The Controlling Influence of Carbon Dioxide. 151 



Table X. — Effect of Carbon Dioxide upon Floating Inspiration (Anaerobic) 

 obtained by Subtraction Method. 



Concentrations of C0 2 

 in N 2 . 



Anaerobic C0 2 produced (c.c. per 10 



grm. per 10 hours). 



By starch leaves. 



By starved leaves. 



By floating respiration 

 (by subtraction). 



per cent. 













20 



7-8 



12 2 



35 



8-8 



8-4 



0-4 



85 



7-1 



5 9 



1 -2 



Conducted in dark. 15 grrn. of whole Cherry Laurel leaves in each experiment. Starch 

 leaves kept after cutting five days under artificial illumination, petioles in H 2 0. Starved leaves 

 kept after cutting five days in dark, petioles in H 2 0. 



Temperature 25° C. Time 46 hours (second and third day after setting). 



Table XL — Effect of Carbon Dioxide upon Floating Respiration (Aerobic) 

 obtained by Subtraction Method. 



Concentration of C0 2 

 present. 



C0 2 produced in 



normal respiration ( 

 per 10 hours). 



c.c. CO ; per 10 grm. 



By starch leaves. 



By starved leaves. 



By floating respiration 

 (by subtraction). 



per cent. 









10 



18 -5 



6-7 



11-8 



25 



15-7 



7-9 



7-8 



40 



16 -4 



10 -4 



6-0 



60 



15-8 



12 -4 



3*4 



Conducted in the dark. Ten whole Lilac leaves, 8 grm., in each experiment. Starch leaves, 

 newly cut after 12 hours' sunshine, showed abundant starch. Starved leaves, newly cut from 

 shoots kept previously six days in dark, showed complete absence of starch. 



Temperature of experiments 20° C. Time 75 hours. Estimation by analysis. 



These results indicate that floating respiration may be retarded to practical 

 inhibition under the action of carbon dioxide. This is the case, moreover, 

 both in the presence and in the absence of oxygen. Upon protoplasmic 

 respiration, on the other hand, the action of carbon dioxide is shown to be of 

 a different nature. The tentative conclusions reached can, therefore, be 

 stated as follows : — (1) That the distinction drawn by Blackman between 

 floating respiration and protoplasmic respiration is confirmed. (2) That the 

 retarding and inhibiting action of carbon dioxide upon the general respiration 

 of plant tissues (most marked in the case of seeds and seedlings so far as 

 these experiments have as yet gone) is an effect, in the main, only upon the 

 floating respiration and is in the nature of a direct action inhibiting it. 



VOL. LXXXIX. — B. O 



