The fibril angle distribution of a black spruce sample was determined by the reflectance method on the polarized microscope. This was compared with the azimuthal distribution of intensity obtained from the (002), (101), and (101) planes of the X-ray pattern of the corresponding piece of wood. Obviously, the X-ray intensities do not give directly the fibril angle distribution function of the sample. However, using for example Cave's theory, one can predict the X-ray distribution of intensity from the fibril angle distribution function, or vice-versa, assuming that the sample is made of cylindrical fibers
