56 MICRO-NUTRIENT PROBLEMS 



trees bearing the leaves was due to a deficiency of copper. 

 Anderssen's work is referred to in more detail in the next 

 chapter. 



Storey and Leach (1933) were interested in a disease of the 

 tea plant known as 'yellows', which, as the name implies, in- 

 volves a chlorosis of the leaves. They traced this to a deficiency 

 of sulphur. Among other pieces of evidence which led them to 

 this conclusion was the effect of introducing various salts into 

 plants growing in the field. The injection of any particular salt 

 was effected by cutting a small side shoot under water and 

 immersing the cut end of the shoot in a solution of the salt. The 

 quantity of solution was maintained by daily additions, and 

 every fourth day the immersed shoots were cut farther back to 

 give a fresh absorbing surface of unchoked wood. It was found 

 that when a 0-5 per cent solution of sodium sulphate, potassium 

 sulphate or magnesium sulphate was used the normal green 

 colour was regained by the leaves on the branch beyond the cut 

 shoot, but that no such recovery resulted when other salts, such 

 as chloride or nitrate, of these metals were used. 



