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? We have 

 seen that to release 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 oxygen, 

 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 reach 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 necessity for oxygen 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 up during the germination of the seeds ? 

 To answer this question let us carefullj r 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 

 presence of carbon dioxide in the jar. The 

 carbon of the foodstuffs of the pea united with 

 the oxygen of the air, forming carbon dioxide. The limewater test; the 

 Growth stopped as soon as the oxygen was ex- tube at the 

 hausted. The presence of carbon dioxide in 

 the jar is an indication that a very important 

 process which we associate with animals rather than plants, that 

 of respiration, is taking place. 



Problem XII. A study of young plants until they are inde- 

 pendent (seedlings). (Laboratory Manual, Prob. XII.} 



Germination. If you plant a number of soaked kidney beans 

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



shows the effect of 

 carbon dioxide. 



