As the names indicate, the non-cellulose component in the first group is lignin; in the second, pectic substances; and in the third, fats or waxes.

Pectine and Pectic Acid.—These substances are met with in many fruits and roots, as, for instance, in the apple, the carrot, and the turnip.

Pectic Acid.—This is the chief impurity found in raw cotton.