Carnegiea gigantea, Giant Saguaro

Southwest Desert Flora

Home to the plants of the Sonoran, Chihuahuan and Mojave Deserts

Cirsium ochrocentrum, Yellowspine Thistle

Glossary

The botanical glossary used in Southwest Desert Flora is an alphabetical list of words or terms relevant to the descriptions here. In addition to the more difficult or unusual words defined here the glossary also provides definitions to some of the more common day-to-day botanical words that are not necessarily understood by all readers. This glossary is regularly updated or modified.

Alphabetical Listings
[A] [B] [C] [D] [E] [F] [G] [H] [I] [J] [K] [L] [M] [N] [O] [P] [Q] [R] [S] [T] [U] [V] [W] [X] [Y] [Y] [Z]

[A]

Abaxial
The side away from the axis, for instance the lower surface of a flowering plant leaf; compare Adaxial.
Acaulescent
An adjective descriptive of a plant that has no apparent stem, or at least none visible above ground. Examples include some species of Agave, Oxalis and Attalea.
Acerate
Acerose; needle-shaped (long and pointed)
Achene
A small dry indehiscent one seeded fruit. see Cypsela
Achene or Cypsela
Generally a cypsela is formed from an inferior ovary and may have a pappus, and an achene is formed from an superior ovary and does not have a pappus attached.
Actinomorphic
Regular; radially symmetrical; may be bisected into similar halves in at least two planes. Applies e.g. to steles and flowers in which the perianth segments within each whorl are alike in size and shape; compare Regular; contrast with Asymmetrical, Irregular, Zygomorphic.
Aculeate
Armed with prickles; e.g. the stem of a rose.
Acuminate
Tapering gradually to a point.
Acute
Sharply pointed; converging edges making an angle of less than 90°; compare Obtuse.
Adaxial
The side next to the axis; e.g. the upper surface of a flowering plant leaf; compare Abaxial.
Adnate
Grown or fused to an organ of a different kind, especially along a margin; e.g. a stamen fused to a petal; compare Connate and Caudex.
Alkaline soil
Alkaline or alkali, soils are clay soils with high pH (> 8.5), a poor soil structure and a low infiltration capacity. Often having a hard 'pan' or hard calcareous layers from 1½ feet or deeper.
Alluvial fan
A fan or cone-shaped deposit of granular fertile soil deposited by streams or other drainage from mountainous terrain. The formation of one or more alluvial fans into a single fan against a slope is called a bajada (see Bajada).
Alluvial soil
A fine-grained fertile soil deposited by water flowing over flood plains or in river beds.
Alternate
Leaves or flowers borne singly at different levels along a stem includes spiralled parts; or (as preposition) when something occurs between something else, for example stamens alternating with petals; compare Opposite
Androecium
Male parts of flower; the stamens of a flower collectively.
Androgynous
With male and female flowers in the same inflorescence.
Angiosperms
Flowering plants; plants with developing seeds enclosed in an ovary.
Annual
A plant that completes its life cycle and dies within one year.
Anther
Pollen-bearing part of the stamen.
Anthese
1. (of a flower) the period during which pollen is presented and/or the stigma is receptive.
2. (of a flowering plant) the period during which flowers in anthesis are present. note: not defined for some cases, such as when pollen is released in the bud.
Antrorse
Directed towards or upwards, e.g. of hairs on a stem. See also Retrorse.
Apetalous
Of a flower, without petals Without petals.
Apex
(plural apices) The tip; the point furthest from the point of attachment.
Appendage
A secondary part attached to the main structure; an external growth that seldom has any obvious function.
Appressed
Pressed closely, but not fused; e.g. leaves against a stem.
Arachnoid
Cobwebby, from being covered with fine white hairs.
Arborescent
Tree-like in growth or general appearance.
Areole
(from areola) As with cacti, the area between the veinlets of a leaf or the region of a cactus bearing the flowers and/or spines.
Aromatic
Having a pleasant, noticeable, distinctive or strong smell.
Arroyo
Also called a wash, is a dry creek, stream bed or gulch that temporarily or seasonally fills and flows after sufficient rain. Flash floods are common in arroyos following thunderstorms.
Ascending
Spreading horizontally, then becoming erect.
Asexual
Of reproduction that does not involve the gametes; i.e. vegetative reproduction.
Asymmetrical
Irregular, unequal, lacking any plane of symmetry.
Auricle
(adj. auriculate) usually of leaves; basal appendages shaped like an ear or earlobe.
Auriculate
(adj. auriculate) usually of leaves; basal appendages shaped like an ear or earlobe.
Awn
Fine bristle-like appendage; e.g. terminating or on the back of glumes and/or lemmas of some grass spikelet’s.
Axil
The upper angle between one part of a plant and another; e.g. the stem and a leaf.
Axillary
Borne in or arising from the axil, usually referring to the axil of a leaf.

[B]    ↵ Return to top

Baccate
A plant that bears berries is said to be bacciferous or baccate (a fruit that resembles a berry, whether it actually is a berry or not, can also be called "baccate".
Bajada
An alluvial fan of deposits of sediment by a stream settling onto flats at the front of a mountain. Derived from the Spanish word bajada; meaning with a sense of “descent” or “inclination” (see Alluvial fan).
The upper or top petal of a pea-flower.
Barbed
With (barbs pointing in one direction.
Barbellate
(barbellae) With barbed hairs.
Basal
At the base, situated or attached at the base.
Beak
A prominent pointed terminal projection, especially of a carpel or fruit. adj. beaked.
Berry
An indehiscent fruit, with the seeds immersed in the pulp, for instance tomato.
Biennial
Plant which completes its life cycle and dies within the second year; usually also forms a basal rosette of leaves the first year and flowers and fruits the second year.
Bifoliolate
Of a compound leaf with two leaflets.
Bigelow, John Milton
John Milton Bigelow, (1804-1878), American physician and botanist; Dr. Bigelovii was a professor of botany who collected in the western United States under Joseph Whipple Congdon in the Pacific Railroad Survey of 1853-1854. In addition, he worked with 3 top American botanists of the day, John Torrey, Asa Gray, and George Engelmann; and had a significant collection of California plants that yielded many new species.
Bilabiate
Having two lips; e.g. the form of the petals in many irregular flowers.
Bilateral
Arranged on opposite sides; e.g. leaves on a stem.
Bipinnate
Twice pinnate; for example of a compound leaf with individual leaflets pinnately divided.
Bipinnatisect
A pinnatisect leaf with deeply dissected segments.
Bisexual
Plant flowers bearing both male and female reproductive organs; usually, flowers with both stamens and carpels; hermaphrodite. See Perfect.
Blade
The lamina or flattened part of a leaf, excluding the stalk.
Bloom
A fine white or bluish waxy powder occurring on plant parts, usually stems, leaves and fruits. It is easily removed by rubbing.
Bract
Modified leaf associated with flower or inflorescence, differing in shape, size or color from other leaves (and without an axillary bud).
Bracteate
Having, possessing or bearing bracts.
Bracteole
Bracteole (Small bracts borne singly or in pairs on the pedicel or calyx. The state of having bracts is referred to as bracteate or bracteolate. Also see bract.
Bramble
1. A prickly shrub of the genus Rubus of the rose family, including the blackberry and the raspberry.
2. A prickly shrub or bush.
Bristle
Straight stiff hair (smooth or with minute teeth).
Browse
(Re; herbivorous animals, generally, a reference to herbivores that feed off of the ground and mainly eat leaves, fruits, soft shoots and twigs of high growing trees and shrubs; compare Graze
Bulb
(adj. bulbiferous), thick storage organ, usually underground, consisting of a stem and leaf bases (the inner ones fleshy).
Bur or Burr
Loosely, a prickly fruit; a rough or prickly propagule consisting of a seed or fruit and associated floral parts or bracts.

