VEGETABLE PRODUCTS — LIGNIN. 165 



produce of the root of Beta vulgaris, and is extensively manufactured 

 in many parts of the Continent. Manna Sugar, or Mannite, differs' 

 from the others in not being fermentescible. Its composition is Ce 

 Hj4 Oj. It is the chief ingredient of Manna, which exudes from the 

 Ornus europ»a and rotundifolia. Prom Sicily and Calabria it is 

 imported under the name of flake-manna. Mannite is found in the 

 juices of Mushroom, in Celery, and in Laminaria saccharina, and 

 Eucalyptus mannifera. Dr. Stenhouse has determined the quantity 

 of Mannite in some sea-weeds as foUows :- 



Laminaria sacoharina 

 Halydris siliquosa . 

 Laminaria digitata 

 Fucus serratus 

 AJaria esculenta 

 Ehodymenia palmata 

 Pucus vesiculosus . 

 Pucus nodosus 



12 to 15 per cent of Mannite. 

 5 to 6 per cent „ 



4 to 5 per cent „ 



rather less „ 



about the same 

 2 to 3 per cent 

 1 to 2 per cent 

 nearly the same 



Knop and Schnederman have detected Mannite in Agaricus piperatus, 

 and other chemists have found it in Cantharellus esculen'tus, and 

 Clavellaria coralloides. 



Grape Sugar, called also Starch sugar or Glucose, is composed of 

 Og H,5 Og. It occurs in the juices of many plants, and is a product of 

 the metamorphosis of starch, cane sugar, and lignin. Vj may be 

 extracted from dry grapes, and may be prepared from starch by the 

 action of an infusion of malt, or of a substance contained in malt, 

 called Diastase. 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. 



Lignin is the substance which gives hardness and solidity to the 

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

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

 and lignin or sclerogen, forming the encrusting matter in the in- 

 terior. The latter dissolves in strong nitric acid, forming oxalic acid, 

 while the former is left undissolved. Lignin cannot be separated in 

 the pure state, and hence its exact composition is unknown. 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 everything soluble in 

 these agents is removed, a white fibrous mass reniains. This fibrous 

 matter exists in linen and paper • and these substances, when sub- 

 jected to the action of sulphuric acid, are converted into grape sugar. 

 Lignin 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 



