FAT8 107 



The starch is found in definite bodies known as starch 

 grains within the cells of the plant, and can be seen readily 

 with the aid of the microscope. The size and form of the starch 

 grains vary in different plants. 



Sugar is another plant product very similar to starch, but 

 it occurs in a much greater variety of forms. The most com- 

 mon type is the cane sugar (CoHioOg) which is abundant in 

 many plants and forms a valuable food product. It is found 

 in the cell-sap and can be readily detected by simple experiments. 

 It is especially abundant in sugar beets, sugar maple, sugar 

 cane and ripened fruits. We all recognize the value of sugar 

 for food and as an article of commerce. One of the great prob- 

 lems of the plant breeders is to increase the percentage of 

 sugar in the sugar-producing plants. (Chapter XV.) The 

 amount of sugar in the sugar beet has been increased from 7 

 to 15 per cent by scientific methods of plant breeding. 



Carbohydrates, — The cell-walls are composed of cellulose 

 which is made up of the same elements as starch and sugar, but 

 they are also infiltrated with various other substances. Cellu- 

 lose is the most important plant compound in the manufacture 

 of paper. Cellulose is also used extensively in the manufacture 

 of the many celluloid articles on the market, and it is also used 

 in the making of gun cotton and other high explosives. Many 

 plants also produce gums which are composed of these same 

 elements and some of which are important articles of com- 

 merce. The starch, sugar, gums, and cellulose are known as 

 carbohydrates ; that is, their hydrogen and oxygen is always in 

 the ratio of two to one. 



Fats. — Many plants also contain fats and oils which are 

 composed of the same elements as the carbohydrates (i.e., hydro- 

 gen and oxygen), but the hydrogen and oxygen ratio is never 

 two to one. The fats and oils are known as hjjdrocarhons and 

 are usually most abundant in the seeds, especially nuts. They 



