124 BIOLOGY OF PLANTS. 



to in this place. When the sugar-cane is used, the green canes 

 are ground in a mill, and the juice evaporated or boiled. 



The sugar-maple is tapped, and the juice received in buck- 

 ets or troughs, and then boiled until the water is all evaporated. 

 The beet* is sliced and pressed to obtain the juice. Many 

 other vegetables contain sugar, as the sap of the birch, butter- 

 nut, elm, and a great variety of trees ; but only those which 

 have been mentioned are employed for this purpose to any con- 

 siderable extent. It is a substance of universal consumption. 



Liquid sugar is distinguished from common sugar, by the 

 fact, that it is incapable of a-ijstalb'zation. It exists in various 

 fruits and vegetable juices. It constitutes a considerable por- 

 tion of the molasses in the sugar of the cane. It exists also in 

 the grape, peach, apple, and other fruits.f 



Zea Maiz, or Indian corn, also contains liquid sugar. Sugar 

 of grapes is not so white as connnon sugar, but it crystallizes 

 much more readily. 



Manna was long regarded as a substance which fell from the 

 heavens, until it was found to exude from several trees, of which 

 a species of ash [fraxinus ornus), found in Sicily, is the most 

 productive. Manna has the form of oblong globules, of a yel- 

 lowish-white color, and is used in medicine. A substance 

 called mannite, or mushroom sugar, is similar to manna. 



Sugar of liquorice is obtained from a plant growing in Spain. 

 The root is the common liquorice-root, and the black balls, sold 

 under the name of liquorice-balls, is the sugar. 



2. Amylaceous substances include common starch, hordein, 

 lichnin, inulin, lignin, diastase, etc. 



Common starch is secreted in most of the grains, the potato, 

 arrow-root, tapioca, sago, and, in small quantities, in nearly all 

 trees, seeds and fruits. When wheat-flour is formed into paste, 

 held under a stream of water, and kneaded until the water 

 runs off clear, a tough substance remains called gluten, while 

 there is deposited in the water a white sediment, which is 

 known as common starch. 



Arrow-root is a very pure starch, extracted from the root of 

 the maranta arundinacea, a plant which is native in South 

 America. 



Tapioca is also a very pure starch, obtained from the root of 

 a South American i)lant, iatropha marihot. The roots ai'c sub- 



* Thompson's Organic Bodies, p. G"-20. Chaptal's Ag. Chemistry. 

 Child's Beet Sugar. t Prout. 



