I). M\ IV IJakKKK AM) (*. T. GiMINGlIAM 



19 



be detected in the ash of treated leaves, but on the other hand there is 

 seldom any noticeable injury to the cuticle. 



The cuticle of potato leaves is of quite a different type to that of 

 apple leaves and either all the cells or some only (possibly the haiis) 

 are evidently capable of exerting a slight solvent action upon the copper 

 compounds, which gives rise to a limited absorption insufficient to cause 

 injury to the cells. Copper absorbed in such a manner as this appears 

 to be rapidly translocated and dispersed without harm to the living cells 

 through which it passes. Possibly the removal is sufficiently rapid to 

 prevent the toxic dose being reached at any one point. 



Another series of experiments showed that copper can be absorbed 

 by potatoes through their roots. A number of potato plants were grown 

 in pots in soil mixed with considerable quantities of various Bordeaux 

 mixtures, so that the tubers were actually in contact with the copper 

 containing compounds. Samples of foliage were taken from each plant, 

 dried, ashed, and the ash tested for the presence of copper. 



The following are the notes obtained from this series on testing the 

 foliage on two occasions separated by about a month : 



Here again we have apparently an absorption and translocation 

 of copper through the plant from the roots to the aerial parts without 

 injury to cells during transmission. There is in this case some local 

 injury to the surface of the root. 



Precisely the same thing was found to occur with broad beans when 

 these were grown with their roots in contact with the basic copper 

 sulphate ; an appreciable amount of copper was found to be present 

 in the leaves. Analysis of the foliage of control plants showed absence 

 of copper. The influence of the absorbed copper was not, so far as could 

 be observed, injurious, the amount of growth often being equal to that 

 of the control plants, and where appreciably less, probably this was 

 attributable to the disorganisation of the root system. 



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