The most important thing to remember when using this (or any other) glossary is that just because some aspect of an organism is dignified by a sesquipedalian term, this by no mean signifies that it is "real". Humans make and define botanical terms, and we use them to facilitate communication. This raises a second important point. As mentioned in the Introduction, definitions should as far as possible follow current usage, rather than etymology or original definitions (see, e.g. Rickett 1954-56). However, current usage may not be consistent, and this is one of the major failings of botanical terminology. As Rickett (1954 p. 2; emphasis in original) noted, "To be uncertain whether "glabrous" means "free from hairs and roughness" or only "free from hairs" is as bad as if π [pi] should stand sometimes for the ratio of a circle to its diameter and sometimes for somthing else; or as if Cu meant sometimes "copper" and sometimes "brass". Yet this is the state of affairs in botany today". Over forty years later, this is still true, but we should be attempting to reach consensus here, too.

With any glossary, there is always the question of what to include and what to exclude. We list those terms used in these pages, some of their common synonyms, and also some other terms commonly used in the literature that has been consulted. When there are alternative terms for the one structure, we have chosen the term that seems easiest to use or makes most obvious sense, thus we have prefered "atropous" over "orthotropous", since the latter seems almost an oxymoron, and "odd-pinnate" for "imparipinnate" since the former is closer to plain language yet is no less precise. There will always be tensions when it comes to terms used to describe specific features of the sporophytic and gametophytic generations. Thus we have prefered "nucellus" over "megasporangium wall", although the latter is technically what a nucellus is, and "embryo sac" over "female gametophyte" since the former term is almost always used in the literature dealing with flowering plants. The definitions have been made to agree as far as possible with those in the Plant Ontology Consortium (2004 onwards).

Settling on definitions is often not easy. Thus there is some dispute among wood anatomists over exactly what terms to use and how to define them (cf. Wheeler et al. 1989; Metcalfe & Chalk 1989; Carlquist 2001). Other terms have definitions that can be distinguished only with difficulty, or there are alternative sets of terms that can be used when looking at the same structures, but from different points of view (e.g. cf. a superior ovary and a hypogynous flower).

Since the focus is on terms used when discussing characters of and relationships between major clades, many of the terms used when describing species are omitted. However, Stearn (1992) is a particularly useful source for definitions here.

The basic arrangement is alphabetical, but note that terms that start with single letter contractions like P-protein, CAM, etc., are to be found at the beginning of the appropriate section (in this case, "P" and "C" respectively). This glossary is designed to function hierarchically, and indeed to a certain extent it is like an ontology. If in an entry, one finds "see", this is followed by an enumeration of all the terms used in /APweb/ to describe the variants of the structure just described. Thus under accessory buds, one finds "see collateral, superposed", and there are links to these two terms that are used for describing common variants in the arrangement of such buds. cf., on the other hand, is followed by a listing of contrasting terms used to describe the variants of the structure just described. Thus after the definition of abaxial, we find "cf. adaxial, lateral, median", so linking to all the other terms used to describe the positions of parts of a flower with repect to the axis. However, a few terms are included in contrast sets simply because that is common practice, even if logically they should be excluded.

Thus an entry like "amphiparacytic: of paracytic stomata where the subsidiary cells are parallel to the long axis of the stoma and completely surround the latter, cf. brachyparacytic" first defines the term, making it clear that it is a subtype of paracytic stomata, to which the reader can go for a definition (and also to stomata, as well as subsidiary cells), while being contrasted with brachyparacytic stomata, to which the reader can also go for a definition.

Some synonymy is indicated, e.g. "calcar, calcarate = spur, spurred."

Information for this glossary has been taken from many sources. Informative general morphological glossaries or other sources are Lawrence (1951), Esau (1965, 1977, the latter with a particularly useful glossary), Radford et al. (1974), Endress (1994b), Harris and Harris (1994), Hickey and King (2000), Judd et al. (2002), Bell and Bryan (1991, 2008: beautiful illustrations), and of course Stearn (1992). Metcalfe and Chalk (1979, 1983) also provide much useful information. Chemical formulae and definitions have been taken from American Chemical Society (2004), Harborne and Turner (1984), Harborne and Baxter (1992), Harborne et al. (1999), Robinson (1991), Siegler (1998, 2004), Smith (1976) and Walton and Brown (1999), see also Berenbaum (1999: furanocoumarins), Connolly and Hill (terpenoids), Glasby (1975-1983: alkaloids), Langenheim (2003: resins), and Schleimann (2004: mycorrhizal biochemistry). For wood anatomy, see Wheeler et al. (1989: hardwoods) and Richter et al. (2004: softwoods), for anatomy and morphology, see Dickison (2000), for stomata, etc., see the Leaf Architecture Working Group (1999), for leaf teeth, see Hickey and Wolfe (1975), for venation, see Hickey (1979), for life forms, see Raunkiaer (1934), for inflorescences in particular, but also much else, see Weberling (1992), for pollen terminology, which is particularly difficult, see Reitsma (1970), Walker and Doyle (1975) and Punt et al. (2006, especially useful), for fruit, see Spjut (1994: his definitions may not all be followed here, and few fruit types are included, but his work helped catalyze my thoughts), for monocot seedlings, see Tillich (2007), and for hairs and indumentum, see Payne (1978), Hewson (1988), Stearn (1992), etc. For more information on the general botanical literature in which variation of the characters defined in the glossary is discussed, see the "Characters" page. And last, but not least, the OED (Simpson & Weiner 1989) has been very helpful!

We built this glossary using the excellent Flora of Australia Online Glossary as our inspiration. We are very grateful to to the Australian Biological Resources Study and also to the artists who drew the illustrations for some of the terms in that glossary. Selected links to illustrations in the Flora of Australia Online Glossary are included here (indicated by  ); the illustrators of these images are indicated on the images themselves. Gregor Hagedorn and Volker Bittrich in particular have provided useful comments.

