FORMATION OF CARBOHYDRATES 53 



that the gas be tested the same day that the experi- 

 ment is set up. Especially avoid setting up the ex- 

 periment in the afternoon and testing the gas on the 

 following morning. Why? 



Experiment 30. To demonstrate what gas is taken 

 into the plant in photosynthesis. 



8.. Into each of three large glass evaporating dishes, 

 A, B, and C, place a glass bell-jar having a wide, 

 open tubulature at the top. Into two of the bell- 

 jars, A and B, place vigorous, green-leaved shoots. 

 Into C place no shoot. Under each bell-jar place 

 a piece of lighted candle, 2-3 in. high, supported 

 on a flat cork. Now pour water into the evap- 

 orating dishes until it rises 2 or 3 in. up the side 

 of the bell- jars. The burning of the candles shows 

 that there is enough oxygen in the jars to support 

 combustion. 



9. Now cork the bell- jars air-tight with rubber stop- 

 pers. What soon results to the candle flames? 

 What does this tell you of the amount of oxygen 

 now in the jars? 



10. Cover the jar B, containing a shoot, with opaque, 

 black cloth, and set all three preparations in sun- 

 light. 



11. State, in a well- worded paragraph, the condition in 

 each bell-jar as to light, chlorophyll, and the com- 

 position of the air. 



12. At the end of two or three hours, carefully lower 

 into each jar, successively, a lighted candle attached 

 to the end of a long wire. Record your observation 

 and inference for each jar, and your final inference 

 as to what gas is taken into the plant in photosyn- 

 thesis, and what conditions are necessary to the 

 process, 



