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.
incised: cut deeply, sharply and often irregularly (an intermediate condition between toothed and lobed).
in- (prefix): without, lacking.
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.
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.
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.
indurated = hardened and rather inflexible.
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).
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.
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).
innovation: in plants with intermittent growth, the stem and associated leaves produced during each period of growth.
insectivorous: catching and feeding on insects.
inserted: attached to, arising from.
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.
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.
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.
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.
interrupted: e.g. of an inflorescence, having the flowers unevenly distributed along the axis, with conspicuous gaps.
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.
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.
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.
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.
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).
iso- (prefix): equal in number of parts or appearance, in chemical names, refers to an isomer.
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.
isothiocyanates: esters of isothiocyanic acid, RóN=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.
iteroparous: of reproduction, when there are repeated annual/seasonal bouts of flowering, cf. plietesial, semelparous, cf. more from the point of view of meristem persistence hapaxanthic, monocarpic, pleonanthic, and of plant duration, annual, biennial, ephemeral, perennial.
jaculator: a hardened and hook-like funicle that is conspicuous in the seeds of many Acanthaceae, rare elsewhere.
jugate = paired.
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.
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.
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.
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.
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, ponticulus, postament, raphe.
lamina: the blade of a leaf, usually flattened, dorsiventral, and expanded, often with a midrib, 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.
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 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.
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.
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.
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.
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.
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, cf. pneumathode (on a root).
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.
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.
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.
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.
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.
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.
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.
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).
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.
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.
lupin-type nodule: a type of nodule caused by nitrogen-fixing bacteria in Fabaceae, perhaps indeterminate, with a broad subcortical meristem, and forming a more or less ruff-like structure with a broad attachment to the root, c.f. aeschynomenoid, caesalpinioid, crotalarioid, and desmodioid.
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.
macrozamin: cycad toxin with primoverose.
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.
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.
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.
many: of floral parts, a large an often indefinite number, usually 15 or more.
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.).
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.
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.
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 complexly-branched vascular bundles, cf. microphyll, see also enation.
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.
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.
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.
meristem: a region of a plant in which undifferentiated cells actively divide, the result being new cells that ultimately differentiate, i.e. the cells have a capacity for morphogenesis and growth, see apical and lateral meristems, cf. marginal blastozone.
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 in a flower that characterises a particular species, generally the same for the two perianth whorls, often also for the whorl(s) of stamens, least often for the carpelline whorl, e.g., three-merous, five-merous flowers, see pentamerous, trimerous.
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).
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: 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.
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.
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.
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, ponticulus, 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.
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; but 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.
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.
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, plietesial, 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.
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.
monoecious: having the staminate and carpellate reproductive structures in separate flowers but on the same plant, cf. androdioecious, andromonoecious, dioecious, gynodioecious, gynomonoecious, perfect.
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.
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.
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 lobes the /abaxial/lower lip, see bilabiate, papilionoid, ringent, slit-monosymmetric (variants), cf. peloric, cf. also asymmetric, disymmetric, enantiomorphic, enantiostyly, haplomorphic, oblique, polysymmetric.
monoterpenoids: with a base of C10 H16, they occur in essential oils and are made up of one or two isoprene rings or an open chain of isoprene units; colorless, water-insoluble, volatile, with fragrant odour.
motile: actively moving, self-propelled.
mucro: a sharp, abrupt terminal point, adj. mucronate, cf. acute, attenuate, acumen, apiculum, arista, awn, cuneate, caudate, cuspidate, emarginate, muticous, obtuse, retuse, rounded, truncate, cf. also cordate, hastate, oblique, runcinate, sagittate (esp. of lamina base).
multilacunar: of nodal anatomy in angiosperms, where more than three (e.g. 5, 7) leaf gaps are left in the central vascular cylinder when corresponding numbers of leaf traces depart, cf. split lateral, trilacunar, unlacunar, see also see also flank bridges
muticous: blunt, awnless, cf. acute, attenuate, acumen, apiculum, arista, awn, cuneate, caudate, cuspidate, emarginate, mucronate, obtuse, retuse, rounded, truncate, cf. also hastate, oblique, runcinate, sagittate (esp. of lamina base).
myco-heterotrophic: a variant of heterotrophic nutrition in which a plant, typically lacking chlorophyll, is in close assocation with a fungus, from which it directly or indirectly obtains much of its nutritional needs, cf. hemiparasite, hyperparasite, parasite, saprophyte.
my[i]ophilous: of entomophilous flowers pollinated by flies, often with a distinctive syndrome (small, purplish/dark color; dangling projections, etc.), although flies like bee-flies are attracted to very different-looking flowers, cf. cantharophilous, melittophilous , psychophilous, sapromyophilous, sphigophilous.
myrmeco- (prefix): having to do with ants.
myrmecophyte: loosely used here for a plant in which there is an association, generally mutually advantageous, between it and ants and involving distinctive morphological modifications of the plant; see Webber et al. (2007) for a much more fine-grained approach, distinguishing between mymecophilic. myrmecophytic in the strict sense myrmecodomic and myrmecoxenic.
myxo- (prefix): with mucilage, e.g. myxocarpy and myxospermy, mucilaginous fruits and seeds respectively, the mucilage, especially of seeds, developing only when the seed is moistened.nacreous, of cell walls (e.g. of sieve cells) in transverse section, thick, shining and more or less iridescent, layered.