A

a- (prefix): without.

ab- (prefix): away from.

abaxial: of the side or surface of an organ like a petal or organ system such as a branch, facing away from the axis that bears the organ or organ system, cf. adaxial, lateral, median, a useful set of positional descriptors.

abscission: the normal shedding from a plant of an organ that is mature or aged, e.g. a ripe fruit, an old leaf, see also cladoptosis.

acalymmate: of a pollen tetrad or polyad, when the ectexine is separately differentiated on each grain, there being no common covering of the pollen mass, cf. calymmate.

acaulescent: of habit, without any above-ground stem execept for an inflorescence axis, where present, leaves and inflorescence arising together at ground level, cf. arborescent, dendroid, frutescent, fruticose, herb, liane, rheophyte, suffrutescent, schopfbaum, shrub, subshrub, tree, vine, see also life forms.

accessory bud(s): one or more buds other than the normal single bud occuring in the leaf axil, cf. adventitious, supernumerary, see collateral, superposed.

accessory cell = subsidiary cell.

accessory fruits: fruits, whether derived from a single flower or several, with tissue that is other than carpellary in origin, e.g. the hypocarp, see also anthocarp, cf. aggregate fruits, multiple fruits, simple fruits.

accrescent: continuing to increase in size after maturity, as the calyx of some plants after flowering, cf. caducous, deciduous, deliquescent, fugacious, marcescent, persistent.

accumbent: of an embryo that is folded so that the radicle lies against the edges of the two cotyledons, cf. conduplicate, diplecolobous, incumbent.

acetate: a salt, ester or the conjugate base of acetic acid.

Acetate, C2 H3 O2.

acetogenins: polyketides derived from acetate with 35-37 carbon atoms in a single almost unbranched chain, substituted by 6-8 oxygen atoms.

Acetogenin-G, C19 H22 O3.

Mucoxin, C37 H66 O7.

acetylenes: the simplest of a class of triple-bonded hydrocarbons.

Acetylene, C2 H2.

achene: specifically, a dry, indehiscent fruit formed from a superior ovary of one carpel and containing one seed which is free from the pericarp except at the funicular end, more broadly, dry one-seeded fruits in general, whether formed from one or more carpels and superior or inferior ovaries, see caryopsis, cypsela, nut, utricle for variants which are also often called simply "achenes".

achlamydeous: of a flower, lacking a perianth parts, usually best to describe as such, cf. dichlamydeous, heterochlamydeous, monochlamydeous.

acicular = needle-like.

acorn: a nut or achene sitting in or more or less surrounded by a cup formed by fused bracts, etc. (see Fagaceae).

acrocentric: a chromosome in which the centromere is near one end, the spindle fibers attaching there during nuclear division, cf. holocentric, metacentric, and telocentric.

acrodromous: of palmate leaf venation, with two or more primary or strongly developed secondary veins running in convergent arches towards the apex, cf. actinodromous.

acropetal: produced or differentiated in succession towards the apex of an organ, e.g. of an inflorescence, with flowers arising or developing in a sequence beginning at the base and proceeding towards the apex, see also centripetal, cf. basipetal.

acroscopic = antrorse.

acrotonic: particularly pronounced development of the uppermost branch(es) of a stem or innovation, cf. basitonic.

acteoside = verbascoside.

actinocytic: of stomata, with five or more somewhat radially enlarged or elongated subsidiary cells surrounding the guard cells, cf. allelocytic, anisocytic, anomocytic, cyclocytic, diacytic, helicocytic, laterocytic, paracytic, staurocytic, stephanocytic, tetracytic.

actinodromous: of palmate leaf venation, with three or more primary veins arising from at or near the base, ascending or diverging, whether or not reaching the margin, cf. acrodromous.

actinomorphic = polysymmetrical.

actinostele: a variant of a protostele in which the xylem forms a more or less star-shaped central mass, with phloem between the arms, cf. haplostele, plectostele.

aculeate = prickly, cf. muricate.

acumen: of the apex of a structure, a long, narrowly tapering point with convex sides, hence acuminate, cf. acute, attenuate, apiculum, arista, awn, cuneate, caudate, cuspidate, emarginate, mucronate, muticous, obtuse, retuse, rounded, truncate, cf. also cordate, hastate, oblique, runcinate, sagittate (esp. of lamina base).

acute: of the apex or base of a structure, terminating in a distinct but not protracted point, the coverging sides concave and joining at an angle of less than 90^o, cf. acumen, attenuate, apiculum, arista, awn, cuneate, caudate, cuspidate, emarginate, mucronate, muticous, obtuse, retuse, rounded, truncate, cf. also cordate, hastate, oblique, runcinate, sagittate (esp. of lamina base).

acyclic = spiral.

acylation: stabilization by the introduction of an acid radical from acids such as coumaric, ferulic, or caffeic acids into e.g. acylated anthocyanins.

Cyanidin 3-dimalonylglucoside, C27 H25 O17.

ad- (prefix): towards.

adaxial: of the side or surface of an organ like a petal or organ system such as a branch, facing towards the axis that bears the organ or organ system, cf. abaxial, lateral, median, a useful set of positional descriptors.

addorsed (prophyll) = adaxial (prophyll).

adherent: when tissues or organs of different kinds are stuck together, but without organic fusion, cf. appressed, adnate, coherent, connate, connivent, fasciate, fasciculate, fastigiate, phalangiate.

admedial: towards the midline of the lamina, cf. exmedial.

adnate: a type of concrescence when tissues of one organ are organically fused to those of another organ of a different kind, as a stamen adnate to a petal, cf. connate, also adherent, appressed, coherent, connivent, fasciate, fasciculate, fastigiate, phalangiate.