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Caducous
Falling off early, for example the sepals of poppies, that fall off when the petals begin to open; compare Persistent and Fugacious.
Caespitose
A tufted form or growth; e.g. the growth form of some grasses, growing in tufts.
Calcareous
A soil type rich in calcium carbonate (CaCO3). Southwestern calcareous soils contain heavy amounts of limestone and lime. (see Caliche and Limestone.
Caliche
A hardened natural cement of calcium carbonate (CaCO3) that binds other materials—such as gravel, sand, clay, and silt. It is generally light-colored and occurs in arid or semi-arid regions in the Sonoran and Mojave Deserts. The term caliche is Spanish originally from the Latin calx, meaning lime. see Calcareous and Limestone.
Calyculus
(adj. calyculate) (calyculi)
(1) a cup-shaped structure formed from bracts;
(2) in some Asteraceae, an extra set of bracts or phyllaries just below the involucre simulating a calyx; an involucel.
Calyx
(Plural calyces) the outer whorl of a flower, usually green; the sepals of one flower collectively.
Calyx tube
A tube formed by the fusion of the sepals (calyx), at least at the base.
Campanulate
Bell-shaped.
Canescent
Approaching white in color, covered with dense white (or grayish-white tricomes) down or wool.
Capitulum
A dense cluster of sessile, or almost sessile, flowers or florets; a head.
Capsule
A dry fruit formed from two of more united carpels and dehiscing when ripe (usually by splitting into pieces or opening at summit by teeth or pores).
Carpel
The basic female reproductive organ in flowering plants.
Cassini, Alexandre Henri Gabriel de
Count Alexandre Henri Gabriel de Cassini, (1781–1832), was a French botanist and naturalist, who specialized in Asteraceae, the sunflower family which was known as family Compositae at the time.
Catkin
A spike, usually pendulous, in which the mostly small flowers are unisexual and without a conspicuous perianth; e.g. willows, poplars, oaks and casuarinas. The individual flowers often have scaly bracts; they are generally wind-pollinated. The catkins are usually shed as a unit.
Caudex (plural: caudices)
Literally the stem of a plant, but also used to mean a rootstock, or particularly a basal stem structure or storage organ from which new growth arises. See also Connate
Caudiciform
Literally meaning "stem-like" or "caudex-like", is sometimes used to mean "pachycaul", meaning "thick-stemmed". See also Caudex
Caulescent
Having a leafy stem above ground, as contrasted with Acaulescent and Scapose.
Cauline
Borne on an aerial stem, e.g. leaves, flower or fruits (when applied to the latter two organs, usually referring to older stems.
Chaparral Vegetation
A thicket of dense growth of low growing, mostly small-leaved evergreen shrubs and thorny bushes and brambles.
Chasmogamous
Of flowers that are pollinated when the perianth is open. see Cleistogamous.
Cilia
(singular cilium, adjective ciliate) Generally, hairs more or less confined to the margins of an organ, like eye-lashes; in motile cells, minute, hair-like protrusions which aid motility.
Circinate
(Botany) Used of leaves or similar parts that are coiled on themselves from the apex toward their base.
Circumscissile
Describing any seed-vessel that splits along a circumference, with the upper part coming off as a lid.
Clambering
A plant growing more or less erect by leaning or twining on another structure for support, or by clinging with tendrils.
Clasping
A leaf without a petiole and whose base partially or completely surrounds a stem.
Claw
Narrow, stalk-like basal portion of petal, sepal of bract.
Cleft
Deeply cut about halfway to the midrib, as in many leaves and petals.
Cleistogamous
Of flowers that self-pollinate and never open fully, or self-pollinate before opening; see Chasmogamous.
Climber
A plant growing more or less erect by leaning or twining on another structure for support, or by clinging with tendrils.
Columnar
Shaped like a column.
Community
An assemblage, in nature, of plants that characteristically occur together.
Compound
Composed of several parts, for instance a leaf with leaflets, a gynoecium with several carpels, or an inflorescence made up of smaller inflorescences.
Cone
A fruit, usually woody, ovoid to globular, including scales, bracts or bracteoles arranged around a central axis, e.g. in gymnosperms, especially conifers and Casuarina.
Conifer
Conifers are gymnosperms, non-flowering plants; cone-bearing seed plants; woody, mostly trees, some shrubs. Today, all living conifers belong to the order Pinales within the Pinopyta Division.
Connate
Fused to another organ (or organs) of the same kind; e.g. petals in a floral tube; compare Adnate and Caudex.
Cooper, Dr. James Graham
Dr. James Graham Cooper, (1830-1902), geologist of the Geological Survey of California, who collected plants in the Mojave Desert in 1861. He was the son of William Cooper, one of the founders of the New York City Museum of Natural History.
Cordate
Heart-shaped, with the notch lowermost; of the base of a leaf, like the notched part of a heart.
Coriaceous
Leathery; stiff and tough, but somewhat flexible.
Corm
Fleshy, swollen stem base, usually underground, storing food reserves, with buds naked or covered by very thin scales; a type of rootstock. Adjectives derived from "corm" include "cormose" and "cormous";.
Corolla
Collective term for the petals of a flower.
Corona
(adjective: coronate) literally, crown
1. in flowering plants, ring of structures that may be united in a tube, arising from the corolla or perianth of a flower and standing between the perianth lobes and the stamens. The trumpet of a daffodil is a corona.
2. in grasses, a hardened ring of tissue surmounting the lemma in some species.
Corymb
Corymb (Adjective corymbose) an inflorescence with the flowers growing in such a fashion that the outermost are borne on longer pedicels than the inner, bringing all flowers up to a common level. A corymb has a flattish top superficially resembling an umbel, and may have a branching structure similar to a panicle. Flowers in a corymb structure can either be parallel, or alternate, and form in either a convex, or flat form.
Coulter, Dr. Thomas
John Thomas Coulter, (1793-1843) Irish botanist, physician and explorer. Dr. Coulter studied botany in Switzerland under Augustin de Candolle, discovered the Colorado Desert and was first to collect the Matilija Poppy among other plants. John Thomas Coulter was the first botanist to collect in Arizona. Not to be confused with John Merle Coulter, (1851-1928), also a botanist who was recognized with Erigeron coulteri.
Crenate
Leaf or fruit with blunt, rounded teeth or scalloped margin.
Crenulate
Minutely scalloped.
Crisped
Finely curled. A term generally applied to the edges of leaves and petals.
Cruciform
Cross-shaped.
Culm
In grasses, sedges, rushes, and some other monocotyledons, an aerial stem bearing the inflorescence; strictly, from the base of the plant to the lowest involucral bract (or base of the inflorescence).
Cultivar
The term cultivar is derived from cultivated variety and denotes an assemblage of cultivated plants clearly distinguished by one or more characters (morphological, physiological, cytological, chemical or other); when reproduced (sexually or asexually), the assemblage retains its distinguishing characters. A cultivar may arise in cultivation or be introduced from the wild. It is a variant of horticultural interest or value. Cultivar names are written with single quotation marks around them e.g. 'Blue Carpet', 'Alba'. All new names established after 1 January 1959, must be in common language (that is, not in Latin) but names established in Latin prior to this date are retained in Latin form.
Cuneate
Wedge-shaped; with straight sides converging at base. See Leaf shape.
Cyathia
Plural of cyathium
Cyathium
An inflorescence of unisexual flowers surrounded by involucral bracts, esp. the flowers of Euphorbia.
Cylindric
Tubular or rod-like that is 2 to 3 times as long as wide.
Cyme
(Adjective cymose) Inflorescence in which the main axis (central stem) and all lateral branches end in a flower, terminal flower develops first (each lateral may be repeatedly branched. see Thyrse
Cypsela
A dry, indehiscent, one-seeded fruit formed from an inferior ovary. see Achene
Cypsela or Achene?
Basically a cypsela is formed from an inferior ovary and may have a pappus, and an achene is formed from an superior ovary and does not have a pappus attached.