naked: exposed, uncovered; of ovules or seeds, exposed on the surface of a megasporophyll, i.e., not enclosed within a carpel, see gymnosperm; of flowers, without a perianth, the old achlamydeous; of protoplasts or gametes, lacking a cell wall; of an ovule, where there is no micropyle as such, the integuments not meeting over the apex of the ovule, cf. amphistomal, bistomal, endostomal, exostomal, zigzag, of a resting bud, not enclosed by bud scales, the leaves surrounding it enlarging to more or less normal size when growth recommences (although the bud itself may be covered with dense hairs, etc., and be very well protected), cf. perulate.
narrowly: a qualifier of terms used for outlines and plane shapes when the length:breadth ratio is 6:1 - 2.5:1, cf. broadly, broad-transverse, transverse, the terms qualified being elliptic, obovate, oblong, ovate, rhombic, triangular, trullate.
navicular = boat-shaped.
neck: part of the archegonium, a column of cells within which are the neck canal cells which latter break down at maturity, material from them being secreted from the pore of the neck, the male gamete travelling down the neck, see archegonial chamber, venter, and egg.
nectar guide: markings on the perianth of a flower, whether visibly colored lines and dots or in the ultraviolet, that guide a pollinator to the nectar or other floral reward.
nectarium: a collective term for all the nectaries found in a single flower (cf. pollinium/pollinarium).
nectary: a more or less localized multicellular glandular structure that secretes nectar, when in the flower often with stomata and a phloem supply, adj. nectariferous, the terms for "types" of nectaries are complex indeed (Schmid 1988): see extrafloral and floral nectaries, also extranuptial, nuptial nectaries, also extrareproductive, reproductive nectaries, also gynoecial and receptacular nectaries, also septal nectary.
neolignans: dimers derived from precursors related to those involved in the formation of lignin, i.e. the union of two C6-C units of phenylpropane, cinnamic acid, or their derivatives, dimerization being via the aromatic rings instead by the propanoid tail, cf. lignans.
nitid = shining.
nodal anatomy: specifically, the arrangement of leaf gaps and leaf traces (see also reparatory strand) as the vascular tissue from the central stele or vascular cylinder departs to supply the leaves, see multilacunar, split lateral, trilacunar, unilacunar, see also see also flank bridges.
node-based: a way of defining a clade in which a node on a cladogram is the defining point, e.g. the clade stemming from the most recent ancestor of species 1 and species 2, cf. apomorphy-based, stem-based.
nodule: a more or less hard and irregular swelling, and in nodules caused by nitrogen-fixing bacteria in Fabaceae, of several more or less distinct morphologies, aeschynomenoid, caesalpinioid, crotalarioid, desmodioid, and lupin type, cf. fibrous root, hair root, magnolioid root, nodule, tap root, and tuberous root.
nomen conservandum: a name of a family, genus or species that has been formally accepted under the International Code for Botanical Nomenclature as the correct name contrary to the usual principles of botanical nomenclature, abbreviated nom. cons.
non-protein amino acids: amino acids not associated with proteins, many important in the storage and transport of soluble nitrogen, often present in large quantities in seeds, sometimes poisonous.
normal: used of iridoids, derived from deoxyloganic acid, either directly without oxgenation (normal Route I, carboxylated iridoids) or from epi-deoxyloganic acid directly without decarboxylation (normal Route II).
Normapolles: a pollen type common in Cretaceous and lower Palaeogene times, oblate and triaperturate (triporate) with protruding, elaborate and strongly thickened aperture regions, the apertures themselves often being formed from expansions of the granular infratectal layer (and hence the pollen is triangular in transverse section), etc., produced by Fagales (see Friis et al. 2003a).
nortriterpenoids: subclass of triterpenoids in which some degredation has occurred resulting in a loss of four to eleven carbon atoms; includes limonoids, bufadienolides, cardenolides and quassinoids.
notophyll: in ecology, the blade of a leaf or leaflet 2025-4500 mm2 in surface area, e.g. an elliptic blade from ca 3 in. or 7.6 cm to 5 in. or 12.7 cm long, cf. leptophyll, macrophyll, megaphyll, mesophyll, microphyll, nanophyll.
nucellar cap: a structure in the ovule where the epidermal cells above the megasporocyte(s)/embryo sac divide periclinally, a feature that is independent of whether the ovule is crassinucellate or tenuinucellate, cf. epistase, hypostase, nucellar beak, nucellar endothelium, nucellar pad, obturator, podium, ponticulus, postament, also crassinucellate, incompletely tenuinucellate, nucellar cap, tenuinucellate, weakly crassinucellate (different degrees of development of the nucellus or of the epidermis covering it).
nucellar endothelium: a structure in the ovule where the epidermal cells underneath the integument(s) are enlarged or otherwise distinctive, a feature that is independent of whether the ovule is crassinucellate or tenuinucellate, cf. epistase, hypostase, nucellar beak, nucellar cap, nucellar pad, obturator, podium, ponticulus, postament, also crassinucellate, incompletely tenuinucellate, nucellar cap, tenuinucellate, weakly crassinucellate (different degrees of development of the nucellus or of the epidermis covering it).
nucellar pad: a structure in the ovule made up of radially-elongated epidermal cells at the tip of the nucellus underneath the micropyle, a feature that is independent of whether the ovule is crassinucellate or tenuinucellate, cf. embryo sac, epistase, hypostase, nucellar beak, nucellar cap, nucellar endothelium, obturator, podium, ponticulus, postament, also crassinucellate, incompletely tenuinucellate, tenuinucellate, weakly crassinucellate (different degrees of development of the nucellus or of the epidermis covering it).