Adoxa: an embryo sac type, the types based on variation in megasporogenesis and megagametogenesis, tetrasporic and 8-nucleate, all nuclei haploid, cf. Allium, Drusa, Endymion, Fritillaria, Oenothera, Penaea, Peperomia, Plumbagella, Plumbago, Polygonum, Schisandra.

aduncate = hooked.

advanced (of characters, not recommended) = apomorphy or derived.

adventitious: arising in "abnormal" positions and in "exceptional" circumstances, e.g. roots arising from the shoot system, buds arising elsewhere than in axils of leaves, however, the roots that characteristically occur along the stems of a number of prostrate herbs (see most monocots!), often in fixed positions, are also often called adventitious..., see also accessory, supernumerary.

adventitious (poly)embryony: of reproduction, the production of an embryo/seed directly from somatic tissue of the ovule without fertilisation, cf. agamospermy, apogamy, apomixis, apospory, vegetative reproduction, cf. also cleavage polyembryony, and simple polyembryony.

adventive: introduced to an area recently, whether or not established cf. endemic, native, introduced, naturalised.

aerenchyma: tissue incorporating large, gas-filled spaces interspersed between the cells, often forming characteristic arrangements, cf. collenchyma, parenchyma, sclerenchyma.

aestivation: the arrangement of sepals and petals or their lobes relative to one another in an unexpanded flower bud, cf. ptyxis, vernation, see cochleate, contorted, contortiplicate, crumpled, decussate, imbricate, induplicate, open, quincuncial, reduplicate, valvate.

after-ripening: of germination, when a period of dormancy of the seed and/or growth of the embryo is needed before germination will occur, cf. recalcitrant.

agamospermy: a kind of apomictic (s.l.) reproduction, the development of seeds from ovules without fertilization, equals apomixis s. str, see adventitious embryony, apospory, diplospory, polyembryony.

aggregate fruit: a cluster of fruits formed from the free carpels of one flower, cf. accessory fruit, multiple fruit, simple fruit.

aglycone: the non-carbohydrate group of a glycoside which appears on its hydrolysis (sometimes called aglucone).

ala, alate = wing, winged.

alar, loosely = axillary (Hickey & King 2000), a confusing term.

albumen = endosperm.

albuminous cell = Strasburger cells.

alditol: a polyol with a linear chain of carbon atoms, an acyclic polyol, cf. cyclitol, see arabitol, dulcitol, glycerol, mannitol, and sorbitol.

aleurone: aleurone layer, the outermost layer(s) of the endosperm (or, according to Werker [1997], the innermost layer of the nucellus), living cells containing proteins, the other cells being more or less dead and with much thickened walls, the lumen being more or less occluded e.g. by galactomannans (a hemicellulose), cf. chalazal cyst, haustorium, see also aleurone grain, a garin-like structure conating proteins, etc.

aliform: of paratracheal axial parenchyma, the parenchyma cells associated with the vessels forming a wing-shaped mass in transverse section, cf. banded.

alkanes: simple hydrocarbons, CH₃ (CH₂)_n CH₃, where n = 25-35.

alkaloids: organic, nitrogenous-containing bases, usually with a heterocyclic ring of some kind, but with little in common other than the posession of N, usually somewhat basic, and divided into three main categories: 1) true alkaloids - nitrogen-containing heterocyclic compounds derived from an amino acid, e.g. benzylisoquinoline alkaloids, tropane alkaloids, quinolizidine alkaloids, 2) protoalkaloids - derived from amino acids, but lacking a heterocyclic ring, 3) pseudoalkaloids - derived from terpenes, sterols, aliphatic acids, nicotinic acid, or purines. Note that similar alkaloids can have quite different biosynthetic pathways, indeed, alkaloids are rather like species - you know what they are, but cannot define them...

alkannin: a naphthoquinone derived from the p-hydroxybenzoic acid pathway (S = shikonin isomer), the coloring ingredient of alkanet; alkannin paper is an indicator of acidity, alkalis turning the paper blue, acids red (see the color changes as flowers of some Boraginaceae-Boraginoideae age).

Alkannin, C16 H16 O5.

allelocytic: of stomata, with an alternating complex of three or more C-shaped subsidiary cells of graded sizes surrounding the guard cells, see diallelocytic and parallelocytic, cf. actinocytic, anisocytic, anomocytic, cyclocytic, diacytic, helicocytic, laterocytic, paracytic, staurocytic, stephanocytic, tetracytic.

allitol: a carbohydrate product resulting from the reduction of the aldehyde functional group in D-allose.

Allitol, C6 H14 O6.

Allium: an embryo sac type, the types based on variation in megasporogenesis and megagametogenesis, bisporic (the spores chalazal) and 8-celled, all nuclei haploid, cf. Adoxa, Drusa, Endymion, Fritillaria, Oenothera, Penaea, Peperomia, Plumbagella, Plumbago, Polygonum, Schisandra.

allogamy: fertilisation involving gametes from different flowers or plants, a rather vague term, cf. cross pollination, geitonogamy, cf. also autogamy, self pollination.

allopatric: of the distribution of two speces, when the areas inhabited are mutually exclusive, cf. parapatricsympatric.

allopolyploid: a plant with a chromosome number that is the product of the addition of the diploid numbers of the parent plants, hybridisation having been involved, cf. aneuploid, autopolyploid, diploid, dysploid, haploid, polyploid.

alternate: of leaves or other lateral organs, borne singly at different heights on the axis, when used to describe leaf insertion, often vague and including the more precise spiral and distichous, cf. also bijugate, decussate, opposite, pseudoverticillate, spiromonistichous, tristichous, whorled.

alternate: of floral parts, with members of adjacent whorls borne on alternating radii, e.g. used when describing the position of stamens with respect to petals (alternipetalous), sepals (alternisepalous), etc., cf. opposite.

alternate: of pits, when they are in diagonal rows and, when crowded, hexagonal in surface view, cf. opposite.

alternation of generations: the characteristic life cycle of land plants or embryophytes: the haploid plant body produces gametes via mitotic divisions, the gametes fuse producing the multicellular diploid sporophyte, this produces haploid spores after meiotic events, and the spores germinate to produce the multicellular haploid gametophyte again; a haplodiplontic life cycle.

alveolate: pitted or honeycombed on the surface or throughout the structure.

