EFFECT OF STOMATAL MOVEMENT UPON TRANSPIRATION. 91 



became slow, the stomata being 12 per cent open at 4 p. m., 10 per 

 cent at 5 p. m., 8 per cent at 6, 6 per cent at 7, and 3 per cent at 

 8 p. m. At 9 p. m. closure was complete and the stomata remained 

 closed until after 1 a. m. At 2 a. m. they opened 5 per cent and at 

 3 to 12 per cent. They remained in this condition until 6 a. m. when 

 they opened 30 per cent. At 7 a. m. they were 50 per cent open, at 

 8 a. m. they were 80 per cent, and at 9 a. m. they were again wide 

 open. As with Fouquiera, watering some of the plants caused no 

 change in stomatal movement. The probable reason was that 

 all the plants had sufficient moisture, and the amount added did not 

 result in enough increase to produce a visible change. This was not 

 checked by sampling the soil; hence it can only be inferred. 



As in Fouquiera, the cut stems of Verbena showed no complete 

 closure of the stomata. They were wide open at the start of the 

 experiment and, like the rooted plants, remained open until noon. At 



9 10 II NOON! 



3 * 5 6 7 8 9 10 II MT. I Z 3456 789 10 



FIG. 45. Series w 29, showing average 'movement in"upper and lower stomata 

 of watered and un watered field plants (A) and cut stems (B) of 

 Fouquiera spiendens. 





9 10 II NOON I Z 3 4. 56 7 8 9 IO 1 1 MT. I Z 3 * 5 6 789 10 



FIG. 46. Series 29, showing average movement in upper and lower stomata of 

 field plants (A) and cut stems (B) of Verbena ciliata. 



1 p. m. they closed to 90 per cent, at 2 to 80 per cent, and to 70 per 

 cent at 3 p. m., They remained in this condition until 5 p. m., and 

 then closed to 60 per cent at 6. They closed to 55 per cent at 7 p. m., 

 50 per cent at 8, and 45 per cent at 9 p. m. No further change oc- 



