The Effect of Light on the Transpiration of Leaves. 283 



Experiment 3. — April 19, 1911. P. laurocerasus. 

 Potometer : leaves slit at 10.55 a.m. T 161-17-0 C. 50-62 per cent. 

 Transpiration corrected. 



Time. 



Rate. 



Time. 



Eate. 



11.22 A.M. 



159 



11.55 A.M. 



186 



11.39 „ 



149 



12.8 p.m. 



168 



11.45 „ 



153 



3.8 



187 



11.50 „ 



In dark room 



3.12 „ 



181 



The transpiration had been steady for some time before the plant was 

 placed in the dark room. The only clear effect was a rise in transpiration - 

 rate from 153 to 181, or L/D = 100/118. 



Experiment 4. — April 20, 1911. P. laurocerasus. 

 Potometer : leaves greased and slit 10.30 a.m. T 15-0-16-6 C. 4Ar-4X per 

 cent. 



Time. 



Rate. 



Time. 



Rate. 



10.40 A.M. 



757 



12.2 p.m. 



797 



11.0 „ 



814 



12.43 „ 



610 





Dark room. 



12.45 „ 



Light. 



11.4 „ 



902 



12.48 „ 



493 



11.24 „ 



897 



12.56 „ 



550 



11.51 „ 



816 



3.30 „ 



559 



In this experiment the effect of the dark room is doubtful, as the rate was 

 not steady before darkness. If we assume that the fall in rate was due to 

 darkness, we have the big effect of fall from 902 to 493 or 183/100. The 

 subsequent rise in the light is from 493 to 559 or D/L = 100/113. 



The average of the light and dark effects is L/D = 148/100. 



Experiment 5. — April 22, 1911. P. laurocerasus. 

 Potometer: leaves greased and slit 10.31 a.m. T 19-6-21'l° C. ^ 41- 

 52 per cent. 



Time. 



Rate. 



Time. 



Rate. 



10.47 A.M. 



210 



11.54 A.M. 



157 



10.50 „ 



233 



12.5 P.M. 



162 



10.52 „ 



208 



12.13 „ 



154 



10.58 „ 



213 



12.21 „ 



162 



11.0 „ 



In dark room 



12.32 „ 



171 



11.21 „ 



197 



12.39 „ 



174 



11.47 „ 



176 



12.50 „ 



174 



11.48 „ 



In light 







