ROUGH ANALYSIS OF PLANT SUBSTANCE. 83 



1. Water is formed by the uniting of hydrogen and oxygen as these 



elements are freed from the plant substance by the burning. 



2. Certain gases, one of them is carbon dioxide, formed by the carbon 



from the disorganized plant substance uniting with oxygen of 

 the air during the burning. 



If the dried plant material is burned while oxygen from the air is ex- 

 cluded, the carbon cannot unite with oxygen to form carbon dioxide, 

 but remains in the form of charcoal, which is almost pure carbon. 

 \Vhen plant material is burned with access of oxygen the residuum is a 

 whitish-gray powder called the ash. (See page 64 of the author's 

 larger "Elementary Botany," 2d Ed., revised.) 



Material. Leafy shoots fresh; air-dried leaves, and some soft dry wood 

 (white pine wood, bass wood, or some similar soft wood). 



Apparatus. Bunsen burner to supply gas-flame ; small porcelain cruci- 

 bles with covers; supports to hold crucibles in the flame; test tubes; thistle 

 Vibes; some dry earth. 



