230 NUTRITIVE METABOLISM 



with pumice stone, saturated with sodium hydrate absorbed from 

 moist sticks of that substance mixed with it. A vessel containing 

 a solution of potassium hydrate is also placed in the bell-jar to- 

 gether with a sponge containing water. Small plants cultivated 



FlG. 114. Arisaema triphyllum grown in open air. 



in pots may be set in a glass plate in a position receiving strong 

 diffuse light and the bell-jar set over it. The edge of the jar 

 should be sealed with vaseline, or wax, and all of the joints should 

 be made air-tight. The plant will use all of the carbon dioxide 

 in the jar not absorbed by the potassium hydrate in a few hours, 



