100 SECRBTIOX. 



110. Gum, although a term often used to express 

 substances combining several different compounds, and 

 even containing the principle nitrogen in small quanti- 

 ties, is in consequence of the proportions of its oxygen 

 and carbon noticed here. 



111. Mucilage, or Gum, as found in plants, is a 

 source of considerable nourishment to them, just as 

 Fecula or amylaceous matter. The secretion of it 

 takes place in the cellules ; but it is often found col- 

 lected in what may be termed its receptacles, which are 

 more or less enlarged intercellular passages. Its nature 

 varies in the different species producing it ; but the best 

 known Gum is that obtained from different species of 

 Acacia, Gum Arabic ; it contains a little nitrogen and 

 a small proportion of carbonate and phosphate of lime. 

 A Gum resembling this in its properties is procured from 

 the Ferronia eliphantum, which is praised by painters 

 for mixing with their colours, but it is not brought to 

 England. Gum Tragacanth contains a peculiar princi- 

 ple called Cerasin, into the formation of which Bassorine 

 enters, as also into the different sorts of Cherry-tree 

 Gums, as they are termed. 



112. The quantity of gum secreted by plants is often 

 very great ; a single slit in the bark of Anacardium Occi- 

 dentale afforded a mass of forty-two pounds weight. 

 The Astragali yielding Gum Tragacanth are said to give 

 more of it when mists have been prevailing during the 

 night. 



113. Sugar, unlike starch and gum, is not met 

 with in particular receptacles in the interior of plants ; 

 but is found in solution in the juices, especially of ex- 

 ternal organs, where it is sometimes collected in consi- 

 derable quantity, and appears on the exterior of them in 

 a crystallized state. 



114. This substance presents many varieties, differing 

 in the proportion of their elements, and the compounds 

 they are associated with, the chief of which are Cane 

 Sugar, Grape Sugar, Manna Sugar, etc. 



115. The Sugar Cane was first used by the Chinese 



