STOMATAL RESPONSE TO SUDDEN CHANGE. 



Experiment 117. — Verbena ciliata, June 17, 1905; burette potometer; volumetric 

 readings and weighings compared. 



Table 27. — Rates 0} transpiration for 15 minutes. 



51 



Hour. 



2 h 34 m p. m 



2 49 p. m 



3 04 p. m 

 3 19 p. m 

 3 34 P- m 



3 49 P- m 



4 04 p. m 



4 34 P- m 



5 04 p. m 



A reduction of one-third in the rate of transpiration occurred in 30 minutes, 

 unaccompanied by any change in the size of the stomata (for curve in which 

 the rates are given per hour, see fig. 17). After the lapse of an hour, the 

 stomata were reduced to about three-fourths (0.78) the original dimensions, 

 or, in terms of diffusive capacity, 0.8 +. 



Experiments 163 to 165 inclusive, July 14-15, 1905 (fig. 16). Ocotillo, with young and 

 mature foliage. Placed in dark room at midnight, where they remained till n h 20 m 

 a. m., when they were placed in strong diffused light for 1 hour; temperature of dark 

 room constant (2 8° C.) 



Table 28. — Rates 0} transpiration per hour. 



Time. 



8 h 20 m p. m 



9 20 p. m 



12 20 a. m, 



3 20 a. m. 



4 20 a. m. 



5 20 a. m. 



6 20 a. m, 



7 20 a. m, 



8 20 a. m, 



9 20 a. m 



10 20 a. m 



11 20 a. m 



1 1 40 a. m, 



12 00 day. 



12 20 p. m 



1 20 p. m 



No. 163. 



No. 164. 



c c. c.c. 



0.95 I.I 



0.85 0.95 



0.9 0.93 



1.0 0.73 



1.4 2.35 



1-7 i-35 



2.2 1.7 



2.0 1.7 



1.9 1.6 



1.8 1.5 



1.6 1.4 



1.6 1.4 



Placed in the light. 

 3-75 

 6-3 



No. 165. 



3-6 



6.3 



5.o 



6-5 



c.c. 



0.65 



0.55 

 0.6 



0.67 



0.9 



I . I 



I .2 



1.3 



. I 



.2 



■25 

 .2 



5-i 



Placed in the dark. 

 3-7 5-i 4-4 



Width of stomatal pores. 



Micra. 



2 to 4 (8) ; mean 3. 



4 to 8; mean 6. 

 4 to 6; mean 5. 

 4 to 8; mean 6. 



