The dermal tissue system during primary growth is composed only of the epidermis which is the outermost layer of cells in the root. In cotton, the epidermis is uniseriate (one-layered). Root hairs are cells within the epidermis that grow into long cells with a large surface area. As the roots are the primary site of absorption of water and minerals in the plant, cells with a large surface area, such as root hairs, are appropriate and necessary. In fact, root hairs are where almost all absorption takes place. The photograph below shows a close view of the epidermis with its root hairs.

Below is labeled photograph of the vascular cylinder of the cotton primary root. The root in this picture is more developed than the root used to show the three tissue systems on the previous page. The innermost metaxylem fluoresces in this root while it did not in the other root. This is because the metaxylem in the other root has not been completely lignified yet (the fluorescent berberine stain that was used binds to lignin). Primary xylem matures centripetally (starting closer to the outside of the root and moving towards the inside). In this root the primary xylem is fully developed.

Notice also the difference in the endodermis between the two roots. In the previous photograph the casparian strips (suberized regions of the endodermis) were identifiable as dots around the vascular cylinder. In this cross section, however, the endodermis has become more suberized. The extra suberization occurs in patches opposite the primary phloem. The regions of the endodermis opposite the protoxylem points retain their original casparian strip.