structure of a leaf

blade

Main part of the leaf, rich in chlorophyll; it can vary markedly in shape, depending on the type of rib and size of indentation.

margin

Part that forms the outline of the leaf blade.

tip

Apex of the leaf blade, at the opposite end from the part attached to the petiole; this part can vary markedly in shape.

petiole

Narrow part of the leaf connecting the blade to the stem.

midrib

Hollow projection that extends the petiole into the blade and carries sap; it forms the basis of the leaf’s skeleton.

vein

Branching of the midrib that carries sap to the various parts of the blade; it also functions as the leaf’s skeleton.

sheath

Distension of the petiole, partly or completely surrounding the stem.

stipule

Small outgrowth at the base of the petiole in certain leaves.

leaf axil

Point at which the petiole attaches to the stem node.