I

idioblast: literally, a unique cell, a clearly distinct, specialised and/or differentiated cell, e.g. sclereidal idioblast, myrosinase idioblast, can often be omitted or simply replaced by "cell".

imbricate: in general, of organs overlapping in such a way that part is covered, part exposed, of aestivation, the parts having the edges overlapping in the bud such that at least some parts have one edge oustide, the other inside, see cochleate, contorted, contortiplicate, crumpled, decussate, quincuncial, cf. open, valvate.

imparipinnate = odd pinnate.

imperfect: of flowers, lacking either functional carpels or stamens and thus either either staminate or carpellate, cf. perfect, see carpellate, neuter, staminate.

incised: cut deeply, sharply and often irregularly (an intermediate condition between toothed and lobed).

in- (prefix): without, lacking.

included: enclosed, not protruding; of stamens, etc., in a corolla tube, cf. exserted.

included phloem: in secondary vascular tissue, phloem islands surrounded by xylem, cf. internal phloem, successive cambia, cf. also amphicribral, amphivasal, bicollateral, collateral.

incompletely tenuinucellate: an ovule in which one or more layers of cells (not epidermally derived) separate the megasporocyte(s)/embryo sac from the epidermis, but only laterally so (see Endress 2003c), cf. crassinucellate, nucellar cap, nucellar pad, tenuinucellate, weakly crassinucellate (different degrees of development of the nucellus or the epidermis covering it).

incrassate = thickened.

incumbent: of the orientation of an embryo, with the cotyledons lying face to face and folded sideways so that the radicle lies against the face of one of the cotyledons, cf. accumbent, conduplicate, diplecolobous.

incumbent: in Orchidaceae, of the orientation of an anther, bent adaxially/inwards ca 90°, for other commonly-used terms specific to orchid flowers, see caudicula, column, hamulus, labellum, rostellum, massulae, sectile, stipes, tegula, viscidium, also epichile, hypochile.

incurved: bent or curved inwards, upwards, or adaxially, cf. recurved.

indefinite: variable in number, numerous, = many; of stamens, more than twice as many as the petals or sepals; of ovules, more than fifteen or so, cf. definite.

indehiscent: not opening at maturity, cf. dehiscent.

indeterminate: of growth, a general term used when the apical meristem produces an unrestricted number of lateral organs, in particular, when the axis is not terminated by a flower (see loosely racemose) or by the abortion of the apex, cf. determinate.

indole alkaloids: alkaloids that contain an indole ring, derived from phenylalanine or tryptophane.

Vincamine, C21 H26 N2 O3.

Yohimbine, C21 H26 N2 O3.

indumentum: the overall appearance of the epidermal appendages, e.g. hairs and/or scales, collectively, see arachnoid, arbuscular, canescent, hirsute, hispid, lepidote, puberulous, pubescent, sericeous, stellate, strigose, tomentose, villous (types), see also glabrate, glabrescent (both referring to persistence) and glabrous.

induplicate: of aestivation, valvate, the edges of a sepal or petal are not overlapping, but they are incurved when they meet an adjacent member, cf. crumpled, decussate, open, reduplicate.

induplicate: of plicate leaves, esp. in palms, the units of the leaves having their adaxial surfaces facing each other, V-shaped, cf. reduplicate.

indurated = hardened and rather inflexible.

indusium: a flap of tissue covering the sorus in some ferns; a concave pollen-cup surrounding the stigma in Goodeniaceae.

inferior: of an ovary, borne at least partly below the level of attachment of the other floral parts, cf. superior, cf. also epigynous, hypogynous, perigynous.

inflexed: bent sharply upwards, forwards or adaxially, cf. deflexed.

inflorescence: that part of the stem above the uppermost node with foliage leaves that bears flowers, also, the groupings or arrangements in which these flowers are borne, cf. infructescence, see inflorescence axis, peduncle (parts), also cymose, racemose, also determinate, indeterminate, also monotelic, polytelic, also anauxotelic, auxotelic, also synflorescence, also axillary, cauliflorous, ramiflorous, supra-axillary, terminal (general position).

inflorescence axis: the main axis of an inflorescence bearing inflorescence branches and/or flowers, cf. peduncle.

inflorescence bract: an often more or less reduced leaf subtending a branch of the inflorescence or borne on the inflorescence axis below any branches or flowers, cf. bract, bracteole.

infraspecific: of lower taxonomic rank than species.

infratectum: of a pollen grain, that part of the ectexine between the foot layer and tectum, including columellae, cf. also supractectal structures/sculpture elements.

infructescence: that part of the stem axial system that bears fruits, the grouping or arrangement in which fruits are borne on a plant, cf. inflorescence, see axillary, cauliflorous, ramiflorous, supra-axillary, terminal (general position).

infundibular: e.g. of a polysymmetric corolla, gradually widening from the base to the more or less spreading lobes, generally resembling a funnel, cf. campanulate, rotate, salverform, tubular, urceolate. (funnel-shaped in the image).

ingroup: the clade of immediate interest, cf. outgroup, sister group.

initial: see cambial initials.

initial zone: a part of the shoot apical meristem consisting of slowly-dividing stem cells surrounded by the morphogenetic zone; the initial zone can be divided (different patterns of gene expression) into a centrally-located organizing centre that produces and maintains the stem cells at the summit of the meristem (see Friedman et al. 2004).

inner bark: a non-technical term for the inner part of the bark, specifically the secondary tissues of the phloem, cf. outer bark.

innovation: in plants with intermittent growth, the stem and associated leaves produced during each period of growth.

inolizidine alkaloid: a polyhydroxy alkaloid.

insectivorous: catching and feeding on insects.

inserted: attached to, arising from.

