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 lime 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 



A B 



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. 



