INDUCED RHYTHM IN TRANSPIRATION. 



Experiments 163, 164, and 165. July 14, 15, 1905 (fig. 16). Pieces in vertical tube poto- 

 meters (burettes) set up in the afternoon; readings commenced at 8 h 2o m p. m. Placed 

 in dark room at midnight, where they remained under constant conditions of temper- 

 ature, relative humidity, and darkness. 



In all three curves the early morning maximum is clearly shown as follows : 

 163 at 6 h 2o m a. m. ; 164 at 4 h 2o m , and at 6 h 2o m a. m.; 165 at 7 h 2o m a. m. 

 No. 164 shows a marked irregularity at 4 h 2o m a. m., producing a maximum 

 which is unusual if not abnormal. Otherwise the character of the curve 

 consists well with that of the other two. It is significant, however, that the 

 irregularity occurred in the early morning, near the time when the maximum 

 of induced rhythm is to be expected in the plant. 



Experiments 172 to 175, inclusive. July 18, 1905. 



These four pieces, attached to burette potometers, were in the dark room 

 from 8 p. m., July 18, till 1 2 day, July 19. All showed early morning maxima 

 as follows (see fig. 13) : 172 at 7 a. m. ; 173 at 7 a. m. ; 174 at 4 and 6 a. m. 

 (cf. experiment 164, p. 51); 175 at 7 a. m. 



TABLE 41. Hourly rates of transpiration. 



* Total for two hours. t Data lost. 



The following are experiments with plants which were exposed to normal 

 illumination, and are of interest in the present connection because of certain 

 irregularities in rate which occur in the early morning hours. 



