CHAPTER V. 



WORK OF ROOTS IN ABSORPTION OF WATER AND 

 FOOD FROM THE SOIL. 



55. Absorption of water and food sub- 

 stances from the soil. Land plants absorb 

 water and food solutions chiefly through the root 

 hairs. In the study of seedlings we observed 

 the form of the root hairs and their position on 

 the roots. They are very slender, long cells 

 developed in great numbers over the surface of 

 the root a little distance back from the tip of 

 the root. The root hairs are not permanent 

 as in the case of most of the roots. As the 

 root elongates, new root hairs are formed, while 

 the older ones farther back on the stem die. 

 Thus the root hairs are fresh and in good con- 

 dition for their work of absorption. 



56. How the root hairs absorb water 

 from the soil. Each root hair is a plant cell 

 which is very much elongated. It is formed by 

 the lateral elongation of one of the cells of the 

 skin or epidermis of the root. The outer part 

 or boundary of the root hair is its cell wall. It 

 is thin and white. Inside of the root hair is a 

 granular, whitish, slimy substance. This is the 

 living substance of the cell, and is calleT proto- 

 plasm. It is the living protoplasm in the root 

 hair which enables it to take up water and food 

 solutions. 



There is a thin and continuous membrane of 



Fig. 38. 



Root hair of corn before 

 ,. , , . and after treatment with 



protoplasm which lines the wa^_ Inside of this s per cent salt solution. 



33 