nucellus: the central tissue of an ovule of a seed plant, tissue not of epidermal origin that more or less surrounds first the megaspore(s) (nucellus + megaspore(s) = megasporangium) and then the embryo sac, sometimes much reduced, see crassinucellate, incompletely tenuinucellate, nucellar cap, nucellar endothelium, nucellar pad, tenuinucellate, weakly crassinucellate (different degrees of development of the nucellus or of the epidermis covering it), also epistase, hypostase, nucellar beak, nucellar pad, cf. antiraphe, chalaza, funicle, integument, micropyle, obturator, podium, ponticulus, postament, raphe.
nursery pollination: a variant of entomophilous pollination in which the pollinator lays eggs on the ovary as it pollinates the plant; some of the developing seeds provide food for the developing larvae.
nut: a hard, dry, indehiscent fruit formed from two or more carpels but containing only one seed, a rather vague term, and really an achene in the broad sense, cf. achene s. str., caryopsis, cypsela, utricle.
nyctinasty: the response of plant parts, particularly leaves and flowers, to darkness ("sleep movements").
ob- (prefix): the opposite to the condition described in the rest of the word, e.g., obovate, of a leaf, etc., with the widest point above the middle, rather than below, the latter being ovate.
obdiplostemonous: androecium with twice as many stamens as petals and borne in two whorls, the outer whorl opposite the petals or inner whorl of tepals, cf. diplostemonous, haplostemonous, obhaplostemonous - note that Bachelier and Endress (2009) give a rather different definition: a flower in which there are two whorls of stamens, and the carpels are antepetalous - used only for isomerous flowers or flowers in which the single fertile carpel is opposite a petal.
oblate: a general pollen shape descriptor, a radially symmetrical grain in which the polar axis is shorter than the equatorial diameter, i.e. it is shorter than wide, cf. boat-shaped, globose, prolate, spherical.
oblique: of general floral symmetry, although the flower may be monosymmetric, the major plane of symmetry of that flower is obligue to the axis that bears it, cf. asymmetric, disymmetric, enantiomorphic, enantiostylous, polysymmetric.
oblique: of the basal part of the lamina of a leaf or leaflet, larger on one side of the midrib than on the other, i.e. asymmetrical, cf. acute, attenuate, acumen, apiculum, arista, awn, cuneate, caudate, cuspidate, emarginate, mucronate, muticous, obtuse, retuse, rounded, truncate, cf. also hastate, runcinate, sagittate (esp. of lamina base).
oblong: a term used for outlines and plane shapes, with length:breadth ratio 2:1 - 3:2, the sides almost parallel, see broadly, broad-transverse, narrowly, transverse, cf. elliptic, obovate, ovate, rhombic, triangular, trullate.
obovate: a term used for outlines and plane shapes, with length:breadth ratio 2.5:1 - 3:2, the broadest part is above the middle, see broadly, broad-transverse, narrowly, transverse, cf. elliptic, oblong, ovate, rhombic, triangular, trullate.
obturator: an outgrowth of the funicle (commonest), placenta, or integument, etc., that forms a bridge between the micropyle and other tissues and is believed to faciltate fertilisation; the ponticulus is a variant. When the term "obturator" is used, its origin should be made clear, cf. antiraphe, chalaza, epistase, female gametophyte, funicle, hypostase, nucellar beak, nucellar cap, nucellar endothelium, nucellar pad, obturator, podium, ponticulus, postament, raphe (parts).
obtuse: bluntly pointed at the apex, the converging edges separated by an angle greater than 90o, cf. acute, attenuate, acumen, apiculum, arista, awn, cuneate, caudate, cuspidate, emarginate, mucronate, muticous, retuse, rounded, truncate, cf. also cordate, hastate, oblique, runcinate, sagittate (esp. of lamina base).
obvolute: of leaf vernation in the strict sense, a leaf as if folded in half along the midline so that the adaxial surface disappears from view, and one side is inside and one side outside a similarly folded leaf on the opposite side of the stem, which in turn similarly encloses the next leaf, and so on, cf. convolute and equitant.
Oenothera: an embryo sac type, the types based on variation in megasporogensis and megagametogenesis, unisporic (micropylar cell), 4-celled (no antipodals, only one polar cell), cf. Adoxa, Allium, Drusa, Endymion, Fritillaria, Penaea, Peperomia, Plumbagella, Plumbago, Polygonum.
oligo- (prefix): few.
one-ranked: leaves borne singly and in a single orthostichy up the stem, cf. spiromonistichous, two-ranked (distichous), three-ranked (tristichous), also bijugate, decussate, opposite, pseudoverticillate, spiral, whorled.
operculum: a cap formed by fusion or cohesion of perianth parts and covering the stamens and carpels in the bud, becoming detached at maturity; a more or less hardened, lid-like portion of the seed or fruit, esp. the endocarp of the latter, that becomes detached during germination or at maturity.
opposite: of leaves or other lateral organs, borne at the same level but on opposite sides of the stem, the pairs decussate, often includes bijugate, and in the characterisations here also whorled, cf. also alternate, distichous,spiral, pseudoverticillate, spiromonistichous, tristichous.
orbicular: circular or nearly so.
order: in the taxonomic hierarchy, a monophyletic grouping of families, or sometimes a single family with no apparent close relatives, the name with a termination -ales, the major taxonomic rank between family and class, cf. also genus, species.
ornithophilous: of zoöphilous flowers, with distinctive morphology for pollination by birds (red color, long tube, no scent, etc.), cf. cantharophilous, chiropterophilous, entomophilous, melittophilous , myophilous, ornithophilous, sapromyophilous, sphigophilous.
osteosclereid: a longish but not very narrow sclereid cell with more or less developed rather short, stout branches at both ends, cf. astrosclereid, filiform sclereid, brachysclereid, macrosclereid, trichosclereid.
