2128 



Journal of Applied Microscopy 



9. Effect of Preventing the Access of Carbon Dioxid to Water Plants. The 



apparatus for this experiment is shown in Fig. 7. The bottle and flasks are 

 fitted with rubber stoppers and glass tubing as indicated. The stopper in A is 



provided with three holes. The 

 U-tube is filled with pieces of pumice 

 stone soaked in strong potassium 

 hydroxid and a few pieces of solid 

 potassium hydroxid ; through it air 

 may enter C. A contains a 10 per 

 cent, solution of potassium hydroxid ; 

 B contains water which has been 

 previously boiled and filtered. The 

 clamp between B and C is now closed 

 and the contents of B boiled for 

 fifteen minutes, during which time 

 one perforation in A is opened by 

 removing the glass rod which closed 

 it. As soon as the flame is removed, 

 cautiously insert the glass plug, taking 

 care that none of the solution in A 

 is caused to flow out. B is allowed 

 to stand until cool to the touch. 

 Place one or two healthy shoots of 

 Elodea canadensis or of Seratophyl/i/fn 

 demersum into C. Open the clamp and siphon water from B into C until the 

 flask is half full. If carefully managed the apparatus will contain so little carbon 

 dioxid that its presence may be neglected for ordinary physiological work. 

 When everything is complete close the clamp tightly enough to exclude all air 

 from C and remove A and B ; set C with its U-tube connections in strongly 

 diffused light. 



Fig. 7. 



