This glossary is modified from those of Correll (1956), Lellinger (1986), and Diggs et al. (2006).

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A- A prefix meaning without or not.
ABAXIAL Located on the side away from axis; e.g., lower leaf surface; contrasting with adaxial.
ABORTIVE Imperfectly or incompletely developed; e.g., spores of hybrids such as Equisetum xferrissii.
-ACEAE Suffix denoting the rank of family in the taxonomic hierarchy.
ACROSCOPIC Located on the side facing or toward the leaf apex.
ACUMINATE Having a long, tapering point; longer tapering than acute.
ACUTE Forming a sharp angle of less than 90 degrees; less tapering than acuminate.
AD- A prefix meaning to or toward.
ADAXIAL Located on side towards axis; e.g., upper leaf surface; contrasting with abaxial.
ADNATE United or fused, when the fusion involves dissimilar structures.
ADPRESSED (= Appressed) Lying flat against a surface.
ADVENTITIOUS Referring to structures or organs that develop in an unusual position; e.g., buds or roots that develop out of their usual place; in pteridphytes all roots are adventitious since they arise from rhizomes, rather than from a primary root.
AERIAL Above ground level.
-ALES Suffix denoting the rank of order in the taxonomic hierarchy.
ALKALOID Any of a broad class (> 5,000 known alkaloids) of bitter, usually basic (alkaline), organic compounds that contain nitrogen and typically have a ring in their structure. They are often physiologically active in animals; many are poisonous; many affect the nervous system; there are a number of general types based on chemical structure; well-known examples of alkaloids include caffeine, cocaine, morphine, nicotine, theobromine, and strychnine.
ALLELOPATHY, ALLELOPATHIC Harmful or detrimental chemical effect by one species upon another; e.g., a plant producing phytotoxic compounds that inhibit the germination or growth of other plants.
ALLERGEN Substance capable of inducing an allergic response.
ALLERGENIC Causing an allergic response or an allergy to become manifest.
ALLERGY Hypersensitivity of the body cells to specific substances as antigens and allergens, resulting in various types of reactions (e.g., anaphylaxis, contact dermatitis, hay fever).
ALLOPOLYPLOID An organism with multiple sets of chromosomes derived from different parental species; e.g., allotetraploid.
ALTERNATE Bearing one leaf or other structure at a node; having only one attached at a given point; contrasting with opposite or whorled.
AMPHIBIOUS Capable of growing on land and in the water.
ANASTOMOSING Net-like; with veins connecting by cross-veins to form a network.
ANNUAL Plant or root system living only one growing season (year); completing the growth cycle within one year.
ANNULUS A group or ring of thick-walled cells, on the sporangia of some ferns, that are involved in opening the sporangia and allowing spore dehiscence.
ANGIOSPERM (= Flowering plant) Literally, “vessel seed”; a plant having its seeds enclosed in an ovary (= the proximal part of the carpel or “vessel”); a member of Division Magnoliophyta.
ANTHERIDIUM Male sexual organ borne on the gametophyte and producing male gametes.
APETURE An opening.
APEX (pl. APICES) The tip or summit.
APICAL At the tip or apex; relating to the apex.
APICULATE Having a small sharp point formed by blade or other tissue (e.g., of a leaf or cone) rather than by projection of a rib or vein; with an abrupt tip or projection; having an apiculum.
APICULUM A small sharp point; e.g., apiculum on cones of some Equisetum species.
APOGAMY A type of asexual reproduction that does not involve fertilization; the sporophyte is formed directly from the gametophyte without gamete production.
APOGAMOUS Forming a sporophyte without fertilization (the union of gametes).
APOMIXIS A collective term for reproduction, including vegetative propagation, that does not involve sexual processes; any form of asexual reproduction.
APPENDAGE Any attached structure that is supplementary or secondary.
APPENDICULATE With an appendage.
APPRESSED (= Adpressed) Lying flat against a surface.
AQUATIC Living in water.
ARCHEGONIUM Female sexual organ borne on the gametophyte and producing female gametes.
AREOLATE Divided into small angular spaces; marked with areolae.
AREOLE, AREOLA (pl. AREOLAE) Small space marked out on a surface, usually referring to the space bounded by small veins on the surface of a leaf; a vein-enclosed area.
ARTICULATE (a) Jointed; joined; (b) with a visible discontinuity or place of separation.
ARTICULATION A separation place; joint.
ASCENDING, ASCENDENT Rising at an oblique angle.
ASEXUAL Without sex; reproducing without sex.
ASYMMETRICAL Without symmetry.
ATROPURPUREOUS Dark purple; purple-black.
ATTENUATE Gradually tapering to a very slender tip, the taper more gradual than in acuminate.
ATYPICAL Not typical; deviating from the norm.
AURICLE Earlobe-like lobe or appendage; e.g., at the base of some leaves or other structures.
AURICULATE With an auricle.
AUTOPOLYPLOID An organism with multiple chromosome sets derived from a single parental species.
AWL-SHAPED (= Subulate) Tapering from the base to a slender or stiff point; narrow and sharp-pointed.
AWN Terminal slender bristle or hair-like extension or projection.
AXIL Angle between two organs; e.g., upper angle formed by a leaf and a stem.
AXIS (pl. AXES) (a) the central stem from which organs arise; (b) a portion of a plant from which a series of organs arises radially.


BASE The proximal portion of a structure, that part nearest to the point of attachment.
BASAL (a) Located at the base of a plant or of an organ; (b) the lowest branch on a phylogenetic tree.
BASISCOPIC Located on the side facing or directed toward the leaf base.
BASIONYM The original epithet assigned to a species (or other taxon) by its author.
BI-, BIS- Latin prefix signifying two, twice, or doubly.
BICOLORED Two-colored.
BILATERAL Arranged on two sides; two-sided.
BILATERALLY SYMMETRICAL With only one plane of symmetry; divisible into halves in one plane only.
BINOMIAL The combination of a generic name and a specific epithet given to each species.
BINOMIAL NOMENCLATURE System of nomenclature where each species has a two-part name composed of a generic name and a specific epithet.
BIOGEOGRAPHY Study of geographic distribution of plants and animals.
BIPINNATE (= Twice-pinnate or 2-pinnate) Descriptive of a leaf with leaflets pinnately arranged on lateral axes that are themselves pinnately arranged on the main axis; with the primary divisions (pinnae) themselves pinnate.
BLADE Flat, expanded portion, as the main part of a leaf or petal.
BLUNT Not pointed.
BOSS A protrusion or raised area.
BRANCH A shoot or secondary stem growing from the main stem.
BRANCHLET The ultimate division of a branch.
BRISTLE Stiff, strong but slender hair or trichome.
BRISTLY Bearing bristles.
BROAD (= Wide) Distance across a structure (equal to diameter if tubular); sometimes restricted to signify the width or diameter of three-dimensional structures.
BRYOPHYTA Group containing the mosses, liverworts, and hornworts, land plants that reproduce by spores but do not have vascular tissue. The Bryophyta is not treated in this flora.
BUD (a) undeveloped, much-condensed shoots, containing embryonic (meristematic or growing) tissue, usually covered by scales or bracts. Such buds are usually found at the tips of stems or in the axils of leaves; (b) in ferns, usually a lump of tissue that grows into a new fern plant.
BULB Underground structure composed of a short, disc-like stem and one or more buds surrounded by layers of thickened fleshy leaf bases or scales.
BULBLET Small globular, asexual propagule borne along the rachis or costa that is capable of forming a new plant.
BULBOUS, BULBOSE (a) Having bulbs or bulb-like structures; (b) swollen or nearly spherical.


