\citet{walker2006primary} suggested that at the edge of the cellulose fibrils the cellulose becomes disordered and is consequently able to bond with hemicelluloses, which have a slightly shorter repeat length than the cellulose crystal. \citet{Davidson_2004} provided some evidence for the theory showing an increase in the fraction of interior chains resulted in an increase in repeat length. These hemicelluloses bonded to the outside of the fibril cause the fibril to be compressed in the crystalline centre. An interesting consequence is the contraction of the cellulose due to the hemicellulose bonding should be dependent on the area/volume to circumference/surface area ratio as would be suggested by the results from \citet{Davidson_2004}.