Terms mostly Used in Botany


 Abaxial Surface most distant or away from the axis, the lower or outer surface of organ. Syn: dorsal. (position)

ABC model A model of floral development, in which gene products of the so-called A, B, and C classes combine to produce the four major floral organs: sepals, petals, stamens, and carpels.

acaulescent Lacking an above-ground stem other than the inflorescence axis. (stem habit)

accession number A number assigned to each specimen placed into a permanent herbarium collection.

accessioning The assignment of a number to all new specimens placed into a permanent herbarium collection.

accessory bud Bud(s) lateral to or above axillary buds. (bud type)

accessory part A portion of the mature fruit that is not directly derived from the ovary or ovaries, may include bract(s), stem axes, receptacle, hypanthium, or perianth. (fruit part)

accrescent Parts persistent and continuing to grow beyond what is normal or typical, e.g. calyx of Physalis, Solanaceae. (duration)

acetolysis A standard acid treatment used to dissolve all but the exine of pollen grains in order to better observe pollen wall structure with the light microscope.

achene A one-seeded, dry, indehiscent fruit with seed attached to pericarp at one point only, e.g. unit fruits of sunflowers and other Asteraceae. (fruit type)

achenecetum An aggregate fruit of achenes, e.g. Fragaria (strawberry), in which the achenes are on the surface of accessory tissue, an enlarged, fleshy receptacle. (fruit type)

achlamydeous Lacking a perianth. (perianth merosity)

achlorophyllous Lacking chlorophyll/chloroplasts.

acicular Needlelike, often round in cross-section, with margins straight and parallel, length:width ratio >12 : 1. (shape)

acrocaulis Positioned at the apex of the stem. (position)

acrocidal capsule A capsule dehiscing by means of apical slits. (fruit type)

acrodromous With two or more primary veins or strongly developed secondary veins running in convergent arches toward the leaf apex but not recurved at the base. (leaf venation)

actinodromous With three or more primary veins diverging from one point, inclusive of ternate or palmate venation. (leaf venation)

actinomorphic Radially symmetrical, with 3 or more planes of symmetry. (symmetry)

aculeate With prickles, sharp nonspine, nonthorn appendages. Syn: prickly. (epidermal excrescence).

acuminate Apical margins abruptly incurved (concave), the apical intersection angle <45°. (apex)

acute Apical margins approximately straight, the intersection angle 45° 90 °. (apex)

adaptation a structure or feature that performs a particular function and which results in increased survival or  reproduction.

adaxial Surface toward or nearest the axis, the upper or inner surface of organ. Syn: ventral. (position)

adherent With unlike parts joined, but only superficially and easily separable. (fusion)

adnate With unlike parts integrally fused, not easily separable. (fusion)

advanced Derived.

adventitious roots A root arising from an organ other than a root, usually from a stem. (root type)

adventive embryony Development of an embryo from a cell of the surrounding tissue, such as megasporangial or integument tissue.

aerial roots Adventitious roots that absorb moisture and minerals from the air or runoff, common in some epiphytic plants, e.g. of Araceae and Orchidaceae. (root type)

aestival Appearing in summer. (periodicity)

aestivation Referring to position, arrangement, and overlapping of floral perianth parts. (perianth aestivation)

affinis Implying, within a taxon name, some type of close relationship, presumably an evolutionary relationship, but also that the specimen differs from the cited taxon in some way, e.g. beyond the described range of variation for one or more characters. Abbr: aff.

agamospermy The production of seeds without fertilization.

aggregate fruit A fruit derived from two or more pistils (ovaries) of one flower. (fruit type)

albuminous Endospermous. (seed endosperm type)

albuminous cell A parenchyma cell associated with a sieve cell, derived from a different parent cell than is the sieve cell.

aleurone grain Granular protein deposits in plant cells, functioning as storage compounds; a type of ergastic substance. Syn: proteinoplast.

alignment The process of matching homologous nucleotide positions of two or more sequences of DNA in order to code the data for phylogenetic or other types of analysis.

allautogamy Having both outcrossing and selfing flowers. Adj: allautogamous.

allogamy Outbreeding. Adj: allogamous.

allopolyploidy Polyploidy occurring between different species.

allozyme One of two or more different molecular forms of an enzyme, corresponding to different alleles of a common gene.

alternate One leaf or other structure per node. (arrangement)

alternation of generations haplodiplontic life cycle.

alternipetalous Stamens with point of attachment between the petals or corolla lobes. (stamen position)

alternisepalous Stamens with point of attachment between the sepals or calyx lobes. (stamen position)

alveolar An exine wall structure having numerous, spherical air pockets within the exine.

amb The outline shape of a pollen grain in polar view.

ament Catkin. (inflorescence type)

amoeboid An anther tapetum type in which the tapetal cell walls break down, with release of the cytoplasm of the tapetal cells into the locule. Syn: plasmodialperiplasmodial.

amphiphloic siphonostele A siphonostele in which a ring of xylem is surrounded by an outer and inner layer of phloem.

amphistomal Referring to the micropyle of a bitegmic ovule formed or delimited by both integuments.

amphitropous A general ovule type in which curvature of the ovule during development displaces the micropyle adjacent to the funiculus base, with the nucellus bent along both upper and lower sides.

amplexicaul Sessile and clasping most of stem circumference. (leaf attachment)

amplification The replication of numerous copies of DNA.

amplification fragment length polymorphism The use of amplified DNA fragments that exhibit length polymorphism, enabling the recognition of numerous genetic markers. Abbr: AFLP.

amyloplast Starch grain.

ana-amphitropous An ovule type in which a vascular strand curves, traversing from the base of funiculus to the chalazal region of the nucellus, with the nucellus bent sharply in the middle along both the lower and upper sides, often with differentiated cells (basal body) at the angle of the bend.

ana-campylotropous An ovule type in which a vascular strand curves, traversing from the base of funiculus to the chalazal region of the nucellus, with the nucellus bent only along the lower side, with no basal body.

anatropous A type of ovule in which curvature during development results in displacement of micropyle to a position adjacent to the funiculus base; most common and apomorphic for the angiosperms.

ancestral Referring to a preexisting condition or character state. Syn: plesiomorphicprimitive.

androdioecious/androdioecy Having male flowers on some individuals and perfect flowers on other individuals. (plant sex)

androecium The male organ(s) of a flower; collectively all stamens of a flower. (flower part)

androgynophore A stalklike structure that bears the gynoecium and androecium; e.g. Passiflora. (flower part)

andromonoecious Having both staminate and perfect flowers on the same individual. (plant sex)

anemochory Dispersal of propagules by wind. Adj: anemochorous.

anemophily Pollination by wind. Adj: anemophilous.

anisomerous Having a different number of members in different whorls. (merosity, perianth merosity)

annotated phylogenetic classification A classification in which monophyletic groups are ordered by a sequential listing of derivative lineages from the base to the apex of the cladogram.

annotation label A label affixed to an herbarium specimen that verifies or changes the identity of a specimen or that documents the removal of plant material from the specimen.

annual Plant living 1 year or less. (duration)

annual ring The accumulation of secondary xylem (or phloem) over a single growing season, being evident because of the structural difference between the last cells of the summer wood and the first cells of the subsequent spring wood.

annulus A single row of specialized cells, having differentially thickened cell walls, on the outer rim of a leptosporangium, functioning in its dehiscence.

antepelatous Antipetalous. (stamen position)

anterior Referring to the lower lobe or part, especially in a horizontally oriented structure. (position)

antesepalous Antisepalous. (stamen position)

anther The pollen-bearing part of a filamentous stamen. (stamen part)

anther sac Microsporangium. (anther part)

antheridial wall The outer, sterile layer of cells of the antheridium. Syn: jacket layersterile jacket layer.

antheridiophore A specialized, stalked, generally peltate structure that grows from the gametophyte of some liverworts and bears antheridia.

antheridium The male gametangium of the gametophyte of land plants, producing sperm cells and surrounded by a outer layer of sterile cells, the antheridial wall or jacket layer.

antherode The sterile anther of some staminodes. (stamen type)

anthesis Time of flowering; the opening of flower with parts available for pollination. (maturation, flower maturation)

anthocarp A fruit in which one or more flower parts functions as accessory tissues, e.g. Pontederia (Pontederiaceae), in which an accrescent perianth surrounds and fuses to the achene. (fruit type)

antipetalous Stamens with point of attachment in line with (opposite) the petals or corolla lobes, e.g. Primulaceae, Rhamnaceae. Syn: antepetalous. (stamen position)

antipodal cells In a typical angiosperm female gametophyte, the three haploid cells that are positioned opposite the micropyle, i.e. in the chalazal region.

antisepalous Stamens with point of attachment in line with (opposite) the sepals or calyx lobes. Syn: antesepalous. (stamen position)

antrorse Bent or directed upward, usually referring to small appendages. (orientation)

aperture A specially delimited region of the pollen grain wall.

apetalous Having no petals or corolla. (perianth merosity)

apical (a) At or near the top, tip, or end of a structure. (position) (b) Style arising at the apex of the ovary. (style position) (c) With the placenta at the top of the ovary. Syn: pendulous. (placentation)

apical bud Terminal bud. (bud type)

apical meristem A region of actively dividing cells in the land plants, located at the apex of the thallus, shoot, or root.

apical-axile With two or more placentae at the top of a septate ovary, e.g. Apiaceae. (placentation)

apiculate With a flexible, apical process, usually slightly curled, length : width ratio >3:1. (apical process)

apocarpous With carpels distinct, the pistil or ovary simple. (gynoecial fusion)

apolar Pollen polarity in which polar and equatorial regions cannot be distinguished after pollen grain separation from the microspore tetrad.

apomorphic Derived.

apomorphy A derived condition or character state, representing an evolutionary novelty. Adj: apomorphic.

apomorphy-based A type of phylogenetic classification in which an apomorphy is the basis for grouping, such that all members of a monophyletic group that share a given, unique evolutionary event are grouped together.

apopetalous With distinct petals. Syn: polypetalous. (perianth fusion)

aposepalous With distinct sepals. Syn: polysepalous. (perianth fusion)

apostemonous With distinct stamens. (stamen fusion)

apotepalous With distinct tepals. (perianth fusion)

appressed Pressed closely to an axis oriented upward, with a divergence angle of 0 °15  °from upper axis. (orientation)

aquatic Growing in water. (plant habitat)

arachnoid/arachnose With trichomes forming a cobwebby mass.(vestiture)

arborescent Treelike in appearance and size. (stem habit)

archegonial chamber A cavity between the megasporangium and female gametophyte of gymnosperm seeds, into which sperm cells are released by the male gametophyte.

archegonial wall The outer, sterile layer of cells of the archegonium. Syn: jacket layersterile jacket layer.

archegoniophore A specialized, stalked, generally peltate structure that grows from the gametophyte of some liverworts and bears archegonia.

archegonium The female gametangium of the gametophyte, containing a basal egg cell and surrounded by an outer layer of sterile cells, the archegonial wall, which differentiates into a basal venter and proximal neck.

archesporial cell A single, large cell of an immature ovule that either directly becomes the megasporocyte or that divides once to form a parietal cell and a megasporocyte.

areole A modified, reduced, nonelongating shoot apical meristem bearing spines, e.g. Cactaceae. (stem/shoot type)

aril A fleshy outgrowth of the funiculus, raphe, or integuments (but separate from the integuments), generally functioning in animal seed dispersal, e.g. Sapindaceae. Adj: arillate. (seed part)

aristate With a stiff apical process, usually prolonged and straight, length : width ratio >3:1. (apical process)

arrangement Placement with respect to similar parts. (disposition)

arylphenalenones A class of chemical compounds common in the Haemodoraceae and also found

ascending Directed upward, with a divergence angle of 15 °45 ° from upper axis. (orientation)

ascidiate Referring to a carpel that is not leaflike, but develops from a ring of tissue that grows upward, sometimes assuming a somewhat peltate form.

asepalous Having no sepals or calyx. (perianth merosity)

asterad type A type of embryo development in which the terminal cell divides longitudinally, with both basal and terminal cell derivatives contributing to the mature embryo.

