i6 



NEW YORK STATE MUSEUM 



Serrate (figure 35); when the margin is sharply toothed with coarse 

 teeth, like a saw. When the teeth are rounded inward or are convex, the 



margin is said to be dentate (figure 37). When the 

 margin is formed of rounded teeth it is said to be 

 crenate (figure 36). If the teeth are very small, the 

 diminutives of the above terms are used, namely, 

 serrulate (figure 39), denticulate (figure 40) and 

 crenulate (figure 41). 



39 40 



Compound leaves: 



When a leaf possesses several divisions or seg- 

 ments upon a common petiole or rachis, it is said to be compound. The 

 distinction between a simple leaf, which is deeply divided, and a compound 

 leaf, rests upon the presence of distinct articulation between the leaf seg- 

 ment of the compound leaf and the petiole. Compound leaves may be 

 pinnate (figure 42), when the leaflets are arranged on either side of a com- 

 mon petiole (Ash, Rose, Walnut etc.) or palmately compound (figure 43), 

 when the leaflets all join the petiole at its summit (Horse-chestnut). 



Leaf arrangement: 



Alternate, when the leaves are arranged one at a node and each leaf 

 is opposite and above the preceding leaf; spirally arranged, when the nodes 



