414 Copper Sulphate Solutions on Plants, [oct. 



and epidermis into the cells of the leaves and exercise 

 a chemico-physiological stimulus on the protoplasm of the leaf- 

 cells. Others, again, believe that the copper salts reaching the 

 soil through the spraying are taken up by the roots and so 

 affect favourably the development of the plant. 



With regard to the first of these views Herr Schander regards 

 the explanations given by its supporters as improbable. With 

 regard to the second he states that it follows from experi- 

 ments which have been made that the epidermis of the leaves 

 is able to hinder the penetration of copper solutions, but that 

 the copper, once penetrated, behaves in the same way to- 

 wards the protoplasm of the leaf-cells as to the cells of algae 

 and fungi (referred to in the experiments quoted), and can injure 

 the protoplasm even in such weak solutions as I to 100,000,000. 

 It would appear, therefore, very hazardous to assume that the 

 copper penetrates into the leaf and there exercises a beneficial 

 influence. 



The effect on plants of the copper left in the soil by spraying 

 can never be beneficial. The author points out that in any case 

 the effect must become apparent much later than the application 

 of the solution, as it would be absorbed by the soil and could 

 only reach the roots when washed out by rain. He considers, 

 however, that it is proved by experiment that copper is injuri- 

 ous, and, moreover, that plants could only absorb a very small 

 quantity of it without injury. 



Among the other causes mentioned by the author which might 

 have some effect are the action of the lime in the Bordeaux 

 mixture and the effect of the spraying in preventing insect 

 attacks, and, finally, the influence of the thin coating of copper 

 on the assimilation and transpiration of the leaves. The latter 

 point is one to which Herr Schander devotes considerable atten- 

 tion. He considers that the coating protects the chlorophyll 

 against the prejudicial influence of intense sunshine and 

 diminishes the transpiration of the leaves, thus explaining the 

 beneficial effect which the application of Bordeaux mixture has 

 frequently been observed to have on the leaves. No chemical 

 action takes place, the result being entirely due to the modi- 

 fication in the intensity in the light produced by the thin 

 coating of copper. In the case of the vine, the protection of 