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Deciduous
Falling seasonally, for instance bark, leaves, petals; compare Persistent
Decompound
Divided to more than one level, as in bipinnate leaves for example, in which the leaflets of what otherwise would be a pinnate leaf, are themselves pinnately divided
Decumbent
Plants or plant parts with branches growing horizontally but turned or curving up at the extremity.
Decurrent
Extending downwards beyond the point of insertion e.g. when the base of a leaf or a fungal gill is prolonged downwards along the stem in a raised line or narrow wing.
Decussate
Opposite, with successive pairs borne at right angles to the last; generally applied to the arrangement of leaves.
Deflexed
Bent downwards; compare inflexed.
Dehiscence
(Dehiscent) Splitting at maturity along a built-in line of weakness.
Dehiscent
Breaking open at maturity to release contents. Generally refers to the release of seed from some fruits; also pollen from anthers.
Deltoid
With the shape of the uppercase Greek letter Δ, i.e. like a more or less equilateral triangle. See Leaf shape.
Dentate
Toothed, botanically used to describe leaf margins.
Desertic
Of or pertaining to a desert or deserts; adjective; (comparative more desertic, superlative most desertic).
Desfontaines, René Louiche
René Louiche Desfontaines (1750–1833) was a French botanist born near Tremblay in Brittany. He was elected to the French Academy of Sciences in 1783.
Determinate
Limited, usually in growth; compare Indeterminate.
Dichotomous
Forking into two equal branches. This may result from an equal division of the growing tip, or may be sympodial, in which the growing tip is aborted and replaced. Typically refers to mode of branch growth, as in Aloe dichotoma, but also to other organs, such as the thorns of various species of Carissa (which morphologically are branches) and thalli or hyphae of various algae and fungi.
Diffuse
Spreading widely and loosely.
Dioecious
Of plant, when male and female reproductive structures develop on different individuals; of inflorescence, male and female flowers in separate inflorescence's; compare Monoecious
Disciform
Having a flowering head that contains both filiform and disk flowers, referring to members of the Asteraceae.
Discoid
Resembling a disc or plate, having both thickness and parallel faces and with a rounded margin. Also used to describe the flower head of Compositae where there are no ray florets, but only disc florets.
Disjunct
Occurring in widely separated geographic areas, distinctly separate; applies to a discontinuous range in which one or more populations are separated from other potentially interbreeding populations far enough as to preclude gene flow between them.
Disk or Disc
A plate or ring of structures derived from the receptacle, and occurring between whorls of floral parts: in daisies, the central part of capitulum, hence disk flowers or florets.
Dissected
Deeply divided; cut into many segments.
Distal
Remote from the point of origin or attachment; the free end; compare Proximal.
Diurnal
Of the day; occurring or opening in the daytime.
Divaricate
Wide-spreading.
Divergent
Spreading in different directions, generally upward.
Drupe
A succulent fruit formed from one carpel; the single seed is enclosed by a stony layer of the fruit wall; kernel; e.g. peaches and olives.

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Elliptical (elliptic)
Shaped like a flattened circle, symmetrical about both the long and the short axis; about twice as long as broad, tapering equally both to the tip and the base; oval.
Emory, William Hemsley
William Hemsley Emory, (1811-1887), was born in Maryland of prominent parents and was an Army officer. Boundary surveys were a big part of his life as he was the Director of the Mexican Boundary Survey. Mr. Emory also conducted surveys along the Texas-Mexican border in 1844 and became part of the Northeastern boundary survey between the United States and Canada. Between 1848 and 1853 he conducted a boundary survey along the United States-Mexican border, and surveyed the Gadsden Purchase from 1854 to 1857.
Endemic
Having a natural distribution restricted to a particular geographic region; see Native.
Engelmann, George
George Engelmann, (1809-1884), a German-born St. Louis physician and botanist, and prolific author on cacti, North American conifers and oaks. He was educated at the gymnasium in Frankfurt and then at the University of Heidelberg, the University of Berlin and the University of Wurzburg where he received his M.D. degree.
Entire
1. not divided. 2. (of a margin) having a smooth margin, not lobed or toothed (it may be wavy or scalloped).
Ephemeral
Short-lived.
Epidermis
A non-woody plant organ's outermost layer of cells, usually only one cell thick.
Epipetalous
Of stamens that are attached to the petal.
Erect
Upright, more or less perpendicular to the ground or point of attachment.
Estivate
A period of reduced metabolic rate (dormancy) for reptiles and small mammals to avoid long dry hot summers.
Exfoliation
(Verb exfoliate;) The loss of leaves (or, in some cases, pieces of bark) from a plant.
Exserted
Projected beyond, e.g. the stamens beyond the corolla tube.
Exstipulate
Without stipules.
Extinction, local or extirpated
Local extinction, or extirpation, is the condition of a species (or other taxon) that ceases to exist in the chosen geographic area of study, though it still exists elsewhere. Local extinctions are contrasted with global extinctions.

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Farinaceous
Powderiness that is mealy
Farinose
(adjective farinaceous) Floury, covered with meallike particles, as often seen in Chenopoidum (Amaranthaceae).
Fascicle
(adjective fasciculate) In botany a cluster or bundle of leaves or flowers growing crowed together, e.g. a tuft of leaves all arising from the same node such as pine needles.
Filament
1. Stalk of a stamen. 2. Thread, one or a few cells thick.
Filiform
Thread-like. Pertaining to leaf shapes.
Filiform flower
A type of flower in the Asteraceae which is pistillate (male) and has a very slender, tubular corolla.
Filiferous
Bearing threads, as sometimes the leaf margin.
Fissure
A split or crack, often referring to fissured bark; also, a line or opening of dehiscence.
Floccose
With a soft and woolly covering of hairs.
Floret
Literally a small flower, but usually refers to the individual true flowers clustered within an inflorescence, particularly in inflorescences of the daisy and grass families.
Foliolate
(Referring to the number of leaflets in a compound leaf, as bifoliolate, trifoliate.
Follicle
A dry fruit formed from one carpel, splitting along a single suture, to which the seeds are attached; compare; Pod (of legume).
Funnelform
With a form gradually widening from the base to apex; funnel-shaped; compare Salverform.
Forb/herb
Vascular plant without significant woody tissue above or at the ground. Forbs and herbs may be annual, biennial, or perennial but always lack significant thickening by secondary woody growth and have perennating buds borne at or below the ground surface.
Fremont, John Charles
John Charles Fremont (1813-1890), known as the Pathfinder, Army officer and presidential candidate who collected plants on four hazardous journeys exploring the western United States. Best known for cartography and exploring, he was intensely interested in all natural sciences.
Fruit
Seed-bearing structure in angiosperms formed from the ovary, and sometimes associated floral parts, after flowering.
Fugacious
Disappearing, falling off, or withering; compare Persistent and Caducous.
Fusiform
Rod-shaped and narrowing gradually from the middle towards each end; spindle-shaped.