CA. Latin, circa; abbreviation meaning about, around, approximately.
CALCAREOUS Containing an excess of available calcium, usually in the form of the compound calcium carbonate; containing limestone or chalk.
CALICHE A crust of calcium carbonate formed on stony soils in arid regions.
CAP specialized structure in Azolla attached to the megaspore, consisting of a collar (involved in attaching the floats), 3 (in TX species) floats, and a blue-green algal colony covered by remnants of the indusium.
CAPILLARY Hair-like; very slender.
CAPITATE (a) In heads, head-like, or head-shaped; aggregated into a dense or compact cluster; (b) referring to capitate hairs, like a pin-head on a stalk.
CARCINOGEN A substance potentially inducing cancer or malignancy.
CAUDATE Having a tail or tail-like appendage.
CAUDEX (pl. CAUDICES) Woody or wood-like stem base.
CELL One of the living units of which a plant is composed.
CHLOROPHYLL The light-capturing pigment giving the green color to plants. Because chlorophyll absorbs less green than other wavelengths of light (and thus reflects and transmits relatively more green), leaves appear green to the human eye.
CHROMOSOMES Thread-like “colored bodies” occurring in the nuclei of cells and containing the genetic material.
CILIATE With a marginal fringe of hairs similar to eye lashes.
CILIUM (pl. CILIA) Marginal hair or trichome.
CINNAMON In reference to color, indicating light reddish brown.
CIRCINATE Coiled, with the apex innermost; most ferns have circinate vernation in which young unexpanded leaves are tightly coiled, with appearance of a fiddlehead.
CLASS The unit, category, or rank in classification made up of one or more orders; ending in -ae or -opsida; sometimes divided into subclasses which in turn are made of orders.
CLADE A monophyletic lineage containing a common ancestor and all its descendants.
CLATHRATE Latticed or net-like in appearance; with a series of crossed members.
CLONE A group of individuals of the same genotype, usually propagated vegetatively.
CLUMP A single plant with two to many, more or less crowded stems arising from a branched rootstock or short rhizome.
CM Centimeter; 10 mm; 1/100 of a meter; ca. 2/5 of an inch.
COBWEBBY Cobweb-like, with entangled, slender, loose hairs; thinly pubescent with relatively long, usually appressed and interlaced hairs.
COLONIAL Forming colonies usually by means of underground rhizomes, stolons, etc. The term is commonly used to describe groups of plants with asexual reproduction.
COLONY A stand, group, or population of plants of one species, spreading vegetatively, or from seeds, or both.
COMPOUND (= Composite) Made up of several distinct parts.
COMPOUND LEAF A leaf/frond that is cut completely to the base or midrib into segments (= leaflets/pinnae) resembling miniature leaves; a leaf with two or more leaflets.
CONCAVE Hollow; with a depression on the surface.
CONCOLOR, CONCOLOROUS Of a uniform color.
CONDUPLICATE Folded together lengthwise.
CONE (= Strobilus) A usually globose or cylindrical structure involved in reproduction and composed of an axis with a spiral, usually dense aggregation of sporophylls, bracts, or scales (in pteridophytes these bearing spores, or in seed plants bearing pollen or seeds).
CONFLUENT Blending of one part into another.
CONGESTED Crowded together.
CONICAL, CONIC Cone-shaped.
CONIFEROUS Cone-bearing.
CONNATE United or fused, when the fusion involves two or more similar structures.
CONSERVATION CONCERN Concern that a plant might become extinct locally because it is either so rare or of such limited distribution.
CONSERVED (a) Term applied to a scientific name whose use, even though illegitimate according to nomenclatural rules, is allowed by the International Code of Botanical Nomenclature; e.g., many family names long in use, have been conserved to prevent confusion; (b) unchanged over long periods of evolutionary time.
CONSPECIFIC Of the same species.
CONSTRICTED Tightened or drawn together or narrowed.
CONTINUOUS Not interrupted; not articulated; not jointed.
CONTORTED Twisted or distorted.
CONTRACTED Narrowed or shortened; reduced in size.
CONTRARY In an opposite direction or at right angles to.
CONVERGENT Coming together or approaching.
CONVEX Rounded or bulged on the surface.
CORDATE, CORDIFORM (a) Heart-shaped; with a notch at the base and ovate in outline (the words apply specifically to flat surfaces and to solid shapes, respectively); (b) often referring only to the notched base of a structure; e.g., leaf base.
CORIACEOUS With texture like leather; tough; leathery.
CORM Bulb-like usually subterranean stem base, solid instead of with layers of modified leaves as in a true bulb.
CORMOUS Having a corm.
COSMOPOLITAN Occurring essentially worldwide.
COSTA (pl. COSTAE) Central axis, midvein, or midrib of a pinna.
COSTULE Midvein or midrib of a pinnule.
CREEPING Growing along the surface of the ground and emitting roots at intervals, usually from the nodes.
CRENATE Scalloped with rounded teeth; shallowly roundtoothed or with teeth obtuse.
CROSS-SECTION A slice cut across an object; e.g., a slice of bread.
CROZIER A young coiled leaf of some ferns.
CRYPTOGAM An old term for plants that reproduce without flowers or seeds, instead typically reproducing by spores; contrasting with phanerogam.
CULTIVAR A variety or race of a cultivated plant, generally chosen for a particular desirable trait; abbreviated cv.
CUNEATE, CUNEIFORM Wedge-shaped; triangular with tapering, straight-sided, narrow base.
CURVI- A prefix to denote curved or bent.
CUT A general term for any dissection of a leaf or petal deeper than a lobe.
CUTICLE The waxy, more or less waterproof coating secreted by the cells of the epidermis. The cuticle prevents water loss.
CYLINDRICAL, CYLINDRIC Elongate, circular in cross-section;having the form of a cylinder.


DC. De Candolle, name of a distinguished family of Swiss botanists; specifically Augustin Pyramus, who sponsored early botanical exploration in Texas by Berlandier, and named many Texas species; A. DC.: Alphonse, son of the preceding.
DECIDUOUS Falling away; not persistent over a long period of time.
DECOMPOUND More than once compound.
DECUMBENT Lying flat or reclining with terminal shoots or stem tips ascending.
DECURRENT Extending down the stem and united with it, as in the continuation of leaf bases down the stem as wings.
DEHISCE, DEHISCENT To open at maturity to discharge the contents; e.g.; sporangia releasing spores.
DEHISCENCE The process or act of opening.
DELTATE, DELTOID Shaped like an equilateral triangle, like the Greek letter delta (Δ).
DENTATE With sharp teeth not directed forward.
DENTICULATE Minutely dentate.
DEPRESSED Low as if flattened.
DESCENDING With a gradual downward tendency.
DI-, DIS- Greek prefix meaning two or double.
DICHOTOMOUS Forking regularly into two equal or nearly equal branches.
DIMORPHIC, DIMORPHISM Occurring in two forms.
DIPLOID Possessing two sets of chromosomes in each nucleus; twice the haploid number typical for gametes.
DISCOID Shaped like a disc.
DISCRETE Separate.
DISJUNCT (a) Outside the main range of a species; (b) being divided into separate groups; disconnected.
DISSECTED Divided into numerous narrow or slender segments, the divisions usually deeper than lobes.
DISTAL Located at or toward the apex of a plant or organ; the terminal portion; the end opposite the attachment; contrasting with proximal.
DISTINCT (= Free) Separate, not united or fused.
DISTURBED Referring to a habitat that has been altered or modified but not completely destroyed.
DIVERGENT Spreading, drawing apart from a common point.
DIVIDED (a) Cut 3/4–completely the distance from margin to midrib or from apex to base; (b) generally, cut deeply.
DIVISION The highest rank, category, or taxon in the plant kingdom; made up of classes; ending in -phyta; equivalent to the rank of phylum in the animal kingdom.
DOLOMITE A sedimentary rock, and mineral of the same name, composed of calcium magnesium carbonate, which gives rise to alkaline/basic soils.
DM Decimeter; 10 cm.
DORMANT Not active.
DORSAL Referring to the back or outer surface of an organ; the side away from the axis; the lower or abaxial surface; contrasting with ventral.
DOWNY Closely covered with short, weak, soft hairs.
DROOPING More or less erect at base but with upper part bending downward.


