56o BIOLOGY AND HUMAN LIFE 



8. How are the rings formed by which we commonly tell the age of 

 a tree ? 



9. How are knots produced in wood ? What is the advantage of hav- 

 ing knots ? What is the disadvantage ? How can knots be prevented ? 



10. What objects made of wood could just as well be made of other 

 materials ? What ways are there of saving wood ? How can we make 

 sure that the country will never run out of wood? 



IL If we found suitable substitutes for wood in its various uses, 

 would the forests be of more importance or less ? 



12. How can the forests be made to increase our supplies of energy 

 for industry, transportation, heating, etc. without burning the wood ? 



13. What damage do forest fires do besides burning the trees ? 



14. How does the amount of timber destroyed by fires compare with 

 the amount cut for use ? 



15. How is the maintenance of recreation forests Hke that of city 

 parks ? In what ways are these two different ? 



16. Why should trees be planted in cities ? What are the most com- 

 mon street or roadside trees in your community ? 



17. What lands in your region would be available for forest without 

 loss to farming? When is it better to use land for trees than for 

 agriculture ? 



REFERENCE READINGS 



Moon, F. F. The Book of Forestry. 



LiNViLLE, H. R. Biology of Man and Other Organisms, pp. 265-276. 



PiNCHOT, GiFFORD. A Primer of Forestry. 



Farmers' Bulletin 1208, Trees for Town and City Streets. 



Fanners' Bulletiii i2og, Planting and Care of Street Trees. 



Farmers' Bulletin 1417, Idle Land and Costly Timber. 



United States Department of Agriculture. Circular 265. Arbor Day. 



United States Department of Agriculture. Bulletin 863, Forestry Lessons 



on Home Woodland ; Bulletin 1241, How the United States can 



meet its Present and Future Wood-Pulp Requirements. 

 United States Department of Agriculture. Miscellaneous Circular 75, 



Importance of Forestry and National Forests. 

 United States Department of Agriculture. Yearbook for 1922. Reprint 



886, Timber — Mine or Crop? 

 Annual Report of the Forester. 



