130 BOTANICAL GAZETTE [SEPTEMBER 
per cent or over were killed at any particular combination of current 
intensity and time, this was regarded as the death point. Death 
points were determined for current intensities of 0.6 to 0.05 milli- 
amperes as shown in the tables. Direction of flow of current is 
indicated by arrows. When the current was applied with the posi- 
tive electrode at the tip, the arrow points upward. Under “‘average 
loss or gain”’ is given the loss or gain in length over measurement 
taken just previous to exposure. Final measurement was always 
taken twenty-four hours after exposure. Under the heading ‘‘dead 
above only” is given the number in which the region above the first 
4or5 mm. was killed. This effect was often noticeable as far back 
1G. 3.—Current ge equa required to produce death in roots of 0.7-0.9 
sq. mm. cross-sectional a 
as the cotyledons. The last column gives the number in which the 
entire root was killed. Thus it can be seen from the tables that 
the critical time at 0.6 milliampere is fifty-two seconds; at 0.5 
milliampere sixty-five seconds; at 0.4 milliampere ninety seconds, 
etc. It should be stated that controls were planted with each lot, 
and that all showed a decided increase in length, the increase vary- 
ing from 12-19 mm. at the end of twenty-four hours. 
Plotting the points as shown in the tables into a graph gives 
the death curve (text fig. 3). With current of 0.05 milliampere the 
death point was determined with great difficulty, due to length of 
exposure required, which had a tendency to dry out the root. The 
critical time seems to lie between thirty and thirty-five minutes. 