intectate: a pollen grain lacking a tectum, but with sculpturing.

integument: in general, a covering; specifically one of the layers of tissue that usually cover the ovule, enveloping the nucellus and forming the micropyle where it meets at the apex of the ovule, see endothelium, cf. also antiraphe, chalaza, funicle, embryo sac, raphe.

integumentary tapetum = endothelium.

inter- (prefix): between.

intercalary: between two points, thus intercalary growth, extension or growth from an intercalary meristem, i.e. neither from the apex nor the base of the internode, intercalary inflorescence, an inflorescence that either arises in an internodal position, or one that was originally terminal but ceases to be so when vegetative growth subsequently resumes from the stem apex; cf. axillary, leaf-opposed, supra-axillary.

intercalary meristem: an actively-growing region of primary tissue somewhat removed from the apical meristem and occurring between regions of more or less differentiated tissues, e.g. at the base of a monocot leaf, in some internodal regions, etc.

interfascicular cambium: a lateral meristem developing from tissues in the region between the vascular bundles, and, with the fascicular cambium, making up the vascular cambium.

interfascicular region: tissues in the region between the vascular bundles.

intermediary cell: in minor vein phloem, a type of companion cell that abuts the bundle sheath in which the walls have numerous branched plasmodesmata, the branches being narrower and more numerous in the walls on the intermediary cell side than on the the bundle sheath cell side, cf. transfer cell.

intermediate meristem: of a root apical meristem in which cell files giving rise to different tissues trace to the initials at the apex, but the initials are not clonally distinct, cf. closed meristem, open meristem.

intermediate: of the stem vascular system, in which the sympodia are partly discrete and separate from the others, and partly connected by fusions of vascular bundles, cf. closed, open.

internal phloem: primary phloem that is found adaxially or internally to the xylem in the stem, in the leaf manifest as a bicollateral vascular bundle, cf. included phloem, successive cambia, cf. also amphicribral, amphivasal, collateral.

internode: the portion of a stem between the level of insertion of two successive leaves, leaf pairs or leaf whorls, or branches of an inflorescence, i.e. between two nodes.

interpetiolar: e.g. of stipules, between the petioles of two opposite leaves, cf. intrapetiolar, sheathing.

interrupted: e.g. of an inflorescence, having the flowers unevenly distributed along the axis, with conspicuous gaps.

interxylary phloem (not used here), bands of phloem alternating with xylem, produced by successive cambia.

intine (both Erdtmand and Faegri and Iverson!): the innermost of the major layers of the pollen grain wall, underlies the exine and borders the cytoplasm, not acetolysis resistant and is therefore absent in conventionally prepared palynological material, cf. ectexine, endexine.

intra- (prefix): borne immediately adaxially or admedially to the structure that this prefix qualifies, e.g. intrastaminal nectaries, nectaries borne on the receptacle between the staminal whorl and the ovary; more loosely, intra- = within.

intragynoecial compitum = compitum (but this is a loose equivalence), cf. extragynoecial compitum.

intramarginal vein: a continuous more or less looping vein that runs admedially to/inside the leaf blade margin and which joins the secondary veins, a composite vein usually formed by linking parts of secondary veins, as in brochidodromous venation, cf. fimbrial vein.

intrapetiolar: e.g. of stipules, between a petiole and the stem on which they are borne, cf. interpetiolar, sheathing.

intravaginal squamule = colleter.

intraxylary phloem, a confusing term, = included phloem or internal phloem.

introduced: cf. adventive, native.

intron: part of a gene sequence that is transcribed but not translated, being spliced out before this, cf. exon.

introrse: of anthers, dehiscing adaxially towards the centre of the flower, cf. extrorse, latrorse.

intrusive: pushing into something, e.g. of placentae protruding into the ovary loculus, of endosperm haustoria, pushing into or between cells, or of cell growth, where a cell pushes between neighboring cells that separate along the middle lamella.

intrusive-parietal: of placentation in which the placentae protruding from the margin more or less deeply into the ovary loculus.

intussusception: in cell wall formation, growth by addition of new wall material within previously formed wall, cf. apposition.

inulin: a fructan that acts as a storage polysaccharide, yields fructose on hydrolysis, cf. callose, cellulose, hemicellulose, inulin, pectin, starch.

Inulin, (C6 H10 O5)n.

invasive: of tapetum, = amoeboid.

inversostyly: flowers of a species having different style and stamen arrangements, the lengths not varying and the flowers of any one plant being identical, cf. heterostyly.

involucel: a group of "bracts" surrounding a secondary inflorescence such as the base of an umbellule, or of "bracteoles" surrounding an individual flower, as in Dipsacaceae, although the morphological interpretation of these structures may be a matter of dispute.

involucre: a group of inflorescence bracts surrounding an inflorescence.

involute: of leaf ptyxis, more or less flat, but each margin independently rolled towards the adaxial surface, cf. circinate, conduplicate, conduplicate-flat, conduplicate-involute, conduplicate-plicate, curved, flat, plicate, revolute, supervolute, supervolute-curved, supervolute-involute.

iridoids: subclass of terpenoids, monoterpenoids with lactone substitutions (the right half of the diagram below), usually in glycosidic form, in nearly all deoxyloganic acid or epi-deoxyloganic acid is an intermediary, see route I iridoids (including secoiridoids) and route II iridoids (including carboxylated and decarboxylated iridoids).

Iridoid base.

irregular (of floral symmetry) = = asymmetric, sometimes also used for monosymmetric flowers.

iso- (prefix): equal in number of parts or appearance, in chemical names, refers to an isomer.

isobifacial: of flattened structures, especially leaves, having both surfaces structurally similar, cf. bifacial, dorsiventral, unifacial.

isobilateral: of symmetry, = bisymmetric.

isoflavans: isomeric form of flavones with the most reduced structure of any isoflavonoids that lack hydroxy or ketone groups, i.e. there are no oxygens in the structure; they are common as phytoalexins in Fabaceae.

