The Epidermal Cells of Roots

The initial formation of the root hair is indicated by a general swelling of the outer wall of the epidermal cell. 2. The swelling is produced if the physical resistance of the wall is overbalanced by the higher osmotic pressure which is maintained on the inside of the wall. 3. Further swelling followed by growth takes place at the less resistant portion of the wall. 4. This region bears no relation to the position of the nucleus. 5. The wall of the root hair is composed of two parts, an inner membrane of cellulose and an outer membrane of calcium pectate. 6. The presence of this membrane, together with the fact that the soil particles are held to it by a pectin mucilage, accounts for the high efficiency of the root hair as an absorbing organ.