AUTONOMIC MOVEMENTS IN SUCCULENTS 343 



both soil and plant tissues. The influence of these factors is 

 indirect and acts through other intermediate processes. 



(5) The day-to-night movements have been shown to be 

 caused directly by turgidity changes. 



(6) Opunlia versicolor is less turgid at night than in the day 

 time as is shown by the fact that the plant absorbs more water 

 through its roots in the day time than it loses by transpiration, 

 and at night loses more than it absorbs. This is the opposite 

 of the behavior shown by all non-succulents which have been 

 studied. 



