COPPEE SULPHATE (BLUE VITRIOL). 209 



germinating. The study of this phenomenon was pursued by Mathieu 

 de Dombasle. In 1858 Kuhn examined the comparative action of 

 blue vitriol and green vitriol, alum and sulphuric acid on the spores of 

 rust, an examination which still throws light on the remarkable 

 properties of blue vitriol. In 1885 Millardet found the limit of toxicity 

 of blue and green vitriol on the zoospores of mildew, and found that 

 these could still germinate in a solution of 1 of lime to 10,000 parts 

 of water, of 1 of green vitriol to 100,000 parts of water, and 1 

 of blue vitriol to 10,000,000 parts of water. In 1889 Dufour 

 examined the action of blue vitriol on the spores of Fusicladium 

 pirinum, Claviceps purpurea, Pleospora, Phragmidium, and other 

 fungi, and found that the germination was normal in a solution of 

 1 in 1,000,000, reduced 1 in 100,000, rare 1 in 10,000. In 1891 

 Wuthrich tried, comparatively, potassium nitrate, sodium carbonate, 

 zinc sulphate, zinc chloride, copper sulphate, and mercuric chloride 

 on the spores of Peronospera, Phytophthora, Ustilago, Puccinia, and 

 ClavicejJS, and made very instructive conclusions. Tried on the spores 

 of the most diverse fungi, blue vitriol has been recognized as possess- 

 ing a highly extensive poisonous capacity and capable of combating 

 the greater number of the cryptogamic diseases of plants. Wuthrich 

 was the first who described the action of blue vitriol on spores. He 

 determined the similarity in the action of different salts, and particu- 

 larly in that of blue and green vitriols. It has already been pointed 

 out that their action on spores appears to be inversely proportional to 

 their chemical equivalent, but that blue vitriol, regard being had to 

 these proportions, was ten times more energetic than green vitriol. 

 Wuthrich found that these two salts penetrated into the spores, and 

 that death only supervened after this penetration, whilst blue vitriol 

 could be detected in the cell by yellow prussiate, even in the case 

 where a spore had only undergone a slight alteration in its vitality in 

 contact with this salt. It is not the same with copper, which cannot 

 be detected chemically in the same condition. Spores that have been 

 steeped in a solution of blue vitriol of O'OOOl equivalent per litre, a 

 dose which appreciably affects the vitality of the spores, absorbs so 

 little copper that its presence in the cell cannot be demonstrated by a 

 chemical reagent. The solution in the bath itself, moreover, gives no 

 perceptible tint with prussiate. It is diB'erent when the spore dies as 

 the effect of steeping in the solution of 0*001 equivalent per litre ; in 

 these conditions the dose of copper is sufficient to give a coloration 

 with prussiate. Wuthrich concludes, therefore, that a certain dose of 

 blue vitriol may be absorbed by the spores without killing them, but 

 that this dose does not exceed a certain limit. The table on p. 210 

 shows how the spores of different fungi behave after being steeped in a 

 dilute solution of blue vitriol. 



Hecke, examining the action of blue vitriol on the spores of Ustilago 

 Crameri found that 0-125-1 per cent of blue vitriol did not kill the 

 spores, even those which had manifestly absorbed copper. A sub- 

 sequent washing of the spores with water in no way changed the effect 

 of the treatment, as is the case with spores treated with formol, but 

 washing with 0*5 per cent HCl reimparted to them all their vitality. 



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