82 FAMILIAR LESSONS IN BOTANY. 



moisture from the atmosphere. These meet and combine 

 with the various substances brought up by the ascending- 

 sap, and are assimilated for the growth of the plant. 



214. There are four elements necessary for vegetable life, 

 carbon, oxygen, hydrogen, and nitrogen. Being a solid, 

 carbon has first to be united with oxygen and converted 

 into carbonic acid gas, before it can be taken up by the 

 plant. Oxygen is also absorbed from the atmosphere in 

 combination with nitrogen. Hydrogen is obtained in the 

 same way from the atmosphere, and also in combination 

 with water from the soil, or in union with ammonia. 



215. You were told, in our conversation upon the stomata, 

 how those breathing pores enable a plant to get rid of its 

 superfluous gases and moisture. It is in this way a plant 

 disposes of an excess of oxygen. You were also informed 

 that a great deal of oxygen was required to convert carbon 

 into such a form that the plant could use it. Now, when 

 it has assimilated the carbon, the oxygen is liberated and 

 finds its way again to the atmosphere through the spiral 

 vessels which conduct it to the stomata, and through them 

 to the air. 



216. An excess of carbon is deleterious to animal life, 

 while oxygen is necessary to it; and we see the wisdom of 

 the great God in making these two great supporters of life 

 mutually balancing and counteracting each other, the 

 vegetable kingdom throwing out just what will promote 

 animal life, and absorbing all that would be deleterious, 

 while the animal kingdom throws off what the plant needs. 

 As light is necessary for the decomposition of carbonic 



214. How many elements necessary for vegetable life ? What are they ? How 

 is carbon rendered fit for vegetable food ? How is oxygen absorbed ? flow is 

 hydrogen ? 



215. What are the nses of the stomata ? Why is oxygen in such an excess in 

 plants ? 



216. How do the two kingdoms, vegetable and animal, balance each other? 

 What is necessary for the proper analysis and assimilation of carbonic acid gas? 

 When docs thi? take place then 2 