E East.
E-, EX- Latin prefixes denoting without, that parts are missing.
ECILIATE Without cilia.
ECOLOGICAL INDICATOR An organism that is sensitive to pollution or some other environmental problem and can therefore be used as an indicator or gauge of the condition of an ecosystem.
EDAPHIC Pertaining to soil conditions including such factors as texture, drainage, mineral composition, or pH.
EGG A female gamete or sex cell, in flowering plants contained in an ovule.
EGLANDULAR Without glands.
ELATER Strap- or ribbon-like appendages of Equisetum spores which are hygroscopic, coil and uncoil with changes in humidity, and function in spore dispersal.
ELLIPSOID A solid that is elliptic in outline.
ELLIPTIC Shaped like an ellipse, with widest part at the middle; in the form of a flattened circle usually more than twice as long as wide.
ELONGATE Lengthened; stretched out.
EMBOSSED Apparently pushed into the surface on one side of an object resulting in a raised area on the surface above.
EMBRYO The very young multicellular sporophyte developing from the zygote; a baby sporophyte.
EMERSED, EMERGENT Raised above and out of the water.
ENATION Outgrowth on the surface; epidermal outgrowth; e.g., the small, veinless, scale-like outgrowth on the stems of Psilotum.
ENDEMIC Confined geographically to or native to a single area.
ENTIRE With smooth margins; without teeth.
ENZYME Proteins that catalyze (i.e., increase the rates of ) chemical reactions in living organisms; some serve as plant defense chamicals; e.g., thiaminase can break down thiamine (Vitamin B1) and cause a fatal deficiency in livestock upon eating Pteridium foliage.
EPHEMERAL Lasting for a brief period; e.g., for only one day.
EPI- Greek prefix meaning upon or on.
EPIDERMAL Relating to the epidermis.
EPIDERMIS The cellular covering of plant tissue below the cuticle.
EPIPHYTE A plant growing on another plant for physical support only and not parasitic; e.g., a Pleopeltis species growing on a tree limb.
EPIPHYTIC Having the character of an epiphyte.
EPIPETRIC (= Lithophytic) Growing on rocks.
EPITHET Second word in the scientific name or binomial of a species, e.g., sensibilis in Onoclea sensibilis.
ERECT (a) Growing essentially in a vertical position (e.g., whole plant); (b) a structure perpendicular to the object to which it is attached.
EROSE With ragged margin, as if nibbled or chewed.
ESCAPE A cultivated plant not purposely planted but found growing as though wild.
ESCARPMENT A steep slope.
ETIOLATE Lengthened and deprived of color by absence of light.
EUSPORANGIATE the condition of having large, thick-walled sporangia, each containing from several hundred to thousands of spores, the sporangia developing from several initial cells; found in less than 5% of living ferns, those on the basal branches of the fern evolutionary tree.
EVERGREEN Remaining green through the winter.
EXOTIC Foreign; not native; from another geographic area.
EXSERTED Projecting out or beyond; contrasting with included.
EXTANT Still existing; contrast with extinct.
EXTINCT No longer in existence; descriptive of a species for which living representatives no longer exist. Locally extinct refers to extinction in a given geographic region.
EXUDATE Material coming out slowly through small pores or openings.


F. (a) After an author’s name: abbreviation of filius, the son, or “jr.”; (b) abbreviation of forma or form.
FALCATE Sickle-shaped, with the tip curved to one side.
FALSE INDUSIUM The underrolled, turned-under, or recurved edge of a frond/leaf that serves the same function as an indusium in protecting the sporangia; characteristic of many Pteridaceae.
FAMILY The unit, category, or rank in classification made up of one or more genera; ending in -aceae; sometimes divided into subfamilies, which in turn are made up of genera.
FARINA A wax-like or mealy appearing whitish or yellowish flavonoid material produced by short, capitate, glandular hairs.
FARINACEOUS Bearing farina.
FARINOSE Covered with farina.
FERN ALLIES Term used in the past for all vascular sporebearing plants not considered to be ferns (equisetophytes, lycophytes, and psilophytes); no longer used since equisetophytes and psilophytes have been shown to be ferns with unusual morphologies).
FERTILE Capable of normal reproductive functions.
FERTILIZATION Union of two gametes (e.g., egg and a sperm) to form a zygote.
FIBROUS Resembling or having fibers.
FIBROUS ROOT SYSTEM One with several roots about equal in size and arising from about the same place; contrasting with taproot.
-FID A suffix meaning deeply cut.
FILAMENT A thread or thread-like structure.
FILAMENTOUS, FILAMENTOSE Composed of filaments or threads; thread-like.
FILIFORM Slender; having the form of a thread; filamentous.
FLANGE A rim-like structure.
FLESHY Succulent, juicy, or pulpy.
FLEXUOUS Zigzag; bending or curving alternately in opposite directions.
FLORA (a) Collective term for the plants of an area; (b) a taxonomic work on the plants of an area.
FLOWER An axis bearing stamen(s), pistil(s), or both, and in addition, often floral envelopes (= calyx and corolla); the reproductive structure of an angiosperm.
FLUTED With alternating ridges and grooves.
FOLIAGE Collective term for the leaves of a plant.
FORKED Dichotomous; divided into two equal or nearly equal branches.
FORMA, FORM (abbreviated f.) A taxon below the rank of variety used to refer to minor variations without distinctive geographic occurrence; e.g., occasional albinos or seasonal growth forms.
FREE (= Distinct) Separate from one another.
FROND The leaf of a fern, often compound or decompound.
FURROWED With longitudinal channels or grooves.
FUSED United by normal growth.


GAMETE A sex cell; an egg or sperm.
GAMETOPHYTE The tiny, inconspicuous, gamete-producing, typically haploid (with one set of chromosomes) generation alternating with the sporophyte (= spore-producing, typically diploid); the stage in the life-history of a plant that produces male or female cells (= gametes).
GEMMA A tiny asexual propagule sometimes appearing as, but not homologous with, a vegetative bud, found on some gametophytes.
GENE Unit of heredity, composed of DNA and located on a chromosome, that determines the inheritance of a particular character.
GENUS (pl. GENERA) The unit, category, or rank in classification between family and species; composed of one or more closely related species; sometimes divided into subgenera, which in turn are made up of species.
GLABRATE, GLABRESCENT Becoming hairless with age.
GLABROUS Without hairs.
GLAND A secreting part or appendage, often protruding or wart-like.
GLANDULAR Having or bearing secreting organs, glands, or trichomes.
GLANDULAR-PUBESCENT With gland-tipped, pinhead-like hairs.
GLAUCESCENT Becoming glaucous.
GLAUCOUS With waxy substances forming a whitish or graysilvery covering or bloom.
GLOBOSE Nearly spherical or rounded.
GLYCOSIDE Complex, two-component chemical compound that can break down or hydrolyze under certain conditions, yielding a sugar plus another compound (= aglycone) that can be physiologically active including poisonous; a type of plant chemical defense mechanism.
GYMNOSPERMS Literally, “naked seed”; plants with seeds but without flowers, the seeds “naked,” (= not enclosed in a special structure), often on the surface of thick or thin, sometimes woody cone scales; including conifers, cycads, ginkgo, and joint-firs.
GYPSUM A soft mineral composed of calcium sulfate.


