DAILY RHYTHMS IN CERTAIN ROOTS 
399 
(12) found much the same condition in Zea Mays. While the number of 
waves found in the 24-hour period is higher than in the case of any other 
species studied, yet the fact that mitotic activity proceeds in waves or 
rhythms is none the less clearly demonstrated. 
Vicia faba. Curve 5 shows results obtained from a study of roots of 
Viciafaba. Germination began at 9 A.M. It will be seen that two waves 
of cell division occur in the 24-hour period. Maxima occur at 5 P.M. and 
7 A.M. and minima at i P.M. and i A.M. Comparison of this curve with 
the figures given by Karsten (12, page 9) shows that he, too, found two 
extensive waves of cell division with maxima coming at 10 A.M. and 9 P.M., 
and minima at 4 P.M. and 7 A.M. Thus the maxima of curve 5 come just 
three and four hours earlier, and the minima three and six hours earlier, 
than in Karsten's results. Besides the two more extensive waves it will 
be seen that his figures show two very small waves, one coming in each 
larger wave. He, however, did not take into consideration variations in 
size of the sections counted, and this, taken together with a possible dif- 
ference in time of beginning germination, probably accounts for the differ- 
ences between his results and those of the present paper. 
Allium cernuum. For this study bulbs were collected in the field in 
October, stored in boxes of soil, and kept in the open until ready for use 
the following January. Upon germination each bulb produced from two 
to four roots. Curve 23 shows results from this study; it will be seen that 
four very marked waves occur in the 24-hour period. 
Allium canadense. For this study the small aerial bulblets were col- 
lected in October and stored in a dry, cool place until ready to be used the 
following January. Curve 22 shows results from this study. It will be 
seen that five waves of cell division occur in the 24-hour period. 
A brief summary of the results obtained from this study of cell division 
shows the following facts: (i) the curve of cell division in all plants studied 
exhibits a number of oscillations in the 24-hour period, in the majority of 
plants three; (2) the exact time of occurrence of maxima and minima is 
dependent upon the time of initiation of activity and not on time of day. 
Relation between Elongation and Cell Division 
Historical 
De Wildeman (39) has shown by exact measurements that cells of 
Spirogyra do not elongate during mitosis, while in the staminal hairs of 
Tradescantia there is very slight elongation of the cell during early prophases 
but none at all during the later stages. Ward (38) has shown in his study 
of cell division and elongation of filaments of Bacillus ramosus Fraenkel 
that elongation proceeds in a wave-like fashion and that ''the period of 
cell division entails more or less cessation of growth." Kellicott (14) has 
shown that, in general, the same thing is true of elongation and cell division 