asymmetric Lacking a plane of symmetry. (symmetry)

atactostele A stele consisting of numerous, collateral vascular bundles positioned throughout the stem tissue.

atectate A pollen grain that ancestrally lacks a tectum.

ategmic An ovule lacking an integument.

attenuate Basal margins abruptly incurved (concave), the basal intersection angle <45°. (base)

attractant An aspect of floral morphology that functions to entice an animal pollinator to the flower, either by vision or by odor.

auctorum non The misapplication of a name, such that the type specimen of the name does not fall within the circumscription of the taxon being referred to by that name. Abbr: auct. non.

auriculate With two rounded, basal lobes, margins above lobes concave. (base)

autapomorphy An apomorphy that occurs for a single lineage or taxon.

author The name of the person who first validly published a scientific name.

autochory Self-dispersal. Adj: autochorous.

autogamy Inbreeding occurring within a single flower. Adj: autogamous. Syn: infrafloral selfing.

autonym An automatically created name for infrafamilial, infrageneric, and infraspecific taxa.

autopolyploidy Polyploidy occurring within a species.

autumnal Appearing in fall. (periodicity)

awn (a) bristlelike, apical appendage, e.g. on the glumes or lemmas of grass spikelets. (b) A unit of a pappus type in the Asteraceae that is narrow, elongate, straight, and stiff. (inflorescence part)

axial parenchyma Longitudinally oriented parenchyma cells that occur in some secondary xylem (wood) tissues.

axil The region at the upper (adaxial) junction of leaf and stem. (position)

axile With the placentae positioned along the column in a septate, compound ovary. (placentation)

axillary (a) On the side of a structure or at the nodes of an axis. (position). (b) With the inflorescence positioned in the axil of the nearest vegetative leaf. Syn: lateral. (inflorescence position)

axillary bud Bud in axils of leaves or leaf scars. Syn: lateral bud. (bud type)

baccate Fleshy or juicy, often with reference to a fruit. Syn: succulentcarnose. (texture)

baculate A pollen sculpturing with rod-shaped elements, each element termed a baculum.

baculum A rod-shaped element, as in the wall sculpturing of some pollen grains. Pl: baculi. Adj: baculate.

barbed/barbellate With minute, lateral, sharp appendages (barbs) arising along the surface or margin of a bristle, the barbs typically antrorse or retrorse in orientation. (bristle type)

bark Tissues external to the vascular cambium in stem (and roots) of woody plants, consisting of secondary phloem (inner bark) and derivatives of the cork cambium (outer bark or periderm). (stem/shoot parts)

basal (a) At or near the bottom or base of a structure. Syn: radical. (position) (b) With the placenta at the base of the ovary, e.g. Asteraceae, Poaceae. (placentation) (c) With three or more primary veins diverging from one point at the base of the blade, a subcategory of actinodromous and palinactinodromous. (leaf venation)

basic A type of anther wall development in which both secondary parietal cell layers divide to yield two middle layers.

basicidal capsule A capsule dehiscing by means of basal slits, as in Aristolochia spp. (fruit type)

basifixed Anther attached at its base to the apex of the filament. (anther attachment)

basionym The original, but now rejected, name, part of which has been used in a new combination.

Bayesian analysis/inference A method of phylogenetic inference based upon the posterior probability of a phylogenetic tree.

beak An extended, usually accrescent, basal stylar region, typically functioning in fruit dispersal, e.g. Taraxacum, dandelion. (style structural type)

beard A tuft, line, or zone of trichomes on a perianth or perianth part. Adj: bearded. (perianth part, vestiture)

berry A fleshy fruit with a succulent pericarp, e.g. Vitis, grape. (fruit type)

bicollateral bundle A vascular bundle with phloem to both the inside and outside of the xylem.

bicolor unit An inflorescence unit, possibly an apomorphy of the Malvaceae s.l., consisting of a modified, three-bracted cyme, the bracts modified into an epicalyx in members of the group.

biennial A plant living 2 years, typically forming a basal rosette of leaves during the first year and flowering with an elongate inflorescence stalk in the second year. (duration)

bifid Two-lobed to two-divided, especially at the apex. (division)

bigeminate A compound leaf with two rachillae, each bearing two leaflets. (leaf type)

bilabiate Two-lipped, with two, generally upper and lower segments, e.g. many Lamiaceae. (perianth type)

bilateral Zygomorphic, irregular. (symmetry)

bimerous Referring to a whorl with two members. (merosity, perianth merosity)

binary character A character with only two character states.

binomial Format for the scientific name of species, composed of two names, the genus name and the specific epithet, italicized or underlined.

binucleate Having two nuclei, referring to some angiosperm pollen grains at the time of release.

bipinnate/bipinnately compound A compound leaf with two orders of axes, the second axes (rachillae) bearing leaflets. (leaf type)

bipinnatifid Bipinnately lobed to divided. (division)

biradial Having two planes of symmetry. (symmetry)

biseriate (a) With two whorls of parts. (cycly) (b) Perianth parts in two distinct whorls. (perianth cycly) (c) Having two whorls or cycles of stamens (stamen cycly) Syn (a c): dicyclic. (d) Rays in wood that are made up of two vertical rows of cells.

bisexual Flowers having both carpel(s) and stamen(s). Syn: perfect. (flower sex)

bisporangiate Anther with two microsporangia and typically one theca. Cf: monothecal. (anther type)

bisporic Megasporogenesis in which cytokinesis occurs after the first meiotic division, but not the second, resulting in two cells, each of which contain two haploid nuclei, with one of the binucleate cells contributing to the female gametophyte.

bitegmic An ovule with two integuments, apomorphic for the angiosperms.

biternate/biternately compound A compound leaf with three axes, each of which is ternately compound. (leaf type)

blade The flat, expanded portion of leaf. Syn: lamina. (leaf part)

bootstrap/bootstrapping A method of evaluating cladogramrobustness that reanalyzes the data of the original character ×taxon matrix by selecting (resampling) characters at random, such that a given character can be selected more than once.

bostryx Helicoid cyme. (inflorescence type)

botany The traditional study of photosynthetic organisms (including the green plants, red algae, brown plants, dinoflagellates, and euglenoids, but excepting the photosynthetic bacteria), the true fungi, and groups that used to be treated as fungi, such as the Oomycota and slime molds; inclusive of the plant sciences.

bract A modified, generally reduced leaf, generally found associated with reproductive organs, e.g. subtending the ovuliferous scale of conifers or the flowers or inflorescence axes of flowering plants. Adj: bracteate. (leaf structural type)

bractlet/bracteole A smaller or secondary bract, often borne on the side of a pedicel. Syn: prophyllum. (leaf structural type, flower part)

Bremer support Decay index.

bristle An external hairlike plant structure, but stouter than a trichome.

brochidodromous Pinnate venation in which secondary veins do not terminate at the margin, forming prominent upward loops near the margin, joining other, more distal, secondary veins. (leaf venation)

bud An immature shoot system, often surrounded by protective scale leaves, developing into a lateral branch, a flower, or an inflorescence; may be gametophytic or sporophytic. (plant part, stem/shoot parts, twig part)

bud primordium An immature bud of the shoot, typically located in the leaf axil. (stem/shoot parts)

bulb A short, erect, underground stem surrounded by fleshy leaves, e.g. Allium spp., onions. (stem/shoot type)

bulbel A proliferative bulb arising from existing bulbs at or below ground level. (stem/shoot type)

bulbil A proliferative bulb arising from shoots above ground, typically within an inflorescence. (stem/shoot type)

bullate rugose. (configuration)

bundle cap An outer patch of sclerenchyma fibers associated with a vascular bundle.

bur A multiple fruit of achenes or grains surrounded by a prickly involucre, e.g. Cenchrus (Poaceae), Xanthium (Asteraceae). (fruit type)

burl A swollen, woody underground stem from which arises persistent,

woody, aerial branches, e.g. fire regenerative stems in some Arctostaphylos spp., Manzanita. Syn: lignotuber. (stem/shoot type)

buttress roots Enlarged, horizontally spreading and often vertically thickened roots at the base of trees that aid in mechanical support. (root type)

C4 photosynthesis An alternate photosynthetic pathway of some land plants in which carbon dioxide is initially fixed in the  mesophyll cells by the enzyme PEP carboxylase, producing a four-carbon molecule, which is transported to bundle sheath cells, where the carbon dioxide is released and fixed by ribulose bisphosphate carboxylase in the typical dark reactions.

caducous Dropping off very early compared with what is typical, usually applied to floral parts. (duration)

callose A polysaccharide, composed of beta-1,3-glucose units, which lines the pores of sieve areas and sieve plates of sieve elements and is commonly deposited within pollen tubes.

calyptra An apical region of archegonial tissue that is torn from and lifted up by the elongating sporophyte during the latter development and that may function to protect the young sporophyte apex.

calyptrate Having calyx and corolla fused into a cap that falls off as a unit, e.g. Eucalyptus. (perianth type)

calyx The outermost series or whorl of modified leaves in the perianth, the units of which are sepals. (flower part)

calyx lobes The segments of a calyx that is synsepalous (with connate sepals).

campanulate Bell-shaped, i.e. with a basally rounded, flaring tube about as broad as long and flaring lobes, e.g. Campanula; may also be used for bell-shaped apopetalous corolla or apotepalous perianth. (perianth type)

camptodromous Pinnate venation in which secondary veins do not terminate at the margin. (leaf venation)

campylodromous With several primary veins running in prominent, recurved arches at the base, curving upward to converge at the leaf apex. (leaf venation)

campylotropous A general ovule type in which curvature of the ovule during development displaces the micropyle adjacent to the funiculus base, with the nucellus bent only along the lower side.

canaliculate Longitudinally grooved, usually in relation to petioles or midribs. (configuration)

canescent Covered with dense, fine grayish-white trichomes; whitish-pubescent. (vestiture)

capillary bristle A unit of a pappus type in the Asteraceae that is generally straight, very thin, and threadlike, often barbellate.

capitate Head-shaped; spherical with a short basal stalk. (shape)

capitulum Head. (inflorescence type)

capsule (a) The spore-producing component of the sporophytes of liverworts, hornworts, and mosses. (plant part). (b) A dry, dehiscent fruit derived from a compound ovary. (fruit type)

carinate Keeled, having a sharp, median fold projected on the abaxial side; sharply conduplicate. (perianth type)

carnose Baccatesucculent. (texture)

carpel The unit of the gynoecium of angiosperms; ancestrally, a modified, conduplicate female (mega-) sporophyll of a flower, at maturity enclosing one or more ovules. (flower part, Gynoecium part)

carpophore The stalklike structure that is attached to the mericarps in a schizocarp of mericarps, e.g. Apiaceae. (fruit part)

cartilaginous With the texture of cartilage; hard and tough but flexible, usually whitish. (texture)

caruncle A fleshy outgrowth at the base of the seed, generally functioning in animal seed dispersal, e.g. Viola. (seed part)

caryophyllid type A type of embryo development in which the terminal cell divides transversely, with only terminal cell derivatives contributing to the mature embryo.

caryopsis Grain. (fruit type)

Casparian strip A band or ring of mostly suberin that infiltrates the cell wall of endodermal cells, functioning to force water and mineral solutes to pass through the plasma membrane of these cells.

cataphyll A rudimentary scale leaf found in usually hypogeous (cryptocotylar) seedlings. (leaf structural type)

catkin A unisexual, typically male spike or elongate axis that falls as a unit after flowering or fruiting, e.g. Quercus. Syn: ament. (inflorescence type)

caudate Abruptly acuminate into a long, narrowly triangular (tail-like) apical region. (apex)

caudex A short, thick, vertical or branched perennial stem, underground or at/near ground level. (stem/shoot type)

caudiciform stem A low (at or above ground level), swollen, perennial storage stem from which arise annual or otherwise nonpersistent photosynthetic shoots, e.g. some Dioscorea spp.,  Calibanus. (stem/shoot type)

caulescent Having an above ground, vegetative stem. (stem habit)

cauliflorus Inflorescence growing directly from a woody trunk. (inflorescence position)

cauline Positioned along the length of the stem. (position)

cell The structural unit of all life.

