Growth stresses in normal wood result from the tendency for cells to contract longitudinally and expand tangentially while developing their secondary cell wall, the effect on the stem as a whole is shown in Figures \ref{291842} and \ref{394578}. It is thought these stresses develop in normal wood in order to increase mechanical safety by improving compressional strength \citep{mattheck1997wood}. There are two independent hypotheses as to how growth stresses form. The lignin swelling hypothesis \cite{Boyd1950} argues that the cellulose fibril aggregate network in the cell wall are pushed apart tangentially by the deposition of lignin into the secondary cell wall. Cellulose contraction \citep{Bamber1979,bamber2001general} claims the cellulose chains change their length resulting in the cellular distortion. A combination of the two has also been proposed and shown to fit experimental data well \cite{okuyama1986,Okuyama_1994, Yamamoto_1998,Yamamoto1992,Yamamoto1991}. Regardless of the mechanism the result is a longitudinal contraction and a tangential expansion of the cells, resulting in the stem periphery being under tension and the pith under compression \citep{Archer_1987}.