15. T. P. BvKKKIi AM) (*. T. (llMINGlIAM 17 



The behaviour of apple toHagc in the summer condition towards 

 Bordeaux mixture appears to be typical of that of a variety of other 

 hardy plants. The leaves of wallflowers, privet, and violet have been 

 similarly tested and in each case there has been no scorching of uninjured 

 foUage. It is well known, however, that very great variations in sus- 

 ceptibility to scorching are shown by different plants. Some are 

 peculiarly susceptible, and in such cases the general character of the 

 scorching strongly suggests that a change in the nature of the cuticle 

 or, perhaps, the presence of groups of uncuticularised cells rather than 

 local injury is responsible. It is possible that the cuticle in these 

 instances is normally more or less permeable, just as the cuticle of apple 

 leaves appears to become in autumn. Salmon's work^ on the sus- 

 ceptibility of certain varieties of gooseberries to scorching injury after 

 spraying with lime sulphur washes of various strengths appears to bear 

 out this point ; varieties such as Lancashire Lad, Crown Bob, and 

 Berry's Early remaining unaffected by the spray when treated in early 

 summer, while later a wash of the same strength causes scorching. 

 It was also shown that certain kinds such as Valentine's SeedUng and 

 Yellow Rough were regularly injured, whilst others such as Whinham's 

 Industry, Rifleman and May Duke escaped damage even when a wash 

 of more concentrated strength was used. 



It may be said in conclusion that the evidence seems complete as 

 regards the part played by injuries to the leaves in causing scorching 

 of apple fohage following spraying with Bordeaux mixture ; whilst 

 under some conditions it would seem that scorching might also occur 

 over the general surface of the leaf and unconnected with the occurrence 

 of injuries, though this is less certain. No doubt such action if it takes 

 place is more important in foliage such as peach and apricot where either 

 the cuticle as a whole or certain parts of the leaf surface appears to be 

 less resistant than is the case with the apple. 



The Penetration of Copper from Bordeaux mixture into the Plant. 



The action of the copper of Bordeaux mixture upon plants is not 

 confined to the surface. It is found that under certain conditions plants 

 which have been sprayed absorb some copper either through their foliage 

 or their roots. 



Millardet and Gayon {Journ. d'Agric. Prat. 1887, p. 125) were the 

 first to refer to the absorption of copper by leaves. They proved the 



^ Journ. Bd. Agric. xvir, p. 881 ; xx, p 1057. 

 Ann, Biol, i 2 



