199 



This table shows that when a geotropic stimulus is perceived, 

 the latter does not express itself in the absence of oxygen. 



B. Geotropic experiments with Avena. 

 Fore-period of 3 hours in nitrogen. Stimulation in this 

 gas; 65 minutes after the commencement of stimulation 

 the nitrogen replaced by atmospheric air (PI. XVIII, fig. 5). 



TABLE 21. 

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



Recueil des trav. bot. Néerl. Vol. XIV. 1917. 



H 



