Kettuicotr: PERriopicity IN ROOT OF ALLIUM 535 
Tasre I—Continued 
Dividing cells. | Total | Total re-| Average Average 
ke Tempera- Area | : 
Time Liat z a ieee een eres | divid duced to fi hi oft 
era esariamcinig) NE ST alls. | screed Ba ona pee ngs 
37 I Pigg 45 
13-- 38 Bit Bh ee 5° | 48 
2 i 
Ta.m ee oe 3 de ses a Pee < a Ee See 57 
AG ts He ae ee 69 
11-4 40 eee 66 
44 5 2| 5! 68 
eee Bee Se 
15 35 3 2 40 40 aad 
35 8 oy eee | 44 
3 a.m 14° ee Sew tt, 20: Lleol, SER MGs AM bd Oe ag 42 
48 I 6 55 47 
$7-+ 46 fs) 2} 48 42 44 
- 44 Ob §-pe8 nea De i 
23 I 2 26 pt Fase 
7 4. m. 18° 16 26 I 1 | 28 267 55) 26 24 
22 2 kei BS 23 
occurring at I p.m. The primary minimum in the rate of cell- 
division occurs at 7 a. m. following the primary maximum, the 
Secondary minimum at 3 p. m. following the secondary maximum. 
Thus there are two regular waves of cell-division during each 
twenty-four hours, a more extensive wave extending from late in 
the afternoon until early in the morning, and occupying therefore 
Practically all of the dark period ; its crest occurs shortly before 
midnight. A less extensive but otherwise similar wave occupies 
the light period of the day extending from early morning until 
late in the afternoon. The crest of this wave occurs about noon. 
Both of these waves are remarkably regular with only the slight- 
est secondary fluctuations. : 
The temperature of the air around the bulbs is recorded in the 
Same diagram. It will be seen that there is no correspondence 
between these slight variations in temperature and the rate of cell- 
division, 
(4) Comparisons of other observations, — FIGURE 2 includes 
curves derived similarly from two other series of root-tips. Curve 
/T is introduced simply as another illustration of the normal type 
of curve such as curve J, Here the tips were cut less frequently 
SO that all points of curves J and // do not correspond exactly. 
_ 
