Nitrogen- free Extract — Sugars 81 



substance takes place in the leaves. When, therefore, 

 cell -walls and starch -grains are to be constructed, in 

 the stem and frnit, the building material must be car- 

 ried from the leaves to these parts in forms which will 

 readily pass through intervening membranes. Except- 

 ing certain soluble compounds, closely related to starch, 

 the sugars appear to be the only available bodies fitted 

 for this office. 



It is very seldom that a plant contains only a single 

 sugar. Generally two or more sugars are found to- 

 gether. This is especially the case in the corn plant, 

 sorghum and the juicy fruits, and the proportions of 

 each depend somewhat upon the stage of growth of 

 the plant. 



The most important sugar, commercially considered, 

 is saccharose, which is the ordinary crystallized product 

 of the markets. As a human food it is widely used, and 

 is especially valuable ; and its manufacture and sale con- 

 stitute a prominent industry. This sugar is obtained 

 mostly from two plants, sugar cane and the sugar beet. 

 It also exists abundantly in sorghum and in considerable 

 proportions in ordinary field corn. The first spring flow 

 of sap in one species of maple tree is richly charged 

 with it, and in a few states large quantities of maple 

 sjTup and sugar are manufactured. 



Saccharose is not a prominent constituent of the 

 more common cattle foods. While it occurs in meadow 

 grasses, in sweet potatoes and in roots, and perhaps in 

 minute proportions in certain seeds, it is only when the 

 fresh corn plant, sorghum and sugar beets are fed that 

 it constitutes a material part of the ration. In corn 



