1913] LIPMAN & WILSON—TOXIC SALTS AND ACIDS 413 
weight of the tops as dry matter is recorded. The following tables 
give all other explanatory data and results of the experiments, and 
a discussion follows each table. 
TABLE I 
Errects or CuSO, ON PLANTS 
D GHT O 
DRY WEIGHT OF VETCH oe 
CuSO, ppm. 
Roots gm. Tops gm. Tops gm. 
Oe ole a 4-5 I2.0 18.5 
SH BPR ra oares ranma cay MAUL Dara Sr 1.8 20.5 CG: 
BOG eae Pee oe eae 5:5 20.0 16.2 
SO oe hae Lee ne eis 4.0 aIr.0 17-5 
BO es ha oe ee 5.5 17-5 13.90 
NOD. cs UE Soe See ae ee 3.0 18.0 16.5 
oie ke eg oe ean ae ees 4-5 14.0 17-2 
BOO Ss oo teste ae ee Det. lost 12.0 19.0 
ee ee bus ae 42.7 
IO: cons va Geir fae Wie ay oe 5 13.0 9-7 
To one accustomed to regard CuSO, as an extremely poisonous 
salt for plants, the data in table I offer a surprise. While it is 
true that in the case of the wheat no stimulation from CuSO, is 
evident, its toxic nature likewise cannot be said to manifest itself 
until a concentration of 1000 ppm. is reached, if then. The last 
phrase is used advisedly, since the plants in the 600 and 1000 ppm. 
concentrations of CuSO, were started three weeks later than the 
rest. Germination of the wheat seeds seemed to proceed with 
much greater rapidity in the higher concentrations, but the plants 
though growing fast did not seem to possess the deep green color 
which is so characteristic of plants well nourished. These plants, 
however, matured at about the same time as the other wheat plants 
growing in the lower concentrations of CuSQ,, and produced normal 
eads. 
In the case of the vetch plants, there seems to have been a 
stimulation due to CuSO,, and then what might perhaps be looked 
upon as toxicity in the highest concentrations. It should be noted, 
however, that here, as in the case of the wheat, the vetch plants 
growing in the higher concentrations of copper were planted three 
weeks later than those growing in the soils with lower concentrations 
