PROCEEDINGS OP THE FARMERS' CLUB. 139 



portion of eight pounds of oxygen to one of hydrogen. These in entering 

 into a chemical combination with carbon, lose the liquid state of water, and 

 form the various solid substances which make up the body of the tree. 



In its course the sap undergoes important transformations. The trunks 

 and leaves of trees arc scenes of constant chemical operations, many of 

 them more mysterious than any of the operations of the laboratory. One 

 of these is the decomposition of carbonic acid in the leaf. The aifinity of 

 carbon and oxygen is very strong indeed, and there are few forces in nature 

 that can rend these two elements asunder; but the combined action of light 

 and vegetable life is separating them throughout every day in the leaves 

 of all growing plants. Carbonic acid is absorbed from the atmosphere by 

 the leaf, its two elements are torn apart, the oxygen is returned to the air, 

 and the carbon combining chemically with oilier elements in the sap is 

 carried to the places where new wood is being formed, and is there deposited 

 in its proper place to help build up the structure of the tree. The sym- 

 metrical order in which the carbon is deposited in a tree may be seen by 

 looking at a piece of charcoal. 



If wood is examined under a powerful microscope, it is found that the 

 tubes through which the sap circulates are formed of minute sacs or cells. 

 The substance of which the walls of these cells are formed is called cellu- 

 lose. It has been the subject of a great deal of chemical research, and is 

 found to consist of carbon and water, or more strictly, of carbon and the 

 elements of water, oxygen and hydrogen. Cotton and linen are almost 

 pure cellulose. Each atom of cellulose contains twelve atoms of carbon, 

 ten atoms of hydrogen and ten of oxygen. Starch, gum and sugar all have 

 the same composition. This is one of the wonders of chemistry, that sub- 

 stances composed of the same elements, combined in the same proportion, 

 should have properties so different as gum, starch, sugar, and cottoii or 

 linen fibre. Their different properties must of course result from the dif- 

 ferent modes in which the atoms are arranged. 



Besides these four substances there is one other constituting a consider- 

 al)le portion of the body of trees, which is also formed of the same elements 

 as the others but in slightly different proportions. This is lignin. It is an 

 incrustation on the inner surfaces of the cell walls, and its office appears 

 to be to strengthen and stiffen these walls. Its constitution is twelve atoms 

 of carbon, eight atoms of hydrogen and eight of oxygen. In this case, as in 

 the others, there are just as many atoms of hydrf)gen as of oxygen; these 

 two elements enter into the compound in the same proportion to each other 

 as that in which they unite to form water. If a tree or other plant is 

 thoroughly dried so as to expel all of its uncombined water, nine-tenths of 

 the remaining substance consists of the five compounds, cellulose, lignin, 

 Btarch, gum and sugar, and all of these are composed of hj'drogen and 

 oxygen in the same relative proportion as that in which they exist inwatur, 

 chemically combined with carbon. 



Why it is that the atoms of these substances are so arranged in one part 

 of the plant to form cellulose, and in another to fc^rm starch; wiiy it is that 

 they are so arranged in one tree as to form gum, and in another to form 

 sugar, are mysteries which lie beyond the present boundaries of human 

 knowledge. 



There is one other organic element, and several inorganic, besides those 



