A tentative mechanistic model is proposed that relates variation in crystallite length in wood to some physical conditions under which the crystallite may have been formed, namely the curvature and ultrastructure of the microfibril. Over most of the experimental data range, representing both hardwood and softwood samples, the model allows reasonably good prediction of the effect of crystallite orientation angle and radial distance from the cell center. As the angle increases and radial distance decreases, the average crystallite length becomes smaller
