THE NATURE OE PHOTOSYNTHESIS 91 



TABLE 16 



Respiration and Photosvnthetic Quotient Determined by Maquenne and 



Demoussy. 



Respiratory Photosynthetic 

 Quotient Quotient 



COa _0_ 



Species O COa 



Ailanthus 1.08 1.02 



Aspidistra 0.94 1.00 



Aneuba 1.11 1.10 



Begonia 1.11 1.03 



Cherry-laurel 1.03 0.97 



Chrysanthemum 1.02 1.01 



Dahlia 1.07 1.07 



Geranium 1.02? 1.05? 



Grape-vine 1.01 0.99 



Ivy 1.08 1.00 



Kidney bean (young) 1.12 1.12 



" (average) 1.07 1.07 



Lilac 1.07 1.03 



Lily(?) 1.07 1.00 



Mahonia (autumn) 0.95 0.99 



Pea 1.07 1.04 



Pear 1.10 1.08 



Poppy 1.09 1.09 



Privet 1.03 1.02 



Rhubarb 1.02 1.00 



Ricinus 1.03 1.03 



Rose 1.02 1.10 



Rose Laurel 1.05 1.01 



Spindle-tree 1.08 1.02 



Sorrel 1.04 1.04 



Tobacco 1.03 . 1.04 



Turnip 1.11 1.06 



Wheat 1.03 1.02 



It is probably evident from the foregoing that the cliief difficulty in 

 obtaining an exact determination of the photosynthetic quotient is occa- 

 sioned by the fact that an error in the determination of the respiratory rate 

 also appears in that of the photosynthetic quotient. The separation of the 

 two processes is exceedingly difficult so that no matter v^hether the respira- 

 tion is determined in the dark, with narcotics in the light, or with leaves 

 poor in chlorophyll, every inexactness of the respiratory quotient affects 

 the value of the photosynthetic quotient. Willstatter and Stoll " have 

 endeavored to surmount this difficulty by determining the photosynthetic 

 quotient under conditions in which the photosynthetic activity is very much 

 greater than respiration, so that small errors in the determination of the 

 latter would have but a very slight effect on the accuracy of the photo- 

 synthetic quotient. They made another departure in that instead of 

 using a closed system, a stream of air was passed over the leaves. This 

 is the only method by which the leaves are exposed to constant conditions 



"Willstatter and Stoll, I.e., 325. 



