Effect of Copper Compounds 31 



stronger in some degree, while their life was lengthened. Apparently, 

 treatment increased the chlorophyll content, and, correlated with this, 

 was a rise in the assimilatory capacity, more starch being produced. 

 Rise in transpiration was also observed. While the leaves were the 

 organs most affected, a subsidiary stimulation occurred in the tubers, 

 since the greater quantity of starch produced required more accom- 

 modation for its storage. In different varieties the ratio of tuber 

 formation on treated and untreated plants was 19 : 17 and 17 : 16. In 

 discussing the meaning of this stimulation these writers, following the 

 custom then in vogue, were inclined to hold that it was due to a cata- 

 lytic rather than to a purely chemical action, an idea similar to one 

 which later on came much into prominence in connection with the 

 work of Bertrand's school on manganese, boron and other substances. 



The imputed increase in photo-synthesis seems to have met with 

 approval and acceptance, but nevertheless it did not pass unchallenged. 

 Ewert (1905) brought forward a detailed discussion and criticism of the 

 assumption that green plants when treated with Bordeaux mixture 

 attain a higher assimilation activity than untreated plants. His experi- 

 ments were made to test the effects of differing conditions of life on 

 plants treated in various ways, and his conclusions lead him to assert 

 that "instead of the organic life of the plant being stimulated by 

 treatment with Bordeaux mixture it is rather hindered." 



While Frank and Kriiger indicated a rise in transpiration when 

 copper compounds were applied to the leaves as sprays, Hattori (1901) 

 attributed part of the toxic effect of copper salts, when applied to 

 the roots, to a weakening action on the transpiration stream, and 

 he maintained that the toxic effect of the copper salts is therefore 

 connected with the humidity of the air. No further confirmation or 

 refutation of this statement has so far come to light. 



In certain plants the application of cupric solutions as sprays causes 

 a slight increase in the quantity of sugar present in the matured fruits. 

 Chuard and Porchet (1902, 1903) consider that such a modification in 

 the ripe fruit during the process of maturation occurs in all plants which 

 ripen their fruits before leaf-fall begins. Injection of solutions of copper 

 salts into the tissues of such plants as the vine causes more vigorous 

 growth, more intense colour and greater persistence of the leaves ; in 

 other words the copper acts as a stimulant to all the cells of the organism. 

 A similar effect is produced by other metals such as iron or cadmium. By 

 injecting small quantities of cupric salts into the branches of currants 

 an acceleration of the maturation of the fruits was caused, identical 



