THE ASSIMILATION OF PLANT FOOD 



71 



plant. The portion of the plant root that is covered with 

 root hairs does not elongate. The root elongates from 

 the growing tip. 



FIG. 23. The root system of a corn plant to a depth of three feet. 

 (From McCall's " Studies of Soils.") 



59. Osmosis. When two solutions are separated by a 

 membrane, the weaker solution will flow towards the stronger 

 solution, because water readily passes through the membrane, 



