ROOT HAIRS 



69 



Plumuh 



Roof- hairs 



Root hairs on a corn 



seedling- 



millimeters in length, called root hairs. They vary in length 

 according to their position on the root, the most and the longest 

 root hairs being found some distance back from the tip. They 

 are outgrowths of the outer layer of the root, 

 the epidermis, and are of very great im- 

 portance to ths living plant. 



Structure of a Root Hair. — A single root 

 hair examined under a compound microscope 

 will be found to be a long, threadlike struc- 

 ture, almost colorless in appearance. The 

 cell wall, which is very flexible and thin, is 

 made up of cellulose, through which fluids 

 may easily pass. Clinging close to the cell 

 wall is the protoplasm of the cell, the outer 

 border forming a very delicate membrane. 

 The interior of the root hair contains many 

 vacuoles, or spaces, filled with a fluid called 

 cell sap. Forming a part of the living proto- 

 plasm of the root hair, sometimes in the hairlike prolongation and 

 sometimes in that part of the cell which forms the epidermis, is 

 found a nucleus. The nucleus, the membrane, and the rest of the 

 protoplasm are alive ; the cell wall, formed by the living matter 



in the cell, is dead. The 

 root hair is a living plant 

 cell with a membrane and 

 wall so delicate that water 

 and dissolved mineral sub- 

 stances from the soil can 

 pass through them into the 

 interior of the root. 



The Root Hairs take 

 More than Water out of 

 the Soil. — If a root con- 

 taining a fringe of root hairs 

 is washed carefully, it will be found to have little particles of soil 

 still clinging to it. Examined under the microscope, these particles 

 of soil seem to be cemented to the sticky surface of the root hair. 

 The soil contains, besides a number of chemical compounds of 



merfilm 

 •Soil particle 



Diagram of a root hair, with adjacent root 

 cells and particles of soil. 



