479 



a time-signal is given on a continuous line T. Of course the distance 

 covered by the circumference of the clinostat-axis in successive 6 



Fig. 3. Backview of the whole clinostat. 



minutes must always be the same; so the distance between the 

 time-signals must not vary with a good clinostat. 



Now the various clinostats were tested in two ways; partly 

 without load, partly with an excentric load on the axis. This latter 

 was done, because that very unequal load causes the greatest diffi- 

 culties in practice, especially when in the dark plants have to be 

 fixed on a clinostat, or when we have to try several times in order 

 to get an exact centering, when meanwhile the plants have already 

 been exposed to the unilateral influence of gravitation for a long 

 time. Fig. 4 shows the results of those experiments. 



In I the behaviour of a clinostat of Pfeffer is shown with an 

 excentric load, amounting to 0,26 KG. when calculated on the axis. 



31 

 Proceedings Royal Acad. Amsterdam. Vol. XXV. 



