3. At the other extreme, the cell walls of the hairs on cotton seeds are composed almost entirely of cellulose. Attempts to demonstrate the pathway for the biosynthesis of (1 —>-4)-p-D-glucan were reviewed by Buchala and Meier (1985). They found no direct evidence that UDP-glucose is a precursor of cellulose. By 1997, there was still no clear understanding of how cellulose is synthesized in higher plants (Reid, 1997).