INTUMESCENCES. 141 



The effects of spraying with various solutions on leaves, 

 have been made the subject of numerous investigations, 

 particularly with reference to the action of various fungi- 

 cides on growing leaves. The apparent stimulating effects 

 which various copper solutions in particular have upon 

 crops, have become generally recognized . Rumm 22 ascribed 

 the more vigorous appearance of leaves sprayed with Bor- 

 deaux mixture, to a stimulation exerted hy the copper salt. 

 He, however, left out of consideration the possible influ- 

 ence of the lime. Frank and Kriiger 27 , finding that the 

 development of potatoes was hastened by spraying with 

 Bordeaux mixture, as evidenced by healthier leaves, more 

 chlorphyll, etc., came to the conclusion that the copper 

 was the active agent in stimulating the plants. They 



found no proof that the copper entered into the cells and 



» 



mixtur 



as due to chemotactic stimulation, exerted by the copper, 



mu 



o 



on the influence of Bordeaux mixture on potatoes, came 

 to the conclusion that while the spraying with Bordeaux 

 without question stimulated the growth of certain plants, 

 the beneficial effect may be in part due to the presence 

 of the mixture in the soil as well as on the leaves. Sebelieu 25 , 

 Woods and Bartlett 40 and Pierce 19 , among many others, 

 testify to the beneficial effects of spraying with Bor- 

 deaux mixture; in each case ascribing the beneficial 

 effects to the action of the spray upon the leaves. The 

 general consensus of opinion at this day seems to be that 

 either the copper hydrate or lime, or both acting together, 

 in some way stimulates the leaves of various plants to a 

 healthier activity. 





On the other hand, it has been found now and then that 

 copper sulphate sprays exerted a more or less harmful influ- 

 ence upon the development of sprayed leaves. Dnggai* 1 6 

 reports the production of shot-hole injuries on leaves when 

 anraved with Bordeaux mixture. He also obtained similar 