Isoflavan, C19 H22 O5.

isoflavones: class of flavonoids in which the B ring of flavones is attached to the 3-position (instead of the 2-position), absorbing light in the ultraviolet region and a component of "bee violet".

Base structure, C15 H10 O2.	Luteone, C20 H18 O6.
Wighteone, C20 H18 O5.

isoflavonoids: class of flavonoids in which the B ring of flavones is attached to the 3-position (instead of the 2-position) and that lack the 3-hydroxy group of flavonols.

isokestose: oligosaccharides, inulin trisaccharide, the building block of inulin-type fructans; cf. kestose.

1-kestose, C18 H32 O16.

isomerous: with an equal number of parts in each (floral) whorl, except perhaps the gynoecial whorl, cf. heteromerous.

isopentenyl pyrophosphate: the building unit of terpenes.

Isopentenyl pyrophosphate, C5 H12 O7 P2.

isoprene: a volatile unsaturated branched chain five-carbon hydrocarbon that is the basic unit of terpenes, synthesised via the mevalonic acid pathway.

Isoprene, C5 H8.

isoquinoline alkaloids: type of true alkaloid, formed from a precursor of 3,4-dihydroxytyramine (dopamine) linked to an aldehyde or ketone.

Isoquinoline nucleus.	Berberine, C20 H18 N O4.
Hydrastine, C21 H21 N O6.	Papaverine, C20 H21 N O4.

isothiocyanates: esters of isothiocyanic acid, R—N=C=S, a.k.a. mustard oils, with a pungent smell and a sharp taste, derived from glucosinolates undergoing an enzymatic reaction (via the enzyme myrosinase) when plant tissue is crushed, cf. nitriles.

isovitexin: a glycoflavone.

iteroparous: of reproduction, when there are repeated annual/seasonal bouts of flowering, cf. semelparous, cf. more from the point of view of meristem persistence hapaxanthic, monocarpic, pleonanthic, and of plant duration, annual, biennial, ephemeral, perennial.

J

jaculator: a hardened and hook-like funicle that is conspicuous in the seeds of many Acanthaceae, rare elsewhere.

jugate = paired.

justicin: a lignan.

juvenile: of leaves, those on a young plant different in form from those on an adult, sometimes also occurring on sucker or reiterating shoots, i.e. when the plant is heteroblastic, cf. anisophyllous, heterophyllous.

K

kaempferol: a common flavonol with a single hydroxyl group attathed to the B ring; occurs as a copigment in flowers and fruits.

Kaempferol, C15 H10 O6.

karyotype: the gross morphology of the somatic chromosome set, described at metaphase of mitosis in terms of chromosome number and length, centromere position, etc.

keel: the relatively large paired abaxial petals (in a papilionoid flower), or a single petal (in some other plants) that together or singly are more or less concave and with an abaxial ridge, usually more or less enclosing the stamens, cf. standard, wings; more generally, keeled, of leaves, petals or bracts, folded and ridged along the midrib.

kernel: a vague term, not recommended (it can mean endosperm, embryo, etc.).

key: series of contrasting choices by which an unknown plant may be identified by the process of elimination, see multiple access, polyclave.

kestose: a frutosyl sucrose oligosaccharide, may serve as intermediates in the biosynthesis of fructans, cf. isokestose.

Kestose, C18 H32 O16.

Kranz: distinctive leaf anatomy of many C4 plants in which the regularly-spaced vascular bundles are surrounded by a sheath of large cells, themselves containing large chloroplasts, and then by radially-arranged mesophyll cells.

L

L- (prefix): laevo, handedness of isomers, all naturally-occurring amino acids are L-; see L-tryptophan, L-phenylalanine, etc.

labellum: any rather large and lip-like structure in a flower, usually in the abaxial or lower position, e.g. in Orchidaceae (a perianth member), Zingiberaceae and Costaceae (derived from petaloid staminodes).

labellum: in Orchidaceae, the distinctive median tepal of the inner whorl (see epichile, hypochile) - for other commonly-used terms specific to orchid flowers, see caudicula, column, hamulus, incumbent, labellum, rostellum, massulae, sectile, stipes, tegula, viscidium, also epichile, hypochile.

laciniate: slashed into narrow, pointed lobes.

lactones: cyclic compounds with a 5-6-membered ring in which the chain is closed by ester formation between a carboxyl and a hydroxyl group in the same molecule; see iridoids, sesquiterpene lactones.

Parasorbic acid, C6 H8 O2.

lacuna: a gap or cavity, see nodal anatomy.

lagenostome: a pre-pollination pollen chamber formed at the apex of the megasporangium wall (nucellus) of some gymnosperms by cell degeneration in which pollen may collect, cf. antiraphe, chalaza, epistase, female gametophyte, funicle, hypostase, integument (see also endothelium), megaspore, micropyle, pollen chamber, obturator, podium, postament, raphe.

lalongate: where the longest axis of an endoaperture of the compound aperture of a pollen grain is perpendicular to the longest axis of the ectoaperture, cf. lolongate.

lamella: a thin, plate-like layer, see middle lamella.

lamina: the blade of a leaf, usually flattened, dorsiventral, and expanded, cf. hyperphyll, leaf base, petiole, stipule, Vorläuferspitze, see admedial, exmedial (positional terms); the lamina margin often with teeth, see also biserrate, crenate, dentate, entire, serrate, sinuate, undulate, see also venation.

