21 
put in the dark, but the hght is interrupted for a short time, what 
will be the process of the dark-growth-response ? 
Experiments. The light of 64 M.C. was in the various experiments 
interrupted by dark for 1, 2, 3, 5, 7'/,, 12'/, and 20 minutes. A 
summary result is found in the following table, in which the 
principal moments have been given, while fig. 1 curve 1—7 shows 
the average process. 
TABLE I. Response of growth of cells adapted to 64 M.C. in 
consequence of different times of darkness. 
SSS es = 
en gek B 
bo oe 5 Se Minimum growth | Max. growth 2nd min. 
— vo = r 
Ee. |£as fe in perc. 
22 |26 5 | of the in 
= OS i 
5 Bo Ge Ba 5 after growth after in perc. after ‘perc. 
a et in64M.C. | 
1 min. | 4 —6% | 7 — 9 |85% perc.|11l/e—14 |103% perc. — — 
2 min. | 5 —6% | 7 — 8U 71% „ [10 —12 112 5 — lif 2 
3 min. | Ahh | 7 —9 [83% , 1le13 |118 Fi 19'2—23  |93perc. 
5 min. | 5 —7 10 —12 (14% , | 15% 18124 = 25 —28 85 „ 
Temin. | 42—6' | 8 — 10/2 70 „ | 15 —17 {126 „ | 2224 [19 , 
12min. | 4 --6% | 8 —10 [72 » |19 —21 145 „ | 6/28 (84 , 
20 min. | 5 —Te |10Ve—12/ 74 „ | 28 —29 163 4 342-372 (99 „ 
Nm 
+ 94 perc. perman. 
Perman.| 3'2—5'%2 | 8%%—11 (75 „ \(15Vs- 18%) (98%, 
In connection with fig. 1 the following may be observed. Short 
times of darkness also call forth a typical dark-growth-response. 
With the short darkening of 1, 2, 3 minutes we were already 
struck with the fact, that after the minimum a constantly increasing 
maximum follows. (See esp. the table). When the cell remained in 
the dark, there was to be stated after the minimum also an increase 
of growth till just above the definite rate of growth in the dark, 
as had already been previously ascertained. But now that we dark- 
ened for a short time a maximum occurred, that becomes the greater 
according to the longer duration of the darkening, i.e. according as 
we put off the return of light. 
It appeared that a temporary darkening causes two successive 
reactions resp. a dark-growth-response and a light-growth response. 
In the successive experiments the dark-growth-response is mainly 
to be found on the same spot (see fig. 1 and table I) after 8—12 
minutes. Only where the darkening after 1, 2, 3 minutes, i.e. very 
