1921] MEIER—ROOT TIP 125 
possible to establish in a fairly definite way the quantity of current 
and the time required to produce death of the root. This was 
accomplished by numerous trials using a constant amperage, and 
varying the time factor until exactly the time exposure required 
(using that particular amperage) to produce death was determined. 
This method yielded comparable cytological results. Current and 
.time factors were varied from 0.6 milliampere for fifty-two seconds 
to 0.05 milliampere for thirty to thirty-five minutes. Longer expo- 
sures were also made for as long as two hours at o.o1 milliampere. 
In the determination of whether or not a certain exposure to 
current produced death, roots immediately after treatment were 
planted in moist sawdust as previously described. Examination 
_was made after a lapse of twenty-four hours and record of condition 
made. Roots so treated, current intensity of 0.3 milliampere for 
two and a half minutes or longer, will after twenty-four hours appear 
a chalky white at extreme tip and exhibit considerable shriveling 
in the region of rapid elongation. If such a root is tested by being 
drawn lightly between thumb and forefinger, it offers little resist- 
ance, and flattens readily. It is quite evident that the entire root 
tip of 1.5 cm. is dead. If subjected for a less period than two and 
a half minutes to this current intensity, a majority of the roots will 
show the shriveling in the region of rapid elongation and above, but 
the first 4-5 mm. of the root will be more or less translucent, quite 
different in appearance from the chalky white previously described, 
and quite firm to the touch. It is evident in these cases that such 
roots are dead above the first 4-5 mm. of the tip, and that the cells 
are still in a living condition in the extreme tip. This conclusion 
is further strengthened by the fact that in a great many cases these 
roots will show curvatures at the tip. These curvatures take no 
specific direction with reference to how the current is applied. The 
seedlings were always set into the apparatus with the cotyledons 
toward the front, yet the curvatures appeared in every plane, and 
varied from a slight crook to a right angle curve, or in some cases 
even a bending back on the main axis toa U-shape. These curva- 
tures suggest unilateral injury which stained preparations in no 
case reveal, and indicate a problem of great interest upon which 
it is planned to do further work. 
