65 
circumference, each half, viz. the later anterior or posterior sides, 
will receive, to begin with, half of the energy, '/, a M.C.S. Moreover 
each point, which is turned away from the source of light, receives 
during rotation a further *, of the energy of the illuminated side; 
each half receives therefore altogether £ «x 4a=a M.C.S. 
Here follows a table, taken from tables 24 and 25 of Arisz; I have 
added the numbers representing 
energy difference between front and back La—Ly 
TOO) Soe [ (= 100 x == | 
energy of front Lo 
TABLE Il. 
Energy of Energy of the unilateral after-illumination in M. C.S. 
omnilateral 
eenen 4X5.5 | 8x5.5 | 5x12 | 1012 | 5100 | 10> 100 
ee 22 44 6075 120 500 1000 
0o= 0| 75 + 15 HH 75 A75 44/75 44/75 ++ 
10 5.5= 55| 29.5 + |42.3 HH [47.9 [58.444 [10.2 44 [72.5 HH 
MOCHT + 27.7 A 33,3 | 46.244 65.24 | 69-8 4+ 
865<.12:1= 435) 5.6. (0 | 10.4 -+-71.13.6 23 +. | 48.6 ++ | 58,944 
100 5.5=550| 4.5 Ol 85 O 11.1 +219.4 + [44.444 [55.814 
Me et 1210 | el Ol OF SP ee) [10.8 ET A fa 
Explanation: ++ all plants show strong positive curvature. 
+ all plants show definite positive curvature. 
+? a few plants show slight positive curvature. 
0 no plants curved. 
105.5 means: during 10 sec. omnilateral fore-illumination 
with 5.5 M.C. 
LEE 
< +6 5 55 + 22 
| here assume +? as the threshold value. We see that 
Ca—e 
aN gia! itt and: 10/3; and. it 1s 
for this the quotient 100 X 
Xa 
therefore sufficiently constant. Then y.—y, has become so great that 
a slight positive curvature occurs. If the curvature can be represented 
by f (@a)—f (a,) and also by o( 
as can be readily shown by a simple mathematical consideration. 
Since the region of energy, about which the figures supply information, 
extends from about 300— 900 M.C.S. we may say that this portion 
of the growth retardation curve has a logarithmic course. If the 
\ 5 
Va ® : : 
2e) then f is necessarily ¢ log x 
L a 
Proceedings Royal Acad. Amsterdam. Vol. XXII. 