amb: a general pollen shape descriptor, the outline as seen in polar view, cf. boat-shaped, globose, oblate, prolate, spherical, terms used for the outline as seen in equatorial view.

ament = catkin, amentiferous = catkin-bearing.

amine: amino acid with the carboxyl group removed - very smelly!

amoeboid: of tapetum, where the walls break down, the protoplasts enter the anther sac, fuse, and form a syncytium (= plasmodium?) around the developing microspores or pollen, cf. glandular.

amorphic = haplomorphic.

amphi- (prefix): both, two, complete - so rather confusing.

amphianisocytic = helicocytic.

amphibious: of the general habitat, a plant growing both in water and on land, cf. aquatic, epilithic, epiphytic, lithophytic, terrestrial.

amphicarpy: producing two kinds of fruit, one aerial and one subterranean (or amphi-geocarpy), see also geocarpy, heterocarpy.

amphicribral: vascular bundles with phloem completely surrounding the xylem, cf. amphivasal, bicollateral, collateral, also internal phloem, intraxylary phloem.

amphimixis: reproducing sexually, see androgenesis and gynogenesis (variants), cf. apomixis s. str.

amphiphloic: of a vascular bundle that is surrounded by phloem, the xylem being in the middle, as in a dictyostele, cf. ectophloic.

amphistomal: where the two integuments are at about the same level at the micropyle of an ovule, cf. bistomal, endostomal, exostomal, naked, zigzag.

amphistomatic: of leaves in which stomata are borne on both sides, cf. epistomatic and hypostomatic.

amphitropous: of an ovule, the chalaza basal and the rest of the ovule including the embryo sac being bent as the hypostase into the main body of the ovule, the micropyle ending up next to the funicle, cf. anatropous, atropous, campylotropous, circinotropous, hemitropous.

amphivasal: of vascular bundles, with xylem completely surrounding the phloem, cf. amphicribral, bicollateral, collateral, also internal phloem, included phloem.

amides: a nitrogen containing compound formed by the reaction of of an amine and a carboxylic group to form a -CONR₂ group, cf. amines, ureide.

amines: amino acids minus their carboxyl groups, cf. amides, ureide.

amplexicaul: of a leaf base, clasping and more or less encircling the stem yet free from it, cf. perfoliate.

amyloid: a storage polysaccharide that stains blue, sometimes other colours, with iodine/potassium iodide solution, cf. callose, cellulose, hemicellulose, inulin, pectin, polyol, starch.

amylopectin: a more or less coiled and branched element of starch, insoluble in water, cf. amylose.

amyloplast: a leucoplast in which carbohydrate is stored as starch grains, cf. elaioplast, proteinoplast.

amylose: a more or less coiled but unbranched element of starch, soluble in water, cf. amylopectin.

ana-: (prefix, especially of pollen apertures), located at or towards the distal pole, cf. cata-, rugate, zono-.

analogy: similarity between two structures because they have the same or a similar function, cf. homology, homoeology, paralogy, serial homology.

anaphoric: of distichous shoots, the lamina in bud rotated towards the upper side of the shoot, i.e. towards the parental axis of the shoot, or in spiral shoots, rotated towatrds the next younger leaf, so facing up the genetic spiral (Charlton 1994), cf. cataphoric.

anastomosis: fusion to form a network, e.g. of veins in a leaf blade.

anasulcate: of pollen grains, a common form having an elongate aperture at the distal pole of the grain, cf. tricolpate, tricolporate.

anatomy: internal structure, sometimes opposed to morphology, which is then restricted to external form.

anatropous: of an ovule, inverted 180^o so that the chalaza is apical and the micropyle is basal and faces the placenta, the body of the ovule being parallel to the funicle, cf. amphitropous, atropous, campylotropous, circinotropous, hemitropous.

anauxotelic: applied to inflorescences, parts of inflorescences or axes that terminate in a flower, and in which growth does not continue beyond the flowering region, see also cyme, cf. auxotelic.

ancestral: of a character, a feature of a clade more basal on the tree than that with which it is (implicitly) being contrasted, cf. derived, cf. also plesiomorphic.

ancipital, ancipitous = flattened and two-edged.

androdioecious: having perfect and staminate flowers on separate plants, probably very rare (most apparent examples are functionally dioecious), cf. andromonoecious, dioecious, gynodioecious, gynomonoecious, monoecious, perfect.

androecium: collectively the stamens of one flower, cf. gynoecium, perianth, see diadelphous, fasciculate, monadelphous, phalangiate, syngenesious (connation, etc.), see also didynamous, tetradynamous (different lengths), see also diplostemonous, haplostemonous, obdiplostemonous, obhaplostemonous (general arrangement).

androgenesis: a variant of apomixis s. str. (or amphimixis, I suppose, in which a haploid male gamete in maternal cytoplasm results in the next generation, cf. gynogenesis.

androgynophore: a receptacular stalk bearing both the androecium and gynoecium of a flower above the level of insertion of the perianth, cf. androphore, anthophore, gynophore, stipe.

androgynous: having staminate and carpellate flowers in the same inflorescence, a variant of monoecious.

andromedotoxins: a class of diterpenes causing poisoning in animals.

Rhodojaponin VI, C20 H34 O7.

