CHARACTERISTICS OF LEAVES 



103 



been suggested that compound leaves shade underlying 

 leaves less than simple leaves do. 



219. How to Tell a Leaf. It is often difficult to dis- 

 tinguish compound leaves from leafy branches, and leaflets 



157. A leaf mosaic of Norway maple. Note the varying lengths of petioles. 



from leaves. As a rule, leaves can be told by the follow- 

 ing tests: (1) Leaves are temporary structures, sooner 

 or later falling. (2) Usually buds are borne in their axils. 

 (3) Leaves are usually borne at joints or nodes. (4) They 

 arise on wood of the current-year's growth. (5) They have 

 a more or less definite arrangement. When leaves fall, the 

 twig that bore them remains; when leaflets fall, the main 

 petiole that bore them falls also. 



REVIEW. How may leaves be studied? What is meant by function? 

 What do leaves do? What other parts may perform the function 



