23 
and tightly rolled leaves already mentioned as possessed by plants 
from seed treated with the stronger solutions of copper sulphate. 
In these experiments it was desired to learn the effect of copper sul- 
phate alone, hence it was the only form used. ‘T'schirch! has shown by 
cultures that copper is injurious to plants only when applied in the 
form of the soluble salts, such as the sulphate, nitrate, chloride, ete. 
In experiments made with 36 kinds of plants in water cultures, where 
‘the nutrient solution contained copper oxide (an insoluble compound) 
in considerable quantity, stronger and better appearing plants were 
produced than those grown under similar conditions, except that there 
'was no copper in their solutions. 
It is a well-known fact that carbonate of lime unites with copper 
sulphate, forming a nearly insoluble compound. In order that there 
‘should be no diminution of the effect of the copper sulphate, all seeds 
were planted in almost pure sand, which could not have contained 
much if any lime. It was intended at one time to conduct a series of 
experiments to test the ameliorating effect of lime when applied to the 
‘seed and also when present in the soil, but this was not found neces- 
sary, as all experimenters agree that either milk of lime or powdered 
air-slacked lime applied to seed which have been soaked for many 
‘hours in a solution of copper sulphate, or that lime in the soil capable 
of forming a carbonate, will greatly overcome the injurious action of the 
‘soluble salts of copper. Lime in the soil is immediately attacked by 
the copper on the treated seed and an insoluble compound formed, and 
so long as an excess of lime is present the corrosive effect of the copper 
sulphate on the seed is destroyed. It is highly probable that many 
persons who have unqualifiedly advocated the use of strong solutions 
of copper sulphate for the prevention of smut owed their successful use 
of such strong solutions to the presence of a considerable portion of 
lime in the soil where the seed was planted. The action of lime upon 
the small quantity of copper at once renders it insoluble and no further 
injury can be done the seed, while the smut spores have already become 
powerless to germinate and infect the plant. 
SUMMARY. 
(1) Copper sulphate, as has been shown by many investigators and 
by its long and widely extended use, is capable of preventing to a 
greater or less degree the attacks of grain smuts when the seed is 
soaked in solutions of it prior to sowing. 
(2) Copper sulphate in solution destroys or retards germination of 
seed soaked in it. The amount of injury done depends upon the 
strength of solution and length of time the seeds are soaked. The 
injury is due to the corrosive effect of the fungicide on the embryo, 
which causes the root systems to be greatly stunted. The stronger 
1 Das Kupfer vom Standpunkte der Chemie, Toxicologie, und Hygiene, 1893. 
