THE PRODUCTS OF AEROBIC RESPIRATION 529 



other bacteria as well, is actually liberated by the process of respiration 



(Sect. 102). 



Respiratory ratio. De Saussure was the first to observe that the respiratory 

 ratio (CO 2 : O. 2 ) varied according to the nature of the plant, the stage of develop- 

 ment, c\:c., and that it is usually less than unity during the germination of oily 

 seeds 1 . Numerous researches have confirmed and extended these results 2 . Thus 

 Godlewski, and Bonnier and Mangin, have shown that as soon as the oil of an oily 

 seed is nearly all replaced by starch the respiratory ratio approaches unity, and that 

 this quotient, which in higher plants lies between 0-3 and 1-2, is in most cases not 

 markedly modified by changes of temperature or of the oxygen partial-pressure. 

 Diakonow found that the respiratory quotient for Pcnicillium glauaim when fed 

 with sugar was i; with tartaric acid 2-9; with ethylamine 0-67. Similar results 

 are obtained by comparative analyses of seeds and seedlings germinated in pure 

 water, for these lose almost nothing but carbon dioxide 3 . 



Formation of water. De Saussure showed that the loss of dry weight is greater 

 than can be accounted for by the amount of carbon dioxide evolved, the difference 

 representing the amount of water formed during respiration 4 . Laskovsky has 

 directly proved that water is produced by respiration by determining the amounts 

 present before and after germination 5 . 



Errors due to absorption. Owing to the ready solubility of carbon dioxide it 

 requires a certain interval to saturate a tissue previously free from it and thus 

 render possible the exhalation of the gas produced by respiration. Similarly the 

 transference from an atmosphere rich in carbon dioxide to one poor in it is sufficient 

 to cause a marked temporary increase in the evolution of this gas . On the other 

 hand, it is owing to the production of organic acid that, as de Saussure found, 

 a cactus stem placed in darkness commenced to evolve carbon dioxide only after 

 having absorbed i \ times its own volume of oxygen. The accumulation of carbon 

 dioxide in tissues may be aided by combination with sodium phosphate, &c., by the 



1 De Saussure, Mem. d. 1. Soc. d. Phys. d. Geneve, 1833, T. vi, pp. 547, 554 ; Bibl. univers. d. 

 Geneve, 1842, T. XL, p. 368. 



2 Of the more recent literature may be mentioned: Godlewski, Jahrb. f. wiss. Bot., 1882, 

 Bd. xni, p. 491 ; Bonnier et Mangin, Ann. d. sci. nat., 1884, vi. ser., T. xvn, p. 209 ; T. xvnr, p. 293 ; 

 T. XIX, p. 218; 1886, vii. sen, T. n, pp. 315, 365; T. Ill, p. 5; Deherain et Maquenne, Compt. 

 rend., 1885, T. ci, p. 887 ; Palladin, Ber. d. Bot. Ges., 1886, p. 327 ; Diakonow, ibid., 1887, p. 115 

 (Fungi); Aubert, Rev. gen. d. Bot., 1892, T. iv, p. 330 (Crassulaceae) ; Jumelle, ibid., p. 112 

 (Lichens); Jonsson, Compt. rend., 1894, T. cix, p. 440 (Mosses) ; Purjewicz, Bot. Centralbl., 1894, 

 Bd. LVIII, p. 372 ; Hesse, Zeitschr. f. Hygiene, 1893, Bd. xv, p. 17 (Bacteria); Mesnard, Ann. d. 

 sci. nat , 1894, vii. sen, T. xvm, p. 295 ; Richards, Annals of Botany, 1896, Vol. x, p. 577 ; Gerber, 

 Compt. rend., 1897, T. cxxiv, pp. 1106, 1109 (Fungi and Fruits). The older literature is in part 

 quoted by Bonnier et Mangin, I.e., T. xvn, p. 217. 



3 Cf. Boussingault, Ann. d. sci. nat., 1838, ii. ser., T. X, p. 257; Fleury, Ann. d. chim. et d. 

 phys., 1865, iv. ser., T. IV, p. 47; Sachsse, Keimung v. Pisum, 1872, p. 30; Detmer, Keimung 

 nlhaltiger Samen, 1875, p. 70. 



1 De Saussure, Rech. chim., 1804. p. 17. 



5 Laskovsky, Versuchsst, 1874, Bd. XVII, p. 231. 



6 De Saussure. I.e.. pp. 79. ill ; Borodin, Sur 1. respiration, 1*75. p. (>. 



PFEFFER M 1Y1 



