus when conidia were 
sown upon their under sides, whei'e the disease first manifests 
itself. Elaborate experiments reported by M. Schloesing show 
that the copper is retained with the greatest tenacity by the 
cuticle of the leaves. It is this retention which makes treat- 
ment with sulphate of copper solutions so effective as a preven- 
tive of fungoid attacks. With regard to the potato fungus, 
which appears first upon the under surface of the leaves and 
invades the plant, descending finally to the tubers, the sulphate 
of copper application has been shown by recent experiments to 
prevent the fungus from establishing itself upon the plant, just 
as in the case of the vine disease. It has also been shown 
that applications made after the fungus had been established 
stayed the attack and considerably increased the crop, as com- 
pared with example plots not treated. At the same time, the 
leaves of the plants to which sulphate of copper had been applied 
to cure the disease already present, preserved their greenness 
and vigour, while untreated plants were dead and prostrate. 
The complete rationale of the action of sulphate of copper upon 
plants has yet to be explained. It is expected that the experi- 
ments that are being carried out by the Royal Agricultural 
Society of England in connection with the Board of Agriculture 
may throw some light upon this point. They will, it is fully 
believed, establish the fact that this is a pi'eventive of the potato 
disease, and that in certain stages it will act as a cure for it. 
With all these dangers besetting the crops of the field, the 
orchard, and the garden it is not unnatural to find a desire on 
the partof cultivators to be posted up in the life historiesof destruc- 
tive insects and fungi, and especially to be shown ways and means 
of averting their evil consequences. Miss Ormerod's most 
valuable reports, and those issued by the Agricultural Depart- 
' HeoJiercJies nouvclles sur I'action que les composes ouirreux cxereent sitr le 
developpemc7it du Peronospora de la ViffiiP. Note de MM. Millardet et Oayon, 
prl'M-nUc par M. tSchlwsiiii/, Comptcs-rendns des Seances de V Academie des 
.Sciences, 1887. 
