SEEDS AND SEEDLINGS 



77 



to germinate, but that those in the closed bottle soon stop while 

 those in the open jar continue to grow almost as well as similar 

 seeds placed in an open dish would do. 



"Why did not the seeds in the covered jar germinate? AVe have 

 seen that to roloaso the energy contained in a piece of coal we 

 must burn or oxidize it. To do this we must have a constant 

 supply of fresh air containing oxygen. The seed, in order to re- 

 lease the energy locked up in its food supply, must have oxj-gcn, 

 so that the oxidation of the food may take place. Hence a con- 

 stant supply of fresh air is an important factor in germination. It 

 is important that air should penetrate between the grains of soil 

 around a seed. The frequent stirring of the soil enables the air 

 to roach the seed. Air helps break down (oxidizes) some materials 

 in the soil and puts them in a form that the germinating seed can 

 use. This iiecessit>' for ox^'gen shows us at 

 least one reason why the farmer plows and 

 harrows a field and one important use of the 

 earthworm. 



Food oxidized in the Germinating Seed. — 

 But can it be proved that food substances are 

 burned u]:i during the germination of the seeds ? 

 To answer this question let us carefully re- 

 move the stopper from the stoppered jar and 

 insert a lighted candle. The candle goes out 

 at once. The surer test of limewater shows the 

 l^resence of carbon dioxide in the jar. The 

 carbon of the foodstuffs of the \wa united with 

 the ox>-gen of the air, forming carbon dioxide. 

 Growth stopped as soon as the oxygen was ex- 

 hausted. The presence of carbon dioxide in 

 the jar is an indication that a very important 

 process which we associate with animals rather than plant 

 of respiration, is taking place. 



Problem ATT. .7 .stuchj of yoKii^ plaiit.-i iniHl fhcij are inde- 

 pendent {seedlings). {Laboratory .Maininl. J'roh. .\'IL) 



Germination. — If you plant a numlici of soaked kidnc>- beaiLs 

 in damp soil or sawdust anil at the end of each day remove a single 



The limewater test; the 

 tube at the right 

 shows the eiiect of 

 earbou dioxide. 



that 



