THE A WAKENING OF THE SEED 



53 



much pressure as several layers, nevertheless we get a 

 higher pressure recorded when several layers are used, 

 for the reason that much of the force which is ex- 

 pended in squeezing the seeds together and changing 

 their shapes is not recorded, but this error grows less 

 the more seeds we use. Nevertheless, the result must 

 always be too small, for this reason. 



That seeds exert considerable force in swelling may 

 be simply illustrated by means of a fruit -crusher, as 

 shown in Fig. 40. To calculate the pressure, divide 

 a c by a &, and multiply by the pressure registered on 

 the spring balance. Only a 

 fraction of the pressure can be 

 measured in this apparatus. A 

 still simpler method 

 is to fill a bottle 



40. Apparatus for demon- 

 strating that swelling 

 seeds exert pressure (a 

 portion of the wall is 

 represented as cut away 

 in order to show the 

 seeds). 