ostiole: an opening or pore, e.g. of a microsporangium or anther as it dehisces (little used in flowering plants), or at the apex of a fig.
outgroup: any group that is outside of the clade of immediate interest, more specifically, a taxon or tax that have been included in a study to root the tree or to polarise the characters of the ingroup, cf. in group, sister group.
ovate: a term used for outlines and plane shapes, with length:breadth ratio is 2.5:1 - 3:2, broadest below the middle, see broadly, broad-transverse, narrowly, transverse, cf. elliptic, oblong, obovate, rhombic, triangular, trullate; ovoid, egg-shaped, is ovate in three dimensions and with a rounded apex and base, cf. pyriform.
ovule: a eusporangium in a seed plant enveloped by one or two integuments, a megasporangium within which one (rarely more) megaspores are formed and later the female gametophyte or embryo sac develops, and which finally develops into a seed after fertilisation, or "an indehiscent, integumented megasporangium containing a single functional megaspore" (Sporne 1974, p. 18), see antiraphe, chalaza, epistase, funicle, hypostase, integument (see also endothelium), lagenostome, megaspore, micropyle, nucellus, pollen chamber, obturator, podium, ponticulus, postament, raphe (parts), see also amphitropous, anatropous, atropous, campylotropous, circinotropous, hemitropous ("types"), and apotropous/epitropous/pleurotropous or antitropous/syntropous, curvature of the ovule with respect to the axis or carpel margin respectively.
p-coumaric acid: a hydroxycinnamic acid derived from L-phenylyalanine, involved in formation of phenylpropanoids, readily convertible into salicylic acid, cf. caffeic acid, ferulic acid, p-coumaric acid, sinapic acid.
palea: in a grass floret, the upper of the two "bracts" enclosing a flower, possibly a prophyll/bracteole, perhaps more likely representing two connate perianth members of the outer whorl, cf. glume (of a spikelet), lemma, lodicule.
paleaceous: chaffy, covered by or made up of dry, membranous scales.
palmate: of venation, a general term used in the descriptions for situations where there is a more or less well developed midrib and the secondary veins depart at the base, but are not notably close and do not converge at the apex, see acrodromous, actinodromous, cf. parallel, pinnate.
panicle: of an inflorescence, a compound raceme, an indeterminate inflorescence in which the flowers are borne on branches of the main axis or on further branches of these, adj. paniculate, indeterminate and much branched, cf. also botryoid, corymb, fascicle, spadix, spike, thyrse, umbel.
panto-: (prefix) positional term for pollen grains, of features, especially apertures, usually more than three, borne scattered over the surface of the grain, as in pantoporate, cf. ana-, cata-, zono-.
papilla: a small, elongated protuberance on the surface of an organ, usually projection from an epidermal cell, adj. papillose.
pappus: a tuft of hairs on a fruit; in Asteraceae, a tuft (or ring) of hairs or scales borne above the inferior ovary and outside the corolla and possibly representing the calyx.
paraclade: a lateral branch of a synflorescence which ends in an inflorescence that has the same structure as the inflorescence on the main axis, cf. coflorescence, enrichment zone, florescence, cf. also inflorescence.
paracytic: of stomata, with two subsidiary cells surrounding and parallel to the guard cells, cf. laterocylic, brachyparacytic, see also actinocytic, allelocytic, anisocytic, anomocytic, cyclocytic, diacytic, helicocytic, laterocytic, staurocytic, stephanocytic, tetracytic.
parallel: of leaf venation, as used in the descriptions a general term for leaves in which there are several veins approximately equal in prominence that run more or less parallel the length of the blade, whether initially recurved or not or converging at the apex of the blade or not, inc. actinodromous, paralleldromous, cf. palmate, pinnate.
parallelodromous: of leaf venation, with all veins approximately equal in prominence and running closely parallel to the apex of the blade, cf. acrodromous, actinodromous, brochidodromous, campylodromous, craspedodromous, dichotomous, eucamptodromous, flabellate, semicraspedodromous, simple-craspedodromous.
paraphyletic: a taxon made up of members which, given a particular phylogenetic tree and classification based on it, include only but not all the descendents a common ancestor, likely to be a grade, cf. monophyletic, polyphyletic.
parasite: a heterotroph living on or in a different organism and deriving nourishment from it, see facultative, obligate, cf. hemiparasite, hyperparasite, myco-heterotroph, saprophyte, also biotroph and necrotroph, cf. saprophyte.
paratact: of cochleate aestivation, the petal with its two edges outside those of the adjacent petals immediately next to the one with the two edges both inside, cf. ascending, descending, and apotact.
parenchyma: plant tissue consisting of little-elongated living cells that are relatively compactly arranged and unspecialised in function and usually have cellulosic walls, sometimes rather more elongated and with tapering ends (and then called prosenchyma), cf. aerenchyma, collenchyma, sclerenchyma, see also xylem parenchyma.
parietal: attached to the margins of a structure; of placentation, having the ovules attached to placentae on the wall of the ovary, cf. apical, axile, basal, free central, intrusive-parietal, laminar, marginal.
parietal cell: of ovule, development, referring to the cell(s) cut off from the archesporial cell(s) prior to meiosis and forming part of the nucellus (in the ovule) and the endothecium (in the anther).
Paris-type arbuscular mycorrhiza: an arbuscular mycorrhiza association between a fungus and a plant root where there are no intercellular hyphae, and hyphae form coils and arbuscules within the plant cell, see also Arum type.
