COMPOSITION OF PLANTS AND ANIMALS 67 



not have as good bone nor do they feed so well as when the 

 corn is supplemented with other feeds containing more ash. 

 Protein in the plant is a combination in which nitrogen, 

 especially, plays a very important part, and is combined with 

 carbon, oxygen, hydrogen, and sulphur. There are differ- 

 ent forms of protein, but we do not need to concern ourselves 

 about that fact here. This substance is not usually abundant 

 all through the plant. Rough stalks contain but little. 

 Prairie grass hay has about 8 per cent, red clover hay 13 

 per cent, alfalfa hay 15 per cent, cottonseed 19 per cent, 

 and soy beans 36 per cent. The growing plant usually has 

 its greatest amount of protein when in bloom. Seeds are 

 richest in this substance, for as the plant matures it shifts 

 the protein to some extent from stalk to seed. In some of 

 our mills where seeds are crushed or otherwise treated and 

 the hulls removed, the by-products produced are very rich 

 in protein. Cottonseed meal and peanut meal are good 

 examples. Protein, whether used to feed plants or animals, 

 is the highest priced food constituent the farmer can buy, 

 when we consider the price he must pay on the market. 

 Protein is expensive because it contains so much of the valu- 

 able element, nitrogen. 



The carbohydrates are combinations of carbon, hydrogen, 

 and oxygen, and contain no nitrogen. These are the most 

 abundant of our food substances in plants. There are two 

 kinds of carbohydrates, one known as nitrogen-free extract, 

 consisting mostly of sugar, starch, and gums; the other called 

 fiber or crude fiber, making up the woody part of the plant. 

 Most of the fiber is cellulose, the material composing the 

 walls of plant cells. The chemist may dissolve out the 

 starch and the sugar from the plant cells; what is left is the 

 fiber. The starch, sugar, and fiber are all carbohydrates, 

 but the first two are much better for food, as they are very 

 much more easily digested than the fiber. In general we 

 see carbohydrates all about us in plants and plant products. 



