QUESTIONS AND SUGGESTIONS 257 



and flaccid. 4. Define stomates as to function. 5. Are the guard- 

 cells of advantage to the plant in regulating transpiration ? Explain 

 your answer. 6. Explain the advantage in having most of the sto- 

 mates on the under surface of the leaf. 



C. 7. Define mesophyll and chlorenchyma. 8. Describe the 

 structure of mesophyll, indicating the advantages of the palisade 

 structure. 9. Indicate what goes on in the spongy mesophyll, con- 

 trasting the work of this region with that of the root-hair region. 



D. 10. Describe the structure and position of the veins. 

 Section 58. 1. What are the principal dangers to which the leaf 



is exposed? 2. Name the subtopics of this section and indicate 

 how each has to do with protection. 



A. 3. Define deciduous plants. 4. Discuss the length of life of 

 leaves. 5. Explain why cold and drought have similar effects upon 

 plants. 6. Explain the advantage in the loss of leaves before a cold 

 or a dry season. 7. Compare a pine tree with a maple as to the 

 advantage or disadvantage of their foliage habits. 8. Describe the 

 shedding of leaves, defining absciss layer. 9. Discuss the cause of 

 autumnal colors of leaves, defining anthocyans and xanthophyll. 



B. 10. Describe the movements of the leaves of the sensitive 

 plant, n. • Give other examples of plants with motile leaves. 

 12. Describe the process in the pulvinus which causes leaf movement. 



C. 13. Discuss the advantages of the edgewise position of leaves, in- 

 dicating in what kind of localities it is most advantageous. 14. What 

 are compass plants, and what advantage is there in the compass 

 habit ? 



Section 59. 1. Give examples of plants whose tendrils are leaves 

 in origin, and of those whose thorns are leaves in origin. 



A. 2. Describe the internal structure of needle-like leaves. 



B. 3. Describe the pitcher plant. 4. Describe the sun-dew. 



5. Explain how insects are made available for use as plant food. 



6. Discuss the advantage of the insect-catching habit. 