-partite: divided almost to the base into segments (commonly applied to a style or leaf blade).
parthenocarpy: development of a mature fruit without fertilisation of ovules.
passage cells: cells of the endodermis opposite the protoxylem that remain thin-walled and retain their Casparian band, or a similar short cell in the exodermis, this sometimes adjacent to a tilosome.
patent = erect.
pauci- (prefix): few.
pearl gland or pearl body: a small, sessile or shortly-stalked, spherical, often shining, multicellular gland containing oils and sugars and eaten, hence a food body (as in Vitaceae), cf.Beltian body, colleter (perhaps), Müllerian body, snail gland.
pectin: a highly hydrophilic polysaccharide built up of monomers of alpha-galacturonic acid, an important component of cell walls, cf. amyloid, callose, cellulose, hemicellulose, inulin, polyol, starch.
pedate: of a palmate or palmately-lobed leaf, having the lateral segments divided again.
pedicel: the "stalk" of a flower, i.e. the basal part of the ultimate branch of the inflorescence, often subtended by a bract and bearing one or two bracteole(s), cf. inflorescence axis, peduncle, rachilla.
peduncle: that part of the axis of an inflorescence below the insertion of any flowers or inflorescence branches and above the uppermost node with a foliage leaf or leaves, loosely, the "stalk" of the inflorescence, and in that sense to be compared with the pedicel, the "stalk" of the flower, see also scape, cf. inflorescence axis, rachilla.
peloria: of a flower, although polysymmetric, in its immediate phylogenetic and/or morphological context, it would be expected to be monosymmetric, e.g. flowers of some species of Plantaginaceae, including the flowers of the eponymous mutant of Linaria vulgaris, or the terminal flowers borne at the end of a raceme in Digitalis purpurea.
Penaea: an embryo sac type, the types based on variation in megasporogensis and megagametogenesis, tetrasporic, 16-celled (all haploid, four peripheral groups of three cells each and four polar cells), cf. Adoxa, Allium, Drusa, Endymion, Fritillaria, Oenothera, Peperomia, Plumbagella, Plumbago, Polygonum.
penicillate: tufted, rather like an artist's brush.
penta- (prefix): five of whatever is qualified by the prefix.
pentamerous: especially of a flower, having five segments or parts in each perianth whorl, often stamens in five or multiples of five, and quite often carpels also, cf. tetramerous and trimerous in particular.
Peperomia: an embryo sac type, the types based on variation in megasporogensis and megagametogenesis, tetrasporic, 16-nucleate (all haploid, 8 polar, 6 peripheral-antipodal, 2 polar), cf. Adoxa, Allium, Drusa, Endymion, Fritillaria, Oenothera, Penaea, Plumbagella, Plumbago, Polygonum, Schisandra.
perennating: maintaining a dormant, vegetative state throughout the non-growing seasons.
perennial: of plant duration, a plant whose life span extends over more than two growing seasons, cf. annual, biennial, ephemeral, of flowering with respect to architecture, hapaxanthic, monocarpic, pleonanthic
perfect: a flower with functional stamens and carpels, cf. imperfect, cf. also carpellate, neuter, staminate, cf. also androdioecious, andromonoecious, dioecious, gynodioecious, gynomonoecious, monoecious.
per- (prefix): extremely, complete, or through.
peri- (prefix): surrounding.
periblast: of seedlings, a disc- or even umbrella-like expansion of the collar, perhaps especially found in monocots, cf. epiblast; see apical hook, collet, cotyledon, eophyll, epicotyl, hypocotyl, plumule, primary leaf, radicle, of a monocot seedling, see also < href="glossaryi_p.php#mesocotyl">mesocotyl, coleorhiza, hyperphyll (apocole, haustorium/scutellum, phanomer), hypophyll (cotyledonary sheath, coleoptile), (, periblast).
perianth: a single whorl of non-fertile parts surrounding the fertile organs of a flower (see perigon(e)), or collectively the calyx and corolla, or all the protective parts surrounding the flower, and although often also used where there are two similar whorls, the term tepal is then to be preferred (see also semaphyll), cf. androecium, gynoecium, see achlamydeous, dichlamydeous, heterochlamydeous, homochlamydeous, monochlamydeous (use of these can generally be avoided).
perigynous: of floral architecture, stamens and perianth arising from a cup or tube (hypanthium) that is free from the ovary but extends above its base, cf. epigynous, hypogynous, see also inferior, superior.
persistent: remaining attached to the plant, albeit withered, beyond the expected time of falling, e.g. of sepals not falling after flowering, cf. accrescent, caducuous, deciduous, deliquescent, fugacious, marcescent.
personate: a monosymmetric flower with a bilabiate corolla in which the adaxial lip is arched and the abaxial lip is well-developed and pressed against it, so when pressed laterally the corolla opens to look like the mopen mouth of some animal (remember snapdragons), cf. papilionoid, slit-monosymmetric.
petaloid: like a petal, soft in texture and conspicuously coloured.
petiole: the stalk of a leaf, i.e. that part below the blade or, if the leaf is compond, below the point of insertion of the leaflets and/or beginning of the rachis, cf. hyperphyll, lamina, leaf base, stipule, Vorläuferspitze.
phanerocotylar: of germination, when the cotyledon/s is/are exposed and photosynthetic, whether or not the hypocotyl is elongated, cf. cryptocotylar, see also epigeal, hypogeal (hypocotyl/epicotyl development, not synonyms of the first pair).
phanerophyte: of life forms, plants with resting buds 25 cm or more above the surface of the ground, cf. chamaephyte, cryptophyte (geophyte, helophyte, hydrophyte), hemicryptophyte, therophyte, see also habit.
