Botany. — "On a new clinostat after de Bouter". By Prof. 

 F. A. F. C. Went. 



(Communicated at the meeting of December 30, 1922). 



It has been known to every botanist for nioie than 15 years, 

 that the clinostats in present use are not satisfactory with regard 

 to great precision. Already in 1907 van Harreveld ') made the 

 errois of those instruments known to us in a detailed study. He him- 

 self constructed a much better clinostat, satisfying high requirements, 

 but nevertheless introduced only in a few laboratories. This will be 

 chiefly due to the great costs, unsurmountable for most laboratories. 



To the above fact it has been chiefly due, that Mr. P. A. de 

 Bouter, mechanic of the Botanical Laboratory at Utrecht, asked 

 himself, whether it would not be possible to construct a much 

 cheaper clinostat, nevertheless coming up to high requirements. 

 Those considerations have led to the construction of a new clinostat, 

 the descri|)tion of which follows. 



Fig. 1 sliows the clinostat in a more or less schematic way. 1 is 

 a shuntmotor, running directly full speed, and connected by a belt 

 3, with a flywheel 2, to the axis of which a pinion has been fixed. 

 With the aid of cog-wheels its motion is transmitted to the proper 

 clinostat 5. The axis of the fly-wheel turns on ball-bearings. Now 

 the question is, to make this fly-wheel revolve exactly once a second ; 

 this cannot be attained by altering the speed of the motor or by 

 regulating the diameter of the grooved wheels because of a too 

 great oscillation of the voltage of the town-plant. Neither does the 

 motor run regularly with equal voltage; namely with excentric load. 

 For this reason a different construction has been used here. 



Into the circuit -| of the motor a resistance 12 has been 



inserted in the form of a lamp, in consequence of which the fly- 

 wheel runs a little too slowly, e.g. half a rotation a second. If 

 however this resistance is put out of circuit, the fly-wheel revolves 

 a little too fast, e.g. two rotations a second. This putting out takes 



1) Ph. van Harreveld, Die Unzulanglichkeit der heuligen Klinostaten fur reiz- 

 physiologische Untersuchungen. Recueil des Travaux botaniques néerlandais. III. 

 1907, p. 173. 



