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PHYSIOLOGY OF NUTRITION 



gas sample is removed from the plant chamber and analyzed, the removal 

 of this sample being accomplished as follows: The three-way cock R is so 

 set as to bring the tube b into communication with the container /, after which 

 the similar container I' is lowered, so that some mercury flows from I to V , thus 

 drawing air from the plant chamber into I. Then the cock R is reset so that I 

 communicates with tube d and the sample tube beyond, and the container /' is 

 again raised, thus forcing into the sample tube some of the gas that has just 

 been removed from the plant chamber. 



The volume of the gas in the plant chamber is determined as follows: Some 

 gas is removed and its volume (V) is determined at atmospheric pressure (H). 

 If p is the gas pressure in the apparatus before, and p' is the pressure after, the 

 removal of this gas (these pressures being determined by means of the mano- 



Fig. 92. — Respiration apparatus. (After Bonnier and Mangin.) 



meter, M), then the original gas volume (X) contained in the chamber is found 

 from the equation: 



X = 



VH 



p -p> 



If the absolute amounts of oxygen absorbed and of carbon dioxide given off 

 are not important, then the determination of the total gas volume is not required. 



CO 



In such a case the value of the ratio -^— is derived from the proportions of these 



two gases found in the samples taken at the beginning and end of the experiment. 

 §6. Formation of Water during Respiration. — During germination in dark- 

 ness all seeds lose an appreciable amount of hydrogen, in the form of the water 

 vapor produced by the respiratory process. Very few direct determinations of 

 respiration water are available. Liaskovskii 1 studied the formation of water 

 during the germination of pumpkin seeds. The seeds were germinated under a 

 bell-jar, through which a current of air was drawn, the entire apparatus being 

 weighed from time to time. The amount of water produced by the respira- 

 tory process was obtained from five measured values, as follows: the total 



1 Liaskovskii, 1874. [See note 2, p. 194.] — Also, in this connection, see: Babcock, 1012. [See note 1, 

 p_ IQ2 ] — [Babcock deals with the water of respiration in insects (such as the common clothes moth, which 

 lives on dry wool) as well as in germinating seeds. — Ed.} 



