What Joins a Leaf Blade to the Stem?

Petiolated Leaf Types

• A standard petiolated leaf connects the leaf to the stem at its base or margin; the petiole has a relatively small circumference only a little thicker than the leaf blade. Other appearances a petiole can have include a peltate leaf, when the petiole connects to the lower surface of the leaf; a winged petiole, which has leaf-like blades along its margin; a channelled petiole, which has a groove along its length; a

  pericladial petiole, in which the petiole acts as a sheath wrapping around the stem; a phyllodial petiole, which is flattened; and inflated petiole, which is thickened; and a pulvinal petiole, which has a swollen base.

Sessile Leaf Types

• The standard sessile leaf connects at its base or margin. Other types of sessile leaves grow from the stem in a different way. In a clasping leaf, the leaf connects at the base and its blade extends partly or completely around the circumference of the stem without being connected. In a perfoliate, the leaf's base is completely fused around the stem, making the stem appear to pierce the leaf. Connate-perfoliate is a type of perfoliate leaf in which the stem is located at or near the center of the blade. In a sheathing type, the base of the leaf extends down along the stem and forms a tube-like covering around it. A decurrent type occurs when the leaf blade extends downward on the stem, creating small ridges.

Stipule with Petiole

• Stipules are small spike-, scale- or blade-like structures that can be found at the base of the petioles of certain plants. Adnate stipules are attached to the petiole itself. An ochreate leaf is one in which stipules form a thin tube on the stem above the petiole.

Petiole and Sessile Together

• Certain plants have such drastic leaf variation that the lower-stem leaves are petiolate, while the upper-stem leaves are sessile. Certain species of aster and goldenrod are an example of this.