Glossary of Taxonomic Terms

Commonly Employed in the Identification of Woody Plant

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  Z

A

Achene – A small, dry, one-seeded, indehiscent fruit (one that doesn’t split open), e.g. fruit of members of the Asteraceae.

Acuminate – The shape of a tip (apex) or base of a leaf or perianth segment where the part tapers gradually and often in a concave manner.

Acute – Evenly narrowed into a point at an angle of less than 90 degrees.

Adnate – Grown together or fused, used only to describe unlike parts. For comparison, connate.

Adventitious – Arising from an unusual or irregular position, such as roots along a stem.

Aggregate flower – Heaped or crowded into a dense cluster.

Aggregate fruit – One formed by the fusion of pistils that were distinct in a single flower (e.g. Rubus, raspberry, blackberry).

Alternate – Arrangement of leaves or parts one at a node, as leaves on a stem. For comparison, opposite or whorled.

Ament – A catkin, or scaly spike.

Angiosperm – Having seeds borne within a pericarp. For comparison, gymnosperm.

Anther – Pollen-bearing part of a stamen, borne at the top of a filament.

Apetalous – Without petals, e.g. flowers of grasses.

Apex – The tip or terminal end.

Apical – Describes the apex or tip.

Apiculate – Ending abruptly in a short pointed tip which is not stiff.

Appressed – Pressed close to or lying flat against, as leaves on a stem or hairs on a leaf.

Auriculate – Having ear-like appendages, as the projections of some leaf and petal bases.

Axil – The angle between a stem and an attached leaf.

Axis – The main stem.

Axillary Borne or carried in the axil.

B

Berry – A fleshy, indehiscent, pulpy, multi-seeded fruit resulting from a single pistil, e.g. tomato.

Bipinnate – Twice pinnate, the primary leaflets being again divided into secondary leaflets.

Bloom – A waxy coating sometimes found on a stem, leaf, flower or fruit surface, usually of a grayish cast and easily removed.

Boss – A raised, usually rounded protuberance.

Bract – A much-reduced leaf, often scale-like and usually associated with a flower or inflorescence

Broad-elliptic – Wider than elliptic.

Broad-ovate – Wider than ovate.

Bud scale – A modified leaf or stipule (there may be one, a few, or many) protecting the tissue of the bud.

Bud scale scar – The mark left by the sloughing off of the bud scale.

Bullate – Having a puckered or blistered appearance.

Bundle scar – Seen in the leaf scar, the broken end of the woody vascular strands that connected the leaf to the stem.

C

Caducous – Falling off very early as compared to similar structures in other plants.

Calyx – The outer whorl of perianth, composed of the sepals, usually green in color and smaller than the inner set.

Capsule – A dry dehiscent fruit produced from a compound pistil, e.g. fruit of a tobacco, Catalpa, Dianthus.

Catkin – A spike-like inflorescence, comprised of scaly bracts subtending unisexual flowers, often somewhat flexuous and pendulous, e.g. inflorescence of Salix, willow and Populus, poplar.

Chambered – Pith divided into hollow, horizontally arranged, separated by cross partitions.

Cilia – Marginal hairs.

Ciliate – Marginally fringed with hairs, often minutely so, and then termed “ciliolate.”

Clone – A group of plants, usually derived vegetatively, from one parent plant, identical to each other and to the parent.

Coarse texture – Consisting of large or rough parts.

Compound leaf – A leaf of two or more leaflets.

Cone – A coniferous reproductive structure, having a number of woody, leathery, or fleshy scales, each bearing one or more seeds, and attached to a central axis.

Conical – Cone-shaped, as the young form of many spruces.

Coniferous – Cone bearing.

Connate – Describing similar structures united or fused together.

Cordate – Heart-shaped, with a sinus and rounded lobes.

Corolla – Inner whorl of the perianth, between the calyx and the stamens; a collective term for the petals of a flower.

Corymb – A more or less flat–topped indeterminate inflorescence whose outer flowers open first, e.g. Viburnum, some verbenas.

Cotyledon – The primary leaves of the embryo, present in the seed. One of the first leaves to appear after germination (there may be more than 1).

Crenate – Rounded teeth on margin, e.g. leaves of some coleus.

Crenulate – Having very small, rounded teeth.

Cultivar – A form of a plant derived from cultivation.  Cultivar names are indicated by single quotation marks.