laminar: placentation where the ovules are not localised on placentae but are scattered along the septa, cf. apical, axile, basal, free central, intrusive-parietal, marginal, parietal.

lateral: borne lateral to the axis of symmetry of the flower relative to the inflorescence axis, that is, lateral to the line joining the flower, the bract subtending it, the inflorescence axis on which it is borne, cf. abaxial, adaxial, median.

lateral: of a style or stylulus that arises from the side of the gynoecium, cf. gynobasic, terminal.

laterally compressed: of axillary structures, flattened laterally, so extended in the ad-/abaxially or median plane, cf. laterally compressed, see also angustiseptate and latiseptate fruits.

lateral meristem: a meristem of stem or root arranged parallel with the sides of the organ in which they occur, see cork cambium, cuticular epithelium, master cambium, polyderm, vascular cambium, cf. apical meristem.

laterocylic: of paracytic stomata where the subsidiary cells are parallel to the long axis of the stoma and completely surround the latter, cf. brachyparacytic.

laterocytic: of stomata, with three or more distinct subsidiary cells partially (not at the apex or base) surrounding the guard cells, see actinocytic, allelocytic, anisocytic, anomocytic, cyclocytic, diacytic, helicocytic, paracytic, staurocytic, stephanocytic, tetracytic.

late wood: wood, strictly speaking xylem, produced later in the growing season, often darker in colour and with narrower xylem elements, cf. early wood.

latex: a viscous fluid exuded from the cut surfaces of the leaves and stems, in the strict sense referring to polymers made up of isoprene units in the cis- configuration (gutta has those same units in the trans configuration), borne in laticifers, cf. gums, mucilages, oils, resins, waxes.

laticifers: a system of long multinucleate tubes in which latex is found, see articulated and non-articulated laticifers.

laticiferous cell = non-articulated laticifer.

laticiferous vessel = articulated laticifer.

latiseptate: of a fruit that is flattened in a direction parallel to the septum, which thus traverses the broad axis of the ovary, cf. angustiseptate.

latrorse: turned sideways, i.e. neither towards or away from axis; of anthers, opening laterally towards adjacent anthers, cf. extrorse, introrse.

lauric acid: a saturated fatty acid.

leaf: commonly thought of as one of the three basic parts of the seed plant body, a structure usually of determinate growth, without secondary thickening, and of superficial origin, often flattened and photosynthetic in part, and in the axil of which is found a bud, cf. root, stem (the other main parts of the seed plant body), approximately = phyllome, cf. caulome, see anaphoric and cataphoric (rotation in bud), compound, megaphyll, microphyll, scale, simple (kinds of leaves), also hyperphyll, hypophyll, lamina, leaf base, petiole, stipule, and Vorläuferspitze (parts of angiosperm leaves), frond, stipe (parts of fern leaves), also bifacial, dorsiventral, isobifacial, unifacial (leaf faces), also alternate, bijugate, decussate, distichous, opposite, pseudoverticillate, spiral, spiromonistichous, tristichous, whorled (arrangement), also sporophyll, tropophyll (bearing sporangia or not); see also teeth, venation.

leaf base: the bottom part of a leaf, cf. hyperphyll, lamina, petiole, stipule, Vorläuferspitze.

leaf gap: in nodal anatomy, a parenchymatous interruption in the central vascular cylinder that occurs as a vascular bundle, a leaf leaf trace, departs, see also reparatory strand, cf. perforation.

leaflet: one of the ultimate segments of a compound leaf, see petiolule, stipel.

leaf-opposed: of an inflorescence or bud, arising from the stem opposite the point of insertion of a leaf, cf. axillary, intercalary, ramiflorous, supra-axillary, terminal.

leaf trace: in nodal anatomy, a vascular bundle that diverges from an axial bundle or another leaf trace and that supplies a leaf, cf. leaf gap, see also reparatory strand.

lectins: a group of hemagglutinating proteins (hemagglutinins) found primarily in plant seeds, which bind specifically to the branching sugar molecules of glycoproteins and glycolipids on the surface of cells.

legume: the fruit of some Fabaceae, formed from one carpel and dehiscent along one or both sides, explosively so or not, sometimes also used for other fruits in the family whether dehiscent or indehiscent, winged or not, splitting transversely or not - hence a term of little use; also a crop species in the family Fabaceae.

lemma: in a grass floret, the lower of two bracts enclosing a flower, perhaps a bract s. str., cf. glume (of a spikelet), lodicule, palea.

lenticel: a loosely-packed mass of often more or less rounded cork cells occurring especially in the young stem, bark or even leaf of a plant, visible on the surface as a raised, often powdery-appearing spot, through which gaseous exchange occurs.

lenticular: shaped like a biconvex lens.

lepidote: of indumentum, made up of scales, cf. arachnoid, arbuscular, canescent, hirsute, hispid, puberulous, pubescent, sericeous, stellate, strigose, tomentose, villous, see also glabrescent and glabrate, which refer to stages in the loss of these hairs.

leptocaul: of trees, with more or less slender trunk and branches, cf. pachycaul, see habit.

leptom(e): the sieve elements and associated parenchymatic cells of phloem tissue, cf. hadrom(e), stereom(e).

leptophyll: in ecology, the blade of a leaf or leaflet <25 mm² in surface area, cf. macrophyll, megaphyll, mesophyll, microphyll, nanophyll, notophyll.

leptosporangium: esp. used in ferns, a sporangium that develops from a single superficial cell, the wall of the sporangium being a single cell layer thick, cf. eusporangium.

leucoanthocyanins = proanthocyanidins.

leucodelphinidin: a proanthocyanidin.

leucoplast: a colorless plastid, see amyloplast, elaioplast, proteinoplast, cf. chromoplast, chloroplast, also sieve tube plastid.

