72 Science of Plant Life 



Finally, we must observe that there are in trees all gradations 

 between the deciduous and evergreen habits. In the rainy 

 tropics there are many delicate-leafed evergreens. In the dry 

 tropics the evergreens have thick, fleshy leaves, or they may 

 be quite leafless. ' Some plants, like the holly and the Virginia 

 creeper, may be of the deciduous habit in the North and of the 

 evergreen habit in the South. Some deciduous trees, like the 

 cherry, when planted within the tropics become evergreen; 

 while the magnolia, which is evergreen in the Southern 

 states, becomes deciduous when grown in a colder climate. 

 Evidently leaf habits are adjustments to climatic conditions, 

 especially to conditions of temperature and moisture. 



PROBLEMS 



1. What are the commonest evergreen trees and shrubs of your locality? 



2. What trees of your vicinity develop leaves earliest in the spring? What 

 trees put out their leaves last ? 



3. What trees develop flowers before putting out their leaves? 



4. What trees drop their leaves first in autumn ? What trees drop their leaves 

 last in autumn? 



5. What trees shed part of their leaves during the summer? 



6. During how many months does each of these trees carry on food manu- 

 facture? 



7. During how many months do the evergreen trees of your locality manufac- 

 ture food? 



8. For how many months do the three leading crop plants of your locality carry 

 on photosynthesis? 



