3i8 Transactions of the Canadian Institlte. [V^ol. V'II. 



in a couple of hours afterwards there will be a coating of metallic copper 

 upon the iron wire even if there be but a small trace of copper present. 

 Piano wire will do for this experiment. Chuard and Porchet (1900, p. 

 71), state that copper was not found present in the leaves of grapes 

 which had been sprayed with the bordeaux mixture. They state further 

 that the effect of copper upon growth has been exaggerated, but admit 

 that the sugar content of the grape is increased. The deeper green 

 colour of the leaves, they claim, is not due to an increase in the amount 

 of chlorophyll. This statement is not consistent with experiments 

 performed by the writer, nor with those of Griffon (1900, p. i). A 

 certain stimulus there is, which results in an increase in the size of the 

 chloroplasts, especially in the palisade tissue, and which is referred to in 

 the explanation of the green ring produced by certain solutions applied 

 to the leaves. This green colour may be due in part to a movement of 

 the chloroplasts as noticed by Stahl in the case of other stimuli. 



A long series of experiments was performed b\' Galloway and 

 Woods (1895), to investigate the effects of bordeaux mixture upon the 

 growth of potatoes. The\' used the substances contained in the 

 bordeaux mixture separately and in various combinations in order to 

 determine which constituent had to do with the stimulus to growth, or 

 whether it was due to the effect produced upon the soil by the solution. 

 They show clearly that, while the bordeaux mixture applied to the 

 leaves undoubtedly increases the growth, it is not the copper compound 

 alone that causes the increase. The lime is found to be a very 

 important factor, and they show that spraying with lime-water causes a 

 large increase in leaf surface, showing that the lime-water is very 

 probably absorbed directly by the leaves and utilized there. The 

 spraying of the soil with lime-water caused some increase, but not so 

 much as the spraying of the leaves. 



The writer has shown (Chapter IV.) that Ca(OH).3 in water (lime- 

 water), is absorbed by leaves, and that this substance very probably 

 exerts an active influence upon CO.. of respiration, retaining it for 

 resorption by the plant. 



The experiments of Gallowa)' and Woods show that a spray of 

 water, while not increasing or decreasing the growth of the leaves, 

 produces a decided decrease in the gross weight of tubers produced. 

 This may be due to the loss of substances sustained by the leaves due 

 to the drenching with water. (See experiments. Chapters III. and IV.). 

 The experiments just referred to, corroborated by those of De Saussure, 

 Gaudichaud and Sachs, leave no room for doubt that a very considerable 