HABIT Style or arrangement of growth; general appearance.
HABITAT Type of locality in which a plant grows; e.g., forest.
HAIR An epidermal appendage that is usually slender, sometimes branched, not stiff enough to be called a spine, not flattened as a scale; often used synonymously with trichome.
HAPLOID Having the reduced number of chromosomes typical of gametes; usually with a single set of chromosomes in each nucleus.
HEMI- Greek prefix meaning half.
HEMIDIMORPHIC (= Partly dimorphic) With different sterile and fertile pinnae on the same leaf blade (e.g., as in Osmunda regalis)
HERB A vascular plant lacking a persistent woody stem and typically dying back to the ground each season.
HERBACEOUS (a) Referring to the aerial shoot of a plant that does not become woody; typically dying back to the ground each year; (b) of a soft texture, as green leaves.
HERBARIUM (pl. HERBARIA) A collection of dried pressed plants prepared for permanent preservation.
HETERO- Greek prefix meaning other, various, or having more than one kind.
HETEROCHRONY An evolutionary change in the relative timing of events during development; e.g., in Marsileaceae the leaves complete development at a stage comparable to juvenile leaf stages of other ferns.
HETEROGENEOUS Not uniform in kind.
HETEROPHYLLOUS Having more than one form of leaf.
HETEROSPOROUS Having two spore types (male and female); e.g., Selaginella.
HEXAGONAL Six-angled.
HEXAPLOID Having six sets of chromosomes.
HIRSUTE With straight moderately stiff hairs.
HISPID Resembling hirsute but the hairs stiffer, ± bristly, feeling rough to the touch.
HISPIDULOSE Minutely hispid.
HOLOTYPE The one specimen used or designated by the author of a species or other taxon as the nomenclatural type in the original publication. The holotype is the specimen to which the scientific name is permanently attached; it is not necessarily the most typical or representative element of a taxon.
HOMO- Greek prefix meaning all alike, very similar, same, or of one sort.
HOMOGENOUS Of the same kind or nature; uniform; contrasting with heterogeneous.
HOMOSPOROUS With spores all of one type.
HUMUS Decomposing organic matter in the soil.
HYALINEThin, membranous, and transparent or translucent.
HYBRID (a) A cross between two unlike parents; (b) specifically, the offspring resulting from a cross between two species.
HYDATHODE A microscopic epidermal structure, usually marginal or terminal, that excretes water.
HYDROPHYTE A plant typically growing partially or wholly immersed in water; contrasting with mesophyte and xerophyte.
HYGROSCOPIC Susceptible of expanding, shrinking, twisting, or untwisting on the application or removal of water or water vapor.


ILLEGITIMATE NAME Name unacceptable as the accepted scientific name because it is not the earliest one given to the plant in question, or published without description, or violating some other specific requirement of the International Code of Botanical Nomenclature.
IMBRICATE Overlapping like shingles on a roof.
INCIPIENT Beginning to be; coming into being.
INCISED Cut rather deeply and sharply; intermediate between toothed and lobed.
INCLUDED Not exserted; contained within; not projecting beyond the surrounding organ, as a veinlet within an areola.
INCURVED Curved inward.
INDETERMINATE GROWTH Growth that is not pre-determined in amount; e.g., the elongating leaf midribs (= rachises) of Lygodium have terminal meristems that are able to continue growing indefinitely.
INDIGENOUS Native to an area; not introduced.
INDUMENT, INDUMENTUM Surface coating such as hairs, roughening, bloom, or glands.
INDUSIUM (pl. INDUSIA) Usually thin, delicate epidermal outgrowth covering the sori or sporangia on fern fronds.
INFERTILE Incapable of normal reproductive functions.
INFLATED With an internal air space; bladdery.
INFLEXED Bent inward.
INFRA- Latin prefix meaning below.
INFRASPECIFIC Within the species; referring to a unit of classification below the species; e.g., subspecies, variety, form.
INROLLED Rolled inward.
INSERTED Attached to another part or organ.
INTER- Latin prefix meaning between.
INTERCALARY Medial in position.
INTERCOSTAL Located between the ribs or costae.
INTERGAMETOPHYTIC SELFING A type of cross-fertilization in which a sperm from one gametophyte swims to and fertilizes an egg produced by a different gametophyte.
INTERNODE Area of stem or other structure between two nodes.
INTERRUPTED Not continuous or regular.
INTERSPECIFIC Between different species.
INTRA- Latin prefix used to denote within.
INTRAGAMETOPHYTIC SELFING Condition in which a single bisexual gametophyte can produce both sperm and eggs that can successfully join and produce a sporophyte; the result is a type of self-fertilization.
INTRODUCED Brought from another geographic region; not native.
INTROGRESSION, INTROGRESSIVE HYBRIDIZATION Successive crosses, first between plants of two species, then between the offspring of this cross and plants of one parent species, followed by further interbreeding between mongrels of varying percentage of impurity with purebreds of the parent line. This eventually leads to whole populations of one parent species being contaminated with genes derived from the other.
INTRUDED Projecting inward or forward.
IRREGULAR Structures not similar in size or shape; asymmetrical.
-ISH Suffix meaning “slightly,” often used with color terms.
ISOTYPE A specimen of the type collection other than the holotype; an extra or duplicate specimen made at the same time and place as the holotype.


JOINTED With or apparently with nodes or points of articulation; e.g., jointed stems of Equisetum.


KEEL Prominent longitudinal ridge, shaped like the keel of a boat.
KEELED With a ridge or keel.


L. Linnaeus, Swedish naturalist who established the binomial system of nomenclature; L. f., his son.
LACERATE Irregularly cleft as if torn.
LANCEOLATE Lance-shaped; several times longer than wide, tapering at both ends, widest about a third above the base.
LATERAL Belonging to or borne on the sides.
LATERAL BUD Bud in a leaf axil; contrasting with terminal or apical bud.
LAX (a) Not rigid; (b) spread apart, loose, distant.
LEAF (= Frond in ferns) The primary photosynthetic organ of most plants, usually composed of a expanded blade and a stalk-like petiole.
LEAF GAP Break or gap in the vascular tissue of a stem above the point of attachment of a leaf trace; found in stems of plants with megaphylls, but not in those with lycophylls.
LEAFLET A single, expanded segment or division of a compound leaf.
LEAF TRACE A vascular bundle, one or more in number, extending from the stem into the leaf.
LEATHERY With a tough, leather-like texture; e.g., the leaves of many dry-adapted ferns.
LECTOTYPE A specimen or other material selected by a later worker from the original material studied by the author of the species (or other taxon) to serve as the nomenclatural type when a holotype was not originally designated or was lost or destroyed.
LEPTOSPORANGIATE the condition of having small delicate sporangia, each usually containing 128 spores or fewer, with each sporangium usually developing from a single cell and with sporangial walls only one cell thick; found in more than 95% of living ferns.
LIGULE A minute, tongue-like or triangular, basal protuberance on a leaf; just distal to the sporangium on the adaxial surface of the leaf base in Isoëtes.
LIMESTONE A sedimentary rock composed largely of the mineral calcite (calcium carbonate), which gives rise to alkaline/ basic soils.
LINEAR Resembling a line, long and narrow, with margins parallel to one another.
LITHOPHYTIC (= Epipetric) Growing on rocks.
LITHOPHYTE Plant that grows on rocks but derives its nourishment from the atmosphere and from accumulated humus.
LOBE A usually rounded segment or division of a leaf, petal, or other organ.
LOBED Having deep or coarse indentations of the margin, larger than mere teeth (However, there is no sharp distinction between large teeth and small lobes).
LOBULATE Having small lobes.
LONG-CREEPING Growing horizontally for at least a few centimeters; usually in reference to rhizomes, bearing petiole bases attached some distance from one another.
LONG-DISTANCE DISPERSAL Dispersal of spores, seeds, or other propagules over long distances.
LONGITUDINAL Lengthwise; along the long axis.
LUMPER A taxonomist who in general has the tendency to lump segregates into larger groups; contrasting with splitter.
LYCOPHYLL (= Microphyll) A relatively small leaf with a single unbranched vein, typical of the lycophytes.
LYCOPHYTE A member of the Lycopodiophyta, the ancient group that among living vascular plants is the basal lineage; it includes club-mosses, spike-mosses, and quillworts.


