INTENSITY 113 



Nicolas * found that the presence of anthocyanins was a 

 factor, or rather the symptom of an internal factor, of im- 

 portance in determining the intensity of respiration. Leaves 

 containing a red pigment either as a youth form or as a per- 

 manent character absorbed more oxygen and exhibited an 

 increased respiration as compared with green leaves, whilst 

 leaves turned red either by accident or by stress of conditions f 

 showed a decreased respiration as compared with green leaves, 

 the amount of carbon dioxide being smaller. 



The intensity of respiration commonly is measured by the 

 amount of an end product given off in unit time : in aerobic 

 respiration the final product measured is carbon dioxide, 

 or, in special cases, temperature is measured ; in anaerobic 

 respiration, the production of alcohol may be estimated. 



It is clear that the results obtained by the measurement of 

 carbon dioxide may not be a true expression of the respiratory 

 activity since the exhalation of the gas may be greatly hindered 

 by various circumstances. The surface of the respiring organ 

 is one such : Hoffmann J found that the amount of carbon 

 dioxide evolved in twenty-four hours per kilogram of large, 

 medium and small-sized potatoes was 259, 314 and 326 mg. 

 respectively ; barley gave confirmatory results. He also found 

 that the nitrogen content was important. Further, a depression 

 of the carbon dioxide output is associated with the succulent 

 habit, hence in order to obtain a figure representing a true 

 measure of the activity of respiration, the increase in organic 

 acid content in addition to the gaseous carbon dioxide should be 

 determined. This aspect is considered by Maige and Nicolas, § 

 who point out that in the flowers they examined, the respi- 

 ration intensity increased with age when stated in terms of 

 gaseous exchange, but showed a decrease with age when 

 measured in terms of wet and dry weight. The gynaecium 

 shows, as might be expected from the activity of the contained 



* Nicolas : " Compt. rend.," 1918, 167, 131. 

 f See Vol. I., p. 336. 



+ Hoffmann : " Journ. f. Landw.," 1916, 64, 289. 



§ Maige : " Rev. gen. Bot.," 1907, I9> 1 I " Ann - Sci - Nat - Bot -." I 9". 

 14, 1. Maige and Nicolas : " Rev. gen. Bot.," 1910, 22, 409. 



VOL. II. — 8 



