106 SOILS AND PLANT LIFE 



6. Why will girdling kill a tree ? 



7. How does the arrangement of the water-carrjdng vessels 

 differ in the com and bean ? Of what do the threads in the pith of 

 a cornstalk consist ? 



8. Describe the flow of sap. 



9. What is the cambium layer? How could you find it in a 

 twig? 



10. How, and from what part of hemp and flax do we get our 

 linen thread, rope and twine? 



