28 



The New York State College of Forestry 



or sessile ; a leaf without stipules is estipulate. Stipules, wlierc^ 

 present, are in the majority of cases apparently vestigial struc- 

 tures and have no real function. In other cases they are modi- 

 fied into thorns (as in the Black Locust) or act as bud scales which 

 protect the growing points during the winter (Basswood). 



Leaf Variation ' 



Of the primary plant parts, namely root, stem, and leaves, the 

 latter are by far the most plastic and respond most quickly to 

 an altered environment or habitat. Such external stimuli mani- 

 fest themselves in leaves of various shapes and sizes and result 

 not only in wide differences between the leaves of different 



Fig. ;} — Even piNNATEa>Y Decompounj* 

 Leaf 



Fig. 2 — Odd pinnately Com- 

 pound Leaf 



Tig. 4 — Palmately Compound Leaf 



