FORM AND STRUCTURE 
they are wanting. The Sycamore and Black Willow afford 
excellent examples of stipules. 
ARRANGEMENT. 
When leaves are distributed singly at different heights on 
the stem, they are said to be alternate. When two stand op- 
posite each other at the nodes, they are opposite. When 
more than two are borne at a node in a circle around the 
stem, they are whorled. 
KINDS OF LEAVES. 
Leaves are either simple or compound. 
A Simple Leaf has but one blade. The leaves of the Elm 
are simple. A.Compound Leaf has more than one blade ; 
each blade is then called a leaflet. The leaves of the Sumach 
are pinnately compound; the leaves of the Horse-chestnut 
are palmately compound. 
VERNATION OR PREFOLIATION, 
In the study of the leaves of trees considerable attention 
is given to the way the leaves are folded in the bud; this is 
Fic. 4. Fic. 5. Fic. 6. Fic. 7. Fic. 8. Fic. 9. 
called vernation. It may be studied from two points of 
view; how the leaves are arranged with reference to each 
other, or how the individual leaf is folded. 
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