Abnormal seedling: A seedling that does not have all the essential structures or is damaged, deformed, or decayed to such an extent that normal development is prevented (see normal seedling).

Achene: A dry, hard, one-chambered, one-seeded indehiscent fruit, as in buckwheat (Fagopyrum) or sunflower (Helianthus). The fruit wall is not united with the seed coat.

After-ripening: A term for the collective changes that occur in a dormant seed that make it capable of germination. It is usually considered to denote physiological changes.

Angiosperms: Vascular plants that produce flowers and have seeds enclosed within the fruit (mature ovary).

AOSA: The initials of the Association of Official Seed Analysts, the organization of state and federal seed analysts of the United States and Canada.

AOSCA: The initials representing the Association of Seed Certification Agencies, a non-profit organization founded in 1919 (formally known as the International Crop Improvement Association) in an effort to establish credible standards for the production of high-quality seed. Today, AOSCA has member agencies across the U.S. as well as seven member countries including Canada, Chile, Argentina, Brazil, Australia, New Zealand, and South Africa.

Apical: The distal end of the fruit or seed away from the point of attachment or attachment scar.

Appressed: Pressed close or lying flat against something.

Aril: An outgrowth of the ovule or funiculus.

Awn: A narrow, bristle-like organ, as on the glumes or lemmas of grasses (Poaceae).

Basal: The base of the fruit or seed opposite the apical end.

Bulblet: A small, vegetatively-produced bulb that can function reproductively as a seed (e.g., Allium spp. and Poa bulbosa).

Burr: Has spikelets or flowers that are compressed closely together by lacking a central axis. The spikelet glumes are hard and pointed, e.g. buffalograss.

Callus: The hard base of grass florets or spikelets, just above the point of disarticulation.

Capsule: A dry, dehiscent fruit derived from a compound ovary.

Carpel: One section of a compound ovary.

Caruncle: An appendage or outgrowth of the outer integument of the seed, e.g. leafy spurge.

Caryopsis: The single-seeded fruit or grain of the grass family (Poaceae); the fruit wall (pericarp) is united with the seed coat (testa).

Chalaza: End of seed opposite the micropyle.

Coleoptile: The sheath enclosing the terminal bud of the embryo and the developing leaves of the young seedling of the grass family (Poaceae).

Cotyledon: The modified storage leaf or pair of leaves of an embryo and seedling (see primary leaf).

Cultivar: A variety of cultivated crop.

Dicotyledons: A group of plants so classified because the embryo usually has two cotyledons (see monocotyledons).

Diseased: Showing symptoms of the presence and activity of pathological or detrimental microorganisms.

Disseminule: Detachable plant part capable of being disseminated and of propagating, commonly a seed or fruit.

Dormancy: A physical or physiological condition of a viable seed that makes it resist germination until environmental conditions are favorable for that particular species.

Dorsal: Upper side or back of a seed or fruit.

Elaiosome: A lipid-rich appendage of the seed that serves to attract ants for seed dispersal. It encompasses various seed surface structures, such as arils and caruncles, which can develop from different seed or fruit tissues.

Elliptic: Outline of an ellipse; greatest width midway sloping to an equally pointed apex and base.

Embryo: A rudimentary plant contained in a seed, usually consisting of a more or less differentiated axis and attached cotyledon(s).

Endosperm: Nutritive tissue originating from union of the two polar nuclei with a sperm nucleus.

Enzyme: A catalyst produced in living matter. Enzymes are specialized proteins capable of promoting chemical reactions without themselves entering into the reaction; consequently, they are not changed or destroyed.

Ergot: Dark spur-shaped sclerotium that develops in place of a healthy seed in a diseased (fungus-infected) inflorescence. Ergot sclerotia are toxic to both man and livestock and were an original source of the hallucinatory drug LSD.

Fascicle: Much the same as a burr except the spikelet glumes are soft, e.g. buffelgrass.

Floret: A small flower in a clustered inflorescence (e.g., sunflower, grasses). In grasses, a floret consists of the lemma, palea, stamens, and pistil.

Fruit: A mature ovary and any associated parts.

Funiculus: The stalk that connects an ovule (seed) to the placenta of the ovary wall.

Geniculate: Bent at a sharp angle.

Germ: A term for the embryo of some seeds, especially the cereal grains.

Germination: The resumption of active growth by the embryo culminating in the development of a young plant from seed.

Glabrous: Lacking hairs or pubescence.

Glandular: The surface appearing to be covered with minute glands or spheres.

Glume: The pair of chaffy bracts that occur at the base of a grass spikelet, often completely enclosing it.

Granular: Resembling or consisting of small grains or particles.

Gymnosperm: A vascular plant that produces seeds but no flowers or fruits. The seeds are not borne within an ovary; hence the name from the Greek for "naked seed".

