HOW THE PLANT GROWS 11 



The ash and water of plants together constitute the so-called inorganic 

 matter; the other components crude protein, carbohydrates and fat 

 are termed the organic matter. 



17. Crude protein. The process of determining the nitrogenous con- 

 stituents of feeding stuffs is too complicated for presentation here. 

 Suffice it to say that the nitrogen content is found, and the result multi- 

 plied by 6.25 to give the crude protein, since about 16 per ct. of plant 

 protein is nitrogen (100-^-16=6.25). From the table we learn that 100 

 Ibs. of wheat bran contains 16.0 Ibs. of crude protein, while the amount 

 in wheat is 12.4 Ibs. and in dent corn only 10.1 Ibs. per 100 Ibs. Red 

 clover hay contains over twice as much crude protein as timothy hay. 



18. Fiber. The woody portion of a feeding stuff is determined by 

 boiling a sample thereof successively in weak acid and alkali and wash- 

 ing out the dissolved matter. That which remains is termed fiber. As 

 is shown later (48), fiber, which consists mostly of cellulose, is less digest- 

 ible and hence has a lower nutritive value than the other nutrients of 

 feeding stuffs. Corn contains but 2.0 and wheat only 2.2 per ct. of fiber, 

 while, owing to the woody hulls, oats contain 10.9 per ct. Roughages, 

 especially the straws, are much higher in fiber than the concentrates. 

 Mangels contain but 0.8 per ct. fiber ; were they dried to the same water 

 content as oats they would contain only 7.7 per ct. fiber less than oats. 



19. Fat. A sample of the pulverized dried feed is treated with 

 ether, which dissolves the fats, waxes, resins, chlorophyll, or green color- 

 ing matter, and similar substances. This, called ether extract in works 

 on plant analysis, is for convenience termed fat in this work. The ether 

 extract of seeds is nearly all true fat, or oil, while that of the leaves and 

 stems of plants contains much chlorophyll, wax, etc. Corn and oats carry 

 more fat than the other cereals. Some seeds, such as flax seed, are so 

 rich in oil that it may be extracted from them by crushing and subsequent 

 pressure. 



20. Nitrogen-free extract. The nitrogen- free extract, expressed in the 

 tables in this book as N-fre& extract, embraces the substances that are ex- 

 tracted from the dry matter of plants by treatment with weak acids and 

 alkalies under standard conditions, less the crude protein, fat, and ash. 

 It is determined by difference and not by direct analysis. The total dry 

 matter in a feeding stuff minus the sum of the ash, crude protein, fiber, 

 and fat, equals the nitrogen-free extract. It includes the sugars, 

 starches, pentoses, non-nitrogenous organic acids, etc., of the plant, and 

 in addition some of the more soluble portions of the cellulose and 

 pentosans. The nitrogen-free extract is more soluble and hence more 

 digestible than the fiber, and thus has a higher nutritive value. (48) 

 Over 70 per ct. of both corn and wheat is nitrogen-free extract, chiefly 

 starch. The roughages, carrying much woody fiber, contain less of these 

 more soluble carbohydrates than the concentrates. 



21. Carbohydrates. By the preceding methods of analysis, the carbo- 

 hydrates are separated into the two classes: fiber, which is the part 



