132 missou 



• 



effects of spraying potatoes with Bordeaux mixture and 



ipots 



(?) of copper, notes the formation of some 

 i fch« lpnvfts sit nointfl where the Conner solu- 



tion stuck to the leaves. Not infrequently the entire upper 

 surface of the leaves turned slightly brown. Under these 

 spots the palisade parenchyma cells had stretched to an 

 abnormal extent and had formed wart-like bodies on the 

 surface of the leaves. In extreme cases this stretching of 

 the cells was so large that the epidermis was torn, expos- 

 ing the underlying giaut cells. These generally had very 

 little chlorophyll and were frequently divided by cross walls. 

 It should be noted, however, that Sorauer found these 

 oedemas not only on the plants which were sprayed with 

 the copper, but also on the unsprayed plants. In all 

 cases the epidermal cells overlying the enlarged mesophyll 

 were apparently dead and brown and corky. Sorauer 

 calls attention to the fact that it has been shown for other 

 plants that such intumescences arise when the assimilatory 

 activity of the leaves has been reduced, combined with a 

 large water absorption and high temperature, and he states 

 that the formation of these intumescences in the leaves of 

 the potato is to be regarded as a sign of lessened assimilat- 

 ory activity. He states, furthermore, that this is a fairly 

 regular appearance during later stages of development on 

 the leaves, referring in these cases to plants which have 

 not been sprayed. Referring to the leaves sprayed with 

 copper salts he says, "Where this appearance (intumes- 

 cences) occurs on leaves which are still at the height of 

 their development it must be due to the effect of the cop- 

 per, and the intumescences must be regarded as resulting 



a condition of high turgescence existing in the leaf 



om 



cells, which would not equalize itself throughout the leaf 

 lamina because of the death of certain epidermal areas." 



He reg 



oedemas as a proof that the copper salts inhibit to a certain 

 extent the normal development of the leaf. 





