542 Kewtiicotr: PERIODICITY IN ROOT OF ALLIUM 
delay its normal rhythm. Upon comparing the effects of various 
types of solutions certain tentative inferences may be drawn. The 
effect of a non-electrolytic solution (glucose) is not different from 
that of tap-water alone; in this instance the plant did not tend to 
recover its normal rhythm, 7. ¢., to adapt itself, as did the plant 
placed in water alone, although the first effect was not quite as 
marked. 
The effect of a brief immersion in an electrolytic solution 
(magnesium chloride), however, was the almost complete stoppage 
of cell-division; recovery commenced shortly after removal to 
water. The effect of a solution of peptone is to cause a reduction 
of the rate of cell-division greater than that produced by water 
alone; the rhythm is not affected dissimilarly. 
From the small number of observations made it is obviously 
impossible to make a definite statement regarding the specific ef- 
fect of any of these solutions upon cell-division. The purpose of 
placing the roots in these solutions was not at all to test their 
specific effects, but to determine the effects of liquids in general 
upon the rate and rhythm of cell-division; rather to see whether 
the normal rhythm was actually a definite thing and whether it 
would be maintained or modified under abnormal external condi- 
tions. From this point of view the evidence from the experiments 
was decisive and positive. That the rhythm is a definite occur 
rence is sufficiently indicated by the uniform periods of increase 
and decrease in the rate of mitosis in all series of tips whether 
under normal or abnormal conditions. The result of placing the 
tips in liquids is to prolong the rhythm and so to delay the max!i- 
mal and minimal points, although these tend to recur at the nof- 
mal hour even under abnormal conditions, and to decrease the rate 
of cell-division. This accords with the observations of Sachs,” 
Wacker,* and others that the roots of land plants are shorter when 
grown in water — undergoing a sort of retardation of growth. 
It is noteworthy that in none of the series could there be see” 
any direct effect of change in temperature, The variations how- 
ever were slight, and it almost goes without saying that wide varia- 
* Sachs, J. Arbeiten Bot. Inst: Wiirzburg, 1 
85. 
+t Wacker, J. Die rem des Wachsthums der Wurzeln durch das umge 
bende Medium. Jahrb. Wiss. Bot. 32: 71-116. 1898. 