phanomer: of a monocot seedling, the elongated, photosynthetic part of the cotyledonary hyperphyll (there may well be a persistent haustorium above it), cf. apocole, haustorium/scutellum, phanomer, see also mesocotyl, coleorhiza, hypophyll (cotyledonary sheath, coleoptile), collar (epiblast, periblast).
pharmacophagy: utilization of herbivores of the defensive compounds of plants, sequestering them for their own purposes (defence, pheromones).
phenol: an acidic aromatic compound, a common constituent of organic compounds such as cinnamic acid, "Ph" in some of the chemical diagrams here, as in the various phenyl compounds shown immediately below.
phenylpropanoids: any compound bearing a 3-carbon chain attached to a 6-carbon aromatic ring (C6-C3 compounds), most being formed from cinnamic or p-coumaric acids, volatile compounds in essential oils, e.g. orobanchoside, verbascoside.
phlobaphene: amorphous yellowish, reddish or brownish material probably anhydrous derivatives of proanthocyanidins or non-hydrolyzable tannins and found e.g. in the testa of some seeds, a colored proanthocyanidin whose color change is secondary, either enzymic or chemical, cf. phytomelan.
phloem: the part of the vascular tissue of a plant through which metabolites are transported, the transmitting tissue being made up of sieve elements and companion cells (in gymnosperms sieve cells and Strasburger cells), the sieve elements/cells being joined to form sieve tubes, also with rays and frequently fibers (see stratified phloem), and varying in position with respect to the xylem, for which see amphicribral, amphivasal, bicollateral, collateral, internal phloem, intraxylary phloem; variation in details of phloem anatomy in the minor veins of the leaf connected with sugar transport has been characterised as the open and closed types.
phyllotactic fraction: in a genetic spiral/parastichy, the fraction of the stem separating the points of origin of two successively initiated leaves expressed as a fraction in the Fibonacci series, cf. angle of divergence.
phyllotaxis: the arrangement of leaves (inc. scales and bracts) along the stem, especially as they are initiated at the shoot apex, see alternate, bijugate, decussate, distichous, opposite, pseudoverticillate, spiral, spiromonistichous, tristichous, whorled, see also orthostichy, parastichy (inc. contact parastichy, genetic spiral), and also angle of divergence and phyllotactic fraction, cf. anthotaxis.
phytoalexins: a general term referring to substances that inhibit further development of a fungus in hypersensitive host tissue (also antimicrobial), the first one isolated was an isoflavan, others are sesquiterpenes, etc.
phytoelmata: aquatic habitats that occur as plant-based containers, whether pitchers (carnivorous plants), internodes (bamboos), of cavities in trees: phytoelm (sing.).
phytolith: hydrated SiO2 formed in living plants and left behind after decomposition or burning of plant parts.
pilum: a sexine element, usually standing directly on the nexine, consisting of a rod-like part, the columella, and a swollen apical caput, hence pilate, used to refer to a pollen grain whose surface is made up of such elements, cf. gemmate, retipilate, cf. also baculum, tectum.
pinnate: of venation, as used in the descriptions (and as a formal term) covering those forms in which the secondary veins depart from the midrib along its length, includes brochidodromous, camptodromous, craspedodromous, eucamptodromous, reticulodromous, semicraspedodromous, simple-craspedodromous, cf. parallel, palmate.
pinnatipartite: of leaves with lobing over 2/3 of the distance to the midrib, but the parenchyma is not interrupted.
pinnatisect: of the leaf blade, dissected down to the midrib, the parenchyma being interrupted.
plasmodesmata: complex plasma membrane-lined pores, actually endoplasmic reticulum, transversing the primary wall but not necessarily laid down when the primary cell wall is laid down, part of the symplast, see desmotubule.
plastid: an organelle enclosed by a double membrane, usually containing pigments and/or involved in primary carbon metabolism, see chloroplast, chromoplast, leucoplast, also sieve element/cell plastid.
plastochrone: time interval between two successive events, such as initiation of leaf primordia.
platanoid: a leaf tooth in which the medial secondary vein narrows to the foraminate glandular apex, higher order laterals forming brochidodromous loops that converge on the apex, but do not join it, cf. begonioid, chloranthoid, cucurbitoid, cunonioid, dillenioid, malvoid, monimioid, rosoid, salicoid, spinose, theoid, urticoid, violoid.
pleio- (prefix): (unexpectedly) more numerous.
pleiochasium: very like a dichasium, a cymose inflorescence with opposite branching below the flower which terminates each axis, each branch in turn terminating in a flower, etc., but with three or more branches arising from the cf. inflorescence axis, cf. monochasium.
pleonanthic: of flowering with respect to growth, an axis that is not determinate by flowering, the inflorescences being axillary, cf. hapaxanthic, monocarpic, also iteroparous, plietesial, semelparous, of duration of the plant, annual, biennial, ephemeral, perennial.
plesiomorphic: of a character, ancestral or "primitive", arising in the common ancestor of a clade that includes the smaller clade for which the character is a plesiomorphy, e.g. carpels are an apomorphy of angiosperms but are a plesiomorphy of rosids, cf. apomorphic, autapomorphic, synapomorphic.
plicate: of leaf ptyxis, folded together rather like a concertina or fan, see induplicate, reduplicate, cf. circinate, conduplicate, conduplicate-flat, conduplicate-involute, conduplicate-plicate, curved, flat, involute, revolute, supervolute, supervolute-curved, supervolute-involute.
plietesial: of reproduction, when there a single episode of flowering occuring after some years and synchronized across a large area, followed by fruiting and death of the plants involved, cf. iteroparous, semelparous, cf. more from the point of view of meristem persistence hapaxanthic, monocarpic, pleonanthic, and of plant duration, annual, biennial, ephemeral, perennial.
