THE METABOLISM OF PLANTS. 



303 



structure, to undergo this active self-decomposition and to 

 evolve heat. 



A few instances will suffice to prove that the evolution 

 of heat in the plant is dependent upon destructive meta- 

 bolism. When we were discussing destructive metabolism 

 we found that it is very active in germinating seeds and 

 in opening flowers, and it is just these that afford the best 

 examples of an evolution of heat by plants. The evolution 

 of heat by germinating seeds is a familiar fact in the process 

 of the malting of Barley, and from the extended observations 

 of Goppert we may conclude that it accompanies germina- 

 tion in all cases. 



FIG. 37 (from Prantl, after Sachs). The moist seeds are placed in the funnel r, 

 which is placed in the neck of the bottle / containing some solution of caustic 

 potash / to absorb the carbon dioxide evolved. The whole is covered by the 

 bell-jar g, through the neck of which passes the thermometer / : the bulb of 

 the thermometer is covered by the seeds in the funnel. The cotton-wool w 

 which holds the thermometer in the neck of the bell-jar admits air. 



