102 SCIENTIFIC AGRICULTURE. 



92. What increases the absorbing surface of roots ? Are 

 there such organs as " spongioles " ? 



93. How many kinds of roots are there ? What is said of 

 the mulberry-tree ? What of cornstalks ? 



94. Have roots the power of " excretion " ? Of selection ? 



95. What is evident from what has been said about roots ? 

 By what should the farmer be guided ? 



CHAPTER VI. 

 THE IMPROVEMENT OF SOILS. 



96. What power has inert matter ? What has the seed ? 

 Do we know what the life-principle is ? 



97. Do we understand the connection between the growth 

 of a plant and its surroundings ? What has chemistry taught ? 



98. What is necessary to insure fertility ? What vague no- 

 tions have some men ? 



99. What have some writers asserted ? Is it true ? What 

 can we not control ? 



100. What has science done ? 



101. What of sewage ? What does a perfect system of agri- 

 culture require ? 



102. Upon what are all scientific methods founded ? To 

 what addressed ? What soil cannot be improved ? What can 

 be? 



103. What means can be used for the improvement of soils ? 

 What are mechanical? What chemical? The effect of the 

 first ? Of the second ? 



104. What system of drainage is the cheapest ? 



105. What are the benefits of drainage? 



106. What are the advantages of deep plowing and sub- 

 soiling ? 



107. What additional advantage is mentioned ? What care 

 should be taken ? 



108. Mention an economical and effective method of sub- 

 soiling. 



