This is a cross section of an older rice root that is under flourestic berberine stain with aniline blue counter stain.  Berberine stains suberin and lignin,  thus showing the angular and thick cell walls of the matured cortical fibers (glowing layer toward the center), which is discussed in the ground tissue system.  The epidermal cells are tabular in shape.  As the root develops, the epidermal cells elongate into root hairs.  The breaks occurring in the epidermis cause it to be sloughed from the mature root.      
 
 
 
     
 This is a close-up picture of rice root hairs.  There are many root hairs, which are tubular extensions of the epidermis, in rice roots.  Root hairs increase the absorbing surface of the root.  This is important in transpiration and growth of the plant.