HOW PLANTS GROW 13 



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 lbs. of wheat bran contains 16.0. lbs. of crude protein, while the 

 amount in wheat is 12.4 lbs. and in dent corn only 10.1 lbs. per 100 lbs. 

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

 hay. 



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

 boiling a sample successively in weak acid and alkali and washing 

 out the dissolved matter. That which remains is termed fiber. Fiber, 

 which consists mostly of cellulose, is less digestible and hehce 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. Most 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. 



Fat. — A sample of the pulverized dried fodder is treated with ether, 

 which dissolves out the fats and also the waxes and resins, the chloro- 

 phyll, or green coloring 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. 



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

 tables in this book as N-free extract, embraces the substances that are 

 extracted 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 embraces 

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

 the plant. The nitrogen-free extract is more soluble and hence more 

 digestible than the fiber, and thus has a higher nutritive value. Over 

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

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

 these more soluble carbohydrates than the concentrates. The nitro- 

 gen-free extract and fiber together constitute the carbohydrates. 



Roughages and concentrates. — These terms are used to differen- 



