74 



How a Tree Lives 



As the peas grow they will use up some of the oxygen in the flask 

 (Fig. 37). The carbonic acid gas which they breathe out is absorbed 

 by the lime water, hence the total air in the flask grows less. The 

 original level of the water in the tube must be marked with a label. 



Make a sketch of the apparatus used and mark in it the original 

 level of the coloured water. Look at the flask again to-morrow and 

 see if there is any change in the level of the water. If so mark it 

 in your sketch. 



Is there any change in the lime water ? 



Fig. 37. Practical work. Question 1. To show that germinating 

 seeds use up part of the air. 



2. Moisten the indiarubber tubing leading from the flask of lime 

 water, and place it over the nozzle of your bellows. Blow air through 

 the bellows into the flask. Do you notice any change in the lime 

 water? Now take out the bellows and place your mouth to the 

 tubing. Blow air from your lungs into the lime water. Do you 

 notice any change now ? N.B. The air passing through the bellows 