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Glabrous
Without surface ornamentation such as hairs, scales or bristles.
Glabrescent, Glabrate
Becoming glabrous, hairless, or smooth; glabrate. Becoming glabrous, almost glabrous.
Gland
A secretory structure within or on the surface of a plant; (loosely) a smooth, usually shining, bead-like outgrowth.
Glandular hair
Hairs tipped with a gland.
Glaucous
Glaucous (Botanical adjective), leaves or other herbage that is pale bluish-grey, bluish-green or whitish which describes the pale grey or bluish-green appearance of the surfaces of some plants and that is often easily rubbed off. Often applied to plants with a woolly or arachnoid surface, but properly referring to powdery or waxy surfaces, meaning those with a waxy bloom.
Globose, Globular
Spherical. See also Subglobose.
Globulose
Small or nearly spherical.
Glochid
A barbed hair or bristle, e.g. the fine hairs in Opuntia.
Glomerate
(Crowded, as in a headlike inflorescence.)
Glomerule
(adj. glomerulate) A small headlike inflorescence or division of an inflorescence (cluster) formed by condensation of a cyme.
Glutinous
Sticky, gummy, gluelike. See also Viscid.
Graham, James Duncan
James Duncan Graham, (1799-1865), a West Point Graduate and U.S. Army Officer. Mr. Graham is the namesake of Mount Graham, in Graham County, Arizona, and Graham County, Arizona was named after Mount Graham. Mr. Graham is also one of the founders of the United States army's topographical section and well known for his map making skills.
Gray, Asa
Asa Gray, (1810-1888), one of the most eminent American botanists and professor at Harvard, who played an important part in the identification of many Sierra wildflowers, and whose guides in Yosemite were John Muir and Galen Clark.
Graze
Re; herbivorous animal, generally, a reference to herbivores that feed on low growing plants such as grass and other low growing vegetation - compare with Browse
Great Basin Desert
The Great Basin Desert is defined by its animals and plants, yet the exact boundaries are unclear. It is a temperate desert with hot, dry summers and snowy winters. The desert spans a large part of the state of Nevada, and extends into western Utah, eastern California, and Idaho. The desert is one of the four biologically defined deserts in North America, in addition to the Mojave, Sonoran, and Chihuahuan Deserts.
Gregg, Josiah
Josiah Gregg, (1806-1850) was an American merchant, explorer and naturalist. He was also wrote about the American Southwest and Northern Mexico regions. Mr. Gregg collected many previously undescribed plants on his merchant trips and during the Mexican–American War after which he went to California.
Gymnosperm
A seed-bearing plant with unenclosed ovules borne on the surface of a sporophyll; includes, among others, conifers, Ginkgo, Gnetum and cycads. From gymno = naked, exposed; compare angio = covered, enclosed.

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Halophyte
A plant adapted to living in highly saline habitats; a plant that accumulates high concentrations of salt in its tissues; compare Xerophyte.
Hastate
Leaf description, narrow and pointed but abruptly enlarged at the base into two acute diverging lobes; may refer only to the base of a leaf with such lobes; compare Sagittate.
Helicoid
Coiled; of a cymose inflorescence, when the branching is repeatedly on the same side (the apex is often recurved); see Scorpioid.
Herb
A plant species lacking woody tissue when mature.
Herbaceaus
Not woody; usually green, and soft in texture.
Hirsute
Bearing coarse, rough, longish hairs. compare Hirtellous, See Indumentum.
Hirtellous
Diminutive from Latin hirtus (“hairy”), with -ous; (botany, zoology) pubescent with minute and somewhat bristly, coarse or rigid; compare Hirsute, see Indumentum).
Hispid
Having long erect rigid hairs or bristles, harsh to touch.
Hispidulous
Having short stiff hairs.
Hoary
Covered with a greyish to whitish layer of very short, closely interwoven hairs, giving a frosted appearance.
Holotype
The single specimen designated as the type of a species by the original author at the time the species name and description was published. Also see Lectotype
Honeybees
Honeybees are not native to North America and compete with Native Bees. Honeybees were introduced to North America by early settlers and compete with Native Bees. Honeybees are most important to non-native agricultural crops - see Native bees.
Hypanthium
A tube or cup-like structure in a flower that includes the bases of sepals, petals, and stamens, and may or may not be connected (adnate) to the ovary.

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Imbricate
Overlapping each other; of perianth parts, edges overlapping in the bud (the convoluted arrangement is a special form of imbrication.
Imparipinnate
A pinnate leaf with an odd number of pinnae (terminated by a single leaflet); compare Paripinnate.
Indehiscent
Not opening in any definite manner at maturity; usually referring to fruit. Contrast with degiscent.
Indeterminate
Unlimited, usually in growth; compare Determinate.
Indigenous
Native to the area; its presence in that region is the result of only natural processes with no human intervention; not introduced and not necessarily confined to the region discussed (hardly distinct from ‘native’ but usually applied to a smaller area). The term is equivalent to "native" in less scientific usage. For example, the Joshua Tree (Yucca brevifolia) is native to parts of the southwest but indigenous to Joshua National Park, California. Compare; Endemic; Native.
Indumentum
A collective term for a surface covering of any kind of trichomes, e.g. hairs, scales.
Inflorescence
Several flowers closely grouped together to form an efficient structured unit; the grouping or arrangement of flowers on a plant.
Invasive species
Invasive species; U.S.D.A., Executive Order 13112; an invasive species is defined as a species that is: 1) non-native (or alien) to the ecosystem under consideration and 2) whose introduction causes or is likely to cause economic or environmental harm or harm to human health.
Involucre
A structure surrounding or supporting, usually a head of flowers. In Asteraceae, it is the group of phyllaries (bracts) surrounding the inflorescence before opening, then supporting the cup-like receptacle on which the head of flowers sits. In Euphorbiaceae it is the cuplike structure that holds the nectar glands, nectar, and head of flowers, and sits above the bract-like cyathophyll structure.
Involute
Rolled inwards, for example when the margins of a leaf are rolled towards the adaxial (usually upper) surface; compare Revolute.
Irregular
Cannot be divided into two equal halves through any vertical plane. See also Asymmetrical, compare Zygomorphic, Actinomorphic, Regular.

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Kearney, Thomas Henry
Thomas Henry Kearney, (1874–1956), America Botanist and agronomist known for his work on cotton and date palm breeding, plant taxonomy and the flora of Arizona.
Keel
A prominent longitudinal ridge like the keel of a boat, e.g. the two lowest, more or less united petals of a pea flower in the Fabaceae.
Keystone Species
Keystone species (A species with a disproportionately large effect on its natural environment relative to its abundance. A keystone species is a plant or animal that plays a unique and crucial role in the way an ecosystem functions.

