The angle formed by the stem and leaf stalk is called the axil, and buds formed in the axils are called axillary buds. A leaf can be an important aid in identifying a flower. In some instances, the petiole is absent and the leaf then is sessile on the stem. Leaves can be either simple or compound. For a simple leaf, the blade consists of a single piece.
Leaflets never have axillary buds, but compound leaves always have one at the base.
Leaves and leaflets come in a vartety of shapes and forms. In addition, leaf margins or edges can be smooth, or entire, scalloped, serrate, deeply lobed, toothed, or even double toothed. Another distinguishing feature for leaves is the type of venation. Most monocots, such as grasses and lilies, have parallel venation, in which the veins, orvascular ridge on a leaf, extend the length of the leaf and parallel each other and the leaf margin. Dicots, on the other hand, have netted venation, whereby veins branch and form a netted pattern.