cell differentiation The series of changes that a cell undergoes from the point of inception to maturity, involving the transformation of a meristematic cell into one that assumes a particular structure and function.

cell expansion Growth of a cell in size, often involving axial elongation.

cell theory The postulate that all life is composed of one or more cells, that cells arise only from preexisting cells, and that cells are the units of metabolic processes.

cell wall A layer of the plant cell that is secreted outside the plasma membrane.

cellular endosperm An endosperm in which the endosperm cell divides mitotically, regularly followed by cytokinesis, each endosperm nucleus contained within a cell wall.

cellulose A polymer of glucose sugar units ( =polysaccharide) in which the glucose molecules are chemically bonded in the beta- 1,4 position (â =-1,4-glucopyranoside); a major component of the cell wall of green plants.

cellulose A polysaccharide of glucose units (â-1,4-glucopyranoside), a primary component of plant cell walls.

central At or near the middle or middle plane of a structure. (position)

central cell In a typical angiosperm female gametophyte, the single, relatively large cell in the central region that contains the two polar nuclei.

centric leaf A leaf that is cylindrical in shape, e.g. Fenestraria of the Aizoaceae. (leaf structural type)

centrifugal Developing from the center region toward the outside or periphery; can be applied to parts of perianth, calyx, corolla, androecium, or gynoecium. (flower maturation)

centripetal Developing from the outside or periphery toward the center region; can be applied to parts of perianth, calyx, corolla, androecium, or gynoecium. (flower maturation)

cernuous With tip drooping downward, abaxially. (transverse posture)

cespitose/caespitose Referring to a generally short, bunched, much-branched plant forming a cushion. (stem habit)

chaff One of the bracts subtending flowers in some Asteraceae, e.g. tribe Heliantheae. Syn: palea. (leaf structural type)

chalazal Describing the region of an ovule that is opposite the micropyle.

chalazal Referring to the proximal region of the ovule, opposite the micropyle.

character a feature or attribute of a taxon

character correlation The condition in which one character is interdependent upon and influenced by another character.

character evolution The sequence of evolutionary changes occurring for a given character.

character optimization The representation of characters in a cladogram in a most parsimonious way, such that the minimal number of character state changes occur.

character state one of two or more forms of a character

character step matrix A numerical tabulation of the number of  changes occurring between all pairwise combinations of character states for a given character.

character taxon matrix A numerical tabulation of the characters and corresponding character states for each taxon in a Phylogenetic analysis.

chartaceous Opaque and of the texture of writing paper. (texture)

chasmogamy Referring to typical flowers in which the perianth opens and exposes the sexual organs, with subsequent crosspollination common. Adj: chasmogamous.

cheiropterophily Pollination by bats. Adj: cheiropterophilous.

chenopodiad type A type of embryo development in which the terminal cell divides transversely, with both basal and terminal cell derivatives contributing to the mature embryo.

Chlorobionta A monophyletic group of eukaryotes, consisting of  the green algae and the land plants, united ha ving chloroplasts with chlorophyll a and b, starch, and thylakoids stacked as grana [green plants].

chlorophyll a The primary pigment in the light reactions of photosynthesis, found in the chloroplasts of all photosynthetic eukaryotes and some bacteria.

chlorophyll b An accessory pigment in the light reactions of photosynthesis, an apomorphy of the green plant chloroplast.

chlorophyllous Having chloroplasts at maturity; green.

chlorophyllous cell 1. Any general, chloroplast-containing cell. 2. One of the chloroplast-containing cells in the specialized leaves  of Sphagnum moss the border and surround a hyaline cell.

chloroplast A double membrane-bound organelle with internal thylakoid membranes (lamellae and grana in the green plants), functioning in the reactions of photosynthesis.

chloroplast An organelle of some eukaryotes that functions in photosynthesis.

chromoplast Carotenoid-containing bodies that function to provide yellow, orange, or red pigmentation for a plant organ, as in petals or fruits; a type of ergastic substance.

ciliate With conspicuous marginal trichomes. (margin, vestiture)

ciliolate With minute trichomes protruding from margins; minutely ciliate. (margin, vestiture)

cincinnus Scorpioid cyme. (inflorescence type)

circinate With the leaf (blade plus rachis and rachillae, if present) coiled from apex to base, as in young fern and cycad leaves. (posture: ptyxis/aestivation)

circinate vernation Descriptive of a leaf (including the blade and rachis/rachillae, if present) that is coiled from apex to base when immature, as in young fern and cycad leaves (posture: ptyxis/ aestivation).

circumferential At or near the circumference; surrounding a rounded structure. (position)

circumscissile capsule A capsule having a transverse line of dehiscence, e.g. Plantago. Syn: pyxis/pyxide. (fruit type)

cirrhose With a flexible, greatly curled apical process. (apical process)

clade A sequence of ancestral-descendent populations through time; a set of organisms interconnected through time and space by the transfer of genetic material from parents to offspring, represented as a line on a clado gram. Syn: lineage.

cladistics A methodology for inferring the pattern of evolutionary history of a group of organisms, utilizing grouping of taxa by apomorphies [phylogenetic systematics].

cladistics Phylogenetic systematics.

cladode/cladodophyll A flattened photosynthetic stem, functioning as and resembling a leaf. Adj: phylloclad. (stem/shoot type)

cladodromous Pinnate venation in which secondary veins do not terminate at the margin and branch near the margin. (leaf venation)

cladogram A branching diagram that conceptually represents the best estimate of phylogeny. Syn: phylogenetic tree.

cladogram robustness A measure of the confidence for which a cladogram actually denotes phylogenetic relationships, e.g. by bootstrapping.

clambering Sprawling across objects, without specialized climbing structures. Syn: scandent. (stem habit)

classification The arrangement of taxa (or other entities) into some type of order or grouping.

clava A club-shaped element, as in the sculpturing of some pollen grains. Pl: clavae.

clavate (a) Club-shaped; terete with a gradually tapering thickened and rounded end. (shape) (b) A pollen sculpturing with clubshaped elements, each element termed a clava.

claw An attenuate base of a sepal or petal. (perianth part)

cleft Sinuses extending (pinnately or palmately) one quarter to one half the distance to the midrib, midvein, or vein junction. (division)

cleistogamy Referring to flowers in which the perianth remains closed, such that pollen produced from within the flower pollinates only the stigma(s) of that flower. Adj: cleistogamous.

climbing Growing upward by means of tendrils, petioles, or adventitious roots. (stem habit)

coherent With like parts joined, but only superficially and easily separable. (fusion)

coleoptile A protective sheath surrounding the epicotyl, e.g. in some members of the Poaceae. (seed/embryo part)

coleorhiza A protective sheath surrounding the radicle, e.g. in some members of the Poaceae. (seed/embryo part)

collateral A vascular bundle with an internal strand of xylem and an external strand of phloem.

collateral bud Bud(s) lateral to the axillary bud. (bud type)

collateral bundle A vascular bundle with xylem to the inside and phloem to the outside.

collenchyma A cell type that is live at maturity, has unevenly thickened, pectic-rich, primary cell walls, and functions in structural support, often found at the periphery of stems or leaves.

colleter A structure on the inner surface of connate stipules that secretes mucilage, aiding in protection of young, developing shoots, e.g. Rubiaceae. (leaf parts)

color pattern The distribution of colors on an object. (color)

colporate A pollen grain aperture type that is shaped like a colpus but has a circular region in the center.

colpus A pollen grain aperture that is elongate with a length:width ratio of greater than 2:1. Pl: colpi. Adj: colpate.

columella (a) A central column of sterile (non-spore-producing) tissue within the sporophyte capsule of hornworts. (b) One of the middle, radially elongate elements of a tectate-columellate pollen exine wall. Pl: columellae.

column a. The central axis to which septae  and / or placentae are attached in axile or free-central placentation. (gynoecium part) b. gynandriumgynostegiumgynostemium. (flower part)

combinatio nova Indication that a taxon has recently been transferred to a new position or rank. Abbr: comb. nov.

commemorative A name that is after a person or place.

common name A vernacular name, used by people within a limited geographic region, not formally published and governed by no rules.

comose With an apical tuft of trichomes. (vestiture)

companion cell A parenchyma cell associated with a sieve tube member, derived from the same parent cell as is the sieve tube member and functioning to load and unload sugars into the cavity of the sieve tube member.

complete Having all four major whorls or floral parts: sepals, petals, stamens, carpels. (flower cycly)

complex tissue A tissue that contains more than one cell type.

compound cone The cone of a conifer, consisting of an axis bearing bracts, each of which subtends a modified branch systems, the ovuliferous scale.

compound corymb A branched corymb, consisting of two or more orders of inflorescence axes bearing flat-topped or convex, pedicellate flowers. (inflorescence type)

compound cyme A branched determinate inflorescence, similar to a compound dichasium but lacking a consistent dichasial branching pattern, often by reduction of internodal axes. (inflorescence type)

compound dichasium A many-flowered, determinate inflorescence of repeatedly branching simple dichasia units. (inflorescence type)

compound leaf A leaf divided into two or more discrete leaflets.(leaf type)

compound ovary/pistil An ovary/pistil composed of a two or more carpels, the gynoecium syncarpous. (ovary/pistil type)

compound perforation plate A perforation plate composed of several openings.

compound receptacle A mass of tissue at the apex of a peduncle that bears more than one flower. Syn: torus. (inflorescence part)

compound sieve plate A sieve plate that is made up of two or more aggregations of pores.

compound umbel An umbel with the peduncle bearing rays attached at one point and unit simple umbels attached at the tip of the rays, e.g. many Apiaceae. (inflorescence type)

conduplicate Longitudinally folded at the central axis, with adjacent adaxial sides facing one another. (longitudinal posture)

cone A modified, determinate, reproductive shoot system of many nonflowering vascular plants, consisting of a stem axis bearing either sporophylls (in simple cones) or ovuliferous scales subtended by bracts (in compound cones of conifers). Syn: strobilus. (plant part)

confer Indication that the identity of a specimen is questionable or uncertain and should be compared with specimens of the taxon indicated for more detailed study. Abbr: cf.

configuration Referring to gross surface patterns other than venation or epidermal excrescences. (surface)

connate With like parts integrally fused, not easily separable. (fusion)

connate-perfoliate Two opposite leaves fused basally, such that the blade base of each leaf completely surrounds the stem. (leaf attachment)

connective The tissue or filament extension between the thecae of an anther. (anther part)

connivent Convergent apically without fusion. (orientation)

consensus tree A cladogram derived by combining features in common between two or more cladograms.

conservation of names A principle of the International Code of Botanical Nomenclature stating that scientific names that are well known and frequently used may be retained over other, earlier, but less well-known, names.

consistency index (CI) A measure of the relative amount of homoplasy in a cladogram, equal to the ratio of the minimum possible number of character state changes to the actual number of changes that occur.

contiguous With parts touching but not fused. (fusion)

contorted Convolute. (perianth aestivation)

convergence Homoplasy occurring by the independent evolution of a similar feature in two or more lineages. Syn: parallelism.

convolute Perianth parts of a single whorl overlapping at one margin, being overlapped at the other, e.g. corolla of Malvaceae. Syn: contorted. (perianth aestivation)

cordate With two rounded, basal lobes intersecting at sharp angle, the margins above lobes smoothly rounded. (base)

cordate/cordiform Shaped like an upside-down Valentine heart; approximately ovate with a cordate base. (shape)

coriaceous Thick and leathery, but somewhat flexible. (texture)

cork The outermost layer of the periderm, generated by the cork cambium.

cork cambium A sheath or hollow cylinder of cells that develops near the periphery of the stem or root, undergoing tangential divisionsto form phelloderm to the inside and cork to the outside.

corm An enlarged, solid underground storage stem or stem base, with outer, protective scales. (stem/shoot type)

cormel A proliferative corm arising from existing corms. (stem/ shoot type)

corolla The innermost series or whorl of modified leaves in the perianth, the units of which are petals. (flower part)

corolla lobe A segment of a sympetalous corolla (with connate petals).

corona A crownlike outgrowth between stamens and corolla; may originate from petals or stamens. (perianth part, perianth type)

coronate With a tubular or flaring perianth or staminal outgrowth, e.g. NarscissusAsclepias. (perianth type)

correct name A legitimate, validly published name that is accepted by a particular author or authors.

