Samara: A dry, winged fruit containing one seed.  Example: ash, elm.

Scape:  A leafless stalk of a flower or an inflorescence.

Schizocarp: A fruit developed from two fused ovaries; the two fruit separate from one another at maturity; each fruit contains 1 seed.

Sepal:  the outer layer of floral parts, often (but not always) green and leaf-like in appearance.

Serrate: Toothed

Sessile:  Having no stalk

Simple: A leaf that is not divided into leaflets.

Sinus: The portion of the edge of a leaf that is indented in between two lobes.

Solitary:  A single flower (as opposed to flowers in a cluster or inflorescence.)

Spadix: An inflorescence with a single thickened axis embedded with numerous small flowers.

Spathe:  A large bract that subtends the spadix (the inflorescence found in the aroid family).

Spike:  An inflorescence with a single axis and flowers without stalks.

Spur: A stem with very short internodes.

Stamen: the pollen-bearing organ of a seed plant, usually consisting of an anther and a filament.

Stigma:  The top part of the female pistil.  It receives pollen.

Stigmatic slit:  The opening to the pistil of the milkweeds (Asclepias species)

Stipule: an appendage, often leaf-like

Strobilus: Cone-shaped reproductive structure common in gymnosperms.

Style: The section of the pistil located between the stigma and the ovary.

Subtend:  Situated below another structure.

Tepal:  When petals and sepals cannot be distinguished from one another, they are referred to as tepals.

Trifoliate: A compound leaf with three leaflets.

Triternate:  A compound leaf with three leaflets, each of which is subdivided into three sections.