436 University of California Puhlications in Agricultural Sciences [Vol. 1 



Fig. 10. — Corn cultures grown in soils containing copper as silicate (chryso- 

 colla), from none to 1. per cent Cu. 



ties of Copper Compounds," that precipitated copper carbonate 

 is soluble to the extent of 1.5 parts in 1,000,000 of water, while 

 copper sulphide is soluble to the extent of 0.09 parts of copper 

 in 1,000,000 of water. It is most probable, also, that the finely 

 divided condition of the precipitated carbonate is more favorable 

 to solution, and also to reaction with the acids of plant roots. 



(2) Corn is seen to be distinctly more sensitive to the car- 

 bonate of copper than either beans or squash. With corn, toxic 

 effects appear with 0.02 per cent of copper in the soil, while 

 with beans and squash these toxic effects do not appear until 

 0.035 per cent of copper in the soil is reached. As is suggested 