Grayanotoxin, C22 H36 O7.

andromonoecious: having perfect and staminate flowers on the same plant, cf. androdioecious, dioecious, gynodioecious, gynomonoecious, monoecious, perfect.

androphore: a stalk or tube bearing separate stamens at its apex, cf. androgynophore, anthophore, gynophore, stipe.

androspore: one of the two kinds of spores produced after meiosis in an heterosporous plant and on germination giving rise to the male gametophyte, in angiosperms, a uninucleate pollen grain, see prepollen, true pollen, cf. megaspore = microspore.

anemo- (prefix): wind.

anemochory: dispersal of diaspores by wind, cf. atelochory, autochory, hydrochory, myrmecochory, zoochory.

anemophilous: pollinated by wind, cf. hydrophilous, zoöphilous.

aneuploid: a plant with a chromosome number that is not an exact multiple of the haploid number of related plants, but is clearly similar to it, cf. allopolyploid, autopolyploid, diploid, dysploid, haploid, polyploid.

angiosperm: a seed-bearing plant with the ovules borne enclosed by a sporophyll whose margins are fused, i.e., the ovules are borne in an ovary, cf. gymnosperm.

angle of divergence: in a genetic spiral/parastichy, the smaller angle relative to the stem circumference separating the points of origin of two successively initiated leaves, cf. phyllotactic fraction.

angustiseptate: a fruit flattened at right angles to the septum so the septum crosses the narrowest part of the ovary, cf. latiseptate.

anhydrobiosis: the ability of an organism to undergo essentially complete yet reversable dehydration at some stage of its life history (the plant is an anhydrobiote), see diallagyresurrection plant.

aniso- (prefix): unequal.

anisocytic: of stomata, with three subsidiary cells, two large and one smaller, surrounding the guard cells, cf. actinocytic, allelocytic, anomocytic, cyclocytic, diacytic, helicocytic, laterocytic, paracytic, staurocytic, stephanocytic, tetracytic.

anisophyllous: having leaves of very different sizes and/or shapes at the same node, cf. heteroblastic, heterophyllous, juvenile.

annual: of plant duration, a plant whose life span ends within one year after germination, e.g. a winter annual germinating in the autumn and flowering in the spring (esp. in Mediterranean climates), approximately synonymous to therophyte, cf. biennial, ephemeral, perennial, cf. also of flowering with respect to architecture, hapaxanthic, monocarpic, pleonanthic.

annular: arranged in or forming a ring; annulus, a ring, in ferns, the elastic ring of cells in the sporangium wall that initiates dehiscence, see stomium.

annulus: in ferns, the elastic ring of more or less U-thickened cells in the sporangium wall that initiates dehiscence, see stomium.

annulus: an area of the exine of a pollen< grain/a> surrounding a pore.

anomalous: a term of convenience, kinds of secondary growth that differ from the "ordinary" ones.

anomocytic: stomata lacking differentiated subsidiary cells surrounding the guard cells, cf. actinocytic, allelocytic, anisocytic, cyclocytic, diacytic, helicocytic, laterocytic, paracytic, staurocytic, stephanocytic, tetracytic.

ante- (prefix) equals in front of, e.g. antepetalous inserted in front of (adaxially to, "opposite") the petals, antesepalous, the sepals.

anterior (as used of floral organs) = abaxial, cf. posterior.

anther: the pollen-bearing part of a stamen, with which its connective is usually described as being basifixed, centrifixed, dorsifixed, embedded, or versatile as it joins the filament, made up of an number of sporangia, in angiosperms these typically in pairs or theca, opening by slits or ostioles, pores or valves in either the extrorse, latrorse or introrse directions , the wall development often following the basic, dicotyledonous, monocotyledonous or reduced types, see also theca.

antheridium: the fertile organ of a male gametophyte or the male organ of a bisexual gametophyte, in which male gametes are formed, cf. archegonium.

antherode: the non-funational anther of a staminode.

antherozoid: a flagellated male gamete.

anthesis: the time of full opening of a flower when pollen is presented and/or the stigma is receptive.

anthocarp: a true fruit surrounded by all or just the base of the perianth, as in Nyctaginaceae and many Rosaceae-Pomoideae, really a particular kind of accessory fruit but a term of some use, perhaps also to be used for fruits with persistent sepals, as in Dipterocarpaceae, cf. aggregate fruit, multiple fruit.

anthochlors: a group of usually yellow flavonoids made up of aurones and chalcones, yellow pigments that turn red in an alkaline solution of, say ammonium, or with cigarette or cigar smoke.

anthocyanidins: a class of coloured anthocyanin aglycones (i.e. lacking the sugars) formed from flavan-3,4-diols, also when proanthocyanidins are hydrolyzed with acid (note that they are not formed from proanthocyanidins in the plants); major determinant of flower colour.

anthocyanins: a class of flavonoids based on the cyanidin structure, differing in the presence or absence of hydroxyl groups by methylation or glycosylation (they have sugars at position 3 and sometimes elsehwere), forming red-, pink-, purple- and blue-colored pigments, one of the two main pigment types, cf. carotenoids.

Anthocyanin base.	Pelargonidin, C15 H11 O5.
Delphinidin, C15 H11 O7 Cl.	Cyanidin, C15 H11 O6.

anthophore: a receptacular stalk bearing the corolla, androecium and gynoecium of a flower on a stalk above the level of insertion of the calyx, cf. androgynophore, androphore, gynophore, stipe.

anthotaxis: the arrangement of flowers along the stem, especially as they are initiated at the shoot apex, when bracts are absent, getting at the same thing as phyllotaxis.

anthotelic = determinate.

anthoxanthins: yellow, cream or colorless flavonoids occuring in cell saps.

Anthoxanthin, C21 H20 O12

anthraquinones: quinones in which the aromatic ring is fused to both sides of a benzoquinone ring, occuring as glycosides in plants, often colored.

