544 Ketucotr: PERIODICITY IN ROOT OF ALLIUM 
ture in the dark room varied within narrow limits only and the 
temperature within the pot containing the roots must have been 
nearly constant. Thus the factors of varying illumination and 
temperature were ruled out. 
The facts that the roots were of different lengths and that they 
showed different total amounts of elongation during the periods of 
observation show that the roots were not all in the same phase 
of the grand period of growth. This has to be taken into account 
constantly in comparing the different curves of growth, for some 
will show a general upward course, others a downward or even 
course, depending upon the relative portion of the grand period of 
TABLE II 
ELONGATION OF THE ROOT OF ALLIUM. TOTAL ELONGATION, 24 HRS. == 16.1 MM. 
—S SS ————— —— 
ek Elongation in | jae Elongation in | 
of obser- one hour, in Temperature. | Time of obser- one hour, in | Temperature. 
vation. 1] vation. c nae! 
micrometer micromete! 
spaces. spac 
a | |] - aT SEN I aa 
9 a. m, 10.00 | 31.0° || op. m. 3.00} ae 
eg oe cig ane | eR Ae 8.00 | - 
2 ee 8.50 f Tees 9 a 6.00 5 
i2m 10.00 “ io rep 7.00 = 
p. m 10.00 te Iam 8.00 ei 
pg 9.00 “ a yee 8.00 20.0° 
3 66 9.00 sc |] 4 “cc _0O0 ‘ 
4 ae 9.50 ‘e | 4 ce pa ie 
5 a3 8.75 “ec {| 5 “é 8.00 ou 
6 + 8.75 “ ee: 9.00 es 
ye 8.75 a oa ea 8.00 Ks 
8 « 9.00 es a g.co “e 
growth which is represented. Thus while in the daily curves of 
elongation the actual maximal and minimal points coincide, their 
relative heights might vary somewhat. 
(a) Typical observation.— We may take as an example 4 
record of the elongation of the root showing the hourly elongation 
in micrometer spaces (Leitz horizontal microscope) as given . 
TABLE II. This is expressed as a curve in FIGURE 6, curve J, 
where the observed elongation is multiplied by four to bring out 
better the form of the curve. 
There are seen to be apparently three maxima and three minima 
in the rate of elongation. The most extensive maximum (pri- 
mary maximum) has its apex at 4 p. m. The primary minimum 
has its apex at 10 p. m. Secondary maxima occur at 3 4. ™ 
