VI. THE ORGANS OF NUTRITION IN PLANTS — THE 

 SOIL AND ITS RELATION TO THE ROOTS 



Problem.— What a -plant takes from the soil and how it gets 

 it. 



(a) What determines the direction of growth of roots? 



(b) How is the root built ? 



(e) How does a root absorb water ? 



(d) What is in the soil that a root might take out ? 



(e) Why is nitrogen necessary, and how is it obtained ? 



Laboratory Suggestions 



Demonstration. — Roots of bean or pea. 



Demonstration or home experiment. — Response of root to gravity and 

 to water. What part of root is most responsive ? 



Laboratory work. — Root hairs, radish or corn, position on root, gross 

 structure only. Drawing. 



Demonstration. — Root hair under compound microscope. 



Demonstration. — Apparatus illustrating osmosis. 



Demonstration or a home experiment. — Organic matter present, in soil. 



Demonstration. — Root tubercles of legume. 



Demonstration. — Nutrients present in some roots. 



To the Teacher. — The principle of osmosis, one of the most difficult concepts 

 the child has to grasp, is the keynote of the work of this chapter. The practical 

 side is seen in the reference to crop rotation, nitrogen-fixing bacteria, and the like. 

 Every educated person should be informed on the principles underlying the work of 

 the bacteria of decay and the nitrogen-fixing bacteria in soils. The root as an organ 

 of absorption should be demonstrated fully, with individual laboratory work on 

 root hairs as structural organs, so that the child may realize the extreme delicacy of 

 these absorbing organs. 



Problem 51 : To find out the structure of roots. 



Materials. — Bean, pea, or corn seedlings grown in sawdust. 



Method and Observations. — In the roots of a bean seedling 

 notice the main root. From what part of the embryo did this 

 come? Branches of this main, or primary root, are called sec- 



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