Forms.—Leaves can readily be divided into the three following groups with regard to their general outline:

1. Broadest at the middle. [Orbicular], about as broad as long and rounded. [Oval], about twice as long as wide, and regularly curved. [Elliptical], more than twice as long as wide, and evenly curved. [Oblong], two or three times as long as wide, with the sides parallel. [Linear], elongated oblong, more than three times as long as wide. [Acerose], needle-shaped, like the leaf of the Pine-tree.

2. Broadest near the base. [Deltoid], broad and triangular. [Ovate], evenly curved, with a broad, rounded base. [Heart-shaped or cordate], similar to ovate, but with a notch at the base. [Lanceolate], shaped like the head of a lance. [Awl-shaped], shaped like the shoemaker's curved awl. [Scale-shaped], short, rounded, and appressed to the stem. The Arbor-vitæ has both awl-shaped and scale-shaped leaves.

3. Broadest near the apex. [Obovate], same as ovate, but with the stem at the narrow end. [Obcordate], a reversed heart-shape. [Oblanceolate], a reversed lanceolate. [Wedge-shaped or cuneate], having a somewhat square end and straight sides like a wedge.

These words are often united to form compound ones when the form of the leaf is somewhat intermediate. The term which most nearly suits the general form is placed at the end; thus lance-ovate indicates a leaf between lanceolate and ovate, but nearer ovate than lanceolate; while ovate-lanceolate indicates one nearer lanceolate.

Bases.—Oftentimes leaves are of some general form, but have a peculiar base, one that would not be expected from the statement of shape. An ovate leaf which should have a rounded base might have a tapering one; it would then be described as ovate with a [tapering base]. A lanceolate leaf should naturally have a tapering base, but might have an [abrupt] one. Many leaves, no matter what their general form may be, have more or less notched bases; such bases are called [cordate], deeply or slightly, as the case may be; and if the lobes at base are elongated, [auriculate]. If the basal lobes project outward, the term [halberd-shaped] is used. Any form of leaf may have a base more or less [oblique].

Points.—The points as well as the bases of leaves are often peculiar, and need to be described by appropriate terms. [Truncate] indicates an end that is square; [retuse], one with a slight notch; emarginate, one with a decided notch; obcordate, with a still deeper notch; [obtuse], angular but abrupt; [acute], somewhat sharpened; [acuminate], decidedly sharp-pointed; [bristle-pointed and awned], with a bristle-like tip; spiny-pointed, with the point sharp and stiff (Holly); [mucronate], with a short, abrupt point.

Margins.—[Entire], edge without notches; [repand], slightly wavy; [sinuate], decidedly wavy; [dentate], with tooth-like notches; [serrate], with notches like those of a saw; [crenate], with the teeth rounded; [twice serrate], when there are coarse serrations finely serrated, as on most Birch leaves; serrulate, with minute serrations; crenulate, with minute crenations. Leaves can be twice crenate or sinuate-crenate. Revolute indicates that the edges are rolled over.

When a leaf has a few great teeth, the projecting parts are called lobes, and the general form of the leaf is what it would be with the notches filled in. In the description of such leaves, certain terms are needed in describing the plan of the notches, and their depth and form.

Leaves with palmate veining are [palmately lobed] or notched; those with pinnate veining are [pinnately lobed] or notched. While the term lobe is applied to all great teeth of a leaf, whether rounded or pointed, long or short, still there are four terms sometimes used having special signification with reference to the depth of the notches. Lobed indicates that the notches extend about one fourth the distance to the base or midrib; cleft, that they extend one half the way; parted, about three fourths of the way; and divided, that the notches are nearly deep enough to make a compound leaf of separate leaflets.