84 PLANT PHYSIOLOGY 



comparatively large surface, as a result of gaseous nutrition, the 

 oxygen of the air comes in direct contact with each cell of the 

 plant body. The oxidation processes therefore are not obscured 

 by any accessory features. Naturally, then, the attention of 

 botanists has been continually directed to the study of the nature 

 of this phenomenon, and it is in plant physiology that the ques- 

 tion of the internal chemistry of respiration has received special 

 consideration. 



The study of the process of respiration in the plant organism 

 is connected with the names of the most eminent plant physi- 

 ologists, such as Pfeffer in Germany, Bonnier in France, Black- 

 man in England, and Borodin, Palladin, and Kostytchev in 

 Russia. The attention directed to the study of respiration is 

 explained by the fact that hfe in any organism is closely con- 

 nected with a continuous expenditure of energy obtained from 

 respiration. No wonder then that the study of the respiratory 

 process represents one of the principal problems of general 

 physiology and that a profound penetration into the chemistry 

 and energy relations of this organic function promises a deeper 

 penetration into the essentials of the specific complex of phe- 

 nomena defined by the general term ''life." 



20. Methods of Studying Respiration. Intensity of Respira- 

 tion of Various Plants and of Their Different Parts. — Study of 

 the intensity of the process of respiration is performed by means 

 of methods for determining the quantitative changes in the 

 atmosphere surrounding the plants, i.e., the accumulation of 

 carbon dioxide and the decrease of the oxygen content. 



The first investigations of the process of respiration by Saus- 

 sure had the object of proving the existence of this function 

 in plants and were performed in eudiometers, i.e., in graduated 

 tubes, -sealed at the upper end and with the plants, more fre- 

 quently germinating seeds, placed inside. By immersing the 

 open end of such tubes in water, a definite volume of air is 

 included in them (Fig. 17), which can be analyzed after a certain 

 interval of time. This is accomplished by introducing into the 

 tube first a solution of potassium hydroxide, which absorbs 

 carbon dioxide, and after this a solution of pyrogallol in combina- 

 tion with alkali for absorbing oxygen. The decrease in volume 

 of the gas after the introduction of each of these two reagents 

 will show the amount of carbon dioxide liberated and that of 