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Lanceolate
Lance-shaped, long, wider in the middle.
Laciniate
Of lobes; with ends irregularly divided into deeply divided, narrow, pointed segments; Of margins; deeply divided into pointed segments in an irregular manner.
Lanate
Covered with long woolly hairs.
Leaflet
The ultimate segments of a compound leaf.
Lectotype
A specimen chosen by a later researcher to serve as if it were the holotype (specimen designated in the original description). It is chosen from among the specimens available to the original publishing author (the isotypes, syntypes and/or paratypes) of a scientific name when the holotype was either lost or destroyed, or when no holotype was designated. Also see Holotype.
Legume
1. a fruit characteristic of the family Fabaceae, formed from one carpel and either dehiscent along both sides, or indehiscent.
2. a crop species in the family Fabaceae.
3. a plant belonging to the Fabaceae family).
Lenticel
Typically lens-shaped (lenticular) porous tissue in bark with large intercellular spaces that allows direct exchange of gases between the internal issues and atmosphere through the bark.
Lepidote
Covered with small scales.
Liana
A woody climbing plant, rooted in the ground (liane is also used). Also see Scandent and Vine.
Ligulate
1. Bearing a ligule.
2. Strap-shaped.
Ligulate Flower
A ligulate flower is a 5-lobed, strap-shaped, individual flower in the heads of other members. A ligule is the strap-shaped tongue of the corolla of either a ray flower or of a ligulate flower.
Ligule
1. Small membranous appendage on the top of the sheath of grass leaves.
2. A minute adaxial appendage near the base of a leaf, e.g. in Selaginella.
3. Extended, strap-like corolla of some daisy florets. See Ligulate.
Limestone
A sedimentary rock (CaCO3), composed mostly of skeletal fragments of marine organisms such as coral, forams and molluscs. Its major materials are the minerals calcite and aragonite, which are different crystal forms of calcium carbonate (CaCO3). see Calcareous Calcareous and Caliche Caliche.
Lindley, John
Lindley, John, (1799-1865), the son of a nurseryman, assisted in his father's garden as a boy while collecting wildflowers in nearby areas. John Lindley has a remarkable life and he was one of the most industrious British botanists, author, gardener, orchidologist, and the first professor of botany at London University.
Linear
Very narrow in relation to its length, with the sides mostly parallel.
Linneaus, Carl
Carl Linnaeus, (1707-1778), a Swedish botanist, zoologist and physician known as the “father of modern taxonomy” which is the modern system of classifying all organisms. Dr. Linnaeus has inspired and influenced many generations of biologists.
Loam soil
Loam soil (loam soil is the only soil that is not predominantly sand, silt, or clay; they generally contain more nutrients, moisture, and humus than sandy soils; they have better drainage and infiltration of water and air than silt and clay-rich soils, and are easier to till than clay soils. The different types of loam soils each have slightly different characteristics, with some draining liquids more efficiently than others. Loam soil is suitable for growing most plant varieties.
Lobe
Part of a leaf (or other organ), often rounded, formed by incisions to about halfway to the midrib.
Lobulate
With small lobes or shallowly lobed.
Loment or Lomentum
Loment or lomentum, a pod-like indehiscent legume fruit that develops constrictions between the segments and at maturity breaks into one-seeded segments.
Loomis, Harold Frederick
Harold Frederick Loomis (1896-1976) was born in Farmington, New York and was a botanist and horticulturist by profession. He was also an authority on the millipedes of the West Indies and Central America. Mr. Loomis joined the U.S. Department of Agriculture in 1914 and studied diseases of crop plants.
Lyrate
Lyre-shaped; deeply lobed, with a large terminal lobe and smaller lateral ones.

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Madrean pine-oak woodlands
The Madrean pine–oak woodlands are an ecoregion of the Tropical and subtropical coniferous forests biome, located in North America. They are subtropical woodlands found in the mountains of Mexico and the southwestern United States.
Malodorous
Having a bad odor.
Marcescent
Marcescent refers to the retention of dead and dry elements that normally are shed on a living plant. A marcescent plant is therefore a plant that keeps some organs, most often leaves or flowers, after they die.
Margin
The edge, as in the edge of a leaf blade.
Mericarp
One segment of a fruit (a schizocarp) that splits at maturity into units derived from the individual carpels, or a carpel, usually 1-seeded, released by the break-up at maturity of a fruit formed from 2 or more joined carpels. (see Schizocarp).
Mesa
A mesa is an isolated, flat-topped elevation, ridge or hill, which is bounded from all sides by steep escarpments and stands distinctly above a surrounding plain.
Midrib
The central, and usually most prominent, vein of a leaf or leaf-like organ; see Midvein.
Midvein
see Midrib.
Monocarpic
Flowering and setting seed only once before dying.
Monoecious
Having the stamens and the pistils in separate flowers on the same plant; compare Dioecious.
Monotypic
Containing only one taxon of the next lower rank, e.g. a family with only one genus, or a genus that includes only a single species.

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Native
Naturally occurring in an area, but not necessarily confined to it; see Endemic.
Native bees
North American Natives Bees occur naturally and evolved with and are important to native flowering plants. In North America, Native Bees are found wherever flowers bloom. Honeybees are not native to North America and compete with Native bees - see Honeybees.
Naturalized
Describing a plant, introduced from another region, that grows and reproduces readily in competition with the natural flora.
Nectar
A (usually sweet) fluid produced by the flowers of many plants, collected by bees and other insects.
Nectary
(adjective nectariferous) a specialized gland that secretes nectar.
Nocturnal
Botany: Opening at night; used of flowers.
Node
The part of a stem where leaves or branches arise.
Nut
A hard, dry, indehiscent fruit, containing only one seed.
Nutlet
Nutlet (A small nut, one of the lobes or sections of the mature ovary of some members of the Boraginaceae, Verbenaceae, and Lamiaceae.
Nuttall, Thomas
Thomas Nuttall, (1786-1859), was an English botanist and zoologist who lived and worked in America from 1808 until 1841.

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Obconic
Of a fruit, hypanthium, pistil or calyx structure; an inverted cone shape, attached at apex.
Obcordate
Of a leaf blade; Broad and notched at the tip; heart-shaped but attached at the pointed end.
Oblanceolate
Leaf shape; top wider than bottom.
Oblong
Length a few times greater than width, with sides almost parallel and ends rounded.
Obovate
Of a leaf, a 2-dimensional shape of which the length is about 1.5 times the width, and widest above the center.
Obovoid
Botany; Egg-shaped and solid, with the narrow end at the base: an obovoid fruit.
Obtuse
Blunt or rounded at the tip or apex; converging edges making an angle of more than 90°; compare Acute. See Leaf shape.
Ochrea
(ocrea, ochrea) A sheath, formed from two stipules, encircling the node in Polygonaceae.
Opposite
Leaves or flowers borne at the same level but on opposite sides of the axis; or (as verb) when something occurs on the same radius as something else, for example anthers opposite sepals; compare Alternate.
Orbicular
Flat and more or less circular.
Oval
see Elliptical
Ovate
Shaped like a section through the long-axis of an egg and attached by the wider end.
Ovoid
Egg-shaped, with wider portion at base; 3-dimensional object, ovate in all sections through long-axis.

