INDUCED RHYTHM IN TRANSPIRATION. 



The rate commenced to increase shortly after i a. m. and rose to an early 

 morning maximum at 6 a. m., July 19. 



llajn. Ifxm. 3 5 7 9 II 1a.m. 3 5 7 9 II 



FIG. 21. Curve for experiment 56. Fouguieria splendens. The temperature during the 

 experiment js shown by the broken line. 



Experiments 58, 59, and 60. July 18-19, 1904 (fig. 22). Set up at 5 p. m.; on labora- 

 tory porch till i p. m., then placed in dark room, of which temperature was 32. 5 C., the 

 same as without; dark room remained open until 3 a. m., when it was closed; no 

 variation at this time (32.5 C.) until close of experimentation. 



Experiments 62, 63, and 64 (fig. 23) were conducted simultaneously with the above, but 

 remained without on laboratory porch till 3 a. m. 



Experiments 65 and 66 (controls) were identical with the foregoing in all respects, but were 

 ahowed to remain on laboratory porch under normal diffused illumination. 



NOTE. The maxima occurring in experiments 58 to 60, 62 to 64, at i p. m., toward the 

 close of the experiment, were due to brief exposures to light. 



TABLE 38. Hourly rates of transpiration. 

 [The hourly rates given are derived by measurements of uncalibrated tube potometers.] 



Stomatal pores measured at 9 a. m., 2 to 6 micra wide in all; at I2 h i5 m p. m., 2 to 6 

 micra wide in all; at i2 h 45 m p. m., 2 to 6 micra wide in 64. 



