The Submicroscopic Structure of Pectin in Collenchyma Cell-walls

Up to the present time pectin in cell-walls has been regarded as amorphous and optically isotropic. However, by means of polarization microscopy, X-ray diffraction, and electron microscopy, it is here demonstrated that the pectin in the fresh collenchyma cell-walls of Petasites vulgaris petioles consists of axially oriented submicroscopic fibrils containing axially oriented pectin crystallites and exhibiting negative intrinsic birefringence.