1281 
The values found in the experiments are collected in the following 
table. Each horizontal line represents a separate series. The figures 
in brackets indicate the magnitude of the light stimulus in metre 
candle seconds (MCS) and the duration of the gravitational stimulus 
in minutes. 
ARE BE er 3 Pe bellighe te aR ane 
I | 2.8 (200) | 2.6 (100) | Re. 3.6 (100 +15 min) 0.8 (15 min.) 1.3 (30 min.) 
IL 2.5 (120) 1.9 (60) | 1.0(60—15 min) 2.2 (60415 , ) 0.4 (15 „ }1.6(30 „) 
III | 2.3(120) | 2.1 (60) * 13.2 (60415 , ) 1.0 (15 , {1.6.30 ,, ) 
IV | 2.7(120) | 2.5 (60) | 0.5 (60-20 , ) 3.1 (60-20 , ) 1.7(20,, )2.9(40, ) 
V | 2.2 (120) | 1.6 (60) —0.2 (60—20 , 12.5 (60-20 „)|1.4(20 , )2.1 (40 ,) 
VI | 2.4(120) | 2.1 (60) | 1.2(60—20 , ) 3.4 (60420, ) 1.2(20, ) 2.6 (40 0) 
| 
2.0 (120) | 1.4 (60) |—0.2 (60—20 , ) 2.6 (60420 ,, ) 1.2 (20, )2.0(40 , ) 
| | | | 
5 
The fairly considerable divergence which sometimes occurs between 
the series, is explained by the difference in length of the seedlings 
used; thus those of IV were very tall, those of VIT very short; in 
connection with this comparison should be made with Artsz’ data’) 
for photetropie curvatures and with MaiLunrer’s detailed tables for 
geotropic ones (1912 Lc.) 
When the ‘experiments were taking place it could be noted that 
the phototropic curvatures were often already visible before the end 
of the gravitational stimulation. In those seedlings in which light- 
and. gravitational curvatures acted in opposite direction, the photo- 
tropic one extended already lower down, at the moment when the 
geotropic one became visible at the apex, so that the coleoptile 
temporarily acquired a weak S-shaped bend. 
As the figures show, the curvature which arises when light and 
gravity bring about deviations in the same direction, more or less 
equals the sum of the curvatures which each stimulus calls forth, 
when acting separately. When they act in opposition to one another, 
then the resulting deviation is approximately the same as the difference 
of the separate deviations. In the following table the relative figures 
are once more placed side by side with the sums and differences 
calculated from 2 and 5 placed between brackets after those found, 
1) W‚ H. Arisz, Onderzoekingen over fototropie, Diss. Utrecht, 1914, 
