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Terms commonly used in the identification of trees

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Booklet history

Booklet history

The terms described and illustrated in this paper are among those most frequently used when classifying and identifying trees. The focus is on the arrangement of leaves on stems and the structures of leaves and the shapes of leaves.

Stems and Branches.

The end of a branch or stem normally has a bud on it called the terminal bud. Buds below the terminal bud are called axillary buds and they are usually associated with points on a stem where leaves are attached. A point on a stem where a leaf or axillary bud is attached is called a node. A region on a stem between nodes is called an internode. A terminal bud is labeled T and four axillary buds are labeled A in Figure 1.

Leaf Structure.

A number of features associated with the structure or shape of a leaf are used in the classification of trees. The main portion of a leaf is termed the blade. The stem of the leaf is the petiole. Sometimes there are small leaf-like structures at the base of the petiole. These structures are known as stipules. If there is a single major vein running down the middle of a leaf, it is called a midrib. The edge of a leaf is called its margin. Figure 3 illustrates the basic shape of a leaf. The blade is indicated by B, the petiole by P, and stipules by ST.

Leaves and buds generally are arranged along stems in an alternate or opposite pattern. The stem illustrated in Figure 1 shows an alternate arrangement of leaves and buds while the stem illustrated in Figure 2 shows an opposite arrangement.

A leaf margin is said to be entire when it is smooth as in Figure 3 or it can be wavy (W) or toothed (T) as in Figure 4.

When a leaf is so deeply cut or subdivided that it appears to be several leaves, it is called a compound leaf. Leaves that are not compound are simple. All of the leaves illustrated in Figures 1 through 6 are simple while those in figures 7 and 8 are compound.

The leaf-like divisions of a compound leaf are reffered to as leaflets and if they all branch from a single point, the leaf is compound palmate. See figure 7. 2 Figure 7.

When the margins of a leaf are deeply cut, the leaf is said to be lobed. A leaf is pinnately lobed if it has one main vein (a midrib) and secondary veins branching from it. See Figure 5.

When a lobed leaf has no one, main vein but several, all branching from a single point, it is said to be palmately lobed. See Figure 6.

If the leaflets all originate from a single main vein, the leaf is compound pinnate. See figure 8.

A possible way of avoiding confusion about the difference between a stem with several leaves and a single compound leaf is to remember that stems have buds while there will be no buds on compound leaves found in the Northern Indiana area.

All illustrations on pages 6 and 7were taken, with modifications, from Gray. 1858.

Gray, Asa. 1858. How Plants Grow: A Simple Introduction to Structural Botany. Ivison, Blakeman, Taylor, and Co. New York.

Chapel area

Entry to Holy Cross College and Holy Cross Village

Holy Cross Parkway, Cemetery, and Villas

Did you know ...

When Holy Cross College first opened, the now Holy Cross Parkway was a 2-track switching spur for the University of Notre Dame and Western Railroad that, until the mid-1900’s, carried coal to the ND and Saint Mary’s power plants. It also sometimes carried passengers to ND football games.

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