198 



The strength of the stimulus was of course the same in 

 both séries of experiments. 



I left a few boxes of seedlings in a nitrogen atmosphère 

 in the clinostat for a considérable time after stimulation 

 and in this way followed the course of the process for 

 a somewhat longer time than the normal reaction-time. 



I carried put thèse experiments in order to discover 

 whether there was perhaps in this case, in conséquence of 

 the absence of oxygen, a lengthening of the reaction-time. 

 In no case, however, was a curvature found. In a second 

 séries of experiments, I always stopped the supply of 

 nitrogen after the end of the reaction-time, that is to say, 

 after the period that was found, in the previous chapters 

 to be the reaction-time. Then ordinary air was sucked 

 through the thermostat for some time. In that case after 

 a certain time a curvature took place, albeit a weak one. 



A. Geotropic experiments with Avena. 



Fore-period of 3 hours in nitrogen. Then stimulation 

 in nitrogen, followed by a prolonged-period, also in 

 nitrogen. 



TABLE 20. 

 Strength of stimulus 900 m. g. -secs. Température 20^ C. 