Plumbagella: an embryo sac type, the types based on variation in megasporogensis and megagametogenesis, tetrasporic (3 spores chalazal), 4-celled (the egg, one triploid antipodal, one triploid and one haploid polar), cf. Adoxa, Allium, Drusa, Endymion, Fritillaria, Oenothera, Penaea, Peperomia, Plumbago, Polygonum, Schisandra.
Plumbago: an embryo sac type, the types based on variation in megasporogensis and megagametogenesis, tetrasporic, 8-celled (all cells haploid, 4 cells peripheral, 4 polar), cf. Adoxa, Allium, Drusa, Endymion, Fritillaria, Oenothera, Penaea, Peperomia, Plumbagella, Polygonum, Schisandra.
plumule: the young shoot above the cotyledon(s) of an embryo or seedling, a rather imprecise term, cf. also coleoptile, coleorhiza, collet, eophyll, epiblast, epicotyl, hypocotyl, mesocotyl, primary leaf radicle, scutellum.
Poaceae: the grass floret is much reduced, and there are a number of special terms used to describe it, see caryopsis, glume, lemma, lodicule, palea, for other terms more or less restricted to the family, see culm, tiller.
pod: often used for the fruit of any member of Fabaceae, not recommended, since it can be fleshy, dry, winged or not, dehiscent, indehiscent, etc., etc., a more useful definition might be something like a single-carpellate fruit splitting explosively down both sutures.
podium: a small group of nucellar cells in the ovule not projecting into the embryo sac, cf. antiraphe, chalaza, epistase, female gametophyte, funicle, hypostase, integument (see also endothelium), nucellar beak, nucellar cap, nucellar endothelium, nucellar pad, obturator, ponticulus, postament, raphe (parts).
poikilo- (prefix): little.
poikilhydry: the equilibration of cellular water content with that in the environment, which can be combined with tolerance to dessication, as in mosses and other resurrection plants.
polar nuclei: usually two nuclei in the center of central cell of the eight-nucleate embryo sac, so called because they migrate to the centre from opposite ends/poles of the embryo sac, that fuse with each other and with one of the male gametes to produce the primary endosperm nucleus, which is usually triploid, rarely diploid or some other ploidy level, see antipodals, egg cell, synergids.
pollen chamber: small chamber at the apex of the megasporangium wall (nucellus) of some gymnosperms in which pollen may collect, formed by the brakdown of cells, cf. antiraphe, chalaza, epistase, female gametophyte, funicle, hypostase, integument (see also endothelium), lagenostome, megaspore, micropyle, obturator, podium, ponticulus, postament, raphe.
pollen grain: the microspore of seed plants, containing the partially developed male gametophyte when it is dispersed, and surrounded by a complex wall made up of sporopollenin and sometimes covered with pollenkitt or tryphine or associated with elaters or viscin threads, see endosporic and exosporic for development of the gametophyte, ectexine, endexine, and intine, also baculum, columella, exine, foot layer, pilum, and tectum for Faegri and Iversen terms used for describing the wall (nexine, sexine are specifically Erdtman terms, not used here), and baculate, echinate, fossulate, gemmate, foveolate, pilate (gemmate and retipilate are variants), lophate, psilate, reticulate, retipilate, rugulate, scabrate, striate, and verrucose for some of the terms used specifically for describing the often elaborate surface ornamentation and lumen and murus for describing elements of that ornamentation, see also the basic kinds of apertures (monolete and trilete describe structures on ferns, etc., while anasulcate, tricolpate and tricolporate, are three common pollen "types"), amb, boat-shaped, globose, oblate, prolate, and spherical, terms describing particular aspects of shape, monad, massulae, polyad, pollinia, and tetrad, terms describing aggregations of pollen, prepollen, true pollen, different kinds of pollen in seed plants, and finally the harmomegathic effect, shape changes, cf. pseudopollen.
pollen kitt: material or fluid that is the result of the complete degeneration of the tapetum and rich in plastid-derived lipids and other pigmented compounds, covering the pollen grains, causing them to stick together, to the anther, and/or the pollinator cf. tryphine.
pollinarium: a collective term for the complex structure found in flowers of Apocynaceae-Asclepiadoideae and Orchidaceae where two or more pollinia are attached by translators to a central corpusculum, see also viscidium, also epichile, hypochile.
pollination: the transfer of pollen from the stamen to the receptive region of the ovule (gymnosperms) or carpel, cf. fertilisation, see cross pollination, self pollination, see also anemophilous, hydrophilous, zoöphilous (agents of pollination), nototribic, sternotribic (place of pollen deposition), and nursery pollination (a variant of pollination).
poly- (prefix): many, especially over 15 or so (as in the characterisations), or separate.
polyacetylenes: unsaturated compounds derived from oleic acid by dehydrogenation, highly reactive but with additional functional groups such as alcohols, ketones, acids, esters, furans, or pyrans which tend to stabilize the reactive acetylenic bonds.
polyderm: arises from a lateral meristem that develops in ground tissues located in the pericycle and which cuts off lamellae of paired concentric layers of parenchymatous and endodermal cells, externally, cf. cork cambium, cuticular epithelium, master cambium, vascularcambium.
polyembryony: where more than one embryo per ovule develops, and in a variety of ways, see adventitious (poly)embryony, cleavage polyembryony, and simple polyembryony, the first two being variants of agamospermous reproduction, the asexual formation of seed, cf. adventitious embryony, apogamy, apospory, and diplospory.
polygamodioecious: with perfect and staminate flowers on some plants, perfect and carpellate flowers on others, cf. androdioecious, andromonoecious, dioecious, gynodioecious, gynomonoecious, monoecious, perfect, polygamomonoecious.
polygamomonoecious: with perfect, staminate and carpellate flowers on the same plant, cf. androdioecious, andromonoecious, dioecious, gynodioecious, gynomonoecious, monoecious, perfect, polygamodioecious.
