( 1024 } 
3mm 
8mm 
Jm.m 
6mm 
5mm 
4mm 
Deviation of the apex im m.m. 
2mm. 
20m 40m 60m. 80m. 100m. 120m 140m 160m. 180m 200m 220m. 240m Time 
Fig. 2. 
Course of the phototropic curvature. 
A. stimulated with 800 MCS. B. witi, 112 M.GS. 
C. with +20 MCS. D. with 5 M.GS. 
scopically into a part which can also be perceived macroscopically, 
takes place more or less gradually. 
An obvious break occurs on strong stimulation {see fig. 2 A). 
Braauw’s interpretation, that the curvature here enters on a new 
phase, seems to me very plausible, when we see that just at this 
moment the parts remote from the apex, which in contradistinction 
to the apex itself show a considerable increase in length, begin to 
take part in the curvature. 
On comparison of curves obtained in such a way, it became ob- 
vious that the maximum curvature seen in plants which were illu- 
