72 THE NATURE AND WORK OF PLANTS 



87. The positions of leaves. — Go out into an open 

 woods or meadow and note the positions of the 

 leaves of all the plants you may see. Select a suit- 

 able specimen and walk around it, noting the posi- 

 tions of these organs on every side of the plant. Do 

 they face all the points of the compass? are they 

 horizontal ? Do you note any connection between 

 their position and that from which the rays of light 

 come ? Does every leaf receive direct sunlight at 

 some time of the day, and at the same hour ? 



88. Length of the petioles. — Take a number of 

 leaves from different parts of the same plant, and 

 compare the length of the petioles. Observe the 

 leaves as they are attached to the stems. Does this 

 inequality of the petiole serve any purpose in connec- 

 tion with the light? Take the long-petioled leaves 

 from some plant and put them in the place of short- 

 petioled leaves on another stem. What is the result, 

 so far as receiving light is concerned? 



89. Leaf mosaic. — A close examination will show 

 that length of stalk and size of blade stand in 

 close relation to each other, and that the distance 

 between the points at which the leaves are fastened 

 to the stems is also a factor in their arrangement. 