M Meter; 10 decimeters; 39.37 inches.
MACRO- Greek prefix denoting large or long.
MARCOPHYLL (= Megaphyll) Leaf with branched veins, typical of ferns and seed plants.
MACROSPORE (= Megaspore) A large spore giving rise to the female gametophyte; the larger of two kinds of spores produced by heterosporous plants; a female spore.
MARGIN Edge; the outer portion of a blade or other structure.
MARGINAL Attached to the edge or pertaining to the edge.
MARSH Wet or periodically wet, treeless area.
MASSULA (pl. MASSULAE) Mucilaginous structure enclosing a cluster or mass of microspores in Azolla and usually covered with barbed hairs.
MEDIAL, MEDIAN Central, middle.
MEGA- Greek prefix meaning very large.
MEGAPHYLL (= Marcophyll) Leaf with branched veins, typical of ferns and seed plants
MEGASPORANGIUM Specialized sporangium in which megaspores are formed in heterosporous pteridophytes.
MEGASPORE (= Macrospore) A large spore giving rise to the female gametophyte in heterosporous pteridophytes; the larger of two kinds of spores produced by heterosporous plants; a female spore.
MEGASPORE APPARATUS (also referred to a megaspore complex) Specialized term used to collectively describe the whole unit in Azolla consisting of the megaspore, covered by a perispore layer (which is sometimes distinctively marked, pitted, etc.) and topped with triangular cap consisting of a collar, floats, and a blue-green algal colony covered by remnants of the indusium.
MEGASPOROCARP A specialized structure in Azolla containing the megasporangium; a specialized sorus enclosed by a modified indusium.
MEGASPOROPHYLL A sporophyll (= spore-bearing leaf ) bearing one or more megaspores.
MEIOSIS Type of cell division in which the number of chromosomes in the daughter cells is half that of the parental cells; in pteridophytes usually leading to the formation of spores; sometimes called reduction division.
MEMBRANACEOUS, MEMBRANOUS Having the nature of a membrane, thin, somewhat flexible, translucent.
MERISTEM Embryonic or undifferentiated tissue, capable of developing into various organs.
MERISTEMATIC Pertaining to or with the nature of a meristem.
MESOPHYTE Plant that grows under medium moisture conditions; contrasting with hydrophyte and xerophyte.
MICRO- Greek prefix meaning small.
MICROHABITAT A small, localized, specialized habitat within a larger different habitat, sometimes capable of sustaining rare or unusual species; e.g., cave entrances, granite outcrops.
MICROPHYLL (= Lycophyll) A relatively small leaf with a single unbranched vein, typical of the lycophytes; in contrast to megaphylls/macrophylls.
MICROPHYLLOUS Having small leaves (note: this term is usually used differently from the microphyll/megaphyll distinction), typical of many dry-adapted plants, the reduction in surface area (and thus water loss) apparently being beneficial in dry climates.
MICROPHYLLY The condition of having small leaves.
MICROSPORANGIUM Specialized sporangium in which microspores are produced in heterosporous pteridophytes.
MICROSPORE A small spore giving rise to the male gametophyte in heterosporous pteridophytes; the smaller of two kinds of spores produced by heterosporous plants; a male spore.
MICROSPOROCARP A specialized structure in Azolla containing the microsporangia; a specialized sorus enclosed by a modified indusium.
MICROSPOROPHYLL The sporophyll (= spore-bearing leaf ) upon which microspores are produced.
MIDRIB The central or main rib or vein of a leaf or other similar structure.
MITOSIS Regular cell division where the number of chromosomes in the daughter cells is the same as that of the parent cell.
MM Millimeter; 1000 microns or 1/1000 of a meter.
MONILIFORM Like a string of beads.
MONILOPHYTE Term referring to all species now known to be in the fern lineage including Equisetum and Psilotum.
MONO- Greek prefix meaning one or of one.
MONOMORPHIC One form; contrasting with polymorphic.
MONOPHYLETIC A term previously used to describe a group of organisms with a common ancestor; more recently it has been used to describe a group consisting of a common ancestor and all of its descendants. Some authorities believe that a different term, holophyletic, should be used for a group consisting of a common ancestor and all of its descendants.
MONOTYPIC Having a single type or representative; e.g., a genus with only one species.
MONTANE Pertaining to or living in mountains.
MORPHOLOGY That aspect of biology concerned with form and structure of organisms.
MOSTLY A quantitative term meaning “most of them.”
MUCRO A short and small abrupt tip, as with the midrib extending as a short point.
MUCRONATE With a mucro.
MULTI- Latin prefix for many.
MULTIFID Divided into many narrow segments or lobes.
MYCOHETEROTROPHIC Obtaining food from decaying organic material via a special relationship with a symbiotic fungus.
MYCORRHIZA (pl. MYCHORRHIZAE) A mutually beneficial, symbiotic association of a fungus and the root of a plant. Mychorrhizal relationships are characteristic of most vascular plants, and are particularly important in the Ophioglossaceae and Psilotaceae (with subterranean mycoheterotropic gametophytes).
MYCORRHIZAL Pertaining to mycorrhiza.


N North.
NAKED Lacking various coverings, organs, or appendages, almost always referring to organs or appendages present in other similar plants; e.g., a naked flower lacks perianth.
NATURALIZED Referring to an introduced foreign plant that has become part of the spontaneous, self-perpetuating flora of a region; a species intentionally or accidentally introduced to an area, but now growing wild without human help.
NECTAR A sugar-rich solution secreted by plants, typically produced in nectaries. Nectar production has apparently evolved to attract insects or other animals for pollination or other purposes.
NECTARY A specialized nectar-secreting structure or area; there can be floral nectaries (in the flowers) or extra-floral nectaries (not associated with the flowers).
NEOTYPE A specimen selected by a later worker to serve as the nomenclatural type of a taxon when all material studied by the original author has been lost or destroyed.
NERVE A simple vein or slender rib of a leaf, bract, or other structure.
NERVED Having nerves.
NET-VEINED With veinlets branching irregularly and not uniformly angular, forming a net-like pattern.
NEW WORLD Term used synonymously with Western Hemisphere to refer to the Americas; the new signifying that its presence was not known by people inhabiting other parts of the world until relatively recently.
NITROGEN FIXATION Capture and conversion of atmospheric nitrogen, which is unusable by plants, into nitrogen containing compounds that are of use by plants; the process is carried out by certain bacteria such as those that inhabit the leaves of Azolla.
NODAL Located at or pertaining to a node.
NODE Area of stem or axis at which branches, leaves, bracts, or flower stalks are attached; joint of a stem.
NODDING Hanging down.
NOMENCLATURE The scientific naming of organisms; the naming of plants is governed by the rules of the International Code of Botanical Nomenclature (McNeill et al. 2006).


OB- Latin prefix indicating the reverse or upside-down, as obcordate, meaning cordate or ovate with wider end at top or away from point of attachment.
OBDELTOID Inversely deltoid; triangle-shaped with base pointed.
OBLANCEOLATE Lanceolate with broadest part above the middle and tapering toward the base.
OBLIQUE Slanting; unequal-sided.
OBLONG Longer than wide with sides nearly parallel.
OBOVATE Egg-shaped with attachment at narrow end; inversely ovate.
OBOVOID Inversely ovoid; a solid that is obovate in outline.
OBSCURE Hidden; not obvious.
OBSOLETE Not apparent or evident; rudimentary; vestigial; extinct.
OBTUSE Forming a blunt or rounded angle of more than 90 degrees; not pointed.
OLD WORLD Term used to collectively refer to Europe, Asia, Africa, and Australia.
ONTOGENY The developmental cycle of an individual organism.
OPAQUE Impervious to light.
OPPOSITE Arranged two at each node, on opposite sides of the axis.
ORBICULAR, ORBICULATE With round, approximately circular outline.
ORDER The unit, category, or rank in classification made up of one or more families; ending in -ales; sometimes divided into suborders or superfamilies, which in turn are made up of families.
OVAL Broadly elliptic.
OVATE Egg-shaped with widest part at the base.
OVOID Solid oval or solid ovate.


