SECRETION. 101 



in order to procure the sugar now used in commerce, 

 and their knowledge spread into India, but in the time 

 of the Greeks and Romans this sugar was unknown 

 in Europe, and a saccharine material was employed 

 which was obtained from the juices of certain Palms. 

 In the West Indies especially, it is now obtained in 

 large quantities for commerce by evaporation and crys- 

 tallization of the juice of the Saccharum Ofncinarum. 

 Lime water is added to neutralize vegetable acid, mixed 

 with the juice; albuminous fluids, such as blood, are 

 added to entangle and remove impurities; charcoal to 

 destroy colouring matter; and, according to the most 

 improved plan, the syrup is concentrated for crystalliza- 

 tion by evaporation in vacuo. 



116. The Beet-root and Plane-tree root contain much 

 saccharine matter, and in that obtained as exuding 

 from the bark of Fraxinus ornus, called Manna, a prin- 

 ciple named Mannite, is found. According to Decan- 

 dolle, Manna, occurring, in the form of tears, is caused 

 by the injuries of insects on the bark, but that in 

 masses, by natural exudation in consequence of a super- 

 abundance in the interior of the plant. 



117. The conversion of starch through gummy mat- 

 ter into sugar is seen during germination, and it proba- 

 bly takes place in the floral structures also. 



118. Sugar is decomposed by sulphuric acid, charcoal 

 being deposited, and when acted upon- by nitric acid 

 produces oxalic and other acids. 



Products compos'ed of Oxygen, Hydrogen, and Carbon; 

 the Hydrogen being in excess in relation to the Oxygen 

 to form water. 



119. Wax, best distinguished from the oils by its 

 solidity and solubility in alcohol, is also a product of vege- 

 tation. In the tribe Myricese this substance is very com- 

 mon, the Gales or Dutch Myrtles yielding plenty of it. 

 K 3 



