Gymnospcrmous Plants — Conifers and Their Allies 205 



12. Why would it not be desirable to have the pollen tube preformed rather than 

 form it just as needed? Explain. 



13. What are the chromosome numbers in the sporophyte and the gametophyte? 



14. Why must there be a numerical reduction in the number of chromosomes 

 previous to the union of the sperm and egg? 



15. Explain what is meant by "evergreen." 



16. Contrast and give an example of monecious and diecious. 



17. Contrast between ovules and true seeds. 



18. Contrast between pollination and fertilization, giving examples of each. 



19. Explain why ovules and true seeds are said to be borne exposed (naked) and 

 hence are gymnospcrmous. 



20. Explain the significance of the phenomenon of heterospory. 



21. Describe the structure and function of the micropyle. 



SELECTED REFERENCES* 



Bowers: Cone-bearing Trees of the Pacific Coast, McGraw-Hill Book Co., Inc. 



Chamberlain: The Living Cycads, University of Chicago Press. 



Chamberlain: Gymnosperms, Structure and Evolution, University of Chicago 



Press. 

 Eliot: Forest Trees of the Pacific Coast, G. P. Putnam's Sons. 

 Harlow: Trees of Eastern United States and Canada, McGraw-Hill Book Co., 



Inc. 

 Harrar and Harrar: Guide to Southern Trees, McGraw-Hill Book Co., Inc. 

 Jacques: How to Know the Trees, John S. Swift Co., Inc. 

 Longyear: Trees and Shrubs of the Rocky Mountain Regions, G. P. Putnam's 



Sons. 

 Mathews: American Trees and Shrubs, G. P. Putnam's Sons. 



^Also refer to textbooks in list of references on p. 149. 



