1911.] New Method of Estimating the Aperture of Stomata. 143 



40 



Fjg. 3. — Experiment 75. Curve S is constructed from the square root of the rate of 

 air -flow. - T represents transpiration. The black bar gives the period of darkness. 



It is evident that the agreement of the columns S and T is only a rough 

 one, and that in some points the differences are great. But if we replace 



Times 



S. 



T. 



(roughly). 



•v/Flow. 



Transpiration. 



A.M. 







11.5 



3 -1 



3-7 



45 



3 5 



4-0 



P.M- 







2.10 



1 -o 



1 -o 



48—59 



1 -8 



1-3 



3.50—55 



0-8 



0-5 



the y/ flow by the actual rate of flow, we get a series of figures in which 

 the discrepancy is, on the whole, much greater between transpiration and 

 the porometer record. 



Transpiration. 



§ 5. Light and Darkness. 

 In the following experiments, light means exposure, at a north or east 

 window, to diffused light, the plant being placed as near the glass as may 

 be. Darkness means that the experiment is continued in a dark room. 



