PLANT PHYSIOLOGY 137 
106. Experiment 14.—To see if green leaves absorb 
carbon di-oxide in the sunlight and give out oxygen. 
Apparatus.—Two bell-jars with corks that tightly fit 
the holes at the top, two candles, two large dishes of 
water, beaker, leaves. 
AMethod.—Stand a candle in each dish of water and 
light it. Stand a beaker of 
water containing some leaves 
beside the candle in one dish, ‘| 
cover both leaves and candle 
with the bell-jar, and then cork 
up the top tightly. Cover the 
other candle also with a bell-jar 
and corkitup. Presently both 
candles will go out and at the 
same time water will rise in 
the bell-jars. This is because 
the candle in burning uses up Fic. 75.—Apparatus to Show 
. os that Carbon Di-oxide is 
the oxygen in the jars, and Necessary for Oarbon As- 
forms carbon di-oxide ; and the pee 
gases left do not support combustion. So now we have 
two bell-jars, each containing some carbon di-oxide. 
Place both dishes with their bell-jars in a bright sunny 
place, and leave for three or four hours. Great care 
must be taken to see that the jars are absolutely air- 
tight, and that no air enters them when they are moved. 
Then quickly take the stopper out of each jar, and insert 
a lighted taper. 
Result.—The taper burns in the jar which had leaves 
in it, but goes out in the one that had no leaves. 
Deduction. — The leaves must have absorbed the 
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