PALMATE Attached or radiating from one point, as leaflets in a palmately compound leaf, veins in some leaf blades, or fingers of a hand.
PALMATELY COMPOUND With the leaflets attached at one point at the apex of the petiole, like the fingers all attached to the palm of a hand.
PANICLE-LIKE Resembling a panicle, an indeterminate, branched, usually elongate (not flat-topped) inflorescence with flowers on the branches of the primary axis; e.g., the arrangement of the sporangia in Botrychium.
PAPILLA (pl. PAPILLAE) Small pimple-like or nipple-like projection.
PAPILLATE, PAPILLIFORM, PAPILLOSE Shaped like or bearing papillae.
PARALLEL-VEINED With main veins parallel to each other. Such leaves are typical of many monocots.
PARAPHYLETIC A term used to describe a taxonomic group consisting of an ancestral species and some but not all of its descendants. Paraphyletic groups can give an inaccurate view of phylogeny but are often useful in classification.
PARASITE A plant that derives its food, mineral nutrition, and/ or water wholly or chiefly from another plant (the host) to which it is attached; contrasting with epiphyte, saprophyte, or autophyte.
PEDATE Palmately divided with the lateral segments again divided.
PEDUNCLE Stem or stalk supporting reproductive structures.
PELTATE Shield-shaped, with stalk attached on the undersurface away from the margin or base (sometimes attached at the middle like the axis of an umbrella).
PENDENT, PENDULOUS Hanging down or suspended.
PENTAGONAL Shaped like a pentagon; five-sided or -angled.
PERENNIAL Root system or plant living at least three growing seasons (years); lasting from year to year.
PERIPHERAL On or near the margin.
PERISPORE The outer covering of a spore, sometimes distinctively marked, pitted, etc.
PERSISTENT Remaining attached; not falling off; contrasting with deciduous.
PETIOLAR Pertaining to or located on the petiole.
PETIOLATE With a petiole.
PETIOLE (= Stipe) Stalk of a leaf/frond supporting the blade.
PETIOLULE Stalk supporting a leaflet/pinna.
PHANEROGAM A seed plant or spermatophyte; contrasting with cryptogam.
PHENOLOGY Study of the times at which various events occur in the life of a plant.
PHLOEM The food-conducting tissue in a plant.
PHOTOSYNTHESIS The process by which plants convert carbon dioxide and water into carbohydrates in the presence of light.
PHYLOGENY The evolutionary history of a group.
PHYTOECDYSONES A class of hormone-like compounds that disrupt ecdysis (= molting) in insects and thus serve as a plant defense mechanism.
PILOSE With long, soft, ± straight hairs; softer than hirsute, not flexuous or curved as in villous.
PINNA (pl. PINNAE) A primary division of a compound leaf. A pinna can be simple (and thus equivalent to a leaflet) or compound and divided into leaflets.
PINNATE, PINNATLEY COMPOUND Descriptive of a compound leaf with leaflets distributed along both sides of an elongate axis; feather-like. Bipinnate or 2-pinnate leaves have the leaflets distributed along a secondary axis; tripinnate or 3-pinnate leaves have the leaflets along a tertiary axis, etc.
PINNATIFID Pinnately divided into stalkless segments, but the segments not distinct leaflets (i.e., not divided all the way to the midrib).
PINNULE A secondary pinna; division of a pinna or a leaflet.
PITTED Having little depressions or cavities.
PLANE With a flat even surface.
PLANO- A suffix denoting flat.
-PLOID A suffix used in genetics, prefixed by a term indicating number, to denote the number of sets of chromosomes in the nucleus.
POLY- Greek prefix meaning many.
POLYMORPHIC Of various forms; with three or more forms.
POLYPHYLETIC A taxonomic group having species derived from more than one common ancestor, the species having been placed in the same group because of similarities due to convergent or parallel evolution. Polyphyletic taxa give an inaccurate view of phylogeny.
POLYPLOID A plant with three or more basic sets of chromosomes.
PORE A small aperature or opening.
POSTERIOR Describing the position of an organ located on the side adjacent to the axis.
PROCUMBENT Trailing or prostrate, not rooting.
PROLIFEROUS Bearing or developing offshoots or redundant parts; producing numerous new individuals, or parts, of the same kind; bearing offsets, bulbils, or other vegetative progeny.
PROSTRATE Lying flat.
PROTHALLUS, PROTHALLIUM Gametophyte stage or generation in ferns and lycophytes, bearing the sexual organs.
PROTUBERANCE A protrusion, swelling, bump, or bulge.
PROXIMAL Located nearest to the base or attachment point of a structure; contrasting with distal.
PSEUDO- Greek prefix meaning false, not genuine.
PTERIDOLOGY The study of ferns and lycophytes.
PTERIDOPHYTE General collective term for ferns and lycophytes; any member of the Lycopodiophyta and Polypodiophyta; seedless, spore-bearing, vascular plants.
PUBERULENT Minutely pubescent.
PUBESCENCE The covering or indumentum of hairs on a plant without reference to specific type (e.g., pilose, hirsute).
PUBESCENT (a) General term for covering or indumentum of hairs; (b) sometimes used in a more restricted sense to refer to fine short hairs; downy.
PULVINATE With a pulvinus; cushion-shaped.
PULVINUS A joint-like thickening at the base of a leaf or leaflet involved in movement (e.g., in Marsilea they orient leaflets during the day and cause the leaflets to fold together at night).


QUADR- Latin prefix meaning four.
QUADRANGULAR Four-cornered or sided; square.
QUILL-LIKE Resembling a quill, the hollow stem-like main shaft of a feather, formerly used as writing implements.


RACHIS Main axis of a leaf blade; the midvein or midrib of the blade or the pinnae-bearing central axis of a pinnately compound leaf.
RADIALLY SYMMETRICAL Descriptive of a structure that can be cut into halves from any marginal point through the center.
-RANKED Suffix, when combined with a numerical prefix, indicating the number of longitudinal rows in which leaves or other structures are arranged along an axis or rachis.
RECLINED, RECLINATE Bent or turned downward.
RECURVED Curved downward or backward.
REDUCED Small but probably derived from larger forerunners.
REFLEXED Abruptly bent downward.
RELIC (a) A long-surviving species whose relatives have become extinct; (b) a plant persisting in a relatively small portion or portions of its former range.
REMOTE Widely or distantly spaced.
RENIFORM Kidney-shaped.
RESIN, RESINOID A miscellaneous or catchall term for a variety of amorphous, sometimes semisolid, perhaps gummy substances from plants.
RESINOUS, RESINIFEROUS Producing or bearing resin.
RETICULATE Net-veined or with a net-like pattern.
REVOLUTE With margins rolled down and inward; e.g., revolute leaves.
RHIZOID A filamentous root-like structure (without the anatomy of a root) on the gametophyte of ferns or other non-seed-producing plants.
RHIZOMATOUS Possessing a rhizome.
RHIZOME Stem (typically underground or at ground level) with nodes and scales and bearing the fronds and adventitious roots; the type of stem found in most ferns.
RHIZOMORPHS Root-like stems in Isoëtes (quillworts) that have the nutrient absorption and anchoring functions usually carried out by roots.
RHIZOPHORE In lycophytes, a specialized leafless stem emitting roots.
RHIZOTAXY A regular and precise spiral pattern of “rootlets” around the main “root” (rhizomorph) in Isoëtes unlike the irregular arrangement seen in other plants.
RHOMBIC Somewhat diamond-shaped; shaped like two adjacent equilateral triangles.
RHOMBOID, RHOMBOIDAL A three-dimensional rhombic figure.
RIB One of the principal longitudinal veins of a leaf or other organ.
RIBBED With prominent ribs or veins.
ROOT The portion of the main axis (or one of its subdivisions) of a plant usually found below ground and lacking nodes, internodes, or leaves.
ROOTLET (a) A little root; (b) term often applied to the holdfast roots of certain climbing plants.
ROOTSTOCK According to Shinners (1958), a “weasel-word” indicating an elongate crown, rhizome, or rhizome-like structure; an old inaccurate term for rhizome.
ROSETTE A cluster or whorl of leaves or other organs closely arranged in a radial pattern.
ROTUND Essentially circular in outline.
RUDIMENT A structure very imperfectly developed, nonfunctional, or represented only by a vestige; e.g., rudimentary nonfunctional florets in some grass spikelets.
RUDIMENTARY Having the character of a rudiment.
RUGOSE Wrinkled.
RUGULOSE With slight ridges or wrinkles, a diminutive of rugose.


