398 APPENDIX. 



Provide a piece of plate glass and a bell jar with ground rim, 

 of suitable size to cover a blooming plant growing in a pot. 

 Alongside the pot place a shallow dish of baryta-water ; cover 

 both with the bell, daubing its edge with vaseline to make con- 

 tact with glass plate air-tight. Place in darkness. Note film of 

 barium carbonate on surface of water after a day. Conduct a 

 control experiment, identical but for the absence of plant. Is 

 more or less barium carbonate formed? Why darken? 



27. To show evolution of CO? by respiration of seedlings. 



Fill a wide-mouthed glass jar or bottle of i liter capacity one- 

 third full of peas and beans which have been swollen for a day 

 in water, then rinsed thoroughly in 5 per cent, formalin 

 and again rinsed in water. Cork or cover tightly. After 24-48 

 hours remove cover and thrust in a burning match or candle 

 attached to a wire. If CO 2 has been produced it will extinguish 

 flame. Test also by lowering into jar a vessel of baryta-water. 

 If precipitate or film forms it shows presence of CO 2 - 



28. To show the evolution of heat during respiration. (^[248.) 

 Take three-fifths the amount of dry wheat required to fill two 



3-inch flower pots ; swell in water over night ; rinse one half in form- 

 alin as above ; kill the other by boiling in water for five minutes. 

 Stop bottom hole in pot with a cork; fill one with dead, the other 

 with living seeds, and bring the two to same temperature by run- 

 ning water through the dead and hot one. Insert a thermometer 

 in the center of each mass of seeds ; place both under one box 

 or bell jar. Observe changes of temperature for two days.* 



29. To measure the rate of growth in length. 



Construct an auxanometer as follows : Take a board 30 cm. 

 square, a common spool, a wheat or oat straw 35 cm. long, and a 

 piece of glass tubing 5 cm. long, which will just allow spool to 

 revolve easily on it. Close one end of the glass tube by holding 

 it in the flame of a Bunsen burner ; when hot spread it enough 

 to stop spool from passing over end, by pressing it endwise 

 against a piece of iron. With a fine saw cut a section 5 mm. 

 thick from middle of spool, thus making a wheel. File a groove 

 in edge of this wheel, deep enough to carry a thread. Slip wheel 

 on glass tube and fasten it in board near lower left corner so 

 deep that spool-wheel will revolve smoothly but have no un- 



* Compare thermometers previously to see that they register alike ; if not ascertain 

 the correction. Greater differences in temperature of seeds will be observed if pots are 

 surrounded with cotton batting. 