Hard seed: Seeds that remain hard at the end of the prescribed test period because they have not absorbed water due to an impermeable seed coat.

Head: An inflorescence of stalkless or nearly stalkless flowers attached to a common receptacle that often assumes the appearance of a single flower, but in fact may be a composite of many flowers, e.g. sunflower, clover.

Hilum: The scar on the seed coat at the place of its detachment from the seed stalk (funiculus).

Imbibition: The uptake of water by the seed from the germination substrate.

Inert matter: One of the four components of a purity test; it includes non-seed material and seed material that is classified as inert according to the Rules for Testing Seeds.

Inflorescence: The flowering structure of a plant (e.g., umbel, spike or panicle).

Inhibitor: A chemical substance that retards or prevents a growth process such as germination.

Integuments: The tissues covering or surrounding the ovule, usually consisting of an inner and outer layer that comprise the seed coat (or testa) of the mature ovule.

Involucre: A number of bracts (often leaf-like) that subtend an inflorescence such as the head in sunflowers.

ISTA: The initials of the International Seed Testing Association.

Legumes: A member of the pea family (Fabaceae) characterized by having dry, multi-seeded pods that dehisce along two sutures at maturity.

Lemma: One of two bracts of the grass floret; it is located on the side nearest the embryo and opposite the rachilla.

Lenticular: Lens-shaped, circular in outline with convex sides.

Loment: A usually dry fruit derived from a single carpel that breaks transversely into one-seeded fruit segments, derived from a single, superior, simple ovary.

Mericarp: One-half of a two-sectioned fruit known as a schizocarp (e.g. carrot). Mericarps are indehiscent or dehiscent depending on the species.

Micropyle: Opening in the ovule through which the pollen tube penetrates the embryo sac.

Monogerm: A sugar beet 'seed' (botanically a fruit embedded in receptacle tissue) containing only one ovule in contrast to a multigerm 'seed,' which represents aggregate fruit containing several ovule units (see multigerm seed ball).

Multigerm seed ball: This is the result of the fruit becoming embedded into the flower receptacle as found in Chenopodiaceae. Seed balls with more than one fruit embedded are multigerm as in garden beets.

Normal seedling: A seedling in which all essential structures are present and capable of developing into a plant under favorable conditions; certain defects may be present, as long as they are not so severe as to impede further development of the plant (see abnormal seedling).

Nutlet: A small, dry, indehiscent, one-seeded fruit, derived from the splitting of a schizocarp, with seed attached to pericarp at a single point, e.g. mints

Obovate: Inverted egg shaped with apical end the broadest.

Oval: Broadly elliptic.

Ovate: Egg-shaped with basal end the broadest.

Ovule: The structure within the ovary of the flower that becomes the seed following fertilization and development.

Palea: One of the thin bracts of grass floret enclosing the fruit (caryopsis) that is located on the side opposite the embryo.

Pappus: Modified calyx in Asteraceae, composed of hairs, bristles, awns, or scales. The pappus-like structure attached to milkweed seeds is termed a coma. 

Pedicel: The stalk within an inflorescence supporting a single flower or spikelet.

Pericarp: Fruit wall; derived from the ovary wall.

Perigynium: The saclike bract that subtends the pistillate flower of sedges (Carex), which in fruit becomes a flask-shaped envelope surrounding the fruit (achene).

Perisperm: Nutritive tissues occurring within certain seeds, derived from the nucellus; similar in function to endosperm.

Physiological dormancy: Seed dormancy caused by internal physiological conditions that prevent germination. Often referred to as epicotyl or embryo dormancy.

Physiological maturity: The maturity of seed when it reaches its maximum dry weight. This usually occurs prior to the normal harvest date.

Pistil: The female part of the flower that contains the stigma, style, and ovary. The matured ovary becomes the fruit. Inside the ovary is the ovule(s), which when mature becomes the true seed. 

Pit: The hard, stony inner portion of a fruit formed from a thickened, lignified endocarp that surrounds and protects one or more seeds. Pits occur in certain fleshy or dry indehiscent fruits; when the outer layers of the fruit (such as the mesocarp or a fibrous husk) are removed or break apart, the pit remains as the durable seed‑enclosing unit.

Pod: A dehiscent fruit produced by leguminous plants (beans, peas). Also known as a legume.

Pollination: The process by which pollen is transferred from the anther, where it is produced, to the stigma of a flower.

Prechill: The practice of exposing imbibed seeds to cool (5–10 degrees C) temperature conditions for a few days prior to germination at warmer conditions.

Pubescent: Having hairs.

Pure live seed: The percentage of pure seeds in a seed lot that are alive. The percentage of Pure Live Seeds (PLS) is determined by multiplying the percent of live seeds (germinated plus dormant) by the percent or pure seed and dividing by 100.

