with energy before it is able to digest a variety of foods. The sap of
various plants contains such large quantities of sugar that it can be
crystalized out and secured in dry form. The liquid that remains is
valuable as food, for, by boiling it down, it forms molasses. Sugar is
also present in considerable amounts in all fruits, and much of it is in
a form that can be assimilated, or taken up by the body, quickly. A
sugar very similar to this natural fruit sugar is made from the starch
of corn and is called _glucose_. Much of the carbohydrate found in
vegetables, especially young, tender vegetables, is in the form of
sugar, which, as the vegetables grow older, changes to starch.

Sugar melts upon the application of heat or, if it is in a melted
condition, as sirup or molasses, it boils down and gives off water. When
all the water has boiled away, the sugar begins to caramelize or become
brown, and develops a characteristic flavor. If the cooking is continued
too long, a dark-brown color and a bitter taste are developed. Because
the sugar in fruits and vegetables is in solution, some of it is lost
when they are boiled, unless, of course, the water in which they are
cooked is utilized.

20. CELLULOSE is a form of carbohydrate closely related to starch. It
helps to form the structure of plants and vegetables. Very little
cellulose is digested, but it should not be ignored, because it gives
the necessary bulk to the food in which it occurs and because strict
attention must be paid to the cooking of it. As cellulose usually
surrounds nutritive material of vegetable origin, it must be softened
and loosened sufficiently by cooking to permit the nutritive material to
be dissolved by the digestive juices. Then, too, in old vegetables,
there is more starch and the cellulose is harder and tougher, just as an
old tree is much harder than a sapling. This, then, accounts for the