205 



TABLE 25. 

 Strength of stimulus 900 m.g.-secs. Température 20' 

 Reaction-time 65 minutes. 



It is sufficiently clear from this table that the seedlings 

 in a comparatively low oxygen-content remained for a 

 long time in a condition to perceive a geotropic stimulus 

 in a normal manner. When, however, they remain for 

 24 hours in an atmosphère of an oxygen-content of 4.3 %• 

 an influence is distinctly recognisable which expresses itself 

 by a weaker reaction, of which the cause can only be 

 that the seedlings on account of the deficiency of oxygen 

 were no longer able to perceive the stimulus normally. 



B. Phototropic experiments with Avena. 



(PI. XIX, fig. 4, fore-period of 10 hours, fig. 5 fore- 

 period of 24 hours). 



TABLE 26. 



Strength of stimulus 40 M.C.S. Température 20^ C. 



Reaction-time 75 minutes. 



