486 



BOTANICAL GAZETTE 



[j0NE 



plants was compared with the growth of the check plants during 

 the same days. Many series, made up as indicated, were run. the 

 experiments covering a period of 5 months. It is obvious that the 

 slow growing plants of January are not wholly comparable with 

 the rapid growing plants of April. This matter cannot be controlled, 



TABLE I 



Average increase or decrease in growth during 12 days 



FOLLOWING fumigation 



TABLE II 



Percentage of 4 day periods showing decreased growth 



rate ant) also percentage showing increased 



growth rate 



and introduces an element of error. The time of exposure, length of 

 exposure, temperature, and moisture conditions were similar in all 

 cases. Using the growth of the check lots as 100 per cent, the loss 

 or gain of the treated lots was computed, and from these values the 

 averages shown in tables I and II were secured. 



Consideration of these data shows that with concentrations of 

 cyanide up to o .004 gm. per cubic foot of air space, the effects were 