S South.
SALINE Of or pertaining to salt.
SAP The juice of a plant.
SCABROUS Rough to the touch due to short stiff hairs or the structure of the epidermis.
SCALE A small, muticellular, usually flat and elongate epidermal outgrowth 2 to many cells wide (hairs are similar but only 1 cell wide).
SCARIOUS Membranous, dry, papery, translucent or transparent, not green.
SCATTERED Distributed in an irregular manner; not clustered together.
SCRUB Vegetation of stunted or densely crowded bushes.
SECONDARY COMPOUNDS Naturally occurring plant materials not essential to the primary (= life-sustaining) metabolism of the plant; examples of categories include alkaloids and glycosides. Many are significant because of their physiological activity when given to animals; they are probably important to plants in defense against herbivores or microbes.
SEED An embryo (baby plant) packaged with stored food and surrounded by a protective waterproof coating.
SEEP A moist spot where underground water comes to or near the surface.
SEGMENT One of the parts of a leaf that is divided but not truly compound.
SEGREGATE Term used as a noun or adjective to refer to or describe a taxon that is sometimes recognized separately from a more inclusive group; e.g., depending on authority, the genus Botrychium is sometimes separated into a number of segregate genera.
SELF-FERTILE Capable of self-fertilization (= union of gametes from same plant).
SELF-INCOMPATIBLE Incapable of self-fertilization.
SEMI- Latin prefix meaning half.
SENSU LATO “In a broad sense”; used to refer to the broad treatment of taxa; e.g., a genus sensu lato is one that has not been split into a number of segregates.
SENSU STRICTO “In a narrow sense”; used to refer to a restricted or narrow treatment of a taxonomic group; e.g., a genus sensu stricto is viewed in a more restricted sense than previously as the result of segregating or splitting out various taxa.
SEPARATE Not joined; of individual units.
SEPTATE With partitions or divisions.
SERRATE With pointed teeth sloping forward; saw-toothed.
SERRULATE Finely serrate.
SESSILE Without a pedicel, petiole, or stalk; inserted directly.
SETA (pl. SETAE) A bristle.
SHEATH more or less tubular structure surrounding an organ; portion that clasps or encloses.
SHOOT (a) A young stem or branch; (b) the ascending axis of a plant.
SHORT-CREEPING Growing horizontally for a few centimeters at most; usually in reference to rhizomes, bearing petiole bases all attached in close proximity.
SHRUB A woody perennial usually branching from the base with several main stems.
SILICA Silicon dioxide; a white or colorless, very hard, crystalline mineral substance.
SILICEOUS Containing or composed of silica (the principal component of glass and sand).
SILVERY With a whitish, metallic, more or less shining luster.
SIMPLE (a) Single, of one piece, not compound; (b) descriptive of an unbranched stem, inflorescence, or other structure; (c) descriptive of a leaf that is not compound.
SIMPLE LEAF Single-bladed leaf, not divided into individual leaflets.
SINUATE, SINUOUS Having the margin wavy with regular strong indentations.
SINUS The space or recess between two lobes, segments, or divisions of a leaf or other expanded organ.
SISTER, SISTER GROUP A monophyletic group more closely related to the group in question than any other group; e.g., the Osmundaceae is the sister group to the group composed of all other leptosporangiate ferns.
SMOOTH Not rough to the touch; without vestiture or other special covering.
SOLITARY Borne singly.
SORUS (pl. SORI) A cluster or heap of sporangia.The term is used mainly to refer to the sporangial clusters of ferns.
SPECIES Unit of classification below the rank of genus; a group of individuals that are actually or potentially capable of interbreeding in natural populations and are reproductively isolated from other such groups. Generally there are morphological characteristics that distinguish and can thus be used to separate such groups; the definition is complicated by instances of asexual reproduction.
SPECIFIC EPITHET The second half of the scientific name of a species, the scientific name or binomial being composed of the genus name and the specific epithet.
SPERMATOPHYTE A plant that produces seeds; all gymnosperms and angiosperms.
SPHERICAL Globular; orbicular.
SPIKE-LIKE Resembling a spike, an indeterminate inflorescence with sessile flowers on an elongate floral axis; e.g., the arrangement of the sporangia in Ophioglossum.
SPINE A sharp-pointed structure, usually vascularized and generally modified from part or all of a leaf.
SPIRAL Describing the arrangement of like organs, such as leaves, at regular angular intervals along an axis.
SPLITTER A taxonomist who in general has the tendency to split or divide larger taxa into a number of segregates; contrasting with lumper.
SPORADIC Of irregular occurrence.
SPORANGIOPHORE An appendage holding a sporangium; in Equisetum, a highly modified peltate sporophyll bearing a ring of 5–10 sporangia.
SPORANGIUM (pl. SPORANGIA) The structure within which spores are produced; a spore case or spore sac.
SPORE An asexual, usually one-celled reproductive body; a cell resulting from meiotic cell division in a sporangium representing the first cell of the gametophyte generation.
SPOROCARP A specialized structure containing sporangia; e.g., in Marsilea.
SPOROPHORE The fertile sporangia-bearing portion of the leaves in the Ophioglossaceae, the leaves divided into a fertile sporangia-bearing portion and a sterile blade portion or trophophore.
SPOROPHYLL Spore-bearing leaf.
SPOROPHYTE The spore-producing, typically diploid generation that alternates with the gamatophyte (= gamete-producing, typically haploid); the dominant generation in most plants except mosses and liverworts.
SPREADING Diverging to the side, almost to the horizontal.
SPREADING HAIRS Hairs that are ± erect, not at all appressed.
STALK The supporting structure of an organ; e.g., petiole.
STELLATE Star-shaped or star-like; when used in reference to hairs it means those branched hairs with a central stalk and branch hairs arising at the top of the stalk (like points of light coming out of a star).
STEM A major division of the plant-body in contrast to root and leaf, distinguished from both by certain anatomical features and commonly also by general aspect; the main axis or axes of a plant; the portion of the plant axis bearing nodes, leaves, and buds and usually found above ground.
STERILE Unproductive; without functional sex organs; without spores.
STIPE (= Petiole) Stalk of a leaf/frond supporting the blade of a fern.
STOLON A creeping horizontal stem that loops or runs along the surface of the ground and roots at the nodes.
STOLONIFEROUS Producing stolons.
STOMA, STOMATE (pl. STOMATA) A minute opening (= “breathing” pore) between the epidermal cells of a leaf or stem through which gases and water-vapor enter and leave the plant.
STROBILUS (pl. STROBILI) (= Cone) A usually cone-like, globose or cylindrical structure involved in reproduction and composed of an axis with a spiral, usually dense aggregation of sporophylls, bracts, or scales (in pteridophytes these bearing spores, or in seed plants bearing pollen or seeds).
SUB- Latin prefix meaning almost, somewhat, of inferior rank, beneath.
SUBAPICAL Almost at the apex.
SUBBASAL Almost at the base.
SUBCLASS The unit, category, or rank in classification between class and order, composed of one or more orders; e.g., the Liliidae is a subclass of class Monocotyledonae.
SUBCORIACEOUS Somewhat leathery in texture.
SUBFAMILY The unit, category, or rank in classification between family and genus, composed of one or more genera.
SUBGENUS A unit, category, or rank in classification between genus and species, composed of one or more species.
SUBORDER The unit, category, or rank in classification between order and family, composed of one or more families.
SUBMERGED, SUBMERSED (= Immersed) Growing under water.
SUBSESSILE Almost sessile.
SUBSP. Abbreviation for subspecies.
SUBSPECIES A unit, category, or rank in classification below the level of species and between species and variety; a geographically distinct variant. The categories of subspecies and variety are not used consistently by taxonomists.
SUBTERRANEAN Below ground.
SUBULATE (= Awl-shaped) Tapering from the base to a slender or stiff point; narrow and sharp-pointed.
SUCCULENT Fleshy, thickened.
SUPRA-, SUPER- Latin prefix meaning above.
SUPRAMEDIAL Above the middle; when used to refer to the location of fern sori, it means somewhat beyond the middle of the distance between the leaf segment midvein and margin, but not so much so as to be called submarginal.
SWAMP Wet or periodically wet area with some trees.
SYM- Greek prefix meaning with or together.
SYMMETRICAL Possessing one or more planes of symmetry; regular in number and size of parts.
SYMPATRIC Growing together with or having the same range as.
SYN- Greek prefix meaning united.
SYNANGIUM (pl. SYNANGIA) A cluster of sporangia that have become fused in development; in Psilotum the sporangia are fused in groups of 3 (rarely 2).
SYNONYM A currently unaccepted alternative scientific name for a taxon.
SYNONYMY Referring to the series of names no longer used for a taxon.
SYSTEMATICS Scientific study of the kinds and diversity of living organisms and of the relationships between them. The term is often used synonymously with taxonomy.