Cuneate – Wedge-shaped with essentially straight sides, the acute angle at the base and the structure attached at the narrow end.

Cyme – A more or less flat-topped determinate inflorescence whose outer flowers open last, e.g. Sambucus, elderberry.

D

Dehiscent – Splitting open. The term is commonly applied to anthers or seed pods.

Decompound – Having more than one compound.

Dentate – Having sharp, marginal teeth whose apices are perpendicular to the margin.

Determinate – Describes an inflorescence in which the terminal flower blooms first, thereby halting further elongation of the flowering stem. For comparison, indeterminate.

DicotAngiosperm plant having two cotyledons.

Dimorphic – Having two forms.

Dioecious – Having unisexual flowers, each sex confined to a separate plant, said of species.

Double serrate – Serrations bearing minute teeth on margins.

Drupe – A fleshy, indehiscent fruit whose seed is enclosed in a stony endocarp, e.g. date, cherry.

E

Ellipsoid – Three-dimensional shape of ellipse, football shaped.

Elliptic-oblong – A shape between the two forms.

Elliptical – Having the outline of an ellipse, broadest at middle and narrower at each end.

Emarginate – With a shallow notch at the apex.

Endocarp – The inner layer of the pericarp. For comparison, exocarp, mesocarp.

Entire – Having a margin without teeth or lobes.

Even-pinnate – Results in a lack of the terminal leaflet, since each one is paired.

Exocarp – Outer layer of the pericarp of a fruit. For comparison, endocarp, mesocarp.

Exfoliate – To peel off in shreds or thin layers, as bark from a tree.

F

Falcate – Sickle-shaped.

Fascicle – A close cluster or bundle, e.g. leaves of white pine.

Filiform – Long and very slender; thread-like.

Fine texture – Consisting of small, rather delicate parts.

Flaking – Shreddy, with shorter fragments.

Follicle – A dry dehiscent fruit opening only along one suture and the product of a single carpel (simple ovary), e.g. Paeonia, peony, Aquilegia, columbine, Asclepia, milkweed.

Fruit – Technically a ripened ovary with its adnate parts, the seed-containing unit characteristic of all Angiosperms.

G

Genus – A group of species possessing fundamental traits in common but differing in other lesser characteristics; a taxonomic grouping of similar species (pl. genera); similar genera are grouped into families.

Glabrous – Not hairy. Note: a glabrous surface need not be smooth, for it may be bullate or rugose.

Glandular – Bearing glands.

Glaucescent – Slightly glaucous.

Glaucous – Covered with a waxy bloom or whitish material that rubs off readily, e.g. the bloom on many sorts of grape.

Globose – Having a round or spherical shape.

Grooved – Marked with long narrow furrows or channels.

Gymnosperm – Plant with the ovules borne naked or unprotected, the conifers or cone-bearing plants and their allies. For comparison, angiosperm.

H

Hairy – Pubescent with long hairs.

Hispid – With stiff or bristly hairs.

Hirsute – Pubescent with coarse or stiff hairs.

I

Imbricated – Overlapping, as shingles on a roof.

Imperfect – A flower that lacks either stamens or pistils.

Incised – Cut by sharp and irregular incisions more or less deeply, but intermediate between toothed and lobed.

Indehiscent – Not opening regularly, as a capsule or anther.

Indeterminate – Describes an inflorescence in which the outer or lower flowers bloom first, allowing an indefinite elongation of the flowering stem. For comparison, determinate.

Indumentum – With a generally heavy covering of hair; a general term without precise connotation.

Inferior – Beneath, below; said of an ovary when situated below the apparent point of attachment of stamens and perianth.

Inflorescence – The arrangement of flowers on the axis.

Involucre – One or more whorls or series of small leaves or bracts that are close underneath a flower or inflorescence.

J

Juvenile – An early phase of plant growth, usually characterized by non-flowering, vigorous increase in size, and often thorniness.

L

Lanceolate – Much longer than wide, broadest below the middle and tapering to the apex.

Lateral bud – A bud borne in the axil of a previous season’s leaf.

Latex – Milky sap.

Leaf scar – The mark remaining after the leaf falls off a twig.

Lenticel – A small corky spot on young bark made of loosely packed cells, providing gaseous exchange between the inner tissues and the atmosphere.

Linear – Long and very narrow, as in blades of grass.

Lobe – A projecting part or segment of an organ as in a lobed ovary or stigma; usually a division of a leaf, calyx, or petals cut to about the middle (i.e., midway between margin and midrib).

