ELABORATION OF FOODS INTO PLANT STRUCTURES 97 



is inserted, the temperature of the enclosed air may be raised 10° C. 



and sometimes 20° C. by the heat of res- 

 piration; and the oxygen of the enclosed 



air will usually be so nearly used up that 



the flame of a burning match or splinter 



is extinguished when inserted into the 



jar. {Fig. 92.) To demonstrate the ac- 

 cumulation of carbon dioxide, one may 



pour hme water into the jar where the 



seeds are germinating, in which case the 



calcium hydroxide of the lime water 



unites with the carbon dioxide of the 



enclosed air, forming calcium carbonate 



which is insoluble and when abundant 



gives the solution a milky appearance. 



Since the amount of carbon dioxide in 



ordinary air is not sufficient to give a 



perceptible precipitate, the milky ap- 

 pearance, therefore, indicates that much 



carbon dioxide has been added to the 



enclosed air. Again, the carbon dioxide 



liberated in germination can be quite 



accurately measured by drawing the air 



from over germinat ng seeds through a 



solution of potassium hydroxide, where 



the carbon dioxide is caught and its 



weight calculated from the increased 

 weight of the solution. However, this 

 involves careful weighing as well as see- 

 ing to it that the carbon dioxide already 

 present in the air is removed before the 

 air enters the germinator, and that the 

 increased weight of the potassium hy- 

 droxide is not partly due to added mois- 

 ture. This method discloses that many 

 cubic centimeters of carbon dioxide may 

 be liberated by a small quantity of ger- 

 minating seeds, as shown by the experi- 

 ment in which 3 Beans with a dry weight 

 of only 1 gram produced 9| cubic centimeters of carbon dioxide 



Fig. 92. — A simple ex- 

 periment to demonstrate 

 that heat is produced by 

 germinating seeds. The 

 bottle A contains germi- 

 nating seeds, while the 

 bottle B contains only 

 moist cotton. The higher 

 temperature, commonly 

 shown by the thermometer 

 in bottle A, demonstrates 

 that germination is ac- 

 companied by the pro- 

 duction of heat. If the 

 bottles are protected 

 against the loss of heat, or 

 if bottles like "Thermos" 

 bottles, which have double 

 walls with air-space be- 

 tween, are used, the re- 

 sults are much better. 



