1170 
Since the possibility existed, that especially in the space between the 
cotyl and the first leaf, sufficient oxygen remained for a long time 
to account for the prolonged irritability, I repeated the experiments 
with seedlings of Simapis alba and obtained with them mutatis 
mutandis the same results; we must therefore assume that the 
seedlings, as a result of intramolecular respiration, have sufficient 
energy at their disposal to perceive stimuli for a considerable time, 
albeit in lessening degree. We may not, however, conclude at once 
that no perception of stimulus can occur in the absence of oxygen, 
for it might quite well be that the stimulus is indeed perceived, but 
that the processes in the plant, which cause the reaction, have already 
been so influenced by the want of oxygen, that no curvature was 
possible. For these reasons I carried out geotropic experiments, in 
which the objects had a six hours’ fore-period in nitrogen and 
phototropie ones, in which this period was 8 hours; in both cases 
perception took place in the air, this being therefore the sole pvint 
of difference from the previous set of experiments. 
1. Geotropic experiments. 
TABLE 3. 
Strength of stimulus 900 mgs. Temperature 20° C. Reaction time 65 minutes. 
Paes bia ea | Amount of curvatures in mm. 
Bl | | 
6 hours 8 2 IY, 1 deed dn ere EDS 
7 ETA Eh ies UG ee BP 
7 PMS aad uke, (a TRL Ha 
8 ee Age A11" Ze 
| 
2. Phototropic experiments. 
TABLE 4. 
Strength of stimulus 40 M.C.S. Temperature 20° C. Reaction time 75 minutes. 
| 
| 
| 
Fore-period Number of | . 
in oxygen | seedlings Amount of curvatures in mm. 
8 hours g 4 14 1 1 We Ue Wo Up O 
8 Me Ye 1 1k Vo U 0 
6 th he U 
8 Welter of! Ae Ah 8 