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Palmate
1. leaf with veins radiating out from a central point (usually at the top of a petiole), resembling spread out fingers pointing away from the palm.
2. A compound palmate leaf has leaflets that radiate from a central point (usually at the top of a petiole).
Palmatifid
Deeply divided into several lobes arising from more or less the same level.
Palmatisect
Intermediate between palmate and palmatifid, i.e. the segments are not fully separated at the base; often more or less digitate.
Panicle
(adjective paniculate) a compound raceme; an indeterminate inflorescence in which the flowers are borne on branches of the main axis or on further branches of these.
Papilla
(plural papillae, adjective papillose, papillate) a small, elongated protuberance on the surface of an organ, usually an extension of one epidermal cell.
Pantropical
In biogeography, a pantropical ("across the tropics") distribution is one which covers tropical regions of all continents. The genera Acacia is one example.
Pappus
pl. pappi In daisy florets, a tuft or ring of feather-like hairs, scales or bristles, borne above the ovary and outside the corolla and attached to the seeds, (representing the missing sepals/calyx); a tuft of hairs on a fruit; pappi aid in dispersal by wind. the puff-ball on a dandelion are the pappi.
Paripinnate
Having an even number of leaflets (or pinnae), that is terminated by a pair of pinnae as opposed to a single pinna; compare Imparipinnate.
Parry, Charles C.
Charles C. Parry, (1823-1890), an English-born American botanist and botanical collector with the Pacific Railway Survey who visited the Southwestern mountains and deserts many times and is remembered in the names of more than a score of southwestern native plants. Dr. Parry studied botany under John Torrey, Asa Gray and George Engelmann.
Pedicel
A pedicel is a stem that attaches single flowers to the inflorescence. It is the branches or stalks that hold each flower in an inflorescence that contains more than one flower. The stem or branch from the main stem of the inflorescence that holds a group of pedicels is called a peduncle.
Peduncle
A stalk supporting an inflorescence, which is the part of the shoot of seed plants where flowers are formed.
Pellucid
Transmitting light; for example, said of tiny gland dots in the leaves of e.g. Myrtaceae and Rutaceae that are visible when held in front of a light.
Pendulous
Hanging loosely or freely, suspended so as to swing freely, to sway.
Pepo
A type of berry formed from an inferior ovary and containing many seeds, usually large with a tough outer skin, for instance, pumpkin, cucumber.
Perennial
A plant whose life span extends over several years.
Perfect
A "perfect" flower has both stamens and carpels, and may be described as bisexual; See Bisexual.
Perfoliate
With its base wrapped around the stem (so that the stem appears to pass through it), e.g. of leaves and bracts.
Persistent
Remaining attached to the plant beyond the usual time of falling, for instance sepals not falling after flowering, flower parts remaining through maturity of fruit; compare Deciduous, Caducous.
Petal
In a flower, one of the segments or divisions of the inner whorl of non-fertile parts surrounding the fertile organs, usually soft and conspicuously coloured; compare; Sepal.
Petaloid
Like a petal; soft in texture and coloured conspicuously.
Petiolate
Subtended by a petiole.
Petiole
The stalk of a leaf.
Petiolule
The stalk of a leaflet.
Perianth
Parts of the flower; collective term for the petals (corolla) and sepals (calyx), particularly when both are very similar in appearance; compare Tepal.
Phyllary (plural phyllaries)
An individual bract within an involucre or involucel.
Pilose
Covered with soft, weak, thin and clearly separated hairs, which are usually defined as long and sometimes ascending.
Pinna
(Plural pinnae) a primary segment of a compound leaf.
Pinnate
A compound leaf with leaflets arranged on each side of a common petiole or axis; also applied to how the lateral veins are arranged in relation to the main vein. See pinnately.
Pinnate, Pinnately
In a pinnate fashion (comparative more pinnately, superlative most pinnately)
Pinnately lobed
A simple leaf with rounded or pointed lobes on each side of the midrib or central and most prominent vein of a leaf or leaf-like organ.
Pinnatifid
Having lobes with incisions that extend less than half-way toward the midrib. (Wiki usage notes, deeper incisions are pinnatipartite. Incisions reaching nearly to the midrib are pinnatisect.)
Pinnatipartite
Having lobes with incisions that extend more than half-way, or up to the midrib.
Pinnatisect
Having lobes with incisions reaching nearly to the midrib are pinnatisect. (Wiki usage notes, less deep incisions are pinnatifid.)
Pinnule
Ultimate free division (or leaflet) of a compound leaf, or a pinnate subdivision of a multipinnate leaf.
Pistil
1. A single carpel when the carpels are free.
2. A group of carpels when the carpels are united by the fusion of their walls.
Pistillate
(of a plant or flower) having pistils but no stamens.
Plumose
Like a feather; with fine hairs branching from a main axis.
Pod
1. a legume, the fruit of a leguminous plant, a dry fruit of a single carpel, splitting along two sutures.
2. siliqua and silicula, the fruit of Brassicaceae, a dry fruit composed of two carpels separated by a partition.
Pollen
Powdery mass shed from anthers of flowering plants, (angiosperms), microsporangia, seed-bearing plants, (gymnosperms); the microspores of seed plants; pollen-grains.
Pollination
The transfer of pollen from the male organ (anther) to the receptive region of a female organ (stigma).
Pome
A fruit that has developed partly from the ovary wall but mostly from the hypanthium, e.g., apple.
Prickle
(adjective: prickly) hard, pointed outgrowth from the surface of a plant (involving several layers of cells but not containing a vein); sharp outgrowth from the bark, detachable without tearing wood; cf. thorn.
Procumbent
Spreading along the ground but not rooting at the nodes: not as close to ground as Prostrate
Prostrate
Lying flat on the ground. See Procumbent
Proximal
Near the point of origin or attachment. See Distal
Pseudanthium
A particular form of inflorescence occurring in the Asteraceae and Euphorbiaceae, in which multiple flowers are grouped together to form a flower-like structure, commonly called a head or capitulum.
Puberulous (puberulent)
Covered with minute soft erect hairs.
Pubescent
Downy; covered with short, soft, erect hairs.

