SUGARS, STARCHES, AND CELLULOSE PRODUCTS
Sugars are manufactured by green plants and so are to be found in small amounts, at least, in all individuals. So much of the manufactured product, however, is used directly in the metabolism of the plant that comparatively little is accumulated. Storage sugars are to be found in roots, as in the case of beets, carrots, parsnips, etc.; in stems, as in sugar cane, maize, sorghum, and the sugar maple; in flowers, such as the palm; in bulbs like the onion; and in many fruits. Several types of sugar are to be found, chief among which are sucrose or cane sugar, glucose or grape sugar, and fructose or fruit sugar. These sugars obviously serve as a reserve food supply for the plant.
Sugar likewise is one of the most necessary foods for man. The day has passed when it was considered merely as a luxury to be used for flavoring purposes. It constitutes a perfect food as it is in a form that can be readily assimilated by the human body. Its chief value is as an energy producer, and it is particularly well adapted for use after any type of muscular exertion. Although primarily a food, such a vast industry has been built up in connection with the extraction of the sugar from plant tissues, its purification, and refining, that it seems best to consider sugar as an industrial plant product. Moreover, sugar has become an extremely important industrial chemical with some 10,000 different derivatives.
Sugar is one of the most valuable products of the plant world. It is surpassed in importance only by wheat, corn, rice, and potatoes, and over 35,000,000 tons are produced annually with a value of $2,000,000,- 000. Considering its importance, it is surprising that the sources from which it is obtained are so few in number. Only the sugar cane, sugar beet, sugar maple, maize, sorghum, and a few palms are of commercial interest. In all of these sucrose is the type of sugar stored.
The chief source of sugar at the present time is the sugar cane (Saccharum officinarum). This plant is a vigorous and rapid-growing perennial grass, which reaches a height in cultivation of 8 to 12 ft. or more and a diameter of about 2 in. It grows in clumps (Fig. 109), with bamboolike