QUESTIONS AND SUGGESTIONS 141 



seems to be pulled down into the soil. (See Figure 39.) 

 Rosette is the name given to such a cluster of leaves as the 

 dandelion has. The dandelion rosette not only seems 

 to be pulled down into the soil; it is actually pulled down. 

 It is pulled down by the contraction of its tap-root. How 

 this contraction occurs is not fully understood, but it is easy 

 to understand that it is an advantage to the dandelion to 

 keep its rosette close to the ground. For one thing, it thus 

 escapes the lawn mower. More important, however, is the 

 fact that in this lowly position evaporation is less than in 

 a more exposed position. Plants with this habit are quite 

 common in dry places. They grow in the crevices of rock. 



QUESTIONS AND SUGGESTIONS 



Section 40. 1. What is the principal difficulty in making a school- 

 book about plant life ? 2. What are the topics which form the titles 

 of the chapters of this book? 3. Does your knowledge about plants 

 seem to exist in your mind as separate facts or as facts which are 

 related to each other ? Explain your answer. 4. Is it easier for you 

 to remember facts separately or to remember them as related one to 

 another? Make a list of ten ideas which the word leaf brings to 

 your mind. 



Section 41. 1. State ten of what seem to you the principal facts 

 about roots. 



Section 42. 1. Define primary and secondary roots. 2. Describe 

 the secondary roots of corn. 3. Define tap-root and give examples. 

 4. Of what advantage is a tap-root to the plant ? 5. Describe what 

 is meant by fibrous roots. What advantages have fibrous roots over 

 tap-roots? 6. Describe the process of layering. 7. Describe the 

 growth of the strawberry plant. 8. Pull up a piece of blue-grass sod 

 about as large as a saucer, shake and wash away the soil, and, then 

 examine the structure. Can you be sure where one plant ends and 

 another begins ? Are the roots primary or secondary ? 9. Describe 

 the secondary roots of the banyan. 10. Describe the growth of 

 mangroves, n. How do "water roots" differ in appearance from 