cortex The outer, mostly parenchymatous tissue inner to the epidermis and external to the vasculature. (root part, stem/shoot parts)

corymb An indeterminate inflorescence consisting of a single axis with lateral axes and/or pedicels bearing flat-topped or convex flowers. (inflorescence type)

costa (a) Midrib. (b) The nonvascularized conductive tissue found in the gametophytic leaves of some mosses. (leaf part)

costapalmate Essentially palmately lobed to compound but with an elongate, rachislike extension of the petiole, as in some palms. (leaf type) 

cotyledon A first (seed) leaf of the embryo, often functioning in storage of food reserves. (seed part)

cotylespermous With the food reserve in the cotyledon, part of the embryo. (seed endosperm type)

couplet The pair of contrasting leads in a dichotomous key.

craspedodromous Pinnate venation in which secondary veins terminate at the leaf margin. (leaf venation)

crassinucellate An ovule in which the nucellus develops two or more layers of cells, the inner ones from divisions of a parietal cell.

crassulacean acid metabolism An alternate photosynthetic pathway in some xeric, generally succulent plants and functioning to conserve water, in which initial fixation of carbon dioxide occurs at night (when stomata are open) by the enzyme PEP carboxylase to form malic acid, which is stored within vacuoles of the mesophyll cells; during the day the stomata close and CO2 is released from the vacuoles into the cytoplasm, where it is fixed in the chloroplasts. Abbr: CAM.

crenate With rounded to obtuse, shallowly ascending teeth, cut 1/16 to 1/8 the distance to the midrib, midvein, or junction of primary veins. (margin)

crenulate Diminutive of crenate, teeth cut  ≤1/16 the distance to the midrib, midvein, or junction of primary veins. (margin)

crownshaft The collection of overlapping, sheathing leaf bases at the apex of a palm trunk.

crozier A leaf that is coiled during its development, characteristic of the leptosporangiate ferns (Polypodiales) and Marattiales.Syn: fiddlehead.

cruciate With four, distinct petals in a cross form, e.g. many Brassicaceae. (perianth type)

crucifer type A type of embryo development in which the terminal cell divides longitudinally, with only terminal cell derivatives contributing to the mature embryo. Syn: onagrad type.

crypantherous Inserted. (stamen insertion)

cryptocoylar Hypogeous. (seed germination type)

crystal A deposit of silica or calcium oxalate in plant cells that may function as waste products, as calcium ion sinks, or as an irritant to deter herbivory; a type of ergastic substance.

cucullate Hooded; with an abaxially concave posterior lip. (perianth type)

culm The flowering and fruiting stem(s) of grasses and sedges. (stem/shoot type)

cuneate With basal margins approximately straight, intersection angle 45 °90 °. (base)

cup-shaped Concave-convex along entire surface; may be abaxially or adaxially concave. (longitudinal posture)

cupule A structure that encloses a cluster of unitegmic ovules/seeds, with a small opening near the proximal end, through which pollen grains entered; characteristic of some Pteridosperms, e.g. Caytonia.

curator The person in charge of the day-to-day running of an herbarium.

cuspidate Abruptly acuminate into a triangular, stiff or sharp apex. (apex)

cuticle A protective layer, containing cutin, that is secreted to the outside of epidermal cells and functions to inhibit water loss; found in all land plants.

cutin A polymer of fatty acids, functioning as a sealant in the cuticle layer of land plants, inhibiting water loss.

cyathium An inflorescence bearing small, unisexual flowers and subtended by an involucre (frequently with petaloid glands), the entire inflorescence resembling a single flower, e.g. Euphorbia. (inflorescence type)

cycly Number of cycles or whorls of parts. (number)

cyme General term for a determinate inflorescence. (inflorescence type)

cymule A small, simple dichasium. (inflorescence type)

cypsela An achene derived from an inferior ovary, e.g. Asteraceae. Syn: achene (in general sense).

cystolith A mass of calcium carbonate attached to a stalk from the cell wall, occurring within specialized cells termed lithocysts.

cytoplasm Everything inside the plasma membrane but not including the nucleus.

dark reactions A series of biochemical reactions of photosynthesis in plants, occurring in the stroma of the chloroplast, during which atmospheric carbon dioxide reacts to produce a molecule of glucose, requiring the input of the high-energy compounds ATP and NADPH2.

data information system/database system Referring to the (computerized) organization, inputting, and accessing of information.

decay index A method of evaluating cladogram robustness by calculating how many extra steps are needed (beyond the number in the most parsimonious cladograms) before the original clade is no longer supported; the greater this value, the greater the confidence in a given clade. Syn: Bremer support.

deciduous Parts persistent for one growing season, then falling off, e.g. leaves of deciduous plants. (duration)

decompound A general term for a leaf having leaflets in two or more orders: bi-, tri-, and so on pinnately, palmately, or ter nately, compound; also used for a highly divided leaf. (leaf type, division)

decumbent Basally prostrate but ascending apically. (stem habit)

decurrent Appearing to extend down the stem from the point of attachment, as if fused to the stem, e.g. many Cupressaceae. (leaf attachment)

decussate Opposite leaves or other structures at right angles to the preceding pair. (arrangement)

decussate tetrad A tetrad in which the four grains are in two pairs arranged at right angles to one another.

deflexed Bent abruptly downward. (orientation)

deltate Three-sided, length : width ratio 1:1. (shape)

dendritic Trichomes treelike, with multiple lateral branches. (trichome type)

dendrochronology The scientific study of wood anatomy to infer details about past events.

dentate With sharp, coarse teeth that point outward at right angles to margin outline, cut 1/16 to 1/8 distance to midrib, midvein, or junction of primary veins. (margin)

denticulate Diminutive of dentate, teeth cut to 1/16 or less the distance to the midrib, midvein, or junction of primary veins. (margin)

depressed Pressed closely to axis downward, with divergence angle of 0 °15  °from lower axis. (orientation)

derived Referring to a new condition or character state. Syn: apomorphicadvanced.

dermal tissue The outer region of plant organs, composed of the epidermis.

descending Directed downward, with divergence angle of 15 °45  °from lower axis. (orientation)

descent The sequence of ancestral-descendant populations through time.

description The assignment of features or attributes to a taxon or other entity.

determinate (a) A shoot that terminates growth after a certain period, the apical meristem aborting or converting into a flower, inflorescence, or other specialized structure (stem branching pattern, stem type). (b) An inflorescence in which the terminal flower matures first, maturating from apex to base. (inflorescence


dextrorse Twining helically like a typical, right-handed screw, e.g. some Convolvulaceae. (twisting/bending posture)

diadelphous With two groups of stamens, each connate by filaments, e.g. many Faboideae (Fabaceae). (stamen fusion)

dichasium A determinate inflorescence that develops along two axes, forming one or more pairs of opposite, lateral axes. (inflorescence type)

dichlamydeous Perianth composed of a distinct outer calyx and inner corolla, regardless of total number of whorls. (perianth cycly)

dichogamy A type of outcrossing mechanism that is the result of differences in timing of maturation of male and female floral parts. Adj: dichogamous.

dichotomous With veins successively branching distally into two veins of equal size and orientation, e.g. Ginkgo biloba.(leaf venation)

dichotomous key A key utilizing series of two contrasting statements, each statement a lead, the pair of leads a couplet.

dicotyledonous A type of anther wall development in which only the outer secondary parietal cell layer divides to yield the endothecium and a single middle layer.

dictyostele A dissected amphiphloic siphonostele.

dicyclic Biseriate. (cycly, perianth cycly, stamen cycly)

didymous With stamens in two equal pairs. (stamen arrangement)

didynamous With stamens in two unequal pairs, e.g. many Bignoniaceae, Lamiaceae, Scophulariaceae. (stamen arrangement)

diffuse-porous Wood in which vessels develop more or less uniformly throughout the growth season.

dioecious/dioecy Having unisexual flowers, staminate and pistillate on separate individual plants. (plant sex)

diphthong A two-vowel combination in Latin that is treated as the equivalent of a single vowel.

diplohaplontic life cycle Haplodiplontic life cycle.

diplostemonous Stamens in two whorls, the outer opposite the sepals, the inner opposite petals. (stamen position)

discoid (a) Discus-shaped. (shape). (b) Stigma(s) disk-shaped. (stigma/stigmatic region type)

disk A discoid or doughnut-shaped structure arising from the receptacle at the outside and surrounding the stamens. (extrastaminal disk), at the base of the stamens (staminal disk), or at the inside of the stamens and/or base of the ovary (intrastaminal disk); may be nectar-bearing (nectariferous disk). (flower part)

disk flower Having an actinomorphic, tubular corolla with flaring lobes, e.g. some Asteraceae. (perianth type)

dispersal The movement of an organism or propagule from one region to another, such as the transport of a seed or fruit (by wind, water, or bird) from a continent to an island.

disposition Relative placement of objects or parts of objects, inclusive of position, arrangement, and orientation.

dissected Divided into very fine, often indistinct segments. (division)

distal Away from the point of origin or attachment. (position)

distal pole The intersection of the pollen grain polar axis with the grain surface that is away from the center of the microspore tetrad.

distichous Alternate, with points of attachment in two vertical rows/ranks, e.g. the grasses, Poaceae. (arrangement)

distinct With like parts unfused and separate. (fusion)

distyly Hercogamy in which two floral morphologies occur: pin flowers, with a long style and short stamens, and thrum flowers, with a short style and long stamens. Adj: distylous.

disulculate A pollen grain with two elongate apertures on opposite sides of the grain, parallel to the equatorial plane.

dithecal Anther with two thecae and typically four microsporangia. Cf: tetrasporangiate. (anther type)

diurnal During the day, typically with respect to when flowers open. (periodicity)

divaricate Divergenthorizontalpatent. (orientation)

divergence/diversification The formation of two (or more), separate lineages from one common ancestor.

divided Sinuses extending (pinnately or palmately) 3/4 to almost to midrib, midvein, or vein junction. (division)

dorsal Abaxial. (position)

dorsal vein The central vein of a carpel, corresponding to the midvein of a leaf. Syn: median vein.

dorsifixed Anther attached dorsally and medially to apex of the filament. (anther attachment)

dorsiventral Having a flattened shape, with an upper (adaxial) and lower (abaxial) surface, characteristic, e.g. of leaves.

doubly serrate With large, serrate teeth that have along the margin smaller, serrate teeth. (margin)

downward Anther dehiscing toward the ground in a horizontally oriented flower. (anther dehiscence direction)

drepanium A monochasium in which the axes develop on only one side of each sequential axis, typically appearing coiled at least early in development; sometimes equated with helicoids cymes. (inflorescence type)

drupe A fleshy fruit with a hard, stony endocarp, e.g. Prunus: peach, plum, cherry. (fruit type)

drupecetum An aggregate fruit of drupes, e.g. Rubus: raspberry, blackberry. (fruit type)

druse A spherical crystal with protruding spikes, composed of calcium oxalate; a type of ergastic substance.

duration The length of life of a plant or plant part. (temporal phenomena)

dyad A fusion product of two pollen grains.

ebracteate Lacking bracts. (flower attachment)

echina A spinelike sculpuring element >1 m long, as in some pollen grain walls. Pl: echinae. Adj: echinate.

eciliate Without trichomes on the margins, regardless of presence or absence of teeth. (margin)

ectophloic siphonostele A siphonostele in which a ring of xylem is surrounded by an outer layer of phloem only.

ectozoochory Dispersal by animals in which propagules are carried on the outside of an animal. Adj: ectozoochorous.

egg A nonmotile, evolutionarily enlarged gamete, the end product of oogamy.

ektexine An outer layer of the pollen grain exine wall.

elater (a) One of the hygroscopic appendages arising from the spores of Equisetum, functioning in spore dispersal. (b) A nonsporogenous, elongate, hygroscopic cell with spiral wall thickenings that develops within the sporangia of some liverworts and that functions in spore dispersal.

elliptic Margins curved, widest at the midpoint, the length : widthratio 2 : 1 to 3 : 2. (shape)

emarginate Having an apical incision, cut 1/16 to 1/8 the distance to midrib, midvein, or junction of primary veins. (apex)

embryo An immature, diploid sporophyte developing from the zygote of land plants. (seed part; plant part)

embryo proper That portion of the proembryo that will eventually grow into the new sporophyte.

embryo sac Term for the female gametophyte of angiosperms.

embryogeny The development of the embryo within the seed.

