io6 



GROWTH AND WORK OF PLANTS 



tity of fresh Elodea is placed in a large jar of tap water. A 

 funnel is inverted over it, leaving a few sprigs projecting under 

 the edge of the funnel so as to hold the edge of the funnel off the 

 bottom of the jar and permit a free circulation of water and 

 gases. The small end of the funnel must be immersed. A very 



short section of rubber tubing 

 is slipped over the end of the 

 funnel. A test tube is filled 

 with the water, inverted, and 

 the open end immersed so 

 there will be no air in the 

 tube. It is then slipped over 

 the end of the funnel and 

 squeezed far enough down 

 on .the piece of rubber tubing 

 to hold it firmly in place. 

 The apparatus is now placed 

 in the sunlight, where it will 

 receive the sun during the 

 entire day. The bubbles of 

 gas rise into the test tube 

 and displace the water.* 

 When the tube is nearly full 

 of gas the test can be made. 

 With one hand the tube is 

 removed, at the same time 

 holding the thumb over the 

 mouth to prevent the escape 

 of the gas. The tube is now 

 tipped so that the small amount of water will flow to the bottom. 

 A soft wood splinter is now lighted. After it has flamed for a 

 few seconds the flame is extinguished by blowing. The glowing 



* The water in the jar should be changed each morning until the tube is 

 nearly full of gas. To do this slip the tube off the funnel into a tumbler of 

 water. The funnel can then be removed, the water emptied and fresh water 

 put in the jar. The tube is then placed in position again. 



Apparatus to catch oxygen from aquatic plants. 



