54 THE LEAF 



PRACTICAL QUESTIONS 



i. Why are the outer twigs of trees generally the most leafy? (54, 



'2. Is the common sunflower a compass plant? Is cotton? 



3. Are there any such plants in your neighborhood? 



4. Compare the leaves of half a dozen shade-loving plants of your 

 neighborhood with those of as many sun-loving ones ; which, as a gen- 

 eral thing, are the larger and less incised? 



5. Give a reason for the difference. (53, 56.) 



6. Why do most leaves notably grasses curl their edges back- 

 wards in withering? (17, 60.) 



7. What advantage is gained by doing this ? (60.) 



8. Observe such of the following plants as are found in your neigh- 

 borhood, and report any changes of position that may take place in 

 their leaves and the causes to which such changes should be ascribed : 

 wood sorrel, mimosa (Albizzid), honey locust, wild senna (Cassia ma- 

 rilandica), partridge pea (C. chamachrista). wild sensitive plant (C. nic- 

 titans), red bud, bush clover (Lespedeza), Japan clover (L. striata), 

 Kentucky coffee tree, sensitive brier (Schrankia), ground pea or peanut, 

 kidney bean. 



9. Which of the trees named below shed their leaves from tip to 

 base of the bough (centripetally), and which in the reverse order? Ash, 

 beech, hazel, hornbeam, lime, willow, poplar, pear, peach, sweet gum, 

 elm, sycamore, mulberry, China tree, sumac, chinquapin. 



TRANSFORMATIONS OF LEAVES 



MATERIAL. Any kinds of leaves that can be obtained showing 

 adaptations for protective and other purposes, such as scales, spines, 

 tendrils, glands, etc. Some of those mentioned in the text are : sweet 

 pea, cedar, cactus, asparagus, cabbage, stonecrop, purslane, sarracenia, 

 bladderwort (Iftricularia), sundew (Drosera), Spanish bayonet 

 ( Yucca), stinging nettle (Urtica), horse nettle (Solatium carolinense) . 

 The subject is best studied out of doors, or in a greenhouse. 



66. Besides performing their natural functions, leaves 

 are modified in various ways to do the work of other 

 organs. No part of the plant is subject to more curious 

 and varied metamorphoses, and they are made to serve all 

 sorts of purposes. 



67. Leaves as Tendrils. Examine a leaf of the wild 

 vetch, or of the common garden pea, and it will be seen 