Embryophyta/embryophytes A monophyletic group of eukaryotes united by an outer cuticle, specialized gametangia antheridia and archegonia and an intercalated diploid phase in the life cycle, including the embryo [land plants].

emend Abbreviation of a correction or amendment of a name.

emergent With roots or stems anchored to substrate under water, the aerial shoots above water. (plant habitat)

emersed Occurring under water. (plant habitat)

enantiostyly A type of hercogamy in which the style of different flowers curves either the left or the right. Adj: enantiostylous.

enation A small appendage arising from the stem, resembling a rudimentary leaf but lacking vascular tissue.

endarch An orientation of xylem maturation in which the protoxylem is oriented toward the center of the stele relative to the metaxylem, as occurs in eusteles and atactosteles.

endexine An inner layer of the pollen grain exine wall.

endocarp The innermost wall layer of the pericarp, if the latter is divided into layers. (fruit part)

endodermis A hollow cylinder of cells in roots and some stems that surrounds the vasculature and functions to selectively control passage of solutes from the outside, via Casparian strips. Adj: endodermal. (root part, stem part)

endogenous Arising from the internal tissues, as in the growth of secondary roots from within a primary root.

endoplasmic reticulum A cellular organelle consisting of interconnected phospholipid membranes that may function in material transport and as the site of protein synthesis.

endosperm The triploid tissue that develops from mitotic divisions of the endosperm cell (the product of double fertilization), ultimately enveloping or abutting the embryo and functioning as the nutritive tissue of angiosperm seeds.

endospermous With endosperm as the food reserve in mature seeds. Syn: albuminous. (seed endosperm type)

endospory The development of a gametophyte within the original spore wall. Adj: endosporic.

endostomal Referring to the micropyle of a bitegmic ovule delimited by only the inner integument, the outer one being foreshortened.

endosymbiosis The intracellular cohabitation of one cell within another cell; the process that gave rise to mitochondria and chloroplasts by engulfment of a prokaryote by a eukaryotic cell.

endothecium The outermost cell layer of an anther, typically of enlarged cells with secondary wall thickenings functioning in anther dehiscence.

endozoochory Dispersal by animals in which propagules are eaten but are passed through the gut of the animal unharmed. Adj: endozoochorous.

ensiform Sword-shaped, with length : width ratio greater than 12 : 1, e.g. leaves of Iris spp. (shape)

entire Without teeth on margins; locally smooth. (Note, however, that surface may be divided.) (margin)

entomophily Pollination by insects. Adj: entomophilous.

epicalyx A series of bracts immediately subtending the calyx, e.g. Hibiscus, other Malvaceae. (leaf structural type)

epicotyl (a) The first shoot of a vascular plant that develops from the embryo. (b) The first shoot of a seed plant, derived from the embryo of the seed. (stem/shoot parts, seed part)

epidermal excrescence Referring to surface patterns from structural outgrowths or secretions of the epidermis. (surface)

epidermis The outermost cell layer of all land plant organs, functioning to provide mechanical protection of inner tissue and to inhibit water loss.

pigeous With cotyledon(s) elevated above the ground during germination. Syn: phanerocotylar. (seed germination type)

epigynous With sepals, petals, and stamens attached at the apex of the ovary, the ovary inferior. (perianth/androecial position)

epihypogynous With sepals, petals, and stamens attached at middle of the ovary, the ovary half-inferior. (perianth/androecial position)

epihypoperigynous Hypanthium present, attached at middle of ovary, with sepals, petals, and stamens attached to hypanthium rim, the ovary half-inferior. (perianth/androecial position)

epiperigynous Hypanthium present, attached at apex of ovary, with sepals, petals, and stamens attached to hypanthium rim, the ovary inferior. (perianth/androecial position)

epipetalous With stamens adnate to (inserted upon) petals or corolla. Syn: petalostemonous. (stamen fusion)

epiphytic Growing upon another plant. (plant habitat)

episepalous With stamens adnate to (inserted upon) sepals or calyx. (stamen fusion)

epitepalous With stamens adnate to tepals or the perianth as a whole. (stamen fusion)

epitropous An ovule position in which the micropyle points distally.

epitropous-dorsal An epitropous ovule position in which the raphe is dorsal (abaxial), pointing away from the central floral or ovary axis.

epitropous-ventral An epitropous ovule position in which the raphe is ventral (adaxial), pointing toward the central floral or ovary axis.

epitype A specimen (or illustration) that is selected to serve as the type if the holotype, lectotype, or neotype is ambiguous with respect to the identification and diagnosis of the taxon.

equator The intersection with the pollen surface of a plane at a right angle to the polar axis and passing through the center of the grain.

equatorial view Observing a pollen grain from the equatorial region.

equitant Leaves with overlapping bases, usually sharply folded along midrib. (arrangement)

erect Pointing upward. (orientation)

ergastic substance A cellular substance that does not function in metabolism, generally functioning in storage, waste secretion, and protection.

et Latin for and, used in scientif ic name combinations.

eucamptodromous Pinnate venation in which secondary veins do not terminate at the margin, curving upward near the margin but not directly joining adjacent secondaries. (leaf venation)

euphyll The sporophytic leaf of the euphyll group, growing by means of either marginal or apical meristems, having multiple, branched veins, and having an associated leaf gap. Adj: euphyllous.Syn: megaphyll. (leaf structural type)

eusporangium/eusporangiate sporangium A relatively large sporanigum that is derived from several epidermal cells and having a sporangial wall composed of more than one cell layer.

eustele A primary stem vasculature that consists of a single ring of discrete collateral or bicollateral vascular bundles.

evergreen Persistent two or more growing seasons, e.g. leaves of most conifers. (duration)

evolution Descent with modification; the transfer of genetic material from parent(s) to offspring over time, with a corresponding change in that genetic material.

exalbuminous Lacking endosperm as the food reserve in mature seeds. Syn: nonendospermous. (seed endosperm type)

exarch An orientation of xylem maturation in which the protoxylem is oriented toward the organ periphery relative to metaxylem, as occurs in some protosteles.

exfoliating Bark cracking and splitting off in large sheets. (bark type)

exindusiate Referring to a sorus that lacks an indusium.

exine The hard, outermost, desiccation-resistant layer of a pollen grain wall, providing structural support and inhibiting desiccation.

exocarp The outermost wall layer of the pericarp, if the latter is divided into layers. (fruit part)

exospory The formation of a gametophyte external to the original spore wall. Adj: exosporic.

exostomal Referring to the micropyle of a bitegmic ovule delimited by only the outer integument, the inner one being foreshortened.

explosively dehiscent Referring to a dry, dehiscent fruit that opens with force, in the process ejecting the seeds some distance away. (fruit type)

exserted With stamens protruding beyond the perianth. Syn: phanerantherous. (stamen insertion)

exstipellate Without stipels. (leaf part)

exstipulate Without stipules. (leaf part)

extrastaminal disk A discoid or doughnut-shaped structure arising from the receptacle at the outside and surrounding the stamens; may be nectar-bearing (nectariferous disk). (flower part)

extrorse Dehiscing outward, away from the flower center (anther dehiscence direction)

falcate/falciform Lanceolate to linear and curved to one side; scimitar-shaped. (shape)

false indusium An extension of the blade margin that overlaps the sorus of a leptosporangiate fern.

farinaceous Finely mealy, covered with small granules. Adj: granular, scurfy. (epidermal excrescence)

fascicle (a) A shoot with very short internodes on which flowers or leaves are borne. Syn: short shootspurspur shoot. (stem/shoot type). (b) A raceme-like or panicle-like inflorescence with pedicellate flowers in which internodes between flowers are very short, with pedicel bases appearing congested. (inflorescence

type) Adj: fasciculate.

fat A type of triglyceride compound that may function as highenergy storage compounds or secretion products in plants; a type of ergastic substance.

female (a) Individual with female reproductive organs only. (plant sex) (b) Pistillate. (flower sex)

female gametophyte A gametophyte that bears only archegonia, housing the egg cell. Syn: megagametophyteembryo sac.

female sporophyll A sporophyll that bears one or more megasporangia or seeds. Syn: megasporophyll.

fenestrate Having windowlike holes in the surface, e.g. Monstera deliciosa, Araceae (configuration)

fertile segment The sporangia containing component of the leaf of an ophioglossoid fern.

fiber A sclerenchyma cell that is long and very narrow, with sharply tapering end walls, functioning in mechanical support and often occurring in bundles.

fibrous roots Roots that are adventitious and typically fine and numerous. (root type)

fiddlehead Crozier.

filament A stamen stalk, generally terete in shape. (stamen part)

filamentous (a) With a more or less terete stamen stalk, as opposed to a laminar body. (stamen type) (b) Filament present, as opposed to absent and anther sessile. (stamen attachment)

filiferous Bearing coarse, fiberlike structures. (margin)

filiform Long, thin, and typically flexuous, threadlike, filamentous. (shape)

fissured Bark split or cracked into vertical or horizontal, usually coarse grooves. (bark type)

fistulose/fistular Cylindrical and hollow within. (shape)

flabellate With three or more primary veins diverging from one point and several, equal, fine veins branching toward the leaf  apex, a subcategory of actinodromous. (leaf venation)

flexuous Central axis and tip alternately curved up and down. (transverse posture)

floating Occurring at the water surface. (plant habitat)

floccose With dense trichomes in several patches or tufts. (vestiture)

flora A listing of the plant taxa of a given region, usually accompanied by keys and descriptions. Syn: manual.

floral diagram A diagrammatic, cross-sectional view of a flower

bud, showing the relative relationship of perianth, androecial, and

gynoecial components, and illustrating things such as stamen

position, placentation, and perianth, calyx, or corolla aestivation.

floral formula A symbolic representation of floral morphology,

including cycly (number or whorls or series), merosity (number

of parts per whorl), fusion of parts, and ovary position.

floral tube Hypanthium. (flower part)

floret A unit of a grass (Poaceae) spikelet, consisting of a short,

lateral axis bearing two bracts (lemma and palea) that subtend a

terminal, reduced flower. (inflorescence type)

floristics The documentation of all plant species in a given geographic


flower The reproductive organ of flowering plants; a modified,

determinate shoot bearing sporophylls (stamens and/or carpels)

with or without outer modified leaves, the perianth. (plant part,

inflorescence part)

flower bract A modified, generally reduced leaf subtending a flower. (flower part)

flower bud A bud that develops into a flower. (bud type)

follicetum An aggregate fruit of follicles, e.g. Magnolia. (fruit type)

follicle A dry, dehiscent fruit derived from one carpel that splits along one suture, e.g. Asclepias, milkweed. (fruit type)

foot-layer The inner layer of a tectate-columellate pollen exine wall.

form genus A genus that corresponds to a particular organ of a fossil plant.

fossulate A pollen sculpturing with longitudinal grooves.

foveolate A pollen sculpturing with a pitted surface caused bypores in the surface.

free With unlike parts unfused, separate. (fusion)

free-central With the placenta along the column in a compound ovary lacking septa, e.g. Caryophyllaceae. (placentation)

Fritillaria type A type of tetrasporic female gametophyte in which three of the four megaspores fuse fuse to form a triploid nucleus, followed by two sequential mitotic divisions of the haploid and triploid nuclei, resulting in an 8-nucleate female gametophyte in which the three antipodals and one of the polar nuclei are triploid, the other polar nucleus and the cells of the egg apparatus remaining


frond Specialized term for a fern leaf.

fruit The mature ovary of flowering plants, consisting of the pericarp (mature ovary wall), seeds, and (if present) accessory parts.(plant part)

frutescent Having the habit of a shrub, with numerous, woody, aerial trunks. (stem habit)

fumatory A substance that is smoked by humans, usually for its pleasing or euphoric effects, e.g. tobacco, Nicotiana tabacum.

