Nutrition. 



93 



should be bent at right angles, and a match wedged in it, with 

 I or 2 centimeters of the tip exposed, and the head in contact 

 with the sanded paper. 

 When all is in readiness, 

 lift the bell jar, set the 

 candle burning, and re- 

 place. Arrange the rod 

 bearing the match in 

 the manner described. 

 Seal all joints with 

 vaseline. After a min- 

 ute or two the candle 

 will have used so much 



of the oxygen, and given 



off so much carbon 



dioxide, that combustion 



is impossible, and the 



flame is extinguished. 



Allow the preparation 



to stand in the hght 



for several hours. Pull 



the glass rod upward 



through the cork, draw- 

 ing the match-head 



along the sanded paper. 



After igniting the 



match, twist the rod, 



and place the flame in 



contact with the wick. 



The relighting of the 



candle denotes that 



the carbon dioxide of 



the air has been ab- 

 sorbed by the plant, 



Fig. 64.— Preparation for testing relations of 

 plant to atmosphere. A, candle; B, match; 



C, strip of sanded paper on wooden support ; 



D, glass rod holding match: the dotted line 

 shows position when the match is applied to 

 the candle. 