Quiescence: A resting seed in which none of the germination processes is taking place; usually inferring the absence of environmental conditions favoring growth; growth resumption of the species is not present.

Rachilla: The axis of a spikelet.

Rachis: The central axis of an inflorescence.

Rachis segment: A segment of the central axis of the inflorescence (rachis). In some species (e.g. Andropogon) separation of the sessile spikelets occurs when the rachis disarticulates at the spikelet bases leaving the segment of the rachis between spikelets attached to the lower spikelet.

Radicle: The rudimentary root of the embryo, developing into the primary root after emergence from the seed coat.

Raphe: A seam or ridge found on seeds.

Receptacle: The usually enlarged upper portion of the pedicel to which the parts of the flower are attached.

Reticulated: Resembling a net or network, especially having veins, fibers, or lines crossing the surface.  

Rugose: Having veinlets sunken and areas in between raised. Wrinkled.

Samara: A one-seeded winged fruit. The wing may be on one side as in maples (Acer) or surround the fruit as in elms (Ulmus).

Scabrous: Rough to the touch, covered with minute points of very short, stiff hairs.

Scarification: The process of mechanically abrading a seed coat to make it more permeable to water. This process may also be accomplished by brief exposure to strong acids (e.g. sulfuric acid).

Schizocarp: A dry, two-seeded fruit of the carrot family (Apiaceae) that separates at maturity along a midline into two mericarps. Each mericarp has a dry, indehiscent pericarp enclosing a loose fitting seed.

Scurf: Having flakes on the surface.

Scutellum: A shield-shaped highly modified, single cotyledon in grasses (Poaceae) that absorbs nutrients from the endosperm and provides energy for germination.

Secondary dormancy: A type of dormancy imposed by adverse environmental conditions in previously non-dormant seeds, or seeds in which primary dormancy has been broken.

Seed: A mature ovule consisting of an embryonic plant together with a store of food, all surrounded by a protective coat.

Seed coat: The protective covering of a seed usually composed of the inner and outer integuments. Also called the testa.

Seed unit: The structure usually regarded as a seed in planting practices and in commercial channels, consisting of a true seed with or without accessory structures, as defined in Section 2.6 of the AOSA Rules. See also true seed.

Seedling: A young plant developing from the embryo of a seed.

Sepal: The outermost whorl of leaf-like structures attached to the receptacle. Collectively, all the sepals on a flower are called the calyx.

Sessile: A flower or spikelet with no pedicel therefore attached directly to the central axis (rachis) or other surfaces.

Silicle: A short silique (fruit) usually containing only one seed. Found in Brassicaceae.

Silique: A fruit usually dehiscing by two lateral valves (having a central septum). The fruits can be long or short in length and round or flat in cross section. Contains more than one seed. Found in Brassicaceae.

Spatulate: Having a narrow base and rounded apex. Pear-shaped.

Spike: Has a strong central axis (rachis) on which flowers or spikelets are directly attached (sessile), e.g. wheatgrasses.

Spikelet: One or more florets that are subtended by a pair of bracts called glumes. Spikelets are pedicellate if located on a pedicle and sessile if attached directly to the rachis. Often spikelets with single florets have remnants of a second floret, usually a lemma.

Spiny: slender, stiff, sharp projections oriented in the general plane of the structure

Stamens: The male part of the flower, which contains the anthers (with pollen) and filaments. Collectively, all the stamens are called the androecium.

Stipples: Numerous small dots or specks.

Stylar: The end of the fruit or seed that contains the style or the apical end.

Submitted sample: A representative sample sent to the seed testing laboratory for the purpose of purity or germination testing that will represent the whole seed lot in question.

Testa: The protective covering of a seed usually composed of the inner and outer integuments. Also called a seed coat.

Tetrazolium: Indicates a class of chemicals that have the ability to accept hydrogen atoms (and undergo reduction) from dehydrogenase enzymes associated with living tissue. When this reduction occurs, the tetrazolium (TZ) chemical undergoes a change, usually from colorless to red.

Tolerance: The amount by which a second test may differ from a first test without being attributed to an actual difference in seed quality. Tolerances are usually based on normal random variation, or sampling error.

Transverse: Set crosswise, crossing or at right angles.

True seed: A mature ovule containing an embryo, seed coat (testa), and nutritive tissue, without any attached fruit structures.

Tuberculate: Having small pimple-like protuberances.

Utricle: A one-seeded, usually small, bladdery fruit as found in Atriplex.

Ventral: Adaxial; of the side of an organ facing the axis (compare dorsal).

Viability: Alive. Seed that has the ability to grow containing structures and substances including enzyme systems that give it germination potential.

Weed seed: A seed from a plant generally considered undesirable. The total percentage (by weight) of seed lot that is composed of seed of plants considered to be weeds. One of the four components of purity test.