538 RESPIRATION AND FERMENTATION 



inyces, proteids, even in combination with quinic acid, &c., do not serve to 

 maintain intramolecular respiration for any length of time, whereas nutrient 

 media of this kind satisfy all the requirements of certain anaerobic bacteria. 

 It seems probable therefore that intramolecular respiration is not directly 

 connected with the decomposition of proteid substances. 



The continued exhalation of carbon dioxide in the absence of oxygen was first 

 observed a century ago ', and the formation of alcohol in fruits kept in a chamber 

 devoid of oxygen has been mentioned by several authors 2 , but in these observations 

 the complete absence of oxygen and of micro-organisms was not assured. The 

 latter objection applies to certain of the researches of Lechartier and Bellamy, 

 Pasteur, and Traube 3 , which however along with the experiments by Brefeld 

 and Miintz render it certain that carbon dioxide and alcohol are produced during 

 the intramolecular respiration of the most widely different plants. 



Wortmann supposed that the same amount of carbon dioxide is produced 

 whether oxygen is present or not, but Wilson has shown that the ratio between the 

 respective amounts of carbon dioxide produced by intramolecular and aerobic 

 respiration differs in different parts of the same plants and lies between the limits 

 of 0-2 and unity in different Phanerogams and Agaricineae 4 . Pfeffer then pointed 

 out that the phenomenon was a vital one connected with the normal processes 

 of respiration, and not one of death as Nageli supposed *. Hence in the absence of 

 oxygen intramolecular respiration immediately commences, while as soon as the 

 supply of free oxygen is restored aerobic respiration is resumed. It is only 

 when the plant has been injuriously affected by prolonged exposure that a latent 

 period of recovery intervenes before the oxygen-respiration acquires its full normal 

 activity. Chudiakow has also shown that the ratio between the amounts of carbon 

 dioxide evolved during intramolecular and aerobic respiration remains comparatively 

 constant at different temperature, both forms of respiration being correspondingly 

 affected by a rise or fall of temperature (Sect. 104). 



Alcohol is formed in variable quantities. According to Brefeld (1. c., p. 237), 

 not more than \ per cent, of the weight when moist accumulates in leaves and flowers, 



1 Rollo, Ann. d. chim., 1798, T. xxv, p. 42; Saussure, Rech. cbim., 1804, p. 201; Berard, 

 Ann. d. chim. et d. phys., 1821, T. XVI, p. 714. More recently, Broughton, Bot. Zeitung, 1870, 



-^.-647; Pfeffer, Arb. d. Bot. Inst. in Wiirzburg, 1871, Bd. i, p. 34. 



2 Dumont, Neues Journ. f. Pharmacie,^i$i9, Bd. ill, p. 568; Db'bereiner, Gilbert's Ann. d. 

 Physik, 1822, Bd. LXXII, p. 430. See also Dipping n. Strove, Joum. f. prakt. Chemie, 1847, Bd. XLI, 

 p. 271. 



8 Pasteur, Compt. rend., 1872, T. LXXV, p. 1056, and 1. c. ; Traube, Ber. d. Chem. Ges., 1874, 

 p. 885. 



4 Wortmann, Arb. d. Bot. Inst. in Wiirzburg, 1880, Bd. n, p. 500; Wilson, Flora, 1883, p. 93. 



6 Nageli, Theorie d. Gahrung, 1879, p. 43; Pfeffer, Unters. a. d. Bot. Inst. z. Tubingen, 1885, 

 Bd. I, p. 637, where the apparatus used is described. The same method is still usually employed of 

 removing all oxygen by a current of hydrogen, and collecting the CO 2 evolved in titrated baryta- 

 "iter. These results have been confirmed by Moller, Ber. d. Bot. Ges., 1884, p. 307; Jentys, Bot. 

 jahresb., 1884, p. 89 ; Stich, Flora, 1891, p. 21 ; Amm, Jahrb. f. wiss. Bot., 1893, Bd. XXV, p. I ; 

 Chudiakow, 1894, 1. c. 



