Sagittate: arrowhead-shaped, with two retrorse basal lobes
Salient: projecting outward
Salverform: with a slender tube abruptly expanded into a rotate limb
Samara: dry fruit with wings that do not open when mature, as in maple trees
Sanguineous: blood-red
Sapid: with an agreeable taste
Saponaceous: soapy
Saprophytic: Deriving food from dead or decaying organic material in the soil and usually lacking in chlorophyll
Sarcocaulis: with fleshy stems
Saxatile: growing among rocks or in rocky, arid situations
Scaberulent: slightly scabrous
Scabrous: rough to the touch
Scalariform: ladder-like
Scale: a greatly reduced leaf or other outgrowth on a plant surface
Scandent: climbing
Scape: a leafless flowering stem arising directly from the ground
Scarify: to roughen, score or scrape the hard, outer coating of a seed to assist in the absorption of moisture before germination, a process that many desert wash seeds require
Scarious: thin, dry, membranous and more or less translucent
Scissile: splitting easily
Sclerophyllous: with stiff, firm leaves
Scorpioid: describing a coiled inflorescence
Scurfy: covered with small scale-like or bran-like particles or projections
Sebaceous: tallowy or fatty
Secund: Borne from only one side of an axis
Semi-: prefix meaning half
Sepal: a single segment of a divided calyx
Septate: divided by one or more partitions
Septicidal: said of a capsule, longitudinally dehiscent through the ovary wall at or near the center of each septa, preserving each locule as an intact entity (compare loculicidal, poricidal)
Septum: any kind of a partition, specifically the wall between chambers in a compound ovary
Seriate: arranged in rows or series
Sericeous: covered with long, soft, straight, appressed hairs giving a silky appearance
Serpentine: refers to soils that are low in calcium and high in magnesium and iron, derived from greenish or gray-green rocks that are essentially magnesium silicate, other characteristics of which are a high nickel and chromium content, and a low content of nutrients such as nitrogen
Serrate: having sharp, forward-pointing teeth on the margin
Serrulate: serrate with very small teeth
Sessile: attached directly and without a petiole, pedicel or other type of stalk, said of either leaves or flowers
Setaceous: bristle-like
Setose: covered with bristles
Sheath: a leafy, tubular structure usually on a sedge or grass that envelopes the stem
Shrub: a small, woody plant with several stems
Sigmoid: double-curved, S-shaped
Silicle: a fruit similar to a silique, but much shorter, not much longer than wide
Silique: a type of capsule found in the Brassicaceae, either half of which peels away from a central, transparent, dividing membrane
Simple: a leaf that has one part, not subdivided into leaflets
Sinistrorse: turned to the left or spirally arranged to the left (compare dextrorse)
Sinuate: strongly or deeply wavy, usually referring to a leaf margin
Sinus: the space or division, usually on a leaf, between two lobes or teeth
Sori: clusters of spore sacs on a fern frond (singular: sorus)
Sp: abbreviation for 'species'
Spadix: a floral spike or head in which the flowers are borne on a fleshy axis
Spathe: a large bract or pair of bracts subtending and usually partially enclosing an inflorescence
Spatulate: spoon-shaped, gradually widening to a rounded apex
Specific epithet: the second part of a scientific name which identifies the species
Spicule: a short, pointed, epidermal projection
Spike: an elongated, unbranched inflorescence with sessile or nearly-sessile flowers
Spikelet: in grasses, the smallest aggregation of florets plus any subtending glumes
Spine: a sharp-pointed rigid structure, usually a highly modified leaf or stipule
Spinescent: bearing a spine or spine-like point
Spinose: having a stiff and tough acuminate tip
Spinulose: bearing very small spines
Sporangium: a spore-case or sac in which spores are produced in a fern
Spp: abbreviation for the plural of 'species'
Spumose: foamy or frothy
Spur: a hollow extension of a petal or sepal such as characterizes the larkspurs, and which often produces nectar
Squamate: having or producing scales
Squarrose: having spreading, recurved tips
Ssp: abbreviation for 'subspecies'
Stamen: the male or pollen-bearing organ of a flower, composed of filament and anthers
Staminate: describing a male flower that contains one or more stamens but no functional pistils
Staminode: a sterile stamen or other nonfunctional structure occupying the position and having the overall appearance of a stamen
Standard: also called a banner, this is the upper petal or segment of a papilionaceous flower
Stellate: starlike, with radiating branches and often referring to the pattern of hairs on the surface of a leaf
Stem: the main upward-growing axis of a plant which bears the leaves and flowers
Stenopetalous: with narrow petals
Stenophyllous: with narrow leaves
Stigma: the terminal portion of a pistil, which receives the pollen
Stipe: that portion of a fern frond below the rachis, i.e. below where the leaflets are attached
Stipitate: borne on a stipe or stalk
Stipule: an appendage at the base of a petiole, usually in pairs
Stolon: an elongated horizontal shoot above or below the ground, rooting at the nodes or apex
Stomate: a small pore or opening on the surface of a leaf through which gaseous exchange takes place, i.e. the diffusion of carbon dioxide, oxygen and water vapor
Stone: the hard, woody endocarp enclosing the seed of a drupe
Stramineus: straw-colored
Striate: with fine longitudinal lines or ridges
Strict: very straight and upright
Strigose: covered with rough, stiff, sharp hairs that are more or less parallel to a particular surface
Strobilus: an inflorescence that is characterized by imbricated bracts or scales such as are borne on the ephedras
Style: the narrowed portion of a pistil between and connecting the ovary and the stigma
Sauveolent: fragrant
Sub-: prefix meaning under, slightly, somewhat or almost
Suberose/Suberous: corky-textured
Subspecies: a group of plants within a species that has consistent, repeating, genetic and structural distinctions
Subtend: to occupy a position below and adjacent to
Subulate: awl-shaped
Succulent: fleshy, juicy and thickened
Suffruticose: low shrubby, with the lower part of the stem woody and the upper part herbaceous
Suffused: tinted or tinged
Sulcate: grooved or furrowed
Sulfureous: sulfur-colored
Summer annual: plant with seeds germinating in spring or early summer and completing flowering and fruiting in late summer or early fall (compare winter annual)
Superior ovary: one that is located above the perianth and free of it
Surcurrent: extending upward from the point of insertion, as a leaf base that extends up along the stem (compare decurrent)
Surficial: growing near the ground, or spread over the surface of the ground
Suture: a junction or seam of union, or a line of dehiscence
Swale: a depression or shallow hollow in the ground, typically moist
Sympatric: growing together with, or having the same range as
Sympetalous: having the petals more or less united
Syn-: prefix meaning united
Synandrous: with united anthers
Synoecious: having male and female flowers in the same flowerhead
Synsepalous: having the sepals more or less united