Il8 CHAP. XV. C0 2 -SUPPLY AND PHOTOSYNTHESIS 



my experiments. The solutions were introduced into the 

 plant-vessel without causing any disturbance ; light and 

 temperature were maintained absolutely constant ; the 

 same plant was used throughout the investigation, so that 

 the physiological condition was uniform ; changes due to 

 seasonal variation were excluded ; the observations were 

 completed in the course of less than an hour. The remark- 

 able smoothness of the curves which I obtained testifies to 

 the high accuracy which is secured by the new method. 

 With this it is possible to obtain a physiological constant 

 for the plant which is found to be almost as definite as a 

 physical constant of inorganic matter. 



Determination of Coefficient for 

 C0 2 -Concentration 



We found that the photosynthetic curve for variation of 

 C0 2 -concentration is straight up to 8 to 9 mg. per 100 c.c. 

 We can therefore determine the coefficient by dividing the 

 increment of activity by the increment of C0 2 -concentration 

 which induces it. For unit variation of concentration I will 

 take an increase of 1 mg. per 100 c.c. 



K = — .... (1) 



c — c 



where A c is the activity for the higher concentration c, and 



A c is the activity for the lower concentration c. 



We will first determine the coefficient of the specimen (I.) 

 for two pairs of different concentrations : (a) 3 mg. and 

 5 mg., and (b) 5 mg. and 7-5 mg. ; and then those of other 

 specimens. 



Specimen I. (a) C0 2 -concentrations of 3 mg. and 5 mg. : 



Activity for 3 mg. = 70-96 

 5 mg. =149-50 



K== 149-5 -7Q-96 =39 . 27 