liane: of habit, a climbing or twining plant, usually applied to woody climbers, cf. acaulescent, arborescent, dendroid, frutescent, fruticose, herb, rheophyte, suffrutescent, schopfbaum, shrub, subshrub, tree, vine, see also life forms.

libriform fibre: a fiber, the longest cell in the xylem, that has more or less simple pits, cf. fiber tracheid, tracheid, the three making a continuum of forms.

life forms: a classification of the growth forms of plants based on the position of the resting buds and the duration of the life of the shoot, in part see chamaephyte, cryptophyte (geophyte, helophyte, hydrophyte), hemicryptophyte, phanerophyte, therophyte, see also habit.

light line (of a seed coat) = linea lucida.

lignan: colorless, crystalline, solid, dimeric compounds derived from precursors related to those involved in the formation of lignin, i.e. the union of two units of phenylpropane, cinnamic acid, or their derivatives, through their aliphatic side-chains, they occur in chiral forms (as opposed to lignins), cf. neolignans.

Lignan base.	Sesamin, C20 H18 O6.
Justicidin, A C22 H18 O7.

lignin: a class of polymers formed from mostly C6-C3 monomeric units (cinnamic acid, coumarins), occuring in all plants; lignification, the deposition of lignin e.g. in secondary cell walls, see lignan, neolignans, cf. also cellulose, hemicellulose.

lignotuber: a woody swelling at the base of the shoot system below or just above the ground, containing adventitious buds from which new shoots develop if the top of the plant is cut off or burnt, common in many fire-tolerant shrubs, cf. bulb, bulbil, caudex, corm, creeping stem, dropper, pseudobulb, rhizome, runner, stolon, tuber, tiller, turion.

ligule: a membranous or hairy appendage on the adaxial surface of a bifacial leaf, at the junction between sheath and blade, especially in grasses, or a similar structure at the junction of two parts of a petal, e.g. claw and limb (see also corona); also, an adaxial appendage near the leaf base in some monocots and in Selaginellaceae, etc.; adj. ligulate.

ligule: the strap-shaped corolla limb in ray flowers of Asteraceae, adj. ligulate.

limb: the upper, free, spreading portion of a corolla or perianth that is connate at the base; the expanded portion of a sepal or petal above the claw. (not labelled in image).

limonoids: type of triterpenoid (tetranortripterpenes), bitter compounds, pentacyclic, with a furan ring attached as a side chain.

Dysoxylin, C28 H32 O9.

Limonin, C26 H30 O8.

linea fissura: an inconspicuous line on the surface of the seed coat that delimits a more or less circular area, an areole, as in Fabaceae - Mimosoideae, cf. cf. funicle, micropyle; the linea lucida is an unrelated structure.

lineage: strictly speaking, an ancestral-descendent series of individuals, but often used interchangeably with clade, in which case the latter is preferable.

linea lucida: of the testa or tegmen, a bright line running periclinally through heavily thickened palisade cells (see the Malpighian layer), often separating more or less thickened parts of the cells, the linea fissura is an unrelated structure.

linear: very narrow in relation to the length, and with the sides parallel.

linguiform, lingulate: tongue-shaped.

lithocyst: enlarged epidermal cell, usually of a leaf, containing a cystolith.

lithophyte: a plant that grows on the surface of unweathered rock, cf. amphibious, aquatic, epilithic, epiphyte, terrestrial.

lobed: of the apex of any laminar structure, e.g., petal, leaf blade, divided more than 25% the length of the structure, cf. emarginate, retuse.

locule, loculus: an enclosed compartment within an organ, e.g. an ovary, an anther, pl. loculi, dim. locellus.

loculicidal: of the dehiscence of capsules, along lines down the centres of the outer walls of the loculi or between the placentae when the placentation is parietal, cf. circumscissile, poricidal, septicidal, septifragal.

lodicule: in a grass floret, one of a pair (or three?) of tiny scales or flaps of tissue between the lemma and palea and the stamens, possibly representing reduced perianth segments, see also glume (of a spikelet).

loganin: a routeI iridoid.

lolongate: where the longest axis of an endoaperture of the compound aperture of a pollen grain is parallel to the longest axis of the ectoaperture, cf. lalongate.

lomentum: a schizocarp-type fruit formed from one or more carpels and having distinct transverse constrictions or lines where splitting occurs, breaking transversely into one-seeded segments when mature.

long-day: of a photoperiodic response, where long periods of light alternating with short periods of dark are neeeded for flowering to occur (more accurately, no long uninterrupted period of dark), cf. short-day.

long shoot: a shoot in which all or most of the internodes elongate, cf. short shoot; the comparison is often made between axillary shoots.

lophate: pollen in which the surface is honeycomb-like because of thickenings of the exine, cf. baculate, echinate, fossulate, gemmate, foveolate, pilate (gemmate and retipilate are variants), psilate, reticulate, retipilate, rugulate, scabrate, striate, and verrucose.

lower: of parts of a flower in particular, generally can be replaced by abaxial, cf. upper.

lupinine: a quinolizidine alkaloid.

lumen: (pl. lumina), an element of pollen surface ornamentation, a space enclosed the muri.

luteolin: hydroxylated flavone derivative, common in leaves and flowers.

luteone: an isoflavone.

llycophyll = microphyll.

lysigenous: of cavities in plants, formed by the dissolution of cells, cf. expansigenous, rhexigenous, schizogenous.

