82 BOTANY. 



on the inside of the tube. This water is formed by the rearrangement of 

 some of the hydrogen and oxygen, which is set free by the burning of the 

 plant material, where they were combined with carbon, as in the cellulose, 

 and with other elements. 



Exercise 32. 



152. Formation of charcoal by burning. — Take dried leaves, and shav- 

 ings from some soft wood. Place in a porcelain crucible, and cover about 

 ym deep with dry fine earth. Place the crucible in the flame of a Bunsen 

 burner and let it remain for about 15 minutes. Remove and empty the con- 

 tents. If the flame was hot the plant material will be reduced to a good 

 quality of charcoal. The charcoal consists largely of carbon. 



153. The ash of the plant. — Place in the porcelain crucible dried leaves 

 and shavings as before. Do not cover with earth. Place the crucible in the 

 flame of the Bunsen burner, and for a moment place on the porcelain cover ; 

 then remove the cover, and note the moisture on the under surface from the 

 escaping water. Permit the plant material to burn ; it may even flame for 

 a time. In the course of 15 minutes it is reduced to a whitish powder, 

 much smaller in bulk than the charcoal in the former experiment. This is 

 the ash of the plant. 



What has become of the carbon? In this experiment the air was not ex- 

 cluded from the plant material, so that oxygen combined with the carbon as 

 the water was freed, and formed carbon dioxide, passing off into the air in 

 this form. This it will be remembered is the form in which the plant took 

 the carbon-food in through the leaves. Here the carbon dioxide met the 

 water coming from the soil, and the two united to form, ultimately, starch, 

 cellulose, and other compounds of carbon ; while with the addition of nitro- 

 gen, sulphur, etc., coming also from the soil, still other plant substances 

 were formed. 



Note. — The ash of the plant contains, usually, potash, soda, lime, mag- 

 nesium, ferric oxide, phosphoric acid, sulphuric acid, silica, chlorine. (See 

 page 64 of the author's larger " Elementary Botany," 2d Ed., revised.) 



Synopsis. 



The living plant contains a large amount of water. 



When the plant is dried in the air it still contains a considerable amount 



of water. 

 This water of air-dried plants can only be driven off by artificial heat (at 



a temperature of ioo° F. for some time). 

 When all of the water is dried out of the plant, if the plant is burned so 



that the plant substance is disorganized, several different substances 



are formed. 



