COPPER SULPHATE 



49 



with a Wheat-seedling were immediately obtained under 

 different strengths of solution : 



Normal rate . 



0'5 per cent, solution 



0-30 [JL per second 

 0-15 [^ ,, 



2 -0 



o-o8 



!^ 



Copper Sulphate Solution 



Experiment 25. — A minute dose of copper sulphate 

 solution of about o-i per cent, was found to induce 



Fig. 21 



Fig. 22, 



Fig. 21. Effect of Sulphuretted Hydrogen (Wheat-seedling). 

 Fig. 22. Effect of Copper Sulphate solution. 



immediate enhancement of the rate of growth, whereas 

 a stronger dose of 5 per cent, caused depression of the rate 

 (fig. 22), a remarkable instance of a minute dose of poison 

 acting as a stimulant. The following data relate to the 

 effect of I per cent. CUSO4 solution on the rate of growth. 

 The normal rate of growth of a Wheat-seedhng was 0-45 [i 

 per second ; application of i per cent, solution reduced 

 the rate to 0-13 [jl per second. Long-continued action of 

 the solution caused the death of the plant. 



E 



