538 KELLICOTT: PERIODICITY IN ROOT OF ALLIUM 
respectively, and less definitely-indicated secondary maximum and 
and minimum about 2 p. m. and 6a. m. respectively. In curve 
/I the secondary waves are obscured by the more extensive minor 
variations. 
In general the character of these curves derived from Podo- 
phyllum is quite like those from Ad/ium, maximal and minimal 
points occurring at approximately the same hours. The most 
valuable evidence offered by the Podophyllum, however, is that 
such rhythms are actually present in the rate of cell-division, and 
that the rhythms are definite enough to be susceptible of comparison. 
We may now turn to the third line of evidence upon this 
subject. 
B. EFFECTS OF SOLUTIONS 
In order to test the effects of various solutions upon the rapidity 
and periodicity of cell-division, onions were germinated as before 
in moist sand or sawdust until the roots had reached a length of 
50-75 mm. The bulbs were then placed over glass tumblers 
where the roots were immersed in tap-water and exposed to the 
daylight. Some were left in tap-water and examined at intervals, 
others were removed after being in water a few hours, to certain 
solutions, and examined at intervals. 
The solutions used were: (1) 4.2 per cent. glucose in tap-water, 
as an example of a non-electrolytic solution ; (2) 2 per cent. mag- 
nesium chloride, as an isotonic electrolytic solution ; (3) 2-5 P& 
cent. peptone. : 
(a) Water. — We may consider first the rate of cell-division of 
the tips placed in tap-water and subject to the illumination of the 
laboratory about 2.5 m. from north and west windows. An 
onion with roots about 50 mm. long, grown in sand, was placed 
over tap-water, in such a manner that the roots were completely 
immersed, at 10 a. m. and beginning at 2:30 p. m. tips were 
removed and examined. The numbers of dividing cells at irregular 
intervals during the succeeding thirty-two hours are represented 
in curve J, FIGURE 4. At 2:30 p, m., when the roots had been in 
water for four and one-half hours, the curve is much higher than 
is normal for that hour. During the afternoon it falls normally 
and from 8 p. m. until midnight when the curve usually rises t° 
its greatest height, this curve shows only a very slight rise which 
