278 LEAVES 



Cellulose is partly digestible and the cellulose of plants fed to 

 livestock is of some importance as a soiu'ce of food and energy. 

 Cellulose and its compounds serve us in furnishing fuel, paper, and 

 wood for lumber. From the cellulose fibers of Cotton and Flax 

 much of our clothing is made, and Jute, Hemp, and other plants 

 furnish cellulose fibers for twine and ropes. By chemical pro- 

 cesses man converts cellulose into celluloid, artificial sUk, artificial 

 rubber, and explosives, such as gun cotton. From the trans- 

 formed cellulose in coal and peat, energy is obtained to warm 

 buildings and run steam engines. The indigestible cellulose and 

 its compounds, such as the hulls of cereals, seed coats, rinds of 

 fruits, and the woody and corky portions of hay, straw, fodder, 

 vegetables, etc., are recorded as crude fiber in the chemical analy- 

 ses of plants and not as carbohydrates. In hay, straw, and 

 fodder usually more than one-fourth of the dry weight is crude 

 fiber. In the kernels of cereals it is usually less than 10 percent 

 and the percentage is small in most vegetables. Crude fiber has 

 a value in feeds in that it lightens the ration and stimulates di- 

 gestive action. 



The sugars are of various kinds and are present to some extent 

 in about all plants and in most all parts of plants. In fruits the 

 percentage of sugars, based upon dry weight, ranges from less 

 than one percent in some Pumpkins to as high as 87 percent in 

 some varieties of Apples. In all cereals and vegetables some of 

 the food value is due to sugars present. The sugars, being soluble 

 in water, are present in solution in the sap of plants. The photo- 

 synthetic grape sugar is readily transformed in plants to various 

 other kinds of sugars, most important of which are fructose and 

 cane sugar. 



Grape sugar, called glucose or dextrose and fructose, also called 

 levulose and sometimes fruit sugar, are simple sugars and have the 

 same formula, CeHijOe, but differ in the arrangement of atoms. 

 They occur together in leaves and this suggests that some of the 

 photosynthetic sugar may be fructose although most of it is glu- 

 cose. Glucose and fructose occur in most all fruits, varying 

 from about 1 percent in Lemons to about 17 percent in Grapes. 

 About 75 percent of the sugars in genuine honey consists of 

 glucose and fructose. Glucose and fructose are formed in equal 

 amounts when cane sugar is broken into its components. The 

 formation of glucose and fructose from cane sugar is brought 



