1174 
Ko — 3 =i — 96 
Is ah iC, ae 
K 0 
Se ee, 
oe Leen 
Ku _ 26 Ks 9.95 
Kn Kr sb 
The quotients appear to remain constant up to 30° and after that 
decrease markedly, in agreement with what is observed in other 
vital processes. | refer to the paper of Congen Stuart’) for this point. 
Does the observed influence of temperature only affect perception 
or is the time of curvature (reaction-time) also influenced by tem- 
perature? The reaction took place at 20° C in all the experiments. 
Of course it is conceivable that there is an after-effect of the 
preliminary warming at the temperature investigated. The times of 
curvature (reaction-times) amounted to: 
At 0°C. 120 minutes 
OD 90 * 
eee | ee 90 
ins Cees 90 & 
res: 90 2 
TI 85 ie 
se 85 Ee 
OI 90 cs after 1 to 12 hours’ previous warming 
after longer warming 120’ 
RAE (ae 90 i after long warming 120’ 
3.30 eee LOO “a after long warming 120’ 
Ree 120 e 
DES 2'/, to 3 hours. 
By time of curvature (reaction-time) there is here meant the time 
which elapses till 50°/, of the plants are curved. The reaction-time 
is therefore fairly constant except at O° and at the high temperatures. 
It seems clear from the tables, that, if there is any influence of the 
temperature at which the plant was warmed beforehand, on the 
reaction, this is found exclusively at 0°, 39° and 40° and, when 
the previous warming is of very great duration also at 35°, 37° and 
38°. If may therefore be considered probable that the influence of 
temperature specially acted on perception. 
I hope later to give further theoretical considerations and a review 
of the literature in a fuller communication. 
Utrecht, January 1913. University Botanical Laboratory. 
P. Conen Sruarr. “A study of temperature-coeflicients and van ‘rt Horr’s 
rule”. Proceedings Royal Acad. Amsterdam; Vol. XIV. p. 1159, 1912. 
