NUTRITION, STORAGE, AND RESPIRATION 113 



separation resident in its carbonaceous materials into kinetic energy. 

 This may be exhibited in the movements, or other physiological 

 changes which accompany life ; while the final products may be, like 

 those of combustion, carbon dioxide and water. For the combustion 

 of coal a supply of free oxygen is necessary. The same is the case 

 for the life of ordinary organisms, animal or vegetable. During life 

 they also carry on a gaseous interchange. Free oxygen is absorbed from 

 the air, and carbon dioxide is evolved. To this interchange the term 

 RESPIRATION is applied. 



The evolution of carbon dioxide by living plants is most readily 

 demonstrated in the_case of germinating seeds or of flowers, in which 



FIG. 82. 



Arrangement for demonstrating Respiration, a, shows an earlier stage in the 

 experiment : b, a later stage. See Text. 



respiration is specially active. If a stoppered jar be filled about one 

 third with germinating peas or wheat, the rest of the space being 

 filled with atmospheric air, arid left for say twelve hours, and the gas 

 be then tested with a burning splinter of wood, the flame will be extin- 

 guished, showing that sufficient oxygen is not present to support 

 combustion of the wood. The oxygen in the jar has been absorbed, 

 and it has been replaced by carbon dioxide. But a more satisfactory 

 demonstration of what has happened is given by the apparatus 

 shown in Fig. 82. A globe connected with a long tubular neck is 

 used. Into it a quantity oi; flower-buds are passed, the rest of the 

 space being filled with atmospheric air. It is then fixed with the tube 

 projecting downwards into a mercury bath. The buds are thus in 



B. B. II 



