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