124 PLANT PRODUCTS 



of linseed the crops grown at high temperatures yield most 

 prussic acid. 



Barley, though a starchy cereal, is not used directly 

 for the production of starch. The best is used for beer, the 

 second for bread, and the worst for cattle. It is converted 

 into malt by steeping the grain at a temperature of from 

 50° to 55° Fahr., spread in well-ventilated "spaces, and 

 stirred well to permit germination and oxidation to take 

 place. It is then dried at 100° to 107° Fahr. The higher the 

 temperature, the lower is the diastase activity. It is then 

 thrown on to screens, for the removal of the malt coombes 

 or culms, which latter are used for feeding cattle. 



(c) Cellulose. — Cellulose forms the important chemical 

 compound which constitutes the structural part of nearly 

 all vegetable matter. There are a great many varieties of 

 cellulose, and the term must be taken as denoting a group, 

 and not an individual. Cellulose is much more resistant 

 to chemical reagents than the other carbohydrates, and 

 is isolated from vegetable raw material by hydrolysis with 

 acids and alkalies, or by the more drastic action of chlorine, 

 bromine, or sulphur dioxide. 



All cellulose materials condense a fair amount of moisture 

 on their surface. In the green plant cellulose occurs in a 

 fairly hydrated condition, but by long drying or immersion 

 in alcohol dehydration takes place, so that the amount of cel- 

 lulose obtained from a material by any method of hydrotysis 

 depends upon the degree of hydration to which the cellulose 

 has been subjected. This has an important bearing upon 

 the subject of the feeding of materials containing much 

 cellulose, since grass that is grazed by cattle in a wet condition, 

 and has never become dry, is more digestible than the same 

 grass after it has been dried in the process of making hay. 

 It is well known in practical farming that hay which has been 

 made in exceptionally dry weather is not equal in feeding 

 value to that made in weather which does not permit of 

 such rapid and complete dr^ang. Cellulose enters into a 

 feeble composition with alkalies when treated with sodium 

 hydrate, and produces alkali cellulose, hence many forms of 