M

macro- (prefix): large, often used as an alternate for mega.

macrophyll: in ecology, the blade of a leaf or leaflet 18225-164025 mm² in surface area, roughly 18 x 10 cm to somewhat more than 60 x 25 cm, cf. leptophyll, megaphyll, mesophyll, microphyll, nanophyll, notophyll.

macropodial, macropodous: of an embryo lacking well developed cotyledons and in which the reserves are stored in a massive hypocotyl.

macrosclereid: a sclereid cell ca 2-4 times longer than broad, lacking processes, cf. astrosclereid, filiform sclereid, brachysclereid, osteosclereid, trichosclereid.

macrospore = megaspore.

macrozamin: cycad toxin with primoverose.

Macrozamin, C13 H24 N2 O11.

maesaquinone: a benzoquinone.

male, e.g. of a flower that has functional staminate parts alone, = staminate.

malegametophyte: a plant body or cell lineage formed by vegetative growth of the microspore, see generative cell, sperm, vegetative cell, also binucleate and trinucleate pollen grains, cf. femalegametophyte.

malic acid: a carboxylic acid with the formula HOOC-CH₂-CHOH-COOH, cf. citric acid.

Malpighian layer: a palisade layer of the seed, esp. of the exotesta but of various origins, that has much thickened walls, see linea lucida.

malpighiaceous hair: a unicellular, T-shaped hair with a short stalk and often looking fusiform from above, = unicellular T-shaped hair, cf. colleter, collar rhizoid, dendritic, pearl gland, root hair, snail gland, stellate.

malvoid: a leaf tooth in which the medial vein forms a non-glandular persistent apex, lateral veins are not involved, cf. begonioid, chloranthoid, cucurbitoid, cunonioid, dillenioid, monimioid, platanoid, rosoid, salicoid, spinose, theoid, urticoid, violoid.

mammillate: having small, nipple-shaped projections.

mangiferin, mangostin: two xanthones.

mannans: a cell wall storage polysaccharide in which mannose is the main sugar, forming a matrix that lacks cellulose and pectins in the same proportions as in the primary cell wall, divided into pure mannans, galactomannans and glucomannans, cf. galactans and xyloglucans.

mannitol: a hexitol formed by reduction of mannose or fructose, occurs in gum exudates, cf. dulcitol and sorbitol.

Mannitol, C6 H14 O6.

mannose: a hexose sugar, cf. fructose, glucose.

many: of floral parts, a large an often indefinite number, usually 15 or more.

manoxylic: of xylem produced by vascular cambium, esp. of gymnosperms, containing abundant parenchyma and few tracheids, cf. fugacious, pycnoxylic.

marcescent: withering, but without falling off, cf. accrescent, caducuous, deciduous, deliquescent, fugacious, persistent.

marginal: occurring at or very close to the margin, a kind of placentation usually used when carpels are separate, cf. apical, axile, basal, free central, intrusive-parietal, laminar, parietal.

marginal blastozone: a strip-like portion along the margins of the primordial leaf blade that retains the potential for organogenetic activity.

margo: the peripheral part of the membrane in a bordered pit in gymnosperms, etc., consisting of rather sparse cellulose microfibrils of the primary wall, cf. bars of Sanio, torus.

mast: originally used for the fallen fruits of European Fagaceae, now extended to e.g. Dipterocarpaceae, as good or poor mast years, years with much or little fruiting; masting (adj.).

master cambium: a lateral meristem producing successive cambia and conjunctive tissue internally, c.f. cork cambium, cuticular epithelium, polyderm, vascular cambium.

massulae: in Orchidaceae in particular, a group of pollen tetrads of irregular number and so size and less than the contents of an entire theca, deruved from a single archesporial cell, and making up a sectile pollinium - for other commonly-used terms specific to orchid flowers, see caudicula, column, hamulus, incumbent, labellum, rostellum, stipes, tegula, viscidium, also epichile, hypochile; also in general palynology, cf. monad, polyad, tetrad.

matrotrophic: sometimes used of the embryo of embryophytes, dependent on the gametophyte for its nutrition, lit. "mother-eating" or "mother-food".

median: the plane through an axis and the axis from which it originates, e.g. in a flower, the axis of symmetry of the flower relative to the inflorescence axis, that is, on the plane joining the flower, the bract subtending it, the inflorescence axis on which it is borne, cf. abaxial, adaxial, lateral.

medulla = pith; a medullary bundle is a vascular bundle traversing the pith, cf. cortical bundle.

medullary ray = interfascicular region.

medullated: with pith, used e.g. when talking about stelar morphology.

megagametophyte = female gametophyte.

megaphyll: lit. "a large leaf", a leaf of any size whose vascular supply leaves one or more gaps as it departs from the stem vascular tissue, and the leaf itself generally has a complexly-branched vascular bundles, cf. microphyll.

megaphyll: in ecology, the blade of a leaf or leaflet >164025 mm² in surface area, somewhat more than 60 x 25 cm, cf. leptophyll, macrophyll, mesophyll, microphyll, nanophyll, notophyll.

megasporangium: a sporangium producing megaspores, = nucellus + megaspore(s) in seed plants, cf. microsporangia.

megaspore: one of the two kinds of spores produced after meiosis in a heterosporous plant, and on germination giving rise individually, or rarely with other megaspores in some flowering plants, to the female gametophyte or embryo sac, cf. microspore - n.b. a megaspore is not always larger than a microspore, and a (perhaps unecessary) size-neutral equivalent is gynospore.

megasporocyte: a sporocyte or meiocyte giving rise by a meiotic division to one or sometimes more megaspores, cf. microsporocyte.

megasporophyll: a structure (perhaps a specialised leaf) upon which or in the axil of whic) one or more megasporangia are borne, in flowering plants, a carpel, cf. microsporophyll.

megatherm: an organism that requires warm conditions for growth and development, cf. microtherm.

meiocyte: a sporogenous cell that by meiosis gives rise to spores, see megasporocyte, microsporocyte.

