120 



Both of these papers were followed by an interesting discussion, 

 and the meeting adjourned at lo o'clock. 



C. Stuart Gager, 



Secretary. 



OF INTEREST TO TEACHERS 



Notes on Experiments in Plant Respiration 

 Jane R. Condit 



The experiment designed to show that plants give off carbon 

 dioxide rarely gives satisfactory results with the simple apparatus 

 that can be handled by high school pupils. The withdrawal of 

 the air under water is too complicated for pupils of this age. 

 Contrasting results are not always secured by placing small 

 dishes of lime-water under bell jars with and without growing 

 plants because of the proportionately large amount of air from the 

 room enclosed in each. 



In the following experiments in plant respiration a simple 

 method of obtaining samples of air for the carbon dioxide test is 

 given ; and contrasting results are certain because of the small 

 but equal amount of air in the check bottle. 



A small jar was one-fourth filled with damp germinating barley 

 and placed in the dark. When a lighted match was placed in the 

 jar two days later the flame was extinguished at once, showing 

 that the barley had used so much of the oxygen in the jar that 

 there was not enough left to support combustion, A match 

 placed in a similar check jar without the barley continued to 

 burn for some time. 



A small wide-mouthed bottle was filled with the gas from the 

 barley jar by first filling it with water and then inverting it in the 

 jar. When fresh lime-water was added to the gaseous contents 

 of the bottle, a heavy white precipitate appeared. A similar 

 check bottle full of ordinary air did not show this precipitate 

 when the lime-w-ater was added. This showed that carbon di- 

 oxide must have been given off by the germinating seeds. 



The jar was again sealed, placed in the sun light and left for 

 a week. When the leaves had become green the gas in the jar 