funiculus A stalk that attaches the ovule to the placenta. (Gynoecium part)

fusiform Spindle-shaped; narrowly ellipsoid with two attenuate ends. (shape)

galeate Hooded; with an abaxially concave posterior lip. (perianth type)

gamete A specialized, haploid cell that fuses with another gamete (in sexual reproduction) to form a diploid zygote.

gametophyte The haploid phase in the life cycle of all land plants.

gamopetalous Sympetalous. (perianth fusion)

gamosepalous Synsepalous. (perianth fusion)

geitonogamy Inbreeding occurring between different flowers derived from one individual. Adj: geitonogamous.

geminate A compound leaf with two leaflets arising from a petiole and no rachillae. (leaf type)

geminate-pinnate A compound leaf with two rachillae, each bearing a pinnate arrangement of leaflets. (leaf type)

gemma (a) An asexual propagule produced within the gemmae cups of some thalloid liverworts. (b) One of the globose or ellipsoid elements of a gemmate pollen grain. Pl: gemmae.

gemma cup A cup-shaped organ on the upper surface of the gametophytes of some thalloid liverworts, containing gemmae propagules.

gemmate A pollen sculpturing with globose or ellipsoid elements, each element termed a gemma.

gender The designation of masculine, feminine, or neuter in Latin names.

generative cell One of the two initial, haploid cells in the male gametophyte of angiosperms that mitotically divides to form two sperm cells.

genetic drift Random genetic modification of a population or species, not the result of natural selection.

genet A genetically different individual of a population. Cf: ramet.

geniculate Having a zig-zag posture, e.g. the inflorescence rachis of some grasses. (twisting/bending posture)

genus name The first component of a binomial, always capitalized.

genus novum Meaning that a taxon name, at the rank of genus, is new to science. Abbr: gen. nov.

geophyte A perennial herb, typically with a bulb, corm, rhizome, or tuber underground stem. (plant habit)

girdling A type of anther endothecium in which the secondary wall thickenings form rings with cross bridges between them.

glabrate Nearly glabrous or becoming glabrous with age. (vestiture)

glabrous Without trichomes. (vestiture)

glandular (a) Covered with minute, blackish to translucent glands (epidermal excrescence). (b) Trichomes secretory or excretory, usually having an apical glandular cell. (trichome type)

glandular (tapetum type) Secretory.

glaucous Covered with a smooth, usually whitish, waxy coating, which can be rubbed off with touch. (epidermal excrescence)

globose (a) Spherical in shape (shape). (b) Stigma(s) spherical in shape. (stigma/stigmatic region type)

glochidiate With apical, clustered barblike structures. (bristle type)

glochidium A very small leaf spine with numerous, retrorse barbs along its length, produced in the areoles of opuntioid cacti.Pl: glochidiaglochids. (leaf structural type)

glomerule An inflorescence of sessile or subsessile flowers in which internodes between flowers are very short, with flowers appearing congested. (inflorescence type)

glucosinolate A secondary chemical compound found in many Brassicales that functions to deter herbivory and parasitism and also serves as a flavoring agent in the commercially important members of the Brassicaceae.

glume One of usually two bracts occurring at the base of a grass spikelet. (leaf structural type)

glutinous Viscid. (epidermal excrescence)

golgi body A cellular organelle comprised of parallel stacks of flattened membranes, functioning in transport and modification of compounds.

grain A one-seeded, dry, indehiscent fruit with the seed coat adnate to pericarp wall, e.g. Poaceae, grasses. Syn: caryopsis. (fruit type)

granular Farinaceous.

granum A pancakelike aggregation of thylakoid membranes within the chloroplast of green plants. Pl: grana.

grass spikelet The inflorescence unit of the Poaceae, grass family, consisting of an axis (rachilla) bearing distichous parts: two basal bracts (glumes, sometimes modified or absent) and one or more florets, each floret consisting of a minute lateral axis with two additional bracts (lemma and palea) plus the flower.

green plants A monophyletic group of eukaryotes, consisting of the green algae and the land plants, united ha ving chloroplasts with chlorophyll a and b, starch, and thylakoids stacked as grana [Chlorobionta].

ground meristem The nonvascular, usually parenchymatous tissue between and among the vascular bundles of an atactostele. (stem/shoot parts)

ground tissue Tissue that is inside the epidermis and not part of the vascular tissue, composed of parenchyma, sclerenchyma, and collenchyma cells.

guard cell One of the two cells that together make up a stomate.

gynandrium A fusion product of androecium and gynoecium, e.g. Aristolochiaceae, Orchidaceae. Syn: columngynostegium, gynostemium. (flower part)

gynobasic With style arising at the base and center of a lobed ovary, e.g. Boraginaceae, Lamiaceae. (style position)

gynodioecious/gynodioecy Having female flowers on some individuals and perfect flowers on other individuals. (plant sex)

gynoecium The female organ(s) of a flower, collectively all carpels of a flower. (flower part)

gynomonoecious/gynomonoecy Having both pistillate and perfect flowers on the same individual. (plant sex)

gynophore A stalk of the pistil, usually absent. Syn: stipe. (gynoecium part)

gynostegium columngynandriumgynostemium. (flower part)

gynostemium columngynandriumgynostegium. (flower part)

half-inferior With sepals, petals, stamens, and/or hypanthium attached at the middle of the ovary. (ovary position)

hapaxanthic A determinate shoot that completely transforms into a flower or inflorescence. (stem/shoot type, stem branching pattern, inflorescence development)

haplodiplontic life cycle A life cycle having both haploid and diploid phases, occurring in all land plants. Syn: alternation of generationsdiplobiontic life cycle.

haplontic life cycle A type of sexual life cycle in which the mature, adult phase is haploid, which produces gametes (egg and sperm) that fuse to form a diploid zygote, the latter undergoing meiosis to produce haploid spores, which develop into new haploid adults. Syn: haplobiontic life cycle.

hardwood Wood derived from a nonmonocotyledonous angiosperm, generally (but not always) harder than a softwood because of a greater concentration of fiber cells.

harmomegathy Volume changes of the pollen grain with changes in water content, e.g. humidity, functioning to inhibit desiccation.

hastate With two basal lobes, more or less pointed and oriented outwardly approximately 90 °relative to central axis. (base)

hastula An appendage or projection at the junction of petiole and blade, as in some palms. (leaf part)

haustoria Parasitic roots that penetrate the tissues of a host plant. (root type)

head A determinate or indeterminate, crowded group of sessile or subsessile flowers on a compound receptacle, often subtended by an involucre, e.g. Asteraceae. Syn: capitulum. (inflorescence type)

helicoid cyme A monochasium in which the branches develop on only one side of each sequential axis, appearing coiled at least early in development; may intergrade with scorpioid cyme. Syn: bostryx. (inflorescence type)

helobial An endosperm in which the first mitotic division is followed by cytokinesis, delimiting two cells, with the nucleus of one of the cells dividing without cytokinesis, that of the other cell dividing with cytokinesis.

hemiparasite A chlorophyllous, parasitic plant.

hemispheric Half-sphere-shaped. (shape)

hemitropous/hemianatropous An ovule somewhat intermediate in curvature between anatropous and orthotropous types.

herb A plant with annual above-ground shoots, including a flower or inflorescence, the plant itself being annual, biennial, or perennial. (plant habit)

herbaceous Having a soft or slightly succulent texture. (texture)

herbarium specimen A pressed and dried plant sample that is permanently glued and/or strapped to a sheet of paper, along with a documentation label.

hercogamy/herkogamy The spatial separation of anthers and stigmas, generally enhancing outbreeding. Adj: hercogamous/herkogamous.

hermaphroditic A plant with bisexual flowers. (plant sex)

hesperidium A septate berry with a thick-skinned, leathery pericarp wall and fleshy modified trichomes (juice sacs) arising from the inner walls, e.g. Citris (orange, lemon, grapefruit, etc.). (fruit type)

heteroblasty The condition in which the juvenile leaves are distinctly different in size or shape from the adult leaves, e.g. many Araceae. Adj: heteroblastic. (leaf type)

heterochrony An evolutionary change in the rate or timing of development.

heteropolar Pollen polarity in which the two polar hemispheres are different because of displacement of one or more apertures.

heterospory The formation of two types of haploid spores, microspores and megaspores, within two types of sporangia. Adj: heterosporic.

heterostyly Hercogamy in which the relative lengths or heights of stigmas versus anthers vary among different flowers. Adj: heterostylous.

heterotropous An ovule that varies in orientation.

hilum Funicular scar on the seed coat. (seed part)

hirsute With long, rather stiff trichomes. (vestiture)

hispid With very long, stiff trichomes, often capable of penetrating skin. (vestiture)

holotype The one specimen or illustration upon which a name is based, originally used or designated at the time of publication.

homochlamydeous Perianth composed of similar parts, each part termed a tepal. (perianth cycly)

homology Similarity that is the result of common ancestry. Adj: homologous.

homolog/homologue A specific feature that is homologous to another, cited feature. Cf: homology.

homonym One of two (or more) identical names that are based on different type specimens.

homoplasy Similarity that is not due to homology or common ancestry, but the result of independent evolutionary change.

homospory The formation of one type of haploid spore, by one type of sporangium. Adj: homosporic.

hood A hoodlike appendage arising from the gynostegium of some Asclepiadoids of the Apocynaceae.

hooked With apical hooklike structure. Syn: uncinate. (bristle type)

horizontal More or less horizontally spreading with divergence angle of ≤15 °up or down from horizontal axis. Syn: divaricate; divergentpatent. (orientation)

horn A hornlike appendage, often associated with a hood, arising from the gynostegium of some Asclepiadoids of the Apocynaceae.

hyaline cell One of the nonchlorophyllous cells in the specialized leaves of Sphagnum moss, having characteristic pores and helical thickenings and functioning in water absorption and retention.

hybridization Sexual reproduction between different species (interspecific hybridization) or between different populations or infraspecific taxa within a species.

hydathode A group of specialized cells that secrete excess, transported water (usually due to root pressure) from leaf margins.

hydrochory Dispersal of propagules by water. Adj: hydrochorous.

hydroid A specialized cell that functions in water conduction in

some mosses.

hydrophily Pollination by water. Adj: hydrophilous.

hygroscopic Absorbing moisture from the air, often resulting in


hymenopterophily Melittophily.

hypanthium A cuplike or tubular structure around or atop the

ovary, bearing along its margin the sepals, petals, and stamens.

Syn: floral tube. (flower part)

hypanthodium An inflorescence bearing numerous flowers on

the inside of a convex or involuted compound receptacle,

e.g. Ficus. (inflorescence type)

hyphodromous Pinnate venation with only the primary midrib

vein present or evident, the secondary veins absent, very reduced,

or hidden within the leaf mesophyll. (leaf venation)

hypocotyl A region of the embryo between the root and epicotyl;

may function in seedling development and as an anatomical

transition between root and shoot. (seed part)

hypogeous With cotyledon(s) remaining in the ground during

germination. Syn: cryptocoylar. (seed germination type)

hypogynous With sepals, petals, and stamens attached at the base

of a superior ovary. (perianth/androecial position)

hypotropous An ovule in which the micropyle points proximally.

hypotropous-dorsal A hypotropous ovule in which the raphe is

dorsal (abaxial), pointing away from the central floral or ovary


hypotropous-ventral A hypotropous ovule in which the raphe is

ventral (adaxial), pointing toward the central floral or ovary axis.

hysteranthy Timing in which leaf and flower development do not

coincide. Adj: hysteranthous.

identification The process of associating an unknown taxon or

other entity with a known one.

illegitimate name A name that violates one or more rules of the

International Code of Botanical Nomenclature.

imbricate (a) Leaves or other structures overlapping (arrangement).

(b) With overlapping perianth parts. (perianth aestivation)

imbricate-alternate Outer whorl of perianth parts (sepals or outer

tepals) alternating with, along different radii, the inner whorl of

perianth parts (petals or inner tepals), a typical perianth aestivation.

