71 



LoHNis: Excess of Manganese 



tion, on one and the same plot, tested at various times, is very 

 striking. The higher content of exchangeable manganese in the 

 soil, however, does not result in a higher content in the foliage, 

 as the figures for the latter ranged in 1946 from 100-3510, in 1947 

 from 167-3300 p.p.m. 



The summer of 1947 was exceedingly dry and hot. The fact 



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Textfigure 12.— Manganese content of foliage of Phaseolus vulgaris (Dubbele 

 Prinsesseboon) and exchangeable manganese in the soil (1946). 



that no increase in the intake of manganese occurred may possibly 

 be ascribed to a high concentration of other ions in the soil solu- 

 tion which may have interfered with the intake of manganese. 



A coincidence between injury in bean foliage and a high con- 

 tent of manganese has definitely been established but proof that 

 the high content is the real cause of the injuries had not yet been 



