Leaves or flowers that grow directly from the stem or peduncle of a plant
The perennial wildflower Trillium cernuum possesses three leaves that are sessile at the top of the stem.
In botany, sessility (meaning "sitting", used in the sense of "resting on the surface") is a characteristic of plant parts (such as flowers and leaves) that have no stalk. Plant parts can also be described as subsessile, that is, not completely sessile.
A sessile flower is one that lacks a pedicel (flower stalk). A flower that is not sessile is pedicellate. For example, the genus Trillium is partitioned into two subgenera, the sessile-flowered trilliums (Trillium subg. Sessilium) and the pedicellate-flowered trilliums.
Sessile leaves lack petioles (leaf stalks). A leaf that is not sessile is petiolate. For example, the leaves of most monocotyledons lack petioles.