CONSTITUTION OF WOODY FIBRE. 103 



manufacturer. The flour of grain contains sugar also, and along with it 

 two other substances, in small quantity, gluten and vegetable albumen^ 

 which are of much importance in reference to the nutritive qualities of 

 the different varieties of flour. Sugar is also present in the juices of 

 fruits, but it is there associated with various acid (sour) substances 

 which disappear to a certain extent or change into sugar as the fruit 

 ripens. 



Of these few substances the great bulk of vegetables of all kinds con- 

 sists. They constitute nearly the whole mass of those various crops 

 which the art of culture studies to raise for the use of man and beast. 

 To the study of^lhese substances, therefore, I shall at present confine 

 your attention, and if I shall afterwards be able to make you under- 

 stand how these few compound bodies are produced in the interior of a 

 plant from the food it takes up, I shall succeed in conveying to you as 

 much information in regard to this most interesting branch of our subject 

 as will be necessary to a general explanation not only of the natural 

 growth and increase of plants, but of the nature and efficacy of those 

 artificial means which the practical farmer employs, in order to hasten 

 their growth or enlarge their increase. 



§ 1. Woody fibre or lignin — its constitution and properties. 

 1°. When a portion of the stem of a herbaceous plant, or of the new 

 ly cut wood of the trunk or branch of a tree, is reduced to small pieces, 

 and boiled in successive portions of water an^i alcohol, as long as any 

 thing is taken up, a white fibrous mass remains, to which the name of 

 woody fibre or lignin has been given. This substance has no taste oi 

 smell, and is perfectly insoluble in water. It is nearly identical in its 

 chemical constitution and properties, whether it be obtained from the 

 porous willow, or from the solid box tree, and the fibres of linen and of 

 cotton consist essentially of the same substances. 



According to the analysis of Dr. Prout, this woody fibre when dried 

 at 350° F., consists of 



From Box Woocl. From the Willow. 



Carbon 60-0 49-8 



Hydrogen .... 5*55 5'58 



Oxygen .... 44-45 44-62 



100 100 



It will be recollected that water consists of oxygen and hydrogen, 

 combined in the proportion, by weight, of 8 of the former to 1 of the lat- 

 ter. (See Lecture II., p. 36.) Now if the hydrogen above given be 

 multiplied by 8, the product will be found to be almost exactly the 

 weight of the oxygen given — since 



5-55 X 8 = 44-40, and 

 5-58 X 8 = 44-64. 

 In woody fibre, therefore, the hydrogen and oxygen exist in the same 

 proportion as in water, and its composition, therefore, might be reprC' 

 sented by 



Carbon 50-0 



Water . . 50-0 



100 



