( 67 ) 
Corresponding acceleration Presentation time Product in ^-seconds 
LrX sin 90° = // X i 269" 269 
g X sin 60" = g X 0.866 326" 282 
g X sin 120° = g X 0.866 332" 288 
g X sin 45° = g X 0.7071 366" 259 
g X sin 135° =gX 0.7071 340" 240 
9 X sin 40° =gX 0.6428 441" 284 
9 X sin 30° = <7 X 0.5 540" 270 
g X sin 150° =g X 0.5 538" 269 
9 X sin 25° = <7 X 0.423 607" 257 
g X sin 20° = g X 0.342 735" 251 
g X sin 159° = g X 0.358 730" 262 
9 X sin 15° = g X 0.259 871" 226 
g X sin 165° = g X 0.259 853" 220 
9 X sin 10°—^X 0.174 1405" 244 
g X sin 171° = g x 0.156 1498" 234 
9 X sin 5 ° = gX 0.087 2629" 229 
g X sin 174° = g X 0.105 2233" 234 
In the case of the smaller angles with the normal (15° eh;.), the 
deviation from the standard product (for 90° = 269) is indeed fairly 
large but this is perhaps explained by the rapid change in the sine 
of these angles. The boxes in which the plants were grown could 
indeed be accurately placed in the desired position, but we cannot 
assume that all coleoptiles really grow quite vertically, and in these 
positions a deviation of 1 /.; 0 produces such a change in the effective 
force, that great accuracy is thereby excluded. 
The experiments with centrifugal force were carried out in the 
laboratory in a dark- well-ventilated room in which the gas supply 
was permanently turned off, and at a fairly constant temperature of 
17°. The presentation time for 90° is at that temperature greater 
than at 24°. This influence of the temperature had already been 
observed by Bach. I have found the same influence. 
Thus I found for instance at a deviation of 90° a presentation 
time of 4'13" at 26° C. and of 57" at 21.5° C.; at a deviation of 
60° 5'25" at 24° C., 5'41" at 21.5° C.; at a deviation of 30° 9' at 
24° C., 9 20" at 22°.5 0. 
The standard product is here 300. The seedlings were grown 
in annular boxes of various radii (up to 95 m.m.). The plants 
did not come up in a perfectly regular circle round the centre ;*as 
radius the mean had to be taken of distances, which differed amongst 
themselves by 2—4 m.m. This causes in the product an error of 
^ /•■ With the aid of Mr. D. B. Kagenaar, scientific instrument maker 
5 * 
