396 
RAY C. FRIESNER 
II A.M. and 7 P.M. minima of curve 27; while the 3 A.M. and 7 AM., 
maxima, and the 5 A.M. minimum of curve 28 are each just 6 hours later 
than the corresponding maxima and minimum of curve 27. Thus the 
entire curve 27 is earlier than curve 28 by an amount of time equal to the 
difference in time between the beginnings of germination. As further 
evidence on this point, a third series of root tips were cut at the same 
time and under identical conditions. The seeds for this third series were 
placed in the germinating pots at 8 P.M. Curve 31 shows the results 
of this study. In curve 28 a fourth wave was merely indicated, while in 
curve 31 there are definitely and clearly four waves. It is seen that because 
of the difference between the times when seeds were placed in germinating 
pots there would be expected to be a difference of just eleven hours between 
the times of initiation of activity in curves 27 and 31, and six hours between 
curves 28 and 31. Table 8 shows the maxima and minima of these curves 
correlated in respect to time (after initiation of activity) of their occurrence. 
Table 8. Pisum sativum. Correlation of Maxima and Minima of Curves 27, 28, and ji 
27 
28 
31 
Germination Began 
Germination at 
Diff. from 27 ; 
Germination at 
Diff, from 27; 
Difif. from 28 ; 
at 9 A. M, 
2 P. M. 
5 Hrs. 
8 P. M, 
II Hrs. 
6 Hrs. 
Maxima 
3 P.M. 
7 P.M. 
4 
3 A.M. 
12 
8 
9 P.M. 
3 A.M. 
6 
7 A.M. 
10 
4 
I A.M. 
7 A.M. 
6 
3 P.M. 
14 
8 
II A.M. 
Minima 
II A.M. 
3 P.M. 
4 
9 P.M. 
10 
6 
7 P.M. 
II P.M. 
4 
5 A.M. 
10 
6 
II P.M. 
5 A.M. 
6 
II A.M. 
12 
6 
9 A.M. 
I A.M. 
A study of this table shows that the same relation exists between curves 
28 and 31, and 27 and 31, as is shown above between curves 27 and 28, viz., 
there are in both curves 28 and 31 waves corresponding, in time after initia- 
tion of activity, to each of the three waves shown in curve 27. The extra 
(fourth') waves appearing in curves 28 and 31 not only do not have a corre- 
sponding wave in curve 27, but also seem not to be correlative to each other. 
A further experiment of this same nature was carried out in which two 
series of peas of the smooth-seeded variety were placed in germinating pots 
at 9 A.M. and incubated at 24-25° C. for 48 hours. They were then 
removed from the incubators to a refrigerator where a recording thermometer 
showed the temperature to vary between 6.0° and -0.5° C. for a period of 
48 hours. During the time of refrigeration, control plants were kept growing 
in the glass culture chambers used for elongation studies, and their elonga- 
tion was measured. The elongation figures (omitted for lack of space) 
show that the temperature was sufficiently low to inhibit all but the slightest 