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Raceme
An unbranched flowering stem (inflorescence), continuously growing with flowers containing short stems (pediciles) along its axis.
Rachis
(plural rachises; rachides) the axis of an inflorescence or a pinnate leaf; for example ferns; secondary rachis is the axis of a pinna in a bipinnate leaf distal to and including the lowermost pedicel attachment.
Radial
With structures radiating from a central point as spokes on a wheel, for example, the lateral spines of a cactus.
Radiate
Of daisies, of a capitulum, with ray florets surrounding disc florets.
Radical
Springing from the root; clustered at base of stem.
Rafinesque-Schmaltz Constantine, Samuel
Constantine Samuel Rafinesque-Schmaltz, (1783–1840), was a 19th-century person of wide-ranging knowledge and learning. He was self-educated in France and traveled to the United States, settling in Ohio in 1815, where he made notable contributions to botany and zoology. By 1818, he had collected and named more than 250 new species of plants and animals. Rafinesque published 6,700 binomial names of plants, many of which have priority over more familiar names. Some of the animals named by Rafinesque include the Mule Deer, Odocoileus hemionus, the Black-tailed Prairie Dog, Cynomys ludovicianus and the White-footed Mouse, Peromyscus leucopus. Although he was self taught and excelled in various fields of knowledge as a zoologist, botanist and writer, Rafinesque was thought to be eccentric and an erratic genius by many of his peers. In fact, during his lifetime, he was an outcast in the American scientific community. However, according to historian George Daniels, despite all his faults, “he made enormous contributions to the natural history phase of American science with the establishment of 34 genera and 24 species of American fishes.” He was also a brilliant teacher at Transylvania University. In 1841, Thomas Nuttall named a new genus Rafinesquia after him as he felt indebted to the naturalist, who had inspired his work and given Nuttall's Flora a positive review. The genus now contains two species, Rafinesquia californica California and Rafinesquia neomexicana.
Ray
1. Zygomorphic (ligulate) flowers in a radiate flowerhead, that is, ray-florets/flowers, for example Asteraceae.
2. Each of the branches of an umbel.
Receptacle
The axis of a flower, in other words, floral axis; torus; for example in Asteraceae, the floral base or common receptacle is the expanded summit of the peduncle on which the flowers are inserted.
Regular
See Actinomorphic.
Reniform
Kidney-shaped.
Resinous
(Resin) A sticky, often yellowish substance secreted by a plant.
Retrorse
(adverb retrorsely) Bent backwards or downwards. See also Antrorse.
Revolute
Rolled under (downwards or backwards), for example when the edges of leaves are rolled under towards the midrib; compare Involute.
Rhizomatous
(adj. Creeping rootstock; creeping stems;) A plant whose above ground stem originates from a rhizome. The stems grows horizontally under or along the ground and often sends out roots and shoots. New plants develop from the shoots.
Rhizome
A perennial underground stem usually growing horizontally. See also Stolon.
Rhombic
Like a rhombus: an oblique figure with four equal sides; compare trapeziform, trullate.
Rhomboid
A four-sided figure with opposite sides parallel but with adjacent sides an unequal length (like an oblique rectangle); See also Rhombic
Riparian
A riparian area is the interface between land and a river or stream.
Rose hip
Rose hip, rose haw or rose hep, is the fruit of the rose plant, usually red-to-orange, but ranges from dark purple to black in some species.
Rosette
A rosette is a circular arrangement of leaves, with all the leaves at a similar height. Though rosettes usually sit near the soil, their structure is an example of a modified stem.
Rotate
Circular and flattened; for example a corolla with a very short tube and spreading lobes (for instance some Solanaceae))
Ruderal
A plant that colonises or occupies disturbed waste ground. Ruderal species typically dominate the disturbed area for a few years, gradually losing the competition to other native species. The word ruderal comes from the Latin rudus, meaning rubble.
Runcinate
Sharply pinnatifid or cleft, the segments directed downward.

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Sagittate
Leaf description, shaped like the head of an arrow; narrow and pointed but gradually enlarged at base into two straight lobes directed downwards; may refer only to the base of a leaf with such lobe; compare Hastate.
Saline soil
Soils containing high levels of salts from natural conditions, or from agricultural practices, so as to negatively impact successful plant growth.
Salverform
Trumpet-shaped; with a long, slender tube and a flat, abruptly expanded limb; compare Funnelform.
Samara
A dry, indehiscent fruit with its wall expanded into a wing, e.g. Maple trees (Acer).
Scabrid (scabrous)
Rough to the touch with short hard emergences or hairs.
Scale
1. a reduced or rudimentary leaf, for example around a dormant bud.
2. a flattened epidermal outgrowth, such as those commonly found on the leaves and rhizomes of ferns.
Scandent
Climbing, by whatever means. Also see Vine and Liana.
Scape
(adjective scapose) A stem-like flowering stalk of a plant with radical leaves.
Scapose
Having the floral axis more or less erect with a few leaves or devoid of leaves; consisting of a scape.
Scarious
Of plant parts or surfaces that may be stiff or scaly, dry membranous appearance, shriveled, they are often not green in color but yellowish, whitish or brownish.
Schizocarp
A dry fruit formed from more than one carpel but breaking apart into individual carpels (mericarp) when ripe.
Scorpioid
(Botany - of a cymose inflorescence) Resembling a scorpion's tail, as in a scorpioid cyme; of a cymose inflorescence, when it branches alternately on one side and then the other; compare Helicoid; Circinate.
Schott, Arthur Carl Victor
Arthur Carl Victor Schott, (1814-1875), was German-American naturalist, artist, topographical engineer, cartographer, botanist and geologist. In 1851, Schott worked as a member of William H. Emory's team in mapping the border separating Texas and the adjacent Mexican territory (Mexican Boundary Survey). Schott contributed more field data to the border maps than any other member of the team, and became one of the first surveyors of the Rio Grande.
Scurf
(adjective scurfy) Minute loose, membranous cales on the surface of some plant parts e.g. leaves.
Semiterete
Semiterete (or semi-terete), rounded on one side, but flat on the other; compare Terete.
Sepal
In a flower, one of the segments or divisions of the outer whorl of non-fertile parts surrounding the fertile organs, usually green; compare petal; compare Petal.
Sericeous
Silky with dense appressed fine, straight hairs.
Serrate
Toothed with asymmetrical teeth pointing forward; like the cutting edge of a saw.
Serrulate
Finely serrate.
Sessile
Without a stalk, e.g. of a stigma, when the style is absent or a leaf without a stalk.
Sheathing
Leafy rolled or tubular structure on the lower part of a leaf; clasping or enveloping the stem, most often on sedges or grasses.
Shrub
Perennial, multi-stemmed woody plant that is usually less than 4 to 5 meters (13 to 16 feet) in height. Shrubs typically have several stems arising from or near the ground, but may be taller than 5 meters or single-stemmed under certain environmental conditions. Applies to vascular plants only.
Shrubland
Scrubland, scrub, brush, or bush is a vegetation community dominated by shrubs, may also include grasses and herbs.
Silicle
A fruit (seed capsule) of 2 fused carpels with the length less than three times the width. When the length is greater than three times the width of the dried fruit it is referred to as a silique; compare Silique.
Silique
A fruit (seed capsule) of 2 fused carpels with the length being more than three times the width. When the length is less than three times the width of the dried fruit it is referred to as a silicle; compare Silicle.
Simple
Undivided, for instance a leaf not divided into leaflets (note, however, that a simple leaf may be entire, toothed or lobed) or an unbranched hair or inflorescence.
Sinuate
With deep, wave-like depressions along the margins, but more or less flat; compare undulate. compare Undulate.
Sinuous
Of a serpentine or wavy form: winding, marked by strong lithe movements. compare Sinuate, Undulate.
Solitary
Single, of flowers that grow one plant per year, one in each axil, or widely separated on the plant; not grouped in an inflorescence.
Spathe
(adj. spathaceous), a large bract ensheathing an inflorescence. Traditionally any broad flat blade.
Spathulate (spatulate)
Spoon-shaped; broad at the tip with a narrowed projection extending to the base.
Spike
(adjective spicate) an unbranched, indeterminate inflorescence in which the flowers are without stalks; cf. raceme.
Spine
(adjective spinose) a stiff, sharp structure, formed by the modification of a plant organ that contains vascular tissue; e.g. a lateral branch or a stipule; includes thorns.
Spinescent
Ending in a spine; modified to form a spine.
Spreading
Extending horizontally, for example branches; standing out at right angles to axis, for example leaves or hairs.
Stalk
The supporting structure of an organ, usually narrower in diameter than the organ.
Stamen
(adjective staminate) Male organ of a flower, consisting (usually) of a stalk (Filament) and a pollen-bearing portion (Anther).
Staminate
(of a plant or flower) having stamens but no pistils.
Stellate
Star-shaped, for example a type of hair.
Stigma
The pollen-receptive surface of a carpel or group of fused carpels, usually sticky; usually a point or small head at the summit of the style.
Stipitate
Stalked; borne on a stipe; of an ovary, borne on a gynophore.
Stipulate
Bearing stipules.
Stipule
Small appendage at the bases of leaves in many dicotyledons.
Stolon
Slender, prostrate or trailing stem, producing roots and sometimes erect shoots at its nodes. See also Rhizome.
Straggly
Growing or spreading out in an irregular, untidy or messy way.
Stramineous
Stramineous, Straw colored, pertaining to or made of straw.
Striate
Striped with parallel, longitudinal lines, ridges or furrows.
Strigose
(Strigillose, Strigulose; Diminutive of Strigose) Having stiff, straight, closely appressed hairs or bristles: strigose leaves.
Style
An elongated part of a carpel, or group of fused carpels, between the ovary and the stigma.
Subglobose
Inflated, but less than spherical. See also Globose.
Subshrub
Low-growing shrub usually under 0.5 m (1.5 feet) tall, never exceeding 1 meter (3 feet) tall at maturity. Applies to vascular plants only. A dwarf-shrub in the FGDC classification.
Subtend
To stand beneath or close to, as in a bract at the base of a flower.
Subulate
Very narrow, linear, and tapering gradually from the base to a fine point, awl-shaped.
Suffrutescent
Comparative more suffrutescent, superlative most suffrutescent. Slightly woody or shrubby at the base. Subshrub or undershrub.
Suffrutex
A subshrub.
Sulcate
Furrowed or grooved.
Symmetrical
Capable of being divided into at least two equal, mirror-image halves (e.g. zygomorphic) or to have rotational symmetry (e.g. Regular, Actinomorphic). Contrast with Irregular, Asymmetrical.
Sympatric
With more or less similar or overlapping ranges of distribution.
Sympetalous
With united (connate or fused) petals.

