191 



2. The material has only apparently been deprived of 

 air for ail thèse hours, since it is quite possible that 

 besides in the intercellular cavities of the cells there still 

 remains after a long time a certain quantity of air in the 

 cavity between the coleoptile and the fîrst leaf. Conse- 

 quently oxygen-respiration continues at fîrst in sufïîcient 

 degree to explain the occurrence of the reaction. In order 

 to décide between thèse two possibilities I hâve carried 

 out the same experiments with seedlings of Sinapis alba, 

 because in them the cavities under the cotylédons are absent. 



C. Geotropic experiments with Sinapis. 



The experiments were therefore repeated in the same 

 manner, namely, a fore-period in nitrogen, afterwards 

 geotropic stimulation also in nitrogen, by placing the 

 seedlings for 10 minutes in a horizontal position. Then 

 atmospheric air was passed through in order that a possible 

 reaction might take place. 



TABLE 16. 



Strength of stimulus 600 m. g. -secs. Température 23^ C. 



Reaction-time 45 minutes. 



