404 BOTANICAL GAZETTE [JUNE 
1.5™™ apochromatic objective and compensating oculars were used 
in studying the preparations. 
This investigation was begun in 1904, at the suggestion of Dr. 
RopneEY H. TRUE, to whom I am indebted for constant advice and 
criticism. Iam also under obligations to Dr. G. F. KtuGH, who was 
of great assistance with the seedling cultures. 
Experimental 
In all work with the radicles which involved measurement of 
growth, and in the preparation of material for killing and fixing, great 
precautions were taken to guard against the introduction of undesir- 
able factors, such as loss of moisture, change in temperature, or shock 
in handling, which might interfere with the results sought. 
THE EFFECT OF COPPER SULFATE SOLUTIONS ON GROWTH 
Growth and cell activity in the root tips of Vicia Faba upon which 
copper sulfate solutions of various concentrations had acted continu- 
ously were the first subjects of study. Seedlings were placed in a 
series of solutions with a constant difference of dilution of m/10,000, 
in order to determine the concentrations in which the toxic effect 
would not be so strong as to prevent growth to some degree, after 
allowing time for recovery from the shock due to the change of medium 
and for partial acclimatization to the toxic substance. Table I 
shows the average growth of four seedlings in the various concentra- 
tions used, and also the growth made by the corresponding controls 
in distilled water. From the table it is apparent that, in the lower 
concentrations, the effect of a difference in dilution of m/10,000 is 
masked by the variability of the individual groups of seedlings, and 
in the higher dilutions this difference was increased many fold before 
changes in the growth rate were observed which could be reasonably 
ascribed to the action of the toxic solution. A comparison of the 
average growth per hour in the copper solution and in distilled water 
shows that there is a wide range of toxic effect between the concen- 
trations ”/20,000 and m/s500,000, with a probable corresponding 
difference in cell activity, as shown by the slower rate of elongation 
in the stronger solutions. 
