80 



FIRST STUDIES IN PLANT LIFE 



partly because these lower leaves do not get enough 

 of light and air. 



7. How the leaves differ on the same plant. 

 Again, look at a Virginia creeper and you will find 

 that the larger leaves are outside in the full light, 

 while the smaller leaves are in the shade. In the 

 .Japanese ivy creeper there is a difference not onlj' in 

 size but in shape. There is no chance about all this 

 difference of size or shape. Pluck a leaf from an elm 

 tree, and try to get another to match it exactly. You 



notice that 

 the one half 

 of the blade 

 of each leaf 

 is smaller 

 than the other 

 half (fig. .".()). 

 Stand lielow 

 an elm tree 

 and watch 

 how the leaves 

 hang, and try 

 to see how 

 this strange shape helps the leaves to do the best they 

 can for themselves, without cutting off the light from 

 the other leaves. Find out also why the end leaf in 

 an elm-twig is more regular in shape than the others. 



8. The original home of the tree must be con- 

 sidered. We see, then, that nearly all the differences 

 in the shapes of leaves are caused by the eagerness of 

 the plant to get as much sunlight as possible ; and 

 that we can often, while standing before a tree, see 

 how the shape or position of its leaves helps it in this 



Side leaves and end Ijaf of elm. 