meiosis: the two-stage division of a diploid nucleus during which gene recombination occurs and the number of chromosomes is halved, occurring once in every life cycle, sporic meiosis occurs in land plants immediately prior to the production of haploid spores during the alternation of generations (haploid and diploid generations alternating), gametic meiosis occurs in animals and some "algae" and leads directly to the production of haploid gametes (individuals are diploid), while zygotic meiosis occurs in some other viridiplantae and occurs immediately after the formation of the diploid zygote (individuals are haploid), cf. mitosis.

meiospore: a spore produced by meiosis, as in land plants, see megasporocyte, microspore.

mellitophily: a kind of entomophilous pollination, flowers pollinated by bees, see also bee purple and buzz pollination, monolectic, oligolectic and polylectic, cf. cantharophilous, myophilous, psychophilous, sapromyophilous, sphingophilous.

meranthium: of a flower that consists of two or more functionally independent units from the pollinator's points of view, as in Iris, the other extreme from pseudanthium.

mericarp: one segment of a fruit of a schizocarp that has dehisced at maturity into units (often derived from the individual carpels) consisting of pericarp plus seed(s), cf. nutlet.

meristele: "we would like to seee the term eliminated from textbooks and from discussions of stelar morphology" (Beck et al. 1982), very often = vascular bundle.

meristem: a region of a plant in which embryonic undifferentiated cells divide to produce new cells that ultimately differentiate, i.e. that have a capacity for morphogenesis and growth, see apical and lateral meristems.

meristemoid: a dividing cell, or small group of dividing cells, surrounded by more or less differentiated and undividing cells, e.g. a stomatal meristemoid, a cell whose immediate derivatives produce the stomata and sometimes subsidiary cells.

-merous, -mery: the number of parts per whorl that characterises a particular flower (generally constant for the perianth whorls, often for the whorl(s) of stamens also, least often for the carpelline whorl), see pentamerous, trimerous.

mesarch: of a procambial strand, esp. xylem, in which the first-differentiated elements are in the centre of the strand, cf. endarch, exarch.

mescaline: a protoalkaloid.

mesifixed: attached by or at the middle, e.g. of anthers, see basifixed, embedded, versatile; of hairs, see malpighiaceous, T-shaped.

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

mesocarp: the fleshy middle portion of the wall or pericarp of a succulent fruit, cf. endocarp, exocarp.

mesocotyl: the internode between the haustorium/scutellum and the coleoptile in a monocot embryo or seedling, in fact an epicotyl that is congenitally fused with the base of the coleoptile (Tillich 2007), cf. hypocotyl, of a monocot seedling, see also coleorhiza, hyperphyll (apocole, phanomer), hypophyll (cotyledonary sheath, coleoptile), collar (epiblast, periblast), also, an internode developing between the unequal cotyledons in some Gesneriaceae-Cyrtandroideae and -Epithematoideae after germination (see de Vogel 1980).

mesogamy: fertilisation during which the pollen tube penetrates the ovule laterally by way of the integuments, cf. chalazogamy, porogamy.

mesogenous: of stomatal ontogeny in which the subsidiary cells are produced from the same cell (meristemoid, initial) that gives rise to the guard cell initials, cf. mesoperigenous, perigenous.

mesoperigenous: of stomatal ontogeny in which at least one of the subsidiary cells is produced from the same cell (meristemoid, initial) that gives rise to the guard cell initials, other subsidiary cells not arising from this meristemoid, cf. mesogenous, perigenous.

mesophyll: photosynthetic tissue in the leaf in particular, see palisade, spongy.

mesophyll: in ecology, the blade of a leaf or leaflet 4500[an elliptic leaf ca 5 in. or 12.7 cm. long]-18225 mm² in surface area, cf. leptophyll, macrophyll, megaphyll, microphyll, nanophyll, notophyll.

mesophyte: of vegetation, characteristic of moist habitats and with soft, fairly large leaves predominating, cf. sclerophyll, xeromorph, xerophyte.

mesopodium: an internode that separates the prophylls, cf. epipodium, hypopodium.

mestome sheath: the inner and endodermal layer of cells - the walls being thick and with suberized lamellae - of a two-layered bundle sheath surrounding a vascular bundle, cf. parenchyma sheath, starch sheath.

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

metatopy: dislocation of organs from their normal position by unequal growth, cf. concaulescent, recaulescent.

metaxylem: later-formed primary xylem differentiating from the procambium, the tracheary elements having more or less continuously thickened walls with pits, cf. protoxylem.

metaxyphyll: a more or less scale-like bract not subtending a flower and borne immediately below the terminal flower and above the lateral flowers of a botryoid inflorescence (see Wu et al. 2007 and references); if this is the correct definition, it seems like a term that can be done without...

methylazoxymethanol: toxic aglycone of cycasin and macrozamin.

Methylazoxymethanol, C2 H6 N2 O2.

methylflavones: derivatives of chalcones.

Methylflavone, C16 H12 O3.

methyl glucosinolates: a class of aliphatic, straight chain glucosinolates, see also sinapine.

Methyl glucosinolate, C8 H15 N O9 S2.

Glucocapparin, C8 H15 N O9 S2.

metopies: , cf. concaulescent, recaulescent.

mevalonic acid: a carboxylic acid precursor of sterols, terpenes and other isoprenoids.

