THE A WAKENIXG OF THE SKED 63 



the start and oiio-lialf inch at the finish the equation 

 Avill be 



1 = Pressure at finish. 

 % 15 pounds per square inch. 



whence thirty pounds per square inch equals pressure 

 at finish 



The results are approximate only and will vary 

 according to the charactei* of the membrane, the 

 strength of the syrup, etc., and cannot be regarded 

 as indicating what the same solution would do with a 

 different kind of membrane (such as is to be found 

 in the plant, for example) , but the pressure is clearly 

 demonstrated and one method of measuring it illus- 

 trated. 



In our apparatus the sugar attracts^ the water with 

 considerable force so as to generate the pressure we 

 have observed; we believe the pressure manifested by 

 swelling seeds to be generated in much the same way, 

 by substances within the seed (sugar, proteids, etc.) 

 which attract water with considerable force. We 

 have already learned that if we add water - attracting 

 substances, such as sugar or salt, to the water in 

 which the seeds are submerged, these substances exert 

 a counter - attraction which hinders or prevents the 

 absorption of water by substances within the seed. 

 We may even withdraw water from the seed by plac- 

 ing it in a sufficiently strong solution of salt or sugar. 



' This expression is used onlj' for the purpose of describing the fact in 

 popular language. 



