286 



Sir F. Darwin. 



Experiment 8. — April 28, 1913. P. laurocerasus. 

 Leaves, five in number, vaselined and cut into strips at 9.40 a.m. Vertical 

 potometer, 60 cm. from window of dark room, shutter open. T 152-16-2. 

 ->|r 63-65 per cent. Transpiration corrected for -\|r. Dull day. 



lime. 



Reading 



Rates per hour. 





c.c. 







c.c. 



9.51 A.M. 



0-080 









10.0 „ 



0-103 







0-156 



10.15 „ 



-142 







0-152 



10.34 „ 



0-190 







0-151 



10.45 „ 



0-217 







0-147 





Shutters closed. 



Dark. 





10.50 ,. 



0-233 







0-192 



11.0 „ 



0-254 







0-126 



11.15 „ 



0-292 







152 



11.30 „ 



0-326 







0-136 



11.45 „ 



0-361 



Shutters opened. 





Light. 



-140 



12.0 NOON 



0-394 







0-132 



12.15 P.M. 



0-430 







0-144 



12.30 „ 



0-463 







0-132 



12.45 „ 



0-497 







0-136 



12.46 „ 



Shutters closed. 



Dark. 





2.30 „ 



0-715 







0-125 



I have usually estimated the transpiration by taking the average of the 

 two last readings in each period, Light (L) or Dark (D), as the case may be. 

 But in Experiment 8 the first L reading should clearly be the average of 

 the last L and the first D reading, i.e. 170. The other averages are D 138, 

 L 134, D 125 ; they are included in the general average. 



The results of the above-named eight experiments show considerable 

 irregularity and no clear impression is gained by inspection. I have therefore 

 taken the average of 31 readings from the series, 18 representing transpira- 

 tion in light, and 13 in dark. They are as follows : — 



Light. 



Dark. 



Light. 



Dark. 



153 



155 





134 





125 



214 







200 





157 



186 



183 





161 





141 



216 







224 





181 



170 



166 





212 





152 



130 



122 





170 





138 



120 







149 







96 



118 





110 





100 



170 



138 





104 







Average 162 : 

 or 113 : 



100 } L/D = 113/100. 





