SEEDS AND SEEDLINGS 



75 



are absolutely necessary for germination. One of these factor?, 

 is the presence of a certain amount of moisture. 



Water a Factor. We can 

 prove that the bean seed will 

 take up a considerable 

 amount of water and that 

 it swells during the process. 

 Fill a flowerpot or a thin 

 glass bottle almost to the 

 top with dry beans, cover 

 securely as shown in the 

 illustration, and place in 

 water overnight. The force 

 exerted by the swelling seeds 



The expansive force of germinating seeds. 

 The flowerpot to the left was filled with 

 dry beans, a block of wood wired on, and 

 the whole apparatus placed in a pail of 

 water overnight. The result is shown at 

 the right. 



is sufficient to break the 



flowerpot or bottle. It is 



easy to prove that a dry seed will not germinate. The exact 



amount of water which is most favorable for the germination of 



a seed can be determined only by careful experiment. In a very 



Effect of water upon the growth of trees. 



The trees were all planted at the same time in soil that is sandy and uniform. They 

 are irrigated by a small stream running from left to right. Most of the water 

 soaks in before reaching the last trees. 



