The Effect of Light on the Transpiration of Leaves. 297 



Experiment 34.— July 10, 1913. Ivy. 



Shoot having nine leaves, six being of current year, vaselined. 

 July 11, 10.20 a.m. — In potometer at east window. i/r during day 

 66-69 per cent. T 17-18-9° C. Dull morning. 



Time. 



R. Averag 



1 



e. Time. 



i 



E. 



Average. 



10.29 A.M. 



22 -6 



11.52 A.M. 



71 -0 





10.31 





Cut up leaves, 4 cuts 



each 12.6 p.m. 



75-0 1 



75 







leaf. 



12.18 „ 



74-0 J 



10.34 





88-0 



12.20 „ 



Replaced at east window. 



10.40 



» 



83 -0 



1 12.26 „ 



80 -0 





10.49 





85 -0 



12.32 „ 



91 -0 





11.7 



u 



98 -0 



12.44 „ 



89 -0 





11.22 



ij 



93-0 \ q . 

 97 -0 J ! 9o 



12.59 „ 



95 -0 





11.25 





! 1-7 „ 



94-0 





11.26 



J) 



Placed in dark room. 



1.12 „ 



103 -0 \ 



101 



11.34 



3) 



82-0 1 



1.18 „ 



98-0 J 



11.40 



» 



76 -0 









L. D. L. 



Result 95 75 101 Average : L/D = 131/100. 



or 127 100 135 



Experiment 35.— June 22, 1913. Ivy. 



The following experiment may be placed with the above, although 

 transpiration was estimated by weighing instead of with the potometer. 

 The method was the same as that described for laurel. 



June 21, 4.30 p.m. — Branch cut under water and placed in water covered 

 with a layer of oil. The lower surfaces of the leaves (of the current year) 

 carefully vaselined, together with the stem. 



June 22, 9.40 a.m. — Four or five incisions made per leaf. Placed in north 

 window ; the sky fairly bright, ■f from 72 to 80 per cent. T 16-6-19-2 C. 



Time. 





Rate corrected 

 for if. 



Time. 





Rate corrected 

 to ■•p. 



10.18 A.M. 1 



11.20 „ J 

 11.20 „ 1 

 12.34 p.m. J 



Light 

 Dark 



295 

 187 



12.34 p.m. 1 

 1.37 „ J 

 1.37 „ \ 

 2.41 „ / 



Light 

 Dark 



361 

 190 



The average transpiration L/D = 328/189 

 or L/D = 174/100 



The average of the L/D results for ivy, viz., 138, 136, 113, 121, 131, 

 174/100, is 136/100. 



