CHAPTER VI. 



Effect of an Atmosphère with low 

 o X y g e n-c o n t e n t. 



In order to investigate the geotropic and phototropic 

 stimulation-process in an atmosphère with low oxygen- 

 content, I passed the nitrogen from the cyhnder directly 

 through the thermostat without allowing it fîrst to pass 

 through the wash-bottles with pyrogallol and the tube 

 with glowing copper. 



I investigated the influence of such a low oxygen- 

 content on perception only. 



The seedlings consequently underwent a fore-period of 

 several hours in the atmosphère in question: hère stimu- 

 lation also subsequently took place, whilst immediately 

 after this ordinary air was sucked through the thermostat. 

 Since it is évident from a former chapter, that there is 

 no where any question of a lengthening of the reaction- 

 time, but only of a weakening of the reaction, I always 

 measured in this case also the curvatures after the times, 

 which are determined in Chapter III as reaction-times. 



A. Geotropic experiments with Avena. 



(PI. XIX, fig. 2, fore-period of 8 hours, fig. 3, fore-period 

 of 24 hours). 



