METABOLIC PROCESSES IN THE PLAXT. 287 



days fermentation begins. The fluid in d becomes more and more 

 turbid, and we thus see that the Butyric acid organism is able to 

 develop in complete absence of free atmospheric Oxygen. 2 To 

 make the experiment with yeast we use wort as the food solution, 

 and infect it with the smallest possible quantity of pure yeast. 



It is also very convenient to work with the apparatus repre- 

 sented in Fig. 106. The flask K holds about 250 c.c. We fill it 

 with food solution and sterilise this by boiling. After cooling the 

 solution we introduce into it, by passing a fine glass tube through 

 the leading tube R, which is provided with a stop-cock, a small 

 quantity of fluid containing Clostridium or yeast-cells, pass a 

 current of Hydrogen for two hours, put the end of the tube H' 

 under mercury, and at once close the stop-cock H. The bulb Kl 

 has merely the object of rendering it impossible for mercury to 

 pass over into the flask if the temperature of the laboratory should 

 fall considerably. 



1 For further information about fermentation experiments, see Chudiakow in 

 Landwirthschl. Jahrbiicher, Bd. 23. See also Note 2. 



2 Literature for the section: A. Mayer, Lehrbnch d. Gahrungschemie, 1874 f 

 Nachtrag, 1876; Pasteur, Compt. rend., 1861, T. 52; also in the years 1863, 

 1872, and 1875 ; also Etude s. I. biere, 1876 ; Brefeld, Landwirthschl. Jahr- 

 biicher, 1874, 1875, and 1876. On the formation of alcohol in the cells of the 

 higher plants, see Brefeld, Landwirthschl. Jahrb., 1876, p. 324, and Lechartier 

 and Bellamy, Compt. rend., T. 69, 75, and 79. Kespecting anaerobic organisms, 

 see Pasteur's cited papers, and Prazmowsld, Unters. nbe.r einige Bacterien- 

 arten, Leipzig, 1880; Detmer, Lehrbuch der Pflanzenphysiologle, 1883, p. 

 173. 



109. Production of Heat in Plants. Phosphorescence. 



With respiration is necessarily associated in plants a liberation 

 of heat. The proper temperature of plants may under certain 

 circumstances reach a considerable height. It has been found, for 

 example, that actively respiring tissue masses are sometimes 

 warmer by several degrees than their surroundings. In particular 

 the spontaneous development of heat in the spathe of the inflor- 

 escences of Aroids is very considerable ; l but since such material 

 is not always available, we shall first employ germinating seeds to 

 prove that plants produce heat. Experiments with seeds can 

 conveniently be made at any time. We use the apparatus shown 

 in Fig. 107. Under a bell-glass stands a vessel, G, containing 

 strong potash solution. In the funnel T is first placed a small 



