144 VEGETABLE PRODUCTS. LIGNINE. 



307. Grape sugar, called also Starch sugar, or Glucose, is composed 

 of C 12 H 1 * O u . It occurs in the juices of many plants, and is a pro- 

 duct of the metamorphoses of starch, cane sugar, and woody fibre. It 

 may be extracted from dried grapes, and may be prepared from starch 

 by the action of an infusion of malt, or of a substance called Diastase 

 (If 310). It is less soluble and less sweet than cane-sugar." It gives 

 sweetness to gooseberries, currants, apples, pears, plums, apricots, and 

 most other fruits. It is also the sweet substance of the chestnut, of 

 the brewer's wort, and of all fermented liquors. 



308. Lignine is the substance which gives hardness and solidity to 

 the cells and vessels of plants. It exists abundantly in woody fibre, 

 which may be said to be composed of cellulose forming the parietes, 

 and lignine forming the incrusting matter in the ulterior or the Sclero- 

 gen of Payen. The latter dissolves in strong nitric acid, forming oxalic 

 acid, while the former is left undissolved. Lignine is said to be com- 

 posed of C 34 H 2 * O 20 . According to Mulder, the formula for the lig- 

 neous matter of ordinary wood is C 40 H 28 O 26 . When a portion of the 

 stem of a herbaceous plant, or of newly cut wood, is reduced to small 

 pieces and boiled in successive portions of water, alcohol, ether, diluted 

 acids and alkalies, until every thing soluble in these menstrua is 

 removed, a white fibrous mass remains, to which the name of woody 

 fibre is given. It varies slightly in its composition in different trees, 

 thus: 



Oak. Beech. Pine. Willow. 



Carbon, 5-2-53 51-45 50- 49-8 



Hydrogen, 5'69 5'82 5'55 5-58 



Oxygen 41-78 42-73 44-45 44'62 



Iron wood contains 53-44 per cent, of carbon. 



This woody fibre exists in linen and paper; and these substances, when 

 subjected to the action of sulphuric acid, are converted into grape 

 sugar. Lignine gives support to the vegetable texture, and is often 

 deposited in concentric layers. It occurs in large quantity in the 

 wood of trees, and is also present in the stem of herbaceous plants. 

 In some cellular plants it is absent, and the object of many horticul- 

 tural operations, as blanching, is to prevent its formation. Beet-root 

 and white turnips contain only 3 per cent. 



309. All these organic substances, consisting of carbon united with 

 the elements of water, are easily convertible into each other by the 

 action of sulphuric acid and heat. Similar changes are induced during 

 the growth and development of plants, as will be noticed under the 

 head of flowering, fruiting, and germination. In many unazotised 

 matters ths proportion of the elements is the same, or they are 

 isomeric. Thus, cellulose and starch have the same composition, and 

 the difference in their qualities seems to depend on the mode in which 

 the elements are united. Their form is altered by a change in the 



