24 GENERAL BOTANY 



with the carbon in the living substance of the tissues 

 and forms carbon dioxide which is expelled again 

 from the lungs. 



Plants also take in air, which makes its way through 

 the tissues and combines with the carbon of the living 

 substance to form carbondioxide. This process is 

 termed respiration, and is continually going on day and 

 night in all the living parts, being most rapid where life 

 is most active. It is, therefore, most easily observed in 

 parts that are growing quickly, such as buds that are 

 just opening, or seeds that are beginning to germinate. 



There are many ways in which respiration can be 

 shown. A very simple experiment is as follows. 



Take a tall glass jar which is ground at the top 

 to receive a glass stopper or flat glass plate, and fill 

 it about one-third full of germinating barley or paddy- 

 seed, or of flower-buds, or young leaves. 



Close it tightly, with vaseline on the glass stopper 

 or plate to make it really air-tight, cover it over to 

 exclude all light, and leave for a day. Do the same 

 with another jar, but first kill the seeds or flower- 

 buds, or whatever it may be, by boiling them in water 

 and then thoroughly drying them. Next day open 

 the first jar and quickly let down into it a small piece 

 of lighted candle. 



It will at once go out. This means that there is 

 no oxygen, and that there is carbon dioxide, for car- 

 bon dioxide will put out a flame. 



Now do the same with the jar containing the dead 

 seeds. The flame burns for a little while, showing 

 that there is some oxygen, and that there is no 

 carbon dioxide. 