(perianth aestivation)

imparipinnate/imparipinnately compound A pinnately compound

leaf with a terminal leaflet, typically odd-pinnate. (leaf type)

imperfect (a) Unisexual. (flower sex) (b) With lateral primary

veins covering less than two thirds of the leaf blade area, a subcategory

of actinodromous and of acrodromous. (leaf venation)

in Abbreviation for in the publication of, referring to a name

published within a larger work authored by the person(s) following

the in.

inaperturate A pollen grain that lacks any recognizable aperture.

inbreeding The union of gametes derived from a single individual.

Syn: selfing.

incanous Covered with dense, fine, grayish-white trichomes; whitishpubescent.


incised With margins sharply and deeply cut, usually jaggedly. (margin, division)

inclined Directed upward, with a divergence angle of 15 °45 ° from horizontal axis. (orientation)

incompatibility reaction The inhibition of pollen germination or pollen tube growth between genetically similar individuals, mediated by incompatibility genes and functioning to promote outcrossing.

incomplete Lacking one or more of the four major whorls or floral parts: sepals, petals, stamens, carpels. (flower cycly)

incurved Tip gradually curved inward or upward (adaxially). (transverse posture)

indehiscent legume A secondarily modified legume does not split open, e.g. Arachis hypogaea, peanut. (fruit type)

indented phylogenetic classification A classifcation in which

monophyletic groups are ordered in a sequential, hierarchical


indeterminate (a) A shoot that has the potential for unlimited

growth, the apical meristem continuing to grow. (stem/shoot type,

stem branching pattern). (b) An inflorescence in which the basal

flower matures first; maturation from base to apex. (inflorescence


induplicate Plicate, with adjacent adaxial sides facing one another,

being V-shaped in cross-section. (longitudinal posture)

indurate Hardened and inflexible. (texture)

indusium A flap of tissue that covers a sorus, found in some

leptosporangiate ferns. Adj: indusiate.

inferior With sepals, petals, stamens, and/or hypanthium attached

at the apex of the ovary. (ovary position)

inflorescence An aggregate of one or more flowers, the boundaries

of which generally occur with the presence of vegetative leaves

below; may be composed of unit inflorescences. (plant part)

inflorescence bract A modified, generally reduced leaf subtending

an inflorescence axis. (inflorescence part)

inflorescence bud A bud that develops into an inflorescence.

(bud type)

infrafloral selfing Autogamy.

infrafoliar Descriptive of a palm inflorescence that is positioned

below the leaves of the crownshaft. (inflorescence position)

infrapetiolar bud An axillary bud surrounded by a petiole base,

e.g. Platanus, sycamore. (bud type)

infructescence The complete inflorescence at the stage of fruiting.

(fruit part)

infundibular Funnel-shaped; with a narrow base and greatly

expanded apex, e.g. Ipomoea. (perianth type)

ingroup The study group as a whole in a phylogenetic analysis.

inner bark Secondary phloem.

inserted With stamens included within the perianth. Syn:

cryptantherous. (stamen insertion)

integument A sheath or flap of tissue that surrounds the megasporangium

(nucellus) of an ovule and develops into the seed coat of

the seed.

intercalary meristem An indeterminate (having potentially continuous

growth), basal or sub-basal region of actively dividing cells.

interfoliar Descriptive of a palm inflorescence that is positioned

among the leaves of the crownshaft. (inflorescence position)

International Code of Botanical Nomenclature The standardized

system of rules for naming plants, algae, fungi, and or ganisms

traditionally treated as fungi, governing specific names

assigned to taxa and the endings that denote taxon rank, and

utilized for naming new taxa and determining the correct name

for previously named taxa. Abbr: ICBN.

internode (a) The region between two adjacent nodes of a shoot.

(stem/shoot parts, twig part) (b) A cladogram lineage that spaces

between two nodes (points of divergence). Syn: stem.

intine The innermost layer of a pollen grain wall, composed

primarily of cellulose and pectines.

intrastaminal disk A discoid or doughnut-shaped structure

arising from the receptacle at the inside of the stamens and/or

base of the ovary; may be nectar-bearing. ( nectariferous disk )

(flower part)

intravaginal (axillarysquamules Trichomes found in the axils of

sheathing leaves, possibly functioning in secreting a protective mucilage,

e.g. many Alismatales. (trichome type)

introgression Hybridization between two species followed by

backcrossing to one or both parents.

introrse Dehiscing inward, toward the flower center. (anther

dehiscence direction)

involucel A group or cluster of bracts subtending a unit of an

inflorescence. (inflorescence part)

involucral bract Phyllary. (leaf structural type)

involucre A group or cluster of bracts subtending an inflorescence.

Adj: involucrate. (inflorescence part)

involute (a) Margins or outer portion of sides rolled inward

or upward over adaxial surface (longitudinal posture, margin).

(b) Valvate with each perianth part induplicate, folded longitudinally

inward along central axis. (perianth aestivation)

iridoid A secondary chemical compound characteristic of many


irregular Zygomorphicbilateral. (symmetry)

isomerous Having the same number of parts in different whorls.

(merosity, perianth merosity)

isomorphic Appearing identical, e.g. the gametes of some green


isopolar Pollen polarity in which the two polar hemispheres are

the same but can be distinguished from the equatorial region.

isotype A duplicate specimen of the holotype, collected at the same

time by the same person from the same population.

iteropary Referring to plants that reproduce more than one time

in the life of the plant, typically in regular cycles. Adj: iteroparous.

jacket layer Antheridial wall; archegonial wall.

jacknife/jacknifing A method of evaluating cladogram robustness

that reanalyzes the data of the original character _ taxon matrix

by selecting (resampling) characters at random, such that a given

character can be selected only once, the resultant resampled data

matrix being smaller than the original.

jaculator Funiculi of the seeds that are modified into rigid, often

hook-shaped structures that function to disperse the seeds by

a catapulting mechanism, characteristic of the Acanthaceae.

Syn: retinaculum.

key/taxonomic key An identification device, consisting of contrasting

statements used to narrow down the identity of a taxon.

Kranz anatomy A leaf anatomy in which chloroplasts of the

bundle sheath cells are typically much larger than those of the

mesophyll cells, correlated with C4 photosynthesis.

labellum A modified, typically expanded, median petal, tepal, or

perianth lobe, such as in the Orchidaceae. (perianth part)

lacerate With sinuses irregularly cut, lobes appearing torn.


laciniate Cut into narrow, ribbonlike segments. (division)

laevigate Lustrous, polished. (epidermal excrescence)

lamellar An exine wall structure having stacked, tangentially

oriented, planar structures, often constituting the inner wall layer.

lamina Blade. (leaf part)

laminar (a) With a dorsiventrally flattened, leaflike structure

bearing the thecae. (stamen type) (b) With ovules arising from the

surface of the septae. (placentation)

lanate Villous. (vestiture)

lanceolate Margins curved, widest near base, length:width ratio

between 6:1 and 3:1. (shape)

lance-ovate Margins curved, widest near base, length:width ratio

between 3:1 and 2:1. (shape)

land plants A monophyletic group of eukaryotes united by an

outer cuticle, specialized gametangia antheridia and arche gonia

and an intercalated diploid phase in the life cycle, including the

embryo [embryophytes/Embryophyta].

lateral (a) Axillary (position, inflorescence position). (b) Style

arising at the side of an ovary. (style position)

lateral bud Axillary bud (bud type)

lateral meristem A cylindrical sheath of cells, functioning in

secondary growth, that increases width or girth of stems or roots

in woody plants; includes the vascular cambium and cork


lateral root A root that arises from another root, derived endogenously

from the pericycle. (root type)

lateral vein Ventral vein.

laticifer Cells located in the periphery of some tissues that secrete

and store latex, functioning to deter herbivory and to seal and

protect plant tissue upon wounding.

latrorse Dehiscing laterally relative to the flower center. (anther

dehiscence direction)

layer One of the ecological criteria of plant communities based on

height and plant habit, including the canopy, subcanopy, shrub or

subshrub layer, and herb layer.

lead One of the two contrasting statements in a dichotomous key.

leaf A generally dorsi-ventrally flattened organ, usually functioning

in photosynthesis and transpiration, either gametophytic (in mosses

and some liverworts) or sporophytic (in vascular plants), often

variously modified. (plant part)

leaf gap A region of nonvascular parenchyma tissue interrupting

the vasculature of the stem at a node, associated with euphylls.

leaf primordium An immature leaf of the shoot. (stem/shoot parts)

leaf scar A mark indicating the former place of attachment of a

leaf. (twig part)

leaf spine A sharp-pointed leaf, e.g. cactus spines or glochidia.

Cf: pricklethorn. (leaf structural type)

leaflet A distinct and separate segment of a leaf. (leaf part)

leaflet spine A sharp-pointed leaflet, e.g. some palms, such as

Phoenix. (leaf structural type)

lectotype A specimen that is selected from the original material to

serve as the type when no holotype was designated at the time

of publication, if the holotype is missing, or if the original type

consisted of more than one specimen or taxon.

legitimate name A name that is in accordance with the rules of the

International Code of Botanical Nomenclature.

legume A dry, dehiscent fruit derived from one carpel that splits

along two sutures, e.g. Fabaceae. (fruit type)

lemma The outer and lower bract at the base of the grass floret.

(leaf structural type)

lenticel A pore in the bark, generally functioning in gas exchange.

(twig part)

lenticular Lens-shaped; disk-shaped with two convex sides.(shape)

lepidote Covered with scales or scalelike structures. (vestiture)

leptoid A specialized cell that functions in sugar conduction in some mosses.

leptosporangium The sporangia of the leptosporangiate ferns (Polypodiales), characterized by developing from a single cell and having a single layer of cells making up the sporangium wall. Pl: leptosporangia.

liana/liane A woody, perennial vine, in tropical forests often a component of the canopy layer. (plant habit)

light reactions A series of biochemical reactions of photosynthesis in plants, occurring in the thylakoid membranes of the chloroplast and requiring light as an energy source, during which water is broken down into hydrogen ions, electrons, and molecular oxygen, and producing high-energy ATP and NADPH2, which are utilized in the dark reactions.

lignin A complex polymer of phenolic compounds that impregnates the secondary cell wall of some cells (including tracheary elements and sclerenchyma), functioning to impart strength and rigidity to the wall.

lignotuber Burl. (stem/shoot type)

ligulate Strap- or tongue-shaped; flattened and somewhat oblong

in shape, e.g. ray flowers of some Asteraceae. (perianth type, shape)

ligule (a) A small appendage on the upper (adaxial) side of the leaf,

near the leaf base, found in the Selaginellaceae and Isoetaceae of the

lycophytes. (b) An outgrowth or projection from the top of a leaf

sheath at its junction with the blade, as in the Poaceae. (leaf part)

limb The expanded portion of the corolla or calyx above the tube,

throat, or claw. (perianth part)

lineage Clade.

linear (a) With margins straight, parallel, length : width ratio

between 12:1 and 6:1. (shape) (b) Stigmas or stigmatic tissue long

and narrow in shape. (stigma/stigmatic region type)

linear tetrad A tetrad in which the four pollen grains are arranged

in a straight line, e.g. Typha.

lip Either of two variously shaped parts into which a calyx or

corolla is divided, usually into upper (posterior) and/or lower

(anterior) lips, each lip often composed of one or more lobes,

e.g. Lamiaceae, Orchidaceae. Cf: labellum. (perianth part)

lithocyst A specialized cell that contains a cystolith. Cf: cystolith.

lobe (a) A segment of a synsepalous calyx or sympetalous corolla.

(perianth part) (b) A segment of a divided leaf. (leaf part)

lobed (a) Sinuses extending (pinnately or palmately) one eighth

to one fourth the distance to midrib, midvein, or vein junction.

(b) A general term meaning having lobes. (division)

locule An ovary cavity, bounded by ovary walls and septa.

(gynoecium part) (b) A compartment of the anther, usually the

result of two microsporangia fusing within a theca. (anther part)

loculicidal capsule A capsule in which longitudinal lines of

dehiscence are radially aligned with the locules. (fruit type)

lodicule One of the (2 3) modif ied perianth parts of a grass

(Poaceae) flower, which collectively upon swelling function to

open the floret by separating the lemma from palea. (perianth type)

loment A secondarily modified legume that splits transversely

into 1-seeded segments. (fruit type)

long-branch attraction A condition in which taxa with relatively

long branches (having numerous character state changes) tend

to come out as close relatives of one another in a phylogenetic

analysis because of random effects.

longitudinal dehiscence Dehiscing along a suture parallel to the

long axis of the thecae. (anther dehiscence type)

longitudinal posture Placement of margins with respect to a

horizontal plane. (disposition)

lower epidermis The abaxial epidermis of a leaf.

lumen The space between muri in a reticulate pollen grain.

