( 220 ) 
in this vessel there were always also two little basins of water as 
humidity was found to have a great influence. 
The titration of the baryta water was carried out with HC1, with 
phenolphthalein as indicator. 
Generally I made observations at intervals of 5°; in most cases 
an experiment lasted 6 hours. A difficulty, which cannot be obviated, 
is that, when seeds are kept for a long time, the respiration is very 
different at different periods. The figures thus become much less 
comparable; in the following table I therefore give a series of ex¬ 
periments which were made within as short an interval as possible. 
Most of the experiments were made with Pisum sativum; these 
will be considered in greatest detail. For every experiment 100 
seedlings were used, which had germinated for one day in water 
and for two days in saw-dust. 
Temp. 
mgr 
. C0 2 liberated during 
Average 
per houi 
1 st hour|2"d hour 
[ 3 rd hour j 4th hour 1 5th hour 
6th hour 
0° 
4 
3.6 . 
4 
3.8 
3.9 
5° 
6.7 
6 
5.6 
5.7 
,8 
6.1 
10° 
12 
11.2 
11.1 
11.4 
1 
11.3 
11.4 
15° 
18.6 
19 
19.4 
19.4 
20 
20.2 
19.4 
20° 
28.6 
30.3 
30.3 
30.6 
30.4 
30 
25° 
43.3 
42.4 , 
42.2 
41.7 
40.7 
40.9 
42 
30° ' 
51.7 
50.9 
52.2 
53.6 j 
53.5 
53 5 
52.6 
35° 
68.7 
62.8 
60.1 
61.7 
60.9 
60.9 
40° 
73.3 
55.2 
49 
45.3 
43 
41.2 
45° 
73.5 
48.4 
41.9 
35.9 
31.9 
28.0 1 
50° 
74 
38.8 
17.8 
12 
8 
5.9 1 
It is already clear from the averages between 0° and 20° that the 
proportion for any rise of temperature of 10° lies between 2 and 3; 
from the mean of all the observations I find the following relation: ) 
A l0 10.3 A.' 18.5 A t0 29.1 A„ 40.3 2 
A, ~ 4.3 ~ 2 ' 4 A, ~ 3-1 A„~ 17.8 ' 
The rule of van t’ Hoff-Arrhenjus holds good therefore up to 20, 
*) Ac means respiration at 0°, etc. 