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Talus Slopes
Rock fragments of any size or shape derived from and lying at the base of a cliff or very steep rock slope. The cumulated mass of such loose broken rock formed chiefly by falling, rolling, or sliding.
Tendril
A slender organ (modified e.g. from stem, leaf, leaflet or stipule) used by climbing plants to cling to an object.
Tepal
Part of a flower or perianth segment, either sepal or petal; usually used when the parts of the perianth are difficult to distinguish, e.g. the petals (caylx) and sepals (corolla) share the same color, or the petals are absent and the sepals are colorful.
Terete
Circular in cross-section; more or less cylindrical without grooves or ridges; compare Semiterete.
Terminal
Situated at the tip or apex.
Ternate
In groups of three; of leaves, arranged in whorls of three; of a single leaf, with the leaflets arranged in groups of three.
Thorn
A sharp, stiff point, usually a modified stem, that cannot be detached without tearing the subtending tissue; a spine; cf. prickle.
Thurber, George G.
George G. Thurber, (1821-1890), was called the most accomplished horticulturist in America and botanist and quartermaster of the United States and Mexican Boundary Survey, 1850-1854. He was also an American pharmacist, self-taught botanist and avid plant collector.
Thyrse
A branched inflorescence in which the main axis is indeterminate (racemose) and the lateral branches determinate; see Cyme.
Tomentose
Tomentose (Leaf or other surfaces covered in dense, soft, often matted short hairs, sometimes woolly.
Torrey, John
John Torrey, (1796-1873), a professor of chemistry and one of the giants of North American botany who described hundreds of plants brought or sent back by such explorers as John C. Frement, William Emory, Charles Wilkes, Joseph Nicollet, Howard Stansbury and Charles Pickering.
Tree
Perennial, woody plant with a single stem (trunk), normally greater than 4 to 5 meters (13 to 16 feet) in height; under certain environmental conditions, some tree species may develop a multi-stemmed or short growth form (less than 4 meters or 13 feet in height). Applies to vascular plants only.
Trichomes
In non-filamentous plants, any hair-like outgrowth from epidermis, e.g. a hair or bristle; sometimes restricted to unbranched epidermal outgrowths.
Trifoliolate or Trifoliate
A compound leaf of three leaflets, for example a clover leaf.
Truncate
Cut off squarely; with an abruptly transverse end.
Tubercle
A small wart-like outgrowth.
Tunicate
Having successive, close-fitting concentric coats, as in an onion bulb.
Turbinate
Shaped like a spinning top or beetroot.
Type
The type of a genus name is a specimen which is also the type of a species name. The species name that has that type can also be referred to as the type of the genus name.

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Umbel
(adjective umbellate) A racemose inflorescence in which all the individual flower stalks arise in a cluster at the top of the peduncle and are of about equal length; in a simple umbel, each stalk is unbranched and bears only one flower; a cymose umbel is an apparent umbel but its flowers open centrifugally.
Undulate
Wavy and not flat; compare Sinuate.
Unisexual
Unisexual (Of one sex; bearing only male or only female reproductive organs, dioecious, dioicous. See Sexual reproduction in plants.
Unispecific
Of one species; monospecific; such as the former Cuscutaceae Family containing the single genus Cuscuta.
Urceolate
Urn-shaped.
Utricle
A small bladder; a membranous bladder-like sac enclosing an ovary or fruit; in sedges a fruit in which the pericarp is larger than, and loosely encloses, the seed.

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Variegated
Irregularly marked with blotches or patches of another color.
Velutinous
Velvety texture due to minute moderately firm hairs or scales of various lengths.
Velvety
Densely covered with fine, short, soft, erect hairs.
Venation
The arrangement of veins in a leaf.
Villous
Abounding in or covered with long, soft, straight hairs; shaggy with soft hairs.
Vine
A plant that climbs by means of trailing, twining stem or runner. Also see Scandent and Liana.
Viscid
Sticky; coated with a thick, syrupy secretion.

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Whorl
A ring of organs borne at the same level on an axis, for example leaves, bracts or floral parts.
Wing
One of the two lateral petals of a flower of subfamily Faboideae of family Fabaceae, located between the adaxial standard (banner) petal and the two abaxial keel petals.
Wislizenus, Frederick, A.
Frederick Adolf Wislizenus, (1810-1889), Army surgeon, explorer, botanist and plant collector of German birth who travelled extensively in the southwestern United States.
Wright, Charles
Charles Wright, (1811-1885), an American botanical collector that collected plants and sending specimens to Professor Asa Gray at Harvard, eventually becoming one of his most trusted collectors. In 1851, with Gray’s help, Mr. Wright became part of the Mexican Boundary Survey, and helped collect many of the 2,600 species that were sent back to Professor John Torrey for description and identification. His name was honored by George Engelman who gave it to a cactus, Opuntia wrightii.

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Xeromorph
Xeromorph (A plant with structural features (e.g. hard or succulent leaves) or functional adaptations that prevent water loss by evaporation; usually associated with arid habitats, but not necessarily drought-tolerant; Also see Xerophyte.
Xerophyte
A plant generally living in a dry habitat, typically showing xeromorphic or succulent adaptation; a plant able to tolerate long periods of drought; compare Halophyte.

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Zygomorphic
Bilaterally symmetrical; symmetrical about one vertical plane only; applies to flowers in which the perianth segments within each whorl vary in size and shape; compare Actinomorphic, Irregular.
References:
Wikipedia contributors, 'Glossary of botanical terms', Wikipedia, The Free Encyclopedia, 20 April 2015, 19:23 UTC,
http://en.wikipedia.org/w/index.php?title=Glossary_of_botanical_terms&oldid=657370054
https://en.wikipedia.org/wiki/ - Definitions