Polygonum: an embryo sac type, the types based on variation in megasporogensis and megagametogenesis, one spore (chalazal), 8 haploid cells, cf. Adoxa, Allium, Drusa, Endymion, Fritillaria, Oenothera, Penaea, Peperomia, Plumbagella, Plumbago, Schisandra.
polymorphic: having more than two distinct morphological forms, either on a single plant or on different plants within a species.
polyol: a carbohydrate produced directly or indirectly by the reduction of aldose or ketose sugars, there are at least thre carbon atoms each with an OH group, see alditol and cyclitol, also hexitol, also arabitol, dulcitol, glycerol, mannitol, and sorbitol, cf. amyloid, callose, cellulose, hemicellulose, inulin, pectin, starch.
polyphyletic: a taxon made up of members which, given a particular phylogenetic tree and classification based on it, include descendents of two or more ancestors, likely to be a grade, cf. monophyletic, paraphyletic.
polysepalous: with free sepals, cf. asepalous, synsepalous.
pome: not used here, a fleshy fruit, formed from an inferior ovary in which the receptacle or hypanthium has enlarged to enclose the ovary, with a more or less developed endocarp, i.e. almost a drupe s.l. or a quasi-berry.
ponticulus: a kind of obturator, a structure developing from the dorsal side of the funicle and faciltating access to the ovule via the chalaza by the pollen tube, cf. also antiraphe, epistase, hypostase, integument (see also endothelium), lagenostome, megaspore, micropyle, nucellus, pollen chamber, podium, ponticulus, postament, raphe.
pontoperculum: a distincly delimited and thickened ectexinous or sexinous structure that covers part of an ectoaperture of a pollen grain, but is linked to the general pollen surface at the two ends of the aperture (which hence can appear disulcate), cf. operculum.
porate (porus, pl. pori): a simple aperture in a pollen grain that is more or less circular in surface view and with a lengt: width ratio of <2:1, also commonly used for compound apertures where the ectoaperture and endoapertures are congruent, here cf. colpate, colporate, pororate, sulcate, sulculate, trichotomosulcate, ulcerate and zona-aperturate.
pore: a general term for any circular opening, thinner area, etc., through which pollen escapes from an anther, or the radicle grows (germination pore), and so on, for anther dehiscence, cf. valve, slit.
pororate: a compound aperture in a pollen grain in which both the inner and outer parts are more or less circular in surface view but are not congruent, cf. colpate, colporate, porate, sulcate, sulculate, trichotomosulcate, ulcerate and zona-aperturate.
postament: a group of persistent nucellar cells in the ovule that project into the embryo sac, cf. antiraphe, chalaza, epistase, female gametophyte, funicle, hypostase, integument (see also endothelium), nucellar beak, nucellar cap, nucellar endothelium, nucellar pad, obturator, podium, ponticulus, raphe (parts).
praemorse: appearing bitten off at the end.
primary: of plant tissues, the cells making them up being produced by the more or less direct derivatives of the primary meristems in the root and shoot, e.g. primary xylem, primary phloem, cf. secondary.
primary endosperm cell or nucleus: the usually tripoid cell formed by the fusion of the male gamete or sperm with the usually diploid central cell of the embryo sac, cf. chalazosperm, chalazal cyst, endosperm, perisperm is the term "primary endosperm also used for haploid gametophytic tissue persisting in the mature seed and forming reserve tissue for the young sporophyte?
primary leaf: the first leaf of an embryo or seedling occuring above the cotyledonary node, cf. cotyledon, eophyll, epicotyl, hypocotyl, plumule, radicle, of a monocot seedling, see also < href="glossaryi_p.php#mesocotyl">mesocotyl, coleorhiza, hyperphyll (apocole, haustorium/scutellum, phanomer), hypophyll (cotyledonary sheath, coleoptile), collar (epiblast, periblast).
primary tissue: tissues by elongation and differentiation of cells derived from the apical meristem.
primary thickening meristem: a variant or part of an apical meristem with extensive primary division localised in the cells of a peripheral, mantle-like zone and forming cells in radial series like a lateral meristem, cf. ground meristem, intercalary meristem, procambium, protoderm.
primary wall: the first visible part of the cell wall deposited during extension growth of the cell and made up of cellulose fibrils, hemicelluloses, pectins, etc., cf. middle lamella, plasmodesmata, secondary wall.
proanthocyanidins: colorless glycosidic anthocyanidins, derived from isomerised flavonoids, usually polymers and based on monomeric flavan-3-ol (catechins) and flavan-3,4-diol units, colorless compounds that yield red anthocyanidins upon heating with acid. Note that they are not precursors to anthocyanidins in the plant.
procambium: a primary meristem near the apex of the stem or root and forming strands down the stem and root, differentiating to form primary vascular tissue, cf. ground meristem, intercalary meristem, primarythickeningmeristem, protoderm.
proembryo: a stage in the early development of the sporophyte between the zygote and the embryo proper, multicellular and globular, but before the differentiation of any tissue systems, see basal cell, hypophysis, suspensor.
prolate: a general pollen shape descriptor, a radially symmetrical grain in which the polar axis is longer than the equatorial diameter, i.e. the grain is longer than broad, cf. boat-shaped, globose, oