Cellulose is a linear insoluble branched polymer of β-(1,4)-D-Glucose residues associated with other cellulose chains by hydrogen bonding and Van der Waals forces. Cellulose chains aggregate together to form microfibrils, which are highly crystalline and insoluble structures, each one about 3 nm in diameter, chemically stable and resistant to enzymatic attack. Cellulose microfibrils comprise the core of the plant cell wall; one third of the total mass of wall is cellulose. The variation of dry weight of cellulose in a dicot such as Arabidopsis thaliana ranges from 15% of leaf to 33% of stem walls. The walls of monocot grass species have approximately 6–10% cellulose in leaves and 20–40% in stems