QUESTIONS. I0 i 



80. What does science teach in reference to the atmospheric 

 agencies ? To what do they contribute ? The effect of their 

 action on solid substances ? 



81. The effect of the atmosphere on organic and inorganic 

 matter ? On a dead animal or plant ? 



82. What knowledge is necessary to understand the growth 

 and development of plants ? 



CHAPTER V. 

 THE SOURCES OF PLANT-FOOD AND HOW OBTAINED. 



83. The sources of plant-food ? What elements are found 

 in air ? 



84. Why cannot carbon enter the plant in a pure state ? In 

 what form is it a gas ? How does it enter ? Why do plants 

 grow faster in daytime than at night ? Where does the carbon 

 of plants come from ? 



85. How do hydrogen and oxygen get into plants ? 



86. How nitrogen ? Does free nitrogen contribute to 

 growth ? Where is it gotten ? 



87. How much nitrogen do plants contain ? How much is 

 in a ton of hay ? Why must it be supplied in the form of salts 

 containing nitrogen ? 



88. Why are the four elements mentioned called organic ? 

 What are the other constituents called ? How do they get into 

 plants ? In what form ? 



89. What are the main parts of a plant ? What does the 

 seed contain ? What does it require for germination ? How 

 does it germinate ? 



90. How does the root grow ? What may be regarded as 

 the lungs of a plant ? What the mouth ? What is said of the 

 roots spreading ? What is necessary for a plant to be thrifty ? 

 Why must its food be near at hand ? 



91. How did Schubert determine the extent of the roots of 

 plants ? How deep did he find the roots of wheat to extend ? 

 What is the total length of the roots of a barley-plant ? 



