This paper reports results of a study of root growth, duration of the division cycle, and cell size for different intervals of root length, associated with different phases of growth, namely, from the onset of growth to the achievement of a steady state characterized by a constant rate of growth. The material is roots of Allium cepa.Steady-state kinetics of growth are achieved only when all components of growth reach a constant value. Although the cell flow remains constant from a root length of 8 mm onwards, the steady condition is only observed when the final size of the epidermal cells reaches its maximum and constant value (at about 12 mm of root length).The equation G=24×10(-5) \N\φ·L is proposed to analyze the growth of Allium roots in its components. G is the growth rate (mm/24 hr), N the number of cells per column in the meristematic ribs, φ the rate of the cell cycle (the reciprocal of its duration x100), and L the average final size of the epidermal cells (in μ).