PHO TOS YN THESIS. 



gests, in view of the well-known reciprocal exchange of carbon 

 dioxide and oxygen in other physiological processes (i.e., 

 animal respiration), that oxygen may be released in Photosyn- 



thesis. 



56. Is the absorption of Carbon dioxide in Photosynthesis ac- 

 companied by a release of Oxygen? 



Answer by Experiment 29. 



Kxi'KKiMENT 29. This may be tested by supplying to a plant 

 under conditions favorable for Photosynthesis a measurable quan- 

 tity of CO- , and after a time testing whether it has been replaced 

 by O; this may be very conveniently effected by burning a candle 

 in a closed chamber, which, it is known, absorbs O and gives off 

 C( ); ; when it has given off about 3^ of CO 2 it goes out and can only 

 burn again after the O has been restored. Early on a bright day 

 prepare three large wide-mouthed bottles and three ordinary saucers, 

 with a pneumatic trough or other large vessel of water (see Fig. 19). 

 On a flat cork smaller than the inside of the neck of the bottles 

 place a small candle, and attach by a tack a string to the middle 





IG. 19. SIMPLE ARRANGEMENT FOR TESTING THE GAS-EXCHANGE IN 



PHOTOSYNTHESIS. One-third the true size. 



of the under side of the cork. Float the cork on the vessel of 

 water with the candle lighted, and hold over it, with the mouth dip- 

 ping into the water, one of the bottles. When the candle goes out 

 withdraw it by the string and treat the other two bottles similarly 