Pl: lumina.

lycophyll The sporophytic leaf of the lycophytes, characterized by

an intercalary meristem, having a single vein, and lacking a gap in

the vasculature of the stem. Adj: lycophyllous. Syn: microphyll.

(leaf structural type)

lyrate Pinnatifid, but with a large terminal lobe and smaller basal

and lateral lobes. (shape)

maculate Spotted; with small spots on a more or less uniform

background. (color pattern)

majority consensus tree A consensus tree in which only those

clades that are retained 50% or more of the time are retained

(i.e. not collapsed to a polytomy).

male (a) Individual with male reproductive organs only. (plant sex)

(b) Staminate. (flower sex)

male gametophyte A gametophyte that bears only antheridia.

Syn: microgametophyte.

male sporophyll A sporophyll that bears one or more microsporangia.

Syn: microsporophyll.

malpighian Trichomes with two arms arising from a common

base, e.g. Malpighiaceae. (trichome type)

manual Flora.

marcescent Ephemeral, but with persistent remains; withering

persistent. (duration)

marginal (a) With the placenta along the margin of a unicarpellate

(simple) ovary, e.g. Fabaceae. (placentation) (b) With three or

more primary veins diverging from one point and reaching the

blade margin, a subcategory of actinodromous. (leaf venation)

massula A group of fused pollen grains in large, often irre gular

numbers, but less than an entire theca. Pl: massulae.

masticatory A substance that is chewed by humans, usually for its

pleasing or euphoric effects, e.g. peyote, Lophophora williamsii.

maturation (a) Acquisition of the mature structural and functional

features of a cell following cell expansion. Syn: specialization.

(b) Relative time of development of parts. (temporal phenomena)

matutinal In the morning, typically with respect to when flowers

open. (periodicity)

maximum likelihood A method of phylogenetic inference that

considers the probability, based on some selected model of evolution,

that each tree explains the data.

mealy Covered with small, fine granules. (epidermal excrescence)

median vein Dorsal vein.

megagametogenesis The process of development of the female

gametophyte from the haploid product(s) of meiosis.

megagametophyte Female gametophyte.

megaphyll Euphyll.

megasporangium A female sporangium, within which megasporocytes

undergo meiosis to produce haploid megaspores.

Pl: megasporangia. Syn (in seed plants only): nucellus. (plant part)

megaspore A female spore, produced via meiosis in the megasporangium

and giving rise to a female gametophyte.

megaspore mother cell Megasporocyte.

megasporocyte A cell within the megasporangium that undergoes

meiosis, forming four megaspores. Syn: megaspore mother cell.

megasporogenesis The process of development of megaspores from the megasporocyte.

megasporophyll Female sporophyll.

melittophily Pollination by bees. Adj: melittophilous. Syn:


membranous Thin and somewhat translucent; membranelike.


mericarp A portion of a fruit that separates from the ovary as a

distinct unit that completely encloses the seed(s). (fruit part)

meristem A region of actively dividing cells.

merosity Number of parts per whorl or cycle. (number)

mesarch An orientation of xylem maturation in which the protoxylem

is surrounded by metaxylem within the vascular tissue, as

can occur in siphonosteles.

mesocarp A middle wall layer of the pericarp, if the latter is

divided into layers. (fruit part)

mesophyll The region of a sporophytic leaf between the outer

epidermal layers and exclusive of the vasculature, containing the

chlorophyllous cells.

mesophytic Having an intermediate texture, between coriaceous

and membranous (texture)

metaxylem The xylem of a group of tracheary elements that

matures later, consisting of larger-diameter cells.

microfibril Microscopic fiberlike units of intertwined cellulose

molecules, forming a meshwork within the cell wall.

microgametogenesis The process of development of pollen grains

from microspores.

microgametophyte Male gametophyte.

microhair A very small trichome, as in the three-celled, glandular

microhairs of the Commelinaceae.

microphyll Essentially equivalent to a lycophyll.

micropylar Describing the region of an ovule that is near the


micropylar Referring to the distal region of the ovule, near the


micropyle A small pore at the distal end of the integument of

a seed, functioning as the site of entry of pollen grains, or in

angiosperms of pollen tubes.

microsatellite A region of DNA that contains tandem repeats,

short (usually 2 5) repeats of nucleotides.

microsporangium A male sporangium, within which microsporocytes

undergo meiosis to produce haploid microspores.

Pl: microsporangia. (plant part)

microspore A male spore, produced via meiosis in the microsporangium

and giving rise to a male gametophyte.

microsporogenesis The process of development of microspores

from microsporocytes.

microsporophyll A sporophyll bearing one or more microsporangia;

a male sporophyll.

middle lamella A pectic-rich layer formed between the plasma

membrane of adjacent cells in land plants, functioning to bind

adjacent cells together.

middle layers Anther wall layers that may occur between the

endothecium and tapetum.

midrib The central, main vein of the blade of a simple leaf or of a

compound leaf in some palms. Syn: costa. (leaf part)

midvein The central, main vein of the blade of a leaflet. (leaf


mitochondrion A double membrane-bound, cellular organelle with

invaginations called cristae that function in the electron transport

reactions of respiration. Pl: mitochondria.

mixed bud A bud that produces both flowers and leaves. (bud


mixed craspedodromous Pinnate venation in which some secondary

veins terminate at the margin, but with many terminating

away from the margin. (leaf venation)

monad A single, unfused pollen grain.

monadelphous With one group of stamens connate by their filaments,

e.g. Malvaceae. (stamen fusion)

monistichous Alternate, with points of attachment in one vertical

row/rank, e.g. Costaceae. (arrangement)

monocarpic A perennial or annual plant, flowering and fruiting

once, then dying. (duration)

monochasium A determinate inflorescence that develops along

one axis only. (inflorescence type)

monocotyledonous A type of anther wall development in which

only the inner secondary parietal cell layer divides to yield the

tapetum and a single middle layer.

monocyclic Uniseriate. (cycly, perianth cycly)

monoecious Having unisexual flowers, both staminate and pistillate

on the same individual plant. (plant sex)

monograph A detailed taxonomic study of all species and infraspecific

taxa of a given taxonomic group.

monomorphic character A character that is invariable in character

state values within an OTU.

monophyletic/monophyly Referring to a group that consists of

a common ancestor plus all (and only all) descendants of that


monopodial A branching pattern in which a given axis is derived

from a single apical meristem. (stem branching pattern)

monosporic Megasporogenesis in which meiosis of the megasporocyte

nucleus results in the formation of four haploid megaspore

nuclei, followed by cytokinesis, resulting in four megaspore cells,

only one of which contributes to the female gametophyte.

monosulcate A pollen grain with a single, sulcate aperture.

monothecal Anther with one theca and typically two microsporangia.

Cf: bisporangiate. (anther type)

monoulcerate A pollen grain with a single, ulcerate aperture.

morphocline Transformation series.

movement hercogamy A type of hercogamy involving movement of

floral parts, e.g. the rapid closure of the stigmas upon their being

touched by a potential animal pollinator.

mucilage ducts/canals Specialized cells that secrete mucilage.

mucronate With a stiff, straight apical process, length : width

ratio 1:1 to 3:1. (apical process)

mucronulate With a stiff, straight apical process, length : width

ratio  ≤1:1. (apical process)

multicellular Trichomes having two or more cells. (trichome


multiple fruit A fruit derived from two or more flowers. (fruit


multiseriate (a) Perianth composed of three or more distinct

whorls. (perianth cycly) (b) Trichomes having more than one vertical

row of cells. (trichome type) (c) Rays in wood that are made

up of many vertical rows of cells.

multistate character A character with three or more character


muricate Having coarse, radially elongate, rounded protuberances.

(epidermal excrescence)

murus The structural element of a reticulate pollen grain. Pl: muri.

mycorrhiza A symbiotic association between a fungus and roots,

functioning to increase absorptive surface area and mineral

uptake. Pl: mycorrhizae. (root part)

mycorrhizae A symbiotic association between the root of a

vascular plant and a fungus.

mycotrophic Obtaining nutrition from mycorrhizal fungi in the

soil, as in some Ericaceae.

naked bud A bud lacking surrounding protective scales,

e.g. Viburnum, Caprifoliaceae. (bud type)

narrowly acute Apical margins approximately straight, the intersection

angle <45°. (apex)

narrowly cuneate Basal margins approximately straight, the

intersection angle <45°. (base)

narrowly elliptic Margins curved, widest near midpoint, length :

width ratio between 6:1 and 3:1. (shape)

narrowly oblong Margins straight, parallel, length : width ratio

between 6:1 and 3:1. (shape)

narrowly triangular Three-sided, length : width ratio between

6:1 and 3:1. (shape)

natural selection The directed and nonrandom genetic modification

of a population or species, in which genetic changes that

result in an increase in survivorship and/or reproduction are contributed

to the next generation more.

neck The distal, narrow extension of the sterile jacket cells of the

archegonium, through which a sperm cell must travel to fertilize

the egg.

neck canal cells Cells located within the neck of the archegonium

that break down and are secreted from the pore of the neck at


nectariferous disk A nectary consisting of a disklike or doughnut-

shaped mass of tissue surrounding the ovary base or top;

may be inner to (intrastaminal), beneath (staminal), or outer to

(extrastaminal) the androecium. (flower part, nectary type)

nectary A group of specialized cells that secrete sugar- (or

protein-) rich fluids to the outside, as a reward for pollination or

protection. (flower part)

neotony A type of paedomorphosis caused by a decrease in the

rate of development of a feature.

neotype A specimen derived from a nonoriginal collection that is

selected to serve as the type as long as all of the material on which

the name was originally based is missing.

nerve Vein. (leaf part)

netted With ultimate veinlets forming a reticulum or netlike

pattern. Syn: reticulate. (leaf venation)

network Unrooted tree.

nexine The inner layers of the exine, including both endexine and the

foot-layer of the ektexine.

nitid Appearing lustrous, polished. Syn: shining. (epidermal


nocturnal Occurring during the night, typically with respect to

when flowers open. (periodicity)

node (a) The point of attachment of a leaf to a stem. (stem/shoot

parts) (b) The region of stem at which leaf, leaves, or branches

arise. (twig part) (c) The point of divergence of one clade into

two; the point in time and space of the most common ancestor of

the two divergent clades.

node-based A type of phylogenetic classification in which a node

(common ancestor) of the cladogram (and all descendants of that

common ancestor) serves as the basis for grouping.

nomen conservandum Meaning a conserved name. Abbr:

nom. cons.

nomen novum Meaning a new name. Abbr: nom. nov.

nomen nudum Meaning a name published without a description

or diagnosis, making the name invalid. Abbr: nom. nud.

nomenclatural type A specimen that acts as a reference for a

scientific name, upon which the name is based. Syn: type;

type specimen.

nomenclature The formal naming of taxa according to some

standardized system; for plants, algae, fungi, and or ganisms

traditionally treated as fungi, governed by the International Code

of Botanical Nomenclature.

non Latin for not.

nondecussate Opposite leaves or other structures (e.g. leaflets)

not at right angles to the preceding pair; may be superficially the

result of stem twisting. (arrangement)

nondisjunction An irregularity during meiosis in which homologous

chromosomes do not segregate, which may result in the production

of gametes that are unreduced, i.e. have two sets of


nonendospermous Exalbuminous. (seed endosperm type)

nonporous Referring to wood having only tracheids.

nucellar beak A proliferation of cell divisions of the nucellus at

the micropylar region of the ovule.

nucellus Term for the megasporangium of a seed. Adj: nucellar.

nuclear endosperm An endosperm in which the early mitotic

divisions are not followed by cytokinesis.

nucleus A double membrane-bound, cellular organelle that

contains DNA.