Anthraquinone, C14 H8 O2.	Chrysophanol, C15 H10 O4.
Asphodelin, C30 H18 O8.

anti- (prefix): in front of, e.g. antipetalous inserted in front of (adaxially to, "opposite") the petals, antisepalous, the sepals.

anticlinal: e.g. of cell walls, those at right angles to the surface of the organ, cf. periclinal.

anticous: as used of floral organs, = abaxial, cf. posticous.

antipodals: cells, commonly three in number as in the eight-nucleate embryo sac, located at the other end of the embryo sac from the female gamete, more or less persistent, multiplicative or not, cf. also central cell, egg apparatus, polar nuclei, synergids.

antiraphe: on the other side of the ovule to the raphe, cf. also chalaza, funicle, embryo sac, integument, lagenostome, megaspore, micropyle, nucellus, pollen chamber, obturator.

antirrhinoid (of a floral aestivation) descending cochleate.

antitropous: of the curvature of an ovule with respect to the carpel margin that bears it, curvature in the opposite direction to the curvature of the margin, cf. syntropous, see also apotropous, epitropous, pleurotropous.

antitropous: of the folding of the leaf blades of leaves on opposite sides of the stem in Marantaceae, the same side of the leaf being inrolled inside the other (actually different sides if the leaves are considered individually!), cf. homotropous.

antrorse: bent, and pointing towards the apex, cf. retrorse, erect.

apert (of aestivation) = open.

aperture: a distinctly delimited part of a pollen grain in which thick intine is covered by thin exine and through which the pollen tube emerges, whether a compound or simple aperture, see colpate, colporate, porate, pororate, sulcate, sulculate, trichotomosulcate, ulcerate and zona-aperturate, of apertures, see also operculum, pontoperculum (covering of aperture), stephano-, also ana-, cata-, panto-, zono- (distribution of the aperture(s) with respect to the basic polarity of the pollen grain), also ectoaperture, endoaperture, also Fisher's rule, Garside's rule (distribution of apertures), and annulus and oncus (elements of apertures).

apetalous: without petals, cf. polypetalous, sympetalous.

apical: of placentae, at the top of the ovary, and hence the ovules pendulous, c.f. axile, basal, free central, laminar, marginal, parietal.

apical cell: the upper (chalazal) cell formed after the first division of the zygote, which further divides to produce the bulk of the embryo proper, cf. basal cell.

apical: a hook-like strucutre which develops at the apical part of the of an hypocotyl in dark-grown seedlings of broad-leaved angiosperms with epigeal germination.

apical meristem: the meristem at the apex of stem or root, of which the ground meristem, intercalary meristem, procambium, protoderm can rather loosely be considered parts, cf. lateral meristem, see root apical meristem, shoot apical meristem, also initial and morphogenetic zones (terms describing cytohistological differentiation that can be applied to all land plants), and histogens (descriptors used in an old theory of the construction of the apical meristem).

apiculum: a short, abrupt, flexible point, adj. apiculate, but it has other meanings as well, and overall it is better replaced (along with cuspidate) by a suitably-qualified mucronate (see Rickett 1956), cf. acumen, acute, attenuate, arista, awn, cuneate, emarginate, muticous, obtuse, retuse, rounded, truncate, cf. also cordate, hastate, oblique, runcinate, sagittate (esp. of lamina base).

apigenin: a deoxyanthocyanin occurring in leaves and flowers.

apo- (prefix): separate.

apo- (prefix): the polar region of a zonoaperturate pollen grain delimited by lines connecting the apices of the apertures, cf. meso-.

apocarpous: of the gynoecium, consisting of two or more carpels which are free from one another or almost so, or a single carpel (but not a pseudomonomerous gynoecium), see paracarpous, coenocarpous, syncarpous.

apocole: of a monocot seedling, the elongated, usually subterranean and non-photosynthetic part of the cotyledonary hyperphyll below the haustorium and above the cotyledonary sheath, cf. haustorium/scutellum, phanomer, see also mesocotyl, coleorhiza, hypophyll (cotyledonary sheath, coleoptile), collar (epiblast, periblast).

apogamy: of reproduction, production of offspring from gametophytes without fertilisation, cf. adventitious embryony, agamospermy, apomixis, apospory, vegetative reproduction.

apogeotropic: of roots which grow upwards, cf. geotropic.

apomixis: of reproduction, in the strict sense the production of viable offspring without fertilisation, equals agamospermy above, or, in a more general sense, includes the production of vegetative propagules, i.e. vegetative reproduction (for which, cf. amphimixis), see adventitious embryony, apospory, diplospory, polyembryony.

apomorphy: of a character, derived, an evolutionary novelty arising in the immediate ancestor of a clade and characterising it, cf. autapomorphic, plesiomorphic, synapomorphic.

apomorphy-based: a way of defining a clade in which an apomorphy is the defining point, e.g. the clade stemming from the first species to possess character A (as found in a particular exemplar species), cf. node-based, stem-based.

apopetalous = polypetalous.

apoplast: the continuum formed by the interconnected cell walls in plants, cf. symplast.

apoptosis: programmed cell death.

aporphine alkaloids: group of isoquinoline alkaloids.

Aporphine, C17 H17 N.

aposematic: of insects, etc., with a warning colouration, perhaps because they are loaded with noxious plant secondary metabolites that they have sequestered, cf. cryptic.

apospory: a kind of agamospermy> where unreduced embryo sacs develop from ovular tissue, cf. adventitious embryony, apogamy, diplospory, polyembryony.

apostapetalum: referring to that part of the corolla tube and lobes above the zone with fused/adnate stamens, a term of dubious utility, cf. stapetalum.

apotact: of cochleate aestivation, the petal with its two edges outside those of the adjacent petals not immediately next to the one with the two edges both inside, cf. ascending, descending, and paratact.

apotracheal: of axial parenchyma, parenchyma not associated with the vessels, see banded, boundary, diffuse, cf. paratracheal (aliform, banded).

apotropous: of the curvature of an ovule with respect to the ovary axis, abaxial, cf. epitropous, pleurotropous, see also antitropous, syntropous.

appendage: a general term for any structure that is not one of the conventional parts of an angiosperm plant that arises from the surface of another.

appendicular: of tissues or parts of the plant formed from leaves or structures considered "homologous" with them, cf. axial.

appendicular epigyny: of epigyny, when the floral apex is initially convex, but it early flattens and a central concavity develops due to toral upgrowth of the floral cup. i.e. due to development of appendicular tissues (Kuzoff et al. 2001), cf. receptacular epigyny.

apposition: of branching, as in the formation of a plagiotropic branching system by a series of units, each consisting of a vigorous axillary branch that is initially plagiotropic but whose apex becomes orthotropic, the terminal meristem still remaining active, as in plagiotropy by apposition as in Terminalia branching, cf. substitution.

