5 2 4 



RESPIRATION AND FERMENTATION 



space containing a vessel filled with potash the diminution of volume may serve as 

 an index for the consumption of oxygen and hence for the production of carbon 

 dioxide. The apparatus in Fig. 42 (p. 310) may serve for purposes of demonstration 

 if a little potash is introduced '. In Fig. 64 a large volume of air may be enclosed, 

 the decrease in the volume giving the amount of oxygen absorbed, while by 

 titrating the potash in k the amount of carbon dioxide exhaled can be determined 2 . 

 Or the change in the percentage composition of the enclosed air may be determined 

 by direct analysis 3 , while the loss of carbon can be estimated by comparative 

 analyses of seeds and seedlings, and provided that no organic food is absorbed, 

 and that no carbon has been excreted except in the form of carbon dioxide, 

 this will enable the respiratory activity to be calculated. 



Specific respiratory activity. The respiratory curve for every plant and every 

 organ attains a maximum at a certain period of development, and beyond this it 

 diminishes, although secondary maxima and minima may be exhibited, for even 



when the external conditions are constant the course 

 of the curve for the entire plant is dependent upon 

 the amount of stored food as well as upon the rate 

 of growth, and is moreover merely the resultant of 

 the different activities of the individual cells and 



organs. 



It has long been known that the production of 

 carbon dioxide commences soon after dry seeds have 

 imbibed water 4 , and the path of the respiratory curve 

 in developing seedlings has been studied by Ad. 

 Mayer, Borodin, Rischavi, Godlewski, Bonnier, and 

 Mangin 5 . Mayer found that the respiratory activity 

 of wheat seedlings attained a maximum after fifteen 

 to sixteen days at a mean temperature of i i-8 c C., and 

 after eight days at 23-8 C., after which the curve fell rapidly, whereas according to 

 Rischavi in Vicia faba it remained almost parallel with the abscissa-axis for the next 



FIG. 64. (g) air-tight bell-jar, fixed to 

 the plate (/;); (a) experimental object; 

 (k) vessel with potash ; (b) vessel con- 

 taining mercury ; (c) graduated tube ; 

 (d) glass tap. The entire apparatus 

 should be placed under water. 



pp. 68, &c. In certain cases it is preferable to use soda-lime for the absorption of the exhaled carbon 

 dioxide. Cf. Chudiakovv, Landw. Jahrb., 1894, Bd. xxm, p. 400, and plate ii; Kreusler, ibid., 1885, 

 Bd. xiv, p. 916. 



1 This method was first employed by Garreau (Ann. d. sci. nat., 1851, iii. ser., T. xv, p. 8), 

 and later by Wolkoff and A. Mayer (Landw. Jahvb., 1874, Bd. in, p. 489). 



2 A similar apparatus was employed by Godlewski, Jahrb. f. wiss. Bot., 1882, Bd. xili, p. 403, 

 and Bot. Zeitung, 1882, p. 804, and by Stich, Flora, 1891, p. 8. 



3 See Sect. 52. On a mode of automatic registration, cf. Regnard, Compt. rend., 1882, T. xcv, 



P- 77- 



4 Huber, Mem. s. I'influence d. 1'air dans la germination, 1801, p. no; de Saussure, Mem. d. 1. 

 Soc. Phys. d. Geneve, 1833, T. VI, p. 557 ; Fleury, Ann. d. chim. et d. phys., 1865, iv. ser., T. iv, 

 p. 44; Wiesner, Verstichsst, 1872, Bd. XV, p. 135 ; Ewart, Trans. Liverpool Biol. Soc., 1894, Vol. vm, 

 p. 234. 



5 Ad. Mayer, Versuchsst., 1875, Bd. xvm, p. 245 ; Borodin, Sur la respiration d. Plantes, 1875 ; 

 Rischavi, Versuchsst., 1876, Bd. XIX, p. 321 ; Godlewski, Jahrb. f. wiss. Bot., 1882, Bd. xin, p. 491 ; 

 Bonnier et Mangin, Ann. d. sci. nat., 1884, vi. ser., T. xvin, p. 369; 1886, vii. ser., T. II, p. 363. 



