GERMINATION OF SEEDS 63 



and after ten days note the result of growth. This result 

 indicates that some part of the air was used up. What is 

 it ? Test the air in each bottle, using a lighted stick. What 

 gas has been given off by the germinating seeds ? Test with 

 limewater. Result ? See also Experiments 45 and 49. 



47. THE AIR FACTOR 



Object. To find out whether seeds can germinate 

 without oxygen. 



Apparatus Two wide-mouth bottles, glass and rubber tubing, 

 stoppers (perforated for two tubes), hydrogen generator, seeds. 



Method. Select several seeds which have already begun 

 to sprout, carefully remove their testas, and place an equal 

 number of seeds in each bottle. Now fill one bottle with 

 water which has been boiled to drive off the air, insert the 

 stopper, and push it down until the water rises to the top of 

 the short tubes (a) and (6). Now generate hydrogen as in 

 Experiment 4, and when you are quite sure that no air re- 

 mains in the flask (see Note), invert the bottle so that the 

 mouth is submerged, and connect (6) with the delivery tube. 

 The hydrogen will rise through the water and drive it out 

 through the tube (a). When all the water has been ex- 

 pelled, the seeds will be in an atmosphere of hydrogen, 

 which is harmless ; and as long as the mouth remains under 

 water, no oxygen can enter. 



The other bottle is to be filled with air to act as a control 

 in this experiment. 



After some days make observations on the two sets of 

 seeds and see which are in best condition. 



Conclusion. State what you conclude is the effect on 

 growth of depriving germinating seeds of oxygen. 