apposition: in cell wall formation, growth by deposition of layer after layer of wall material, cf. intussusception.

appressed: pressed closely against a surface, often that of another organ, but not united with it, cf. adherent, adnate, coherent, connate, connivent, fasciate, fasciculate, fastigiate, free, phalangiate.

aquatic: of the general habitat, a plant living in or on water for all or a substantial part of the life span, cf. amphibious, epilithic, epiphytic, epiphyllous, terrestrial.

arabinose: (C5 H9 O4)-OH - an aldopentose epimeric with ribose at the 2 carbon, occurring naturally in both D- and L-forms, widely distributed in the form of complex polysaccharides, glycosides, and mucilages; arabinoside is a glycoside of arabinose and occurs widely in plant species as a component of sugars, also in gum arabic.

arabitol: the polyol form of the preceding (an alditol), cf. dulcitol, glycerol, mannitol, and sorbitol

arachnoid: especially of hairs, looking rather like a tangled spider's web, cf. arachnoid, arbuscular, canescent, hirsute, hispid, hirsute, lepidote, puberulous, pubescent, sericeous, stellate, strigose, tomentose, T-shaped, villous, see also glabrescent and glabrate, which refer to stages in the loss of these hairs.

arbuscular mycorrhiza: an endomycorrhizal association between a fungus and a plant root where the fungal hyphae form coils and/or arbuscules or arbusculate coils (branched, something like a small tree or shrub) within the plant cell, see also Arum and Paris types, cf. b>VAM.

arbutin: a benzoquinone.

archegonial chamber: a cavity or space between the megasporangium and the female gametophyte, cf. egg, neck, venter.

archegonium: the fertile organ of a female gametophyte or the female organ of a bisexual gametophyte of an embryophyte, in which female gametes or eggs are formed, see archegonial chamber, neck, venter, and egg, cf. antheridium.

archesporium = tissue that gives rise to megasporocytes or microsporocytes as well as parietal tissue, including the endothecium (in the anther) and the nucellar tissue (in the ovule).

arcuate: curved like a bow.

areole: any small, discretely bounded area; a cluster of hairs/spines/bristles borne at the node of (in Cactaceae) a usually leafless stem; in Fabaceae-Mimosoideae a distinct, oblong or elliptical area on the face of a seed, bounded by a fine line, the linea fissura; in leaf venation, the space bounded by the finest veins on the lamina, adj. areolate.

aril: in the strict sense, an often fleshy outgrowth partly or wholly covering a seed and developed from the funicle or raphe, but also used more generally to refer to a similar structure derived from any part of the ovule as arillode and arilloid, adj. arillate, cf. arillode, caruncle, coma, elaiosome, sarcotesta, strophiole. There has been much and sometimes acrimonious debate over the correct definition of the term, but it seems that "aril", rather like obturator, podium, postament, is best used rather broadly, with its origin being given for clarity.

arillode: not a very useful term - a fleshy structure partly or wholly covering a seed and developed from any part of the ovule, or an elaborate structure at the micropylar end of the seed (Bell & Bryan 2008), cf. aril, caruncle, elaiosome, sarcotesta, strophiole.

arilloid: also used to refer to a fleshy structure partly or wholly covering a seed and developed from any part of the ovule, the same as aril in the broad sense, see aril s. str., arillode, caruncle, elaiosome, sarcotesta, strophiole.

arista: of the apex of a structure, having a stiff, bristle-like awn or tip, adj. aristate, cf. acumen, acute, attenuate, apiculum, awn, cuneate, caudate, cuspidate, emarginate, mucronate, muticous, obtuse, retuse, rounded, truncate, cf. also cordate, hastate, oblique, runcinate, sagittate (esp. of lamina base).

aristolochic acid: a phenanthrene-carboxylic acid derivative of a benzoisoquinoline precursors.

Aristolochic acid, C17 H11 N O7.

article: a segment of a jointed stem, or of a fruit with constrictions between the seeds.

articulated: jointed, e.g. the more or less swollen apex of a petiolule in particular that has a line across the broadest part, with separation commonly occuring here when the leaflets fall, articulation, cf. pulvinus; of a stem, having prominent nodes.

articulated laticifer: of a laticifer, branching, anastomosing and with cross walls, cf. non-articulated.

Arum-type arbuscular mycorrhiza: an arbuscular mycorrhiza association between a fungus and a plant root where the fungal hyphae are intercellular, and also form coilsb and pelotons within the plant cell, see also Paris type.

arylphenalenones: phenalenones with aryl radicals, pigments found in Haemodoraceae, derived from 9-phenylphenalenone.

Haemocorin, C32 H34 O14.

ascending: growing erect after an oblique or semi-horizontal beginning, cf. decumbent, erect, procumbent, repent, or a stem growing about 45-60° from the horizontal, cf. orthotropic, plagiotropic.

ascending cochleate: cochleate aestivation in which one petal has its two edges outside those of the adjacent petals, one has its two edges both inside, and the other petals have one edge outside and the other inside, the petal with the two edges inside being in the median-adaxial position, cf. descending, and apotact, paratact.

ascidiate: pitcher-shaped, more or less tubular and often widening towards a flared mouth and then subpeltate, esp. used of the leaves of several carnivorous plants, or of carpels, cf. conduplicate.

asexual (of reproduction) = apomixis s. lat., sometimes equated with vegetative reproduction.

asperulate: slightly rough to the touch.

asphodelin: a yellow colored anthraquinone.

astrosclereid: a sclereid cell with rather short, stout radiating branches, cf. filiform sclereid, brachysclereid, macrosclereid, osteosclereid, trichosclereid.

