PHYSIOLOGICAL PROCESSES IN PLANTS 121 



e. Plant Zonation 



Observations. 1. Show how the distribution of plants depends largely 

 on the character of the ground they occupy. 



2. How do meadow and forest formations differ ? Sea beach from 

 swamp ? Swamp from pond ? 



3. Study Figure 35. Note the subdivisions into zones. How many 

 are there ? How are they named ? 



Conclusion. What factor has evidently caused most of the differences 

 in the characters of the zones ? 



Observation. Using Figure 35 as a model, make a study of any pond 

 formation and try to make a similar diagram. 



Conclusion. Report your observations, including as many names 

 of plants as possible, also differences in appearance between the zones, 

 etc. Thus : 



Questions 



1. Show how plant societies depend on the variations in 

 surroundings (physiographic conditions). 



2. Which of the plant societies is most directly concerned 

 with man's welfare ? 



3. Why were the valleys of the Euphrates and the Kile 

 centers of early civilization ? 



4. What part of the United States is the most productive ? 

 Why? 



5. Explain the advantages of irrigation in such states as 

 Colorado, Utah, and Arizona, 



