8 Composition and Nutritive Value of Straw. 



chemists indiscriminately cellular or woody fibre. It is in 

 reality generally a mixture of cellulose, the substance of which 

 the walls of the cells of plants consist, and of woody substances 

 which are deposited around the original cell-walls. These 

 woody substances " incrusting matter," as they are called by 

 vegetable physiologists constitute the true wood or woody fibre of 

 plants. In their composition they closely resemble cellulose, 

 which is more abundant in young plants than in those of more 

 advanced growth. The older and harder the plant, the more woody 

 or incrusting matter it contains. In green herbage, the insoluble 

 residue which is obtained by the above-mentioned treatment 

 chiefly consists of cellulose or cellular fibre ; whilst in fully ma- 

 tured and over-ripe herbs, this insoluble residue principally con- 

 sists of incrusting matter or true wood. In intermediate stages 

 between a green, succulent condition and a dry, hard, fully 

 matured stage of growth, we obtain variable mixtures of cellulose 

 and woody fibre. The same process, it will be noticed, which 

 is employed for preparing woody fibre, likewise furnishes cellu- 

 lose. Unfortunately we possess no means of separating the two 

 from each other, and hence the chemical processes by which the 

 woody and cellular fibre in plants is determined in our labora- 

 tories are not calculated to give us more than at the best a very 

 crude idea of the true character of the 'insoluble matter which 

 constitutes the bulk of straw. No difficulty is experienced in 

 determining with precision the amount of starch or sugar in a 

 plant, but when we attempt to ascertain in two or three separate 

 portions the amount of woody fibre in each, it is next to impos- 

 sible to obtain corresponding results. But although we speak 

 of cellulose and of woody fibre as of two separate and distin- 

 guishable substances which exist in plants under conditions as 

 variable in texture and other physical peculiarities as in their 

 physiological effect upon the animal, the chemist is not in a 

 position to distinguish the one from the other by means of 

 analysis ; and it should be remembered that the physical and 

 chemical properties and general character of many organic 

 bodies are often extremely different, whilst their chemical com- 

 position is precisely the same. The mere composition of cellu- 

 lose or woody fibre, therefore, does not afford a sufficient insight 

 into their true character, and leaves altogether untouched the 

 question whether these substances are digestible or not 



As long as we are unacquainted with more perfect analytical 

 methods, we cannot expect to ascertain by analysis whether 

 cellular and woody fibre is digestible, wholly or in part, and to 

 what extent. Here, as in so many other matters which have 

 scarcely been touched upon by scientific men, the agriculturist 

 must be guided by his own experience, and not by the rash 



