KELLICOTT: PERIODICITY IN ROOT OF ALLIUM 543 
tions in temperature would have a very marked effect upon the 
rate of mitosis. Nor could there be observed any effect upon 
mitosis of changes in the feeble illumination of the laboratory. 
Normally, of course, the root is in a constant condition of darkness 
and itis therefore worthy of note that the rhythm in the varying 
illumination of the room had no definite effect upon the rate of cell- 
division, 
Finally then, summing up in regard to periodicity of cell-divi- 
sion, we may say that there is a definite and regular rhythm in the 
root of Adium. Under normal conditions of growth, cell-division 
is Most active just before midnight and just after noon and is least 
active about 6 a. m. and 4 p.m. There may be variations from 
these times within limits of about two hours. 
Very little is possible in the way of comparing these results 
with the work of others. Famintzin,* Strasburger + and others 
have noted that in most algae cell-division is most rapid at night. 
Lewis { in a very brief communication noted that cell-division in 
the root of the onion growing in water and exposed to the light, 
Was most rapid about noon and slowest about 4 p. m., while in 
foots growing in water but in a vessel painted with lamp-black 
cell-division was slowest at midnight and fastest about 4 p. m. 
Insufficient data are given concerning the conditions under which 
these results were obtained to enable us to judge of the value of 
these observations. 
5. Daily periodicity of elongation 
The observations upon the elongation of the root of Adium were 
all made upon the roots of bulbs of uniform size and with approxi- 
Mately equal numbers of roots, z. ¢. about six. The length of 
the roots varied between 35 and 50 mm. at the beginning of the 
Observation. The roots had been grown entirely in the dark, the 
bulbs not having been exposed to the light after germination was 
begun, so that no rhythmic character of elongation could be due 
to the direct influence of alternating illumination. The tempera- 
*Famintzin, A. Die Wirkung des Lichtes auf Algen und einige andere ihnen nahe 
verwandte Organismen. Jahrb. Wiss. Bot. 6: 40. 18 