TAXON (pl. TAXA) (a) General term referring to any unit of classification such as variety, subspecies, species, genus, family, etc.; (b) term used to refer to a specific variety, subspecies, etc.
TAXONOMY The branch of science that deals with classification, identification, and nomenclature.
TEETH (pl. of tooth) Marginal projections, protuberances, serrations, or dentations, usually sharply pointed.
TERMINAL At the tip or apex; distal.
TERMINAL BUD (= Apical bud) Bud at the end (= apex) of a stem or branch.
TERRESTRIAL Growing in the ground; supported by soil; contrasting with aquatic.
TETRA- Greek prefix referring to four.
TETRAD A group of four similar objects; e.g., in Ericaceae, the four pollen grains remaining together.
TETRAHEDAL Four-sided, as a three-sided pyramid and its base.
TETRAPLOID With four sets of chromosomes; twice the normal diploid level.
TOMENTOSE Covered with short, soft, curly, densely matted or entangled hairs.
TOMENTUM Densely matted wool.
TOOTH (pl. TEETH) Any marginal projection, protuberance, serration, or dentation, usually sharp pointed.
TOOTHED With minor projections and indentations alternating along the margin.
TOPOTYPE A specimen from the original or type locality of that species or other taxon.
TRAILING Prostrate, but not rooting.
TRANSLUCENT Allowing the passage of light rays, but not transparent.
TRANSVERSE Lying or being across or in a cross direction.
TREE A woody perennial with usually a solitary trunk or main stem.
TRI- Latin prefix indicating three, or three times.
TRIBE The unit, category, or rank in classification between subfamily and genus, composed of one or more genera.
TRICHOME Any hair, hair-like projection, or bristle from the epidermal surface.
TRICHOTOMOUS Forking into three equal parts.
TRIMEROUS Having the parts in threes.
TRIPLOID Having three sets of chromosomes.
TROPHOPHORE The sterile blade portion of the leaves in the Ophioglossaceae, the leaves divided into a blade portion and a fertile sporangia-bearing portion or sporophore.
TROPHOPOD Modified petiole bases that accumulate food reserves and persist after the leaf blade has withered.
TROWEL-SHAPED Shaped like a gardener’s trowel, somewhat wider basally.
TRUNCATE Ending abruptly as if cut off squarely at the end; appearing “chopped off.”
TUBERCLE A small rounded protuberance or projection from a surface.
TUBERCULATE Covered with tubercles or warty or nipple-like protuberances.
TUBULAR With the shape of a hollow cylinder.
TUFT; TUFTED A cluster or fascicle of trichomes, leaves, or other elongate structures.
TWICE-PINNATELY COMPOUND (= Bipinnate) Descriptive of a leaf with leaflets pinnately arranged on lateral axes that are themselves pinnately arranged on the main axis; with the primary divisions (= pinnae) themselves pinnate.
TYPE A plant specimen to which the name of a taxon is permanently attached.When any new taxon (e.g., species, variety) is named, the name has to be associated with a particular “type” specimen.


ULTIMATE The smallest subdivision; of the lowest order.
ULTIMATE SEGMENT The smallest subdivision of a leaf.
UMBO A rounded, sometimes knob-like elevation or protuberance at the end of or on the side of a solid organ.
UMBONATE With an umbo or projection.
UNDULATE Gently wavy, less pronounced than sinuate.
UNI- Latin prefix meaning one.
UNILATERAL One-sided; developed or hanging on one side.
UNITED Fused into one unit.


VAR. Abbreviation of variety.
VARIETY A unit, category, or rank in classification below the level of species, sometimes treated as a subdivision of subspecies; group of plants with minor characters or differences separating them from other similar plants. The terms variety and subspecies are used inconsistently by taxonomists.
VASCULAR Pertaining to the conducting tissues (xylem and phloem), which transport water, minerals, and sugars.
VASCULAR BUNDLEThread-like fiber of xylem and phloem in a stem or other organ.
VEGETATIVE ORGAN Root, stem, leaf, or other non-reproductive organ of a plant.
VEGETATIVE REPRODUCTION A form of asexual reproduction by which new individuals arise without production of spores or seeds; e.g., via leaf borne bud in Cystopteris bulbifera.
VEIN Strand or bundle of vascular tissue.
VEINLET A little or ultimate vein.
VELUM In Isoëtes, a thin, membranous flap of tissue extending downward over the sporangium.
VENATION The pattern or arrangement of veins.
VENTRAL Situated on or pertaining to the adaxial side (= side toward axis) of an organ; typically the upper or inner surface; contrasting with dorsal.
VERNAL Appearing in spring.
VERNATION The arrangement of leaves or other structures in an unopened bud; e.g., circinate vernation in most ferns.
VESTIGIAL Reduced to a trace, rudiment, or vestige; degenerate; referring to a once more fully developed structure.
VESTURE, VESTITURE Any covering on a surface making it other than glabrous; e.g., hairs, scales.
VICARIANCE The fragmentation of a more continuous distribution, with survivors in only parts of the former range.
VILLOUS, VILLOSE With long, soft, spreading, or ascending, unmatted hairs; shaggy.
VINE A plant that climbs by tendrils or other means, or that trails or creeps along the ground.


W West.
WHORL, WHORLED (= Verticillate) With three or more leaves or other parts attached at the same node; in a circle or ring; e.g., the whorled, scale-like leaves of Equisetum.
WIDE (= Broad) Distance across a structure (equal to diameter if tubular).
WOOLLY (= Lanate) With long, soft, and more or less matted or entangled hairs; wool-like.
WORT An old word of Anglo-Saxon origin meaning the equivalent of herbaceous plant.


XERIC Characterized by or pertaining to conditions of scanty moisture supply; dry.
XERO- Greek prefix signifying dry.
XEROPHYTE A plant that can subsist with a small amount of moisture, such as a desert plant; contrasting with hydrophyte and mesophyte.
XEROPHYTIC Dry-adapted; drought resistant; contrasting with mesophytic and hydrophytic.
XYLEM Vascular tissue that conducts water and minerals.


ZYGOTE Cell produced from fertilization or the union of two gametes; a fertilized egg; the first cell of the sporophyte.