Illustrated Glossary

In order to distinguish one kind of tree from another, it is necessary to learn the major characteristics which the forest trees of Illinois may possess. Illustrated below are several of the most commonly encountered characteristics of leaves and twigs. A thorough understanding of these structures will insure a quicker and more accurate identification.

On the pages following the illustrated glossary are keys to the trees of Illinois. A key is a botanical device which enables the user, through proper selection of a series of choices, to identify a specimen at hand. Separate keys are provided for trees during the spring, summer, and autumn seasons and during the winter season. Begin at the first pair of number 1’s, choose the statement that best fits the unknown specimen, and then go to the next pair of statements beneath. Continue this same procedure until the name of the plant is reached.

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LEAF FORMS AND ARRANGEMENT

SIMPLE

PINNATELY COMPOUND

PALMATELY COMPOUND

DOUBLY PINNATELY COMPOUND

OPPOSITE

ALTERNATE

WHORLED

LEAF SHAPES

LANCEOLATE

OBLANCEOLATE

OBLONG

ELLIPTICAL

OVATE

OBOVATE

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WINTER TWIG CHARACTERS

WINTER TWIG CHARACTERS

BUD SCALE

TERMINAL BUD

LATERAL BUD

LEAF SCAR

LENTICELS

BUNDLE TRACES

{LEAF LAYERS}

UPPER EPIDERMIS

PALISADE LAYER

RIBS AND VEINS

SPONGY LAYER

STOMA

LOWER EPIDERMIS

LEAF TIPS

ACUTE

OBTUSE

LONG-TAPERING

LEAF EDGES

PINNATELY LOBED

WAVY

TOOTHED

DOUBLY TOOTHED

SMOOTH

LEAF BASES

HEART-SHAPED

TRUNCATE

ASYMMETRICAL

ROUNDED

TAPERING

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