The Wohurn Pot- Culture Experiments , 1913. 415 
the sulphate not until December 27. This, however, applied 
to the heavier dressing only ; the others did not seem to have 
any influence on the early growth. 
As the plants grew, it was noticed that, while the lighter 
applications seemed to have no influence (the plants being 
much the same as the untreated ones), the heavier applications 
were distinctly behindhand. Not only were the stems of the 
plants thin, but the plant did not tiller out as well as the others. 
This was especially the case with the application of TO per cent, 
of copper as sulphate, the crop being very poor indeed. The 
same application in the form of carbonate, while also doing 
harm, did not appear to be so toxic as when the sulphate was 
used. 
The application of *05 per cent, of copper as sulphate gave a 
better plant than that of TO per cent., while that of 
*02 per cent, was still better, both it and the next lowei amount 
(*01 per cent.) showing advance upon the untreated sets. 
Smaller quantities did not appear to have had any effect. 
Somewhat similar appearances were observed with the 
carbonate, though, with this, larger amounts of the metal could 
be advantageously used than was the case with the sulphate. 
By July it was clear that anything markedly over '02 per 
cent, of copper as sulphate would do injury, there being 
absolutely no crop where TO per cent, was used, and very 
little where '05 per cent, had been given. . 
With the carbonate TO per cent, alone showed a distinctly 
toxic influence. 
Previously to harvesting, measurements were taken ot tne 
straw and of the ears, and also photographs of the growing crops. 
With amounts of '02 per cent, and '01 per cent, copper 
there was an increase in length of both straw and ear, whethei 
the sulphate or the carbonate had been used. 
The comparative results of the weighing of corn and straw 
are set out in Table II. In Plate 3 are given the appearances 
of the growing crops where sulphate of copper had been used, 
the roots of the corresponding plants being represented m 
4 : 
Plate 5 shows the crops treated with carbonate of copper, 
and Plate 6 the roots of the different plants. 
The untreated crop with which comparison must be made 
is (a) of Plate 1. 
Table II. gives the results on the average of the two 
duplicates, which again were very consistent. 
It will be noted that when sulphate of copper was used TU 
per cent, of the metal was absolutely destructive of the plant, 
and '05 per cent, nearly so ; '02 per cent, and *01 per cent., how- 
ever, showed stimulating action, more corn and more straw 