M

Margin – The edge of a leaf.

Marginal – Pertaining to the margin.

Mature – A later phase of growth characterized by flowering, fruiting, and a reduced rate of size increase.

Mesocarp – Middle layer of the pericarp of a fruit. For comparison, endocarp, exocarp.

Milky sap – Whitish in color, often thicker than water.

Monoecious – A species with unisexual flowers, having both male and female flowers on the same plant, e.g. corn.

Mucro – A short, sharp, abrupt tip.

Mucronate – Abruptly terminated by a mucro.

Multiple buds – A terminal or lateral bud crowded by many accessory buds.

Multiple fruit – A fruit formed when the pistils of separate flowers form a single structure with a common axis (e.g. Morus, mulberry)

N

Naked bud – One without scales.

Native – Inherent and original to an area; pre European influence in the United States..

Needle – The slender leaf of many conifers.

Nerve – A slender rib or vein, especially unbranched.

Node – A joint on a stem, represented by point of origin of a leaf or bud; sometimes represented by a swollen or constricted ring, or by a distinct leaf scar.

Nut – A dry, indehiscent, 1-celled, 1-seeded fruit having a hard and bony mesocarp; the outermost endocarp may be fibrous or slightly fleshy.

O

Obscordate – The apex being cordate.

Oblanceolate – Inversely lanceolate.

Oblique – Lop-sided, as one side of a leaf base larger, wider or more rounded than the other.

Oblong – Longer than broad; rectangular; the sides nearly parallel.

Oblong-lanceolate – a shape in between the two forms.

Oblong-obovate – A shape in between the two forms.

Obovate – Inversely ovate, broadest above the middle.

Obovoid – Three dimensional shape of obovate, pear shaped.

Obtuse – Rounded, approaching the semi-circular.

Opposite – Describing leaves that are situated in pairs at a node along an axis.

Orbiculate – Circular or disk-shaped, e.g. leaf of common nasturtium.

Oval – Twice as long as broad, widest at the middle, both ends rounded.

Ovate – Egg-shaped in outline, broadest below the middle.

Ovate-oblong – A combination of the two forms.

P

Palmate – Digitate, radiating, fan-like from a common point, as in leaflets of a palmately compound leaf or veins or palmately-veined leaf.

Panicle – An indeterminate inflorescence whose primary axis bears branches of pedicelled flowers (at least basally so); a branching raceme.

Pedicel – Stalk of a single flower in an inflorescence.

Peduncle – Stalk of a flower or inflorescence.

Peltate – Having the petiole attached inside the margin, such a leaf is typically shield-shaped.

Pendulous – More or less hanging or declined.

Perfect – Having both functional stamens and pistils (not imperfect); a unisexual flower.

Perianth – A collective term embracing both the corolla and the calyx.

Pericarp – A term used by some to designate a fruit; technically, the ovary wall.

Periderm – A protective layer of corky cells.

Petiole – Leaf-stalk of simple leaves.

Petiolule – Leaflet-stalk of compound leaves.

Pilose – Shaggy with soft hairs.

Pinna – The leaflet of a compound leaf; in ferns, the primary division attached to the main rachis; feather-like.

Pinnate – Compound, with leaflets or pinnae arranged feather-like on either side of a common axis or rachis.

Polygamous – Bearing unisexual and bisexual flowers on the same plant.

Pome – A type of fleshy, indehiscent fruit represented by the apple, pear and related genera, resulting from a compound ovary.

Prickle – An excrescence of bark that is small, weak, and spine-like.

Pseudo-terminal bud – Seemingly the terminal bud of a twig, but actually the upper-most lateral bud with its subtending leaf scar on one side and the scar of the terminal bud often visible on opposite side.

Pubescent – Covered with short soft hairs; a general term.

Pyramidal – Broadest at base, tapering apically; pyramid-shaped.

R

Raceme – A simple indeterminate inflorescence, having a single long axis, with pedicelled flowers.

Rachilla – A diminutive or secondary axis; a branch of a rachis; the minute axis bearing the individual florets in grass and sedge spikelets; the secondary axes of decompound fern fronds.

Rachis – Axis-bearing leaflets or the primary axis of an inflorescence; the axis bearing pinnae of a fern frond.

Ranked – Foliage is arranged in longitudinal planes around the stem.

