It is the graphic representation of the total growth against time. The period or time, in which growth takes place, has been called the grand period of growth by Sachs(1873). The rate of growth is not uniform during the gran period of growth. If total growth is plotted against time, an S-shaped or sigmoid curve is obtained. It consists of four parts - lag phase, log phase(exponential phase), the phase of diminishing growth and stationary phase(steady growth for organs or organisms of indefinite growth).