126 



ROOTS 



substance attracting moisture and assisting in food absorption 

 by rendering soluble the inorganic constituents of the soil. 

 The solution of salts within the root hair is denser than the 

 solution of the soil water; therefore, the soil water passes into 

 the root-hairs, obeying the law of osmosis, which is the 

 equalization of" the density of solutions by passing through 

 an intervening permeable membrane, as the wall of a root- 



FIG. 71. Roots. 1, Fleshy; 2, fibrous; 3, tap root; 4, woody root. 



hair. In like manner the water and salts pass into the par- 

 enchymatic cells and finally into the vessels. As roots grow 

 older, the root-hairs disappear and the epidermis is replaced 

 by a periderm. 



3. Roots transport food and water through the paren- 

 chymatic cells and finally by the vessels or the upward- 

 conducting cells of the root. 



