METABOLIC PROCESSES IN THE PLANT. 2GO 



of Hydrogen over the research material for an hour, then put in a 

 Imryta tube, and pass Hydrogen over the material with the help 

 of the aspirator for an hour, at the rate of 3 litres per hour, so 

 as to determine the amount of Carbon dioxide produced during 

 intramolecular respiration. Finally, the Hydrogen is replaced 

 by air, and we determine once more the intensity of the normal 

 respiration. 



In comparative researches on the respiration of plants in pure 

 Oxygen and in air, we pass pure Oxygen over the research material 

 from a large gasometer, instead of the Hydrogen which is neces- 

 sary in investigating intramolecular respiration. The Oxygen is 

 purified by passage through a wash bottle containing potash 

 solution. The gas is prepared in the usual way by heating a 

 mixture of Potassium chlorate and Manganese dioxide. It is also 

 very convenient to fill the gasometer from a cylinder of compressed 

 Oxygen. It is advisable to have the water intended to displace 

 the Oxygen from the gasometer saturated with Oxygen before 

 being so employed. Seedlings of Pisuni sativum, at first at any 

 rate, germinate as actively in pure Oxygen as in atmospheric air; 

 other seedlings do not behave in exactly the same way. 3 



1 I describe here the methods which have been employed with the best results 

 by myself and my students. See Detmer, Physiolofj. Uniersuckungen iibcr die 

 Keinmnfi, Jena, 1875, and Sitzunysber. d. Jenaischen Gesellschaft f. Medicin n. 

 Xaturiciss., 1831; Clausen, Landwirthschl. Jahrb., 1890, Bd. 19; Amm, 

 Pringsheim's Jahrbiicher, Bd. 25 ; Detmer, Botan. Zeitunf/, 1888, and Bcriclite 

 d. Deutsclien botan. Gesellschaft, Bd. 8, 10, and 11 ; Ziegenbein, Pringsheim's 

 Jahrb., Bd. 25; Aereboe, Wollny's Forsclinnyen avf dem Geliete der Afjricultur- 

 physik, Bd. 16. 



2 See also Sachsse, Ueber einif/e chemische Voradnne bei der Keimun;/ von 

 J'ixiim sativum, Leipzig, 1875 ; Pfeffer, Untersuchungen ans d. botan. Institut 

 zu Tiibiiu/en, Bd. 1, p. 636, and Moller, Bericlite d. Deutschen botan. Gesell- 

 *clwft, Bd. 2. 



3 See Johansen, Untersuchungen aus d. botan. Institut zu Tubingen, Bd. 1. 



103. Carbon Dioxide Production in Normal Respiration. 



After the instructions given under the previous heading, it will 

 not be very difficult to obtain accurate results in investigating 

 normal respiration. For practice in the method we may introduce 

 into the respiratory vessel, say, 25 gr. of fresh petals of Rosa or 

 some other plant, and ascertain how much Carbon dioxide they 