Receptacle – A torus; the distal end of a flower-bearing axis, usually more or less enlarged, flattened, or cup-like on which some or all of the flower parts are borne, e.g. Asteraceae, Onagraceae.

Reflexed – Bent abruptly backward or downward.

Reniform – Kidney-shaped or rounded with a notch at the base.

Resin duct – A lengthwise or transverse canal carrying resins.

Resinous – Secreting a viscid exudate.

Reticulate – Like a net, the interstices closed.

Rhombic – With four nearly equal sides, but unequal angles, diamond shaped.

Rugose – Wrinkled, usually covered with wrinkles.

S

Samara – A dry indehiscent fruit bearing a wing (the wing may be limb-like or envelop the seed and be wafer-like), e.g. Acer, maple, Fraxinus, ash, Ptelea, hoptree.

Scar – The mark left from a former attachment.

Schizocarp – A dry dehiscent fruit that splits into two halves, e.g. Acer, maple.

Sepal – A single segment of a divided calyx.

Serrate – Saw-toothed, the teeth pointing forward.

Serrulate – Minutely serrate.

Sessile – Without a stalk.

Simple – Said of a leaf when not compound, of an inflorescence when unbranched.

Sinuate – With a strongly wavy margin.

Sinus – The space between two lobes, segments, or divisions; as of leaves or perianth parts.

Solitary – Borne singly, not paired or clustered.

Spatulate – Spoon-shaped.

Species – A natural group of plants composed of similar individuals which can produce similar offspring; usually including several minor variations.

Spike – A unbranched, elongated, simple, indeterminate inflorescence whose flowers are sessile; the flowers may be congested or remote.

Spikelet – (1) a secondary spike; (2) one part of a compound inflorescence which of itself is spicate; (3) the floral unit, or ultimate cluster, of a grass inflorescence comprised of flowers and their subtending bracts.

Spine – a sharp-pointed rigid structure, usually a highly modified stem.

Squarrose – With branches spreading and recurved at the ends.

Stalked bud – A bud whose outer scales are attached above the base of the bud axis.

Stamen – Male or pollen-bearing organ of a flower, composed of filaments and anthers.

Stellate – Star-like; with radiating branches or separate hairs aggregated in star-like clusters; often said of hairs that branched.

Stipel – A stipule of a leaflet.

Stipule – A basal appendage of a petiole, usually one at each side, often ear-like and sometimes caducous.

Striate – With fine longitudinal lines, channels or ridges.

Strigose – With sharp, stiff, straight and appressed hairs.

Strobilus – A cone.

Subtend – To occupy a position below and adjacent to.

Sympodial – Continuing growth by the development of an axillary bud and not the terminal bud, season after season.

T

Tendril – A modified stem or leaf, usually filiform, branched or simple, that twines about an object providing support.

Tepal – A segment of perianth not differentiated into calyx or corolla, e.g., tulip, magnolia.

Terminal – At the tip or distal end.

Ternate – Arranged or divided in threes.

Thorn – A modified twig which has tiny leaf scars and buds; can be single or branched.

Tomentose – Densely woolly, the hairs soft and matted.

Translucent – Transmitting light but diffuse enough to distort images.

Trifoliate – Three-leaved, e.g. Trillium.

Truncate – As if cut off at right angles to the primary axis; a term applicable to bases or apices.

U

Umbel – An indeterminate inflorescence, usually but not necessarily flat-topped with the pedicels and peduncles (termed rays) arising from a common point, resembling the stays of an umbrella.

Umbo – A conical projection arising from the surface.

Undulate – Wavy, as in a leaf margin.

Unisexual – Bearing either stamens or pistils but not both.

V

Valvate – (1) dehiscing by valves; (2) meeting at the edges without overlapping, as leaves or petals in the bud.

Variegated – Striped, margined, or mottled with a color other than green, where green is normal.

Variety – Subdivision of a species having a distinct though often inconspicuous difference, and breeding true to the difference. More generally also refers to clones.

Vascular bundle – A discrete group of conducting vessels.

Vascular bundle scar – A minute spot within the leaf scar where the vessels were positioned.

Velutinous – Clothed with velvety indumentum comprised of erect, straight, dense, moderately firm hairs.

W

Whorl – Arrangement of three or more structures arising from a single node.

Woolly – Having long, soft, more or less matted hairs; like wool.

X

× – indicates a hybrid.

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University of Delaware

University of Delaware Botanic GardensNewark, DE 19716Phone: 302 831-0153