540 KeEciicorr: PERIODICITY IN ROOT OF ALLIUM 
normal. This is important as showing that very soon (about 
thirty-two hours in this instance) after being placed in a new or 
unusual environment the process of mitosis, at first seriously de- 
ranged, tends to recover its normal course. In other words the 
roots very soon become adapted physiologically to their new con- 
ditions of growth. 
No correlation could be observed between variations in illumi- 
nation or temperature, and cell-division. In this series the tem- 
perature varied only slightly (FIGURE 4). 
(6) Glucose. — As before, the roots of an onion grown in sand 
until they were 50-75 mm. long were placed in tap-water at 9:30 
a.m. At 2:30 p. m. they were removed to a 4.2 per cent. solu- 
tion of glucose in tap-water and the tips examined at irregular 
intervals during the succeeding 27 hours. The result of the 
examination is shown as curve //, FIGURE 4. The first part of the 
curve is remarkably similar to curve /. In one respect it is more 
typical, namely in the rise just before midnight, where the tips in 
water showed only a pause in the descent. The latter part of the 
curve, however, is more atypical and does not give any sign of a 
delayed tendency to rise as was the case with the roots placed in 
water. This is probably to be correlated with the greater amount 
of stimulation resulting from the presence of an unusual substance 
in solution in such quantity. No later observation was made on 
this bulb. — 
The temperature was as in curve J, so that it is similarly true 
here that the variations in temperature and illumination of the 
laboratory seem to have no effect upon the frequency of mitosis. 
(c) Magnesium chloride. —1t was found that root-tips removed 
from water to a solution of MgCl, isotonic with the 4.2 per cent. 
solution of glucose, 7. ¢., a 2 per cent. solution MgCl,, were seri- 
ously affected. The cells became vacuolated and somewhat 
shrunken and their condition became so abnormal in a few hours 
that there was no cell-division whatever in progress. Consequently 
roots were left in the MgCl, solution for only a short time and 
then were replaced in water. 
For example, the roots of an onion grown in sand were placed 
in tap-water at 9:30 a. m. At 1:30 p. m. the tap-water was 
replaced by a 2 per cent. solution of MgCl, in tap-water and left 
