74 GROWTH AND WORK OF PLANTS 



parted, divided, etc., or palmately lobed, etc., according to the kind 

 of venation. 



22. Compound leaves. Compound leaves are those leaves 

 in which the divisions of the blade are complete and regular and 

 the divisions are set off distinctly from each other somewhat like 

 distinct leaves, or leaflets. 



23. Significance of leaf division. The leaves are impor- 

 tant organs for certain kinds of work for the plant. Within certain 

 limits the work of the leaf is in proportion to its spread of surface. 

 Beyond certain limits of spread, however, thin leaves are in danger 

 of injury, since they would be whipped about more by the wind. 

 Divisions of large leaves permit the currents of air to pass with 



A. 



Fig. 68. 



A. Rose leaf, pinnately compound, odd pinnate, hairy stipules. B. Leaf of pea, pinnately 

 compound, terminal leaflets replaced by tendrils, leaf-like stipules. C. Clover leaf, palmately 

 compound, persistent stipules. 



less danger of injury. The work which leaves perform in con- 

 junction with light is very important and the leaves must have a 

 good light relation. Divided leaves permit the light to shine 

 through to leaves below which otherwise would be too greatly 

 shaded were the large leaves continuous. 