Mevalonic acid, C6 H12 O4.

microgametophyte = male gametophyte.

microphyll: lit. "a small leaf", a leaf not necessarily very small (they can be up to 1 m long) in which the vascular trace supplying it does not interrupt the central vascular cylinder when it departs, i.e. there are no leaf gaps, and the leaf itself generally has a single, unbranched vascular bundle, cf. megaphyll, see also enation.

microphyll: in ecology, the blade of a leaf or leaflet 225-2025 mm² in surface area, e.g. an elliptic blade ca 3 in. or 7.6 cm. long, cf. leptophyll, macrophyll, megaphyll, mesophyll, nanophyll, notophyll.

micropyle: a small canal through the integument(s) at the apex of an ovule, either amphistomal, bistomal, endostomal, exostomal, naked, or zigzag, cf. antiraphe, chalaza, funicle, embryo sac, integument, nucellus, obturator, podium, postament, raphe (the other parts of the ovule), and persisting as a pore on the seed coat, cf. funicle, linea fissura.

microsporangium: sporangium producing microspores, usually many in number, in the life cycle of a heterosporous plant, cf. megasporangium, see theca (arrangement of microsporangia), see also endothecium, exothecium, placentoid, tapetum (all tissues).

microspore: 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, the pollen grain, see prepollen, true pollen, cf. megaspore - n.b. a microspore is not always smaller than a megaspore, and a (perhaps unecessary) size-neutral equivalent is androspore.

microsporocyte: a sporocyte or meiocyte giving rise by a meiotic division to (usually) four microspores, cf. megasporocyte, see callose ring.

microspore mother cell = microsporocyte.

microsporogenesis: the sequence of meiotic divisions that produces microspores, see simultaneous, successive.

microsporophyll: a structure on which one or more microsporangia are borne, in flowering plants, the stamen, cf. megasporophyll.

microtherm: an organism that requires cool conditions for growth and development, cf. megatherm.

middle lamella: the central layer of the wall between two adjacent cells, largely made up of pectinaceous substances, see primary wall, secondary wall.

midrib: the central, and usually the most prominent, vein of a leaf or leaf-like organ, cf. costa.

miltanthaline: a benzylisoquinoline alkaloid.

mitosis: the normal division of a nucleus, whether haploid or diploid, during which chromosomes are replicated, cf. meiosis.

module: of growth, according to Hallé et al. (1978: p. 189) "shoot unit with determinate growth, either by apical abortion or conversion of the apex into an inflorescence", see sympodial unit; module is best used in a more general sense, i.e., modular, of any structure that is made up of a number of largely similar units.

monad: especially of pollen, when each grain, one of the ultimate products of meiosis, is separate, cf. massula, pollinia, polyad, tetrad.

monadelphous: of stamens, united by their filaments into one bundle, i.e. connate, although not necessarily into a tube, cf. diadelphous and polyadelphous, cf. also fasciculate, phalangiate, syngenesious. ("united into tube" in image).

moniliform: cylindrical but constricted at regular intervals, as in a string of beads.

monimioid: a leaf tooth in which the secondary or tertiary vein ends in an opaque persistent glandular cap, not associated with lateral veins (although they seem to be present sometimes - see Hickey & Wolfe 1975), cf. begonioid, chloranthoid, cucurbitoid, cunonioid, dillenioid, malvoid, platanoid, rosoid, salicoid, spinose, theoid, urticoid, violoid.

monistichous: e.g. of leaves, arranged in a single vertical row along the stem (orthostichy), one-ranked, cf. two-ranked (distichous), three-ranked (monistichous), spiromonistichous, cf. also alternate, bijugate, decussate, opposite, pseudoverticillate, spiral, whorled.

monocarpic: (of flowering with respect to architecture), plant flowering and fruiting only once during its lifespan, e.g. Corypha, cf. hapaxanthic, pleonanthic, also iteroparous, semelparous, cf. (of plant duration) annual, biennial, ephemeral, perennial.

monochasium: of a cymose inflorescence, with branches arising from only one of each pair or bracteoles/prophylls, or from the single bracteole/prophyll, adj. monochasial, see bicolor unit, drepanium, helicoid cyme, rhipidium, scorpioid cyme, cf. dichasium.

monochlamydeous: of a flower, having only one whorl of perianth parts, usually = 1-whorled, cf. achlamydeous, dichlamydeous, heterochlamydeous, homochlamydeous.

monoclinous: having staminate and carpellate reproductive organs in the same flower, = perfect as used here, cf. diclinous.

monocotyledonous: anther wall development in which the primary parietal layer gives rise to two secondary parietal layers, the outer producing the endothecium only, the inner producing cells of the middle layer and tapetum, cf. basic, dicotyledonous, reduced.

monocotyledons: clade including those flowering plants whose embryo has only one cotyledon (seed leaf) and whose flower is trimerous and pentacyclic, in the past opposed to dicotyledons, see BLA.

monoecious: having the staminate and carpellate reproductive structures in separate flowers but on the same plant, cf. androdioecious, andromonoecious, dioecious, gynodioecious, gynomonoecious, perfect.

monolectic: in bee pollination, when the bee collects pollen only or mostly from a single species of plant (Michener 1979), cf. oligolectic, polylectic.

monolete: more or less straight scars on the proximal poles of pollen representing the points of junction of the pollen tetrads, weakened areas involved in germination, not occuring in angiosperms, cf. trilete.

monophyletic: of any taxon that includes its common ancestor and all and only its descendents, a monophyletic group is a clade, q.v., cf. paraphyletic, polyphyletic.

monopodial: of growth, with a persistent terminal growing point producing many lateral organs successively, thus a monopodial stem grows in this way, see also indeterminate, racemose (of inflorescences), cf. sympodial.

monosaccharide: a carbohydrate of single hexose or pentose units, see fructose, glucose, and mannose, cf. disaccharides, oligosaccharides, polysaccharides.

monosymmetric: a flower with a single plane of symmetry, the number of corolla elements involved in making up the lips can be denoted by formulae like 3:2, i.e., three corolla lobes making up the adaxial/upper lip, two corolla