Hemicellulose a carbohydrate which occurs in the cell walls of plants. In composition it is intermediate between starch (used by plants as an energy store) and cellulose (which plays a structural role). It is, however, difficult to define satisfactorily. In general, it differs from cellulose in being non-fibrous; in being more readily soluble in alkali and more readily hydrolysed by dilute acids; and in having fewer monosaccharide units per molecule.
Hemicellulose in wood has been studied more than hemicellulose in edible plants. Some is present in such things as fruits and wheat flour. It is indigestible by humans and of use only as roughage.