asymmetric: with no plane of symmetry, such that dividing the structure down its axis does not produce mirror-image or identical halves, e.g. oblique leaf bases; when considering floral asymmetry, there are two main kinds, one is not very striking and is found in the haplomorphic flowers of e.g. Magnolia, where the halves are very similar, but not identical, the differences seemingly being inconsequential(!), and the other, as in Canna, is more striking, and the asymmetry, primarily in the androecium and gynoecium, is clearly connected with the pollination mechanism, see also enantiomorphic, enantiostylous, cf. bisymmetric, monosymmetric, oblique, polysymmetric.

atactostele: a stele in which the vascular bundles are scattered through the ground tissue, cf. eustele, dictyostele, protostele, siphonostele.

atectate: pollen in which the sexine is represented only by isolated baculae, pilae, granules or other elements, cf. semitectate, tectate.

atelochory: diaspores without any dispersal mechanism, cf. anemochory, autochory, hydrochory, myrmecochory, zoochory.

atropous: a erect, straight ovule with funicle, chalaza and micropyle in a straight line, cf. amphitropous, anatropous, campylotropous, circinotropous, hemitropous.

attenuate: tapering gradually to a point, a vague term that is probably better replaced by narrowly acute or acuminate where appropriate, cf. acumen, acute, apiculum, arista, awn, cuneate, caudate, cuspidate, emarginate, mucronate, muticous, obtuse, retuse, rounded, truncate, cf. also cordate, hastate, oblique, runcinate, sagittate (esp. of lamina base).

aucubin: a bitter-tasting route II decarboxylated iridoid.

Aucubin, C15 H22 O9.

aulacospermous: referring to seeds in which individual endothelial cells protrude into the endosperm, the endosperm becoming alveolate (it may appear to be ruminate in cross section), cf. bothrospermous.

aureol: a phytoalexin.

auricle: an ear-shaped appendage at the base of a leaf, leaflet or corolla lobe, adj. auriculate.

aurones: golden-colored flavonoids isomeric with cf. flavones with Z-sterochemistry at the double bond, often found in flowers, cf. chalcones; they are anthochlors.

Aurone base.	Benzofuranone, C15 H10 O2.
Sulfuretin, C15 H10 O5.

autapomorphic: of a character, derived, an evolutionary novelty of a terminal clade in a particular study, at a finer level of analysis a synapomorphy of all members of that clade, cf. also apomorphic, plesiomorphic, synapomorphic.

auto- (prefix): self, alone, single.

autochory: dispersal of diaspores without the aid of any external agent, e.g. by explosive dehiscence of the fruit, cf. anemochory, atelochory, hydrochory, myrmecochory, zoochory.

autoecious: referring to rust fungi in which the aecial and telial stages are on the one host plant, cf. heteroecious.

autogamy: pollination and fertilisation occuring by pollen from within the same flower, cf. allogamy, cross pollination, cf. also geitonogamy, self pollination.

autopolyploid: a plant with a chromosome number that is a multiple of base number (n) of its parent, hybridisation not being involved, represented as 3x, 4x, etc., cf. allopolyploid, aneuploid, diploid, dysploid, haploid, polyploid.

autotroph: an organism independent of others in respect of organic nutrition, being able to fix carbon dioxide by photosynthesis, to form carbohydrates, cf. heterotroph.

autumn wood = late wood.

auxoblast = long shoot.

auxotelic: applied to inflorescences, parts of inflorescences or to axes that do not end in a flower, and in which growth continues beyond the flowering region, cf. anauxotelic, see also raceme.

awn: of the apex of a structure, a long bristle-like appendage, e.g. on the tip or back of the lemma of a grass floret, cf. acute, attenuate, acumen, apiculum, arista, cuneate, caudate, cuspidate, emarginate, mucronate, muticous, obtuse, retuse, rounded, truncate, cf. also cordate, hastate, oblique, runcinate, sagittate (esp. of lamina base).

axicorn: ticcue on the inside of the fruit of Campanulaceae-Campanuloideae which by its drying perforates the fruit wall and allows the dispersal of the seeds.

axial: of tissues or parts of the plant formed from stem (or root) or structures considered "homologous" with them, cf. appendicular.

axial bundle: a major vascular bundle of a sympodium, cf. leaf gap, leaf trace.

axial parenchyma: longitudinally-elongated parenchyma cells in among the tracheary tissue, see aliform, apotracheal, banded and paratracheal, cf. ray parenchyma.

axicorn: a structure involved in the dehiscence of some caspsules which on drying causes holes, flaps, or slits to appear in the walls.

axil: the angle formed by an axis and a leaf borne on it, it; adj. axillary, e.g. of a bud, inflorescence, etc., subtended by a leaf, cf. intercalary, leaf-opposed, supra-axillary, also cauliflorous, ramiflorous, terminal (of inflorescence or infructescence position).

axile: of the placentation of an ovary, usually (unless pseudomonomerous) with septae separating loculi, the ovules being borne on the central axis, cf. apical, basal (these two really just variants of axile placentation), free central, laminar, marginal, parietal.

axillary bud: the bud in the axil of a leaf.

axis: a stem, the term being commonly used for the main stem of a plant or of an inflorescence, see inflorescence axis.

azetidine-2-carboxylic acid: C4 H7 N O2, a non-protein amino acid, an alpha-amino acid with a primary -imino group (-NH) and a carboxyl group attached to the same carbon atom.

B

baccate: berry-like, not strictly a berry, or the adjectival form of berry.

baculum (Erdtman term): in pollen, a cylindrical, free standing element of exine/sexine element more than 1µm in length and less than this in diameter (baculae, baculate), cf. columella, and because a baculum supports nothing, it is an element of pollen ornamentation, cf. also echinate, fossulate, gemmate, foveolate, pilate, lophate, psilate, reticulate, retipilate, rugulate, scabrate, striate, verrucose.

banded: of axial parenchyma, the parenchyma cells forming bands, whether or not associated with vessels, i.e. either apotracheal, cf. boundary, diffuse, or paratracheal, cf. aliform.

banner of a petal = standard.

barbed: terminal or lateral retrorse projections on a structure, each projection being a barb, cf. glochidiate; barbellae, short, straight, stiff hairs or barbs, adj. barbellate.