CH. Il] 



CULTURE WITHOUT CO2. 



25 



the plants must be closed by a rubber cork through 

 which passes a tube of soda-lime like the one shown in 

 fig. 5. 



A similar flask filled with spring water (to which a 

 little extra CO^ may be added by blowing air from the 

 lungs through it) and closed by a U tube containing 

 coarse sand, will serve for a control. 



The COj may also according to Pfeffer' be removed 

 by careful treatment with lime water. 



LaTid-plants. 



Seedlings with their roots in water, or plants of 



Pig. 5. Exp. 34. 

 1 Pfeffer, Physiologie, i. p. 111. 



