416 The Woburn Pot- Culture Experiments , 1913. 
Table II . — Copper Salts on Wheat , 1913. 
/ 
No treatment 
Corn 
Straw 
100 
100 
Sulphate of copper 
*1 
1* 
*1 
11 
11 
11 
Carbonate of copper 
11 
li 
11 
11 
11 
1 1 
11 
11 
10 per 
05 
02 
01 
005- 
0025 
10 
05 
02 
01 
005 
0025 
cent. 
♦ 
copper 
11 
n 
11 
ii 
11 
n 
11 
ii 
11 
}' 
ii 
11 
V 
11 
11 
1* 
11 
r 
11 
ii 
11 
18 
42 
150 
140 
120 
154 
lot 
116 
99 
108 
50 
63 
109 
99 
162 
179 
123 
156 
108 
126 
108 
105 
being alike produced. In smaller amounts copper appeared 
to have no action. 
With the carbonate the results were much the same, though 
not quite so strongly marked ; *02 per cent, and ’01 per cent, 
produced increases in both corn and straw, but lower quantities 
were without distinct effect. 
The examination of the roots proved very interesting. With 
the heavier dressings there was practically no root at all,, and 
the poisoning effect on the plant Avas clearly shown. 
With the heavy dressing of copper, as sulphate, the roots 
went down only 1^ in. into the soil. With ‘05 per cent, they 
were but little better, but with '02 per cent, there was a great 
change visible, and an extensive and very fibrous root-growth 
was produced. With '01 and lower quantities the root was 
much like that of the untreated plants. Carbonate of copper 
gave similar results, though not so marked. 
The general conclusion to be drawn from these results is 
that copper in quantities not exceeding *02 per cent, will have 
a stimulating effect, but that above this amount the influence 
will be a toxic one. 
Further, that in amounts less than *01 per cent, of the metal 
the results will be negative. This latter conclusion is of 
importance in vieAv of work Avhich has been done in regard to 
copper salts when water-culture methods have been employed. 
According to the latter, much smaller amounts than those here 
employed were found to exert a poisoning effect, and this 
would seem to indicate that what is found to be the case in 
water-culture is not necessarily reproduced in the case of plants 
growing naturally in the soil. 
