Effects of Soil upon Toxicity 



179 



Avas 



Onions 



Barley 



Wheat 



Roots 

 In C roots within i in. 

 of pot hole damaged. 

 Both C and W show 

 strong nodule develop- 

 ment 



Very little local effect 

 of Cu just under inner 

 pot hole in C 



No roots in C for space 

 of 1 X 3 in. under inner 

 pot hole 



In C no roots under in- 

 ner pot hole for space 

 of li X 4 in. 



In practically all cases a distinct but very local effect of 

 copper solutions upon plant roots under the inner pot hole was 

 observed. For a distance of a half-inch or less from the small 

 pot hole exposed roots were dead or missing. The soil in this 

 area was observed in two instances to contain 0.25 and 0.45 per 

 cent copper, respectively. In one instance 80 per cent of the 

 copper added was found in the 43 grams of soil just under the 

 bottom of the little pot, showing the rapidity with which copper 

 is removed from its solutions by filtration through the soil. 



The tops of the cultures under consideration in no instance 

 showed injury, but in certain cases were in a distinctly advanced 

 condition. The amounts of copper contained in material derived 

 from these cultures are as follows : 



TABLE XVII (a) 

 Copper Content of Plants Irrigated with Copper Solutions 



Sample 

 No. 



3673 Wheat and barley tops grown in check 



3675 soil containing a trace (.002.5 per 



cent) of copper 32.90 .000100 3.04 



3672 Tops of beans, peas, corn, lettuce, car- 

 rots, cucumbers and avas grown in 

 check soil 133.00 .000350 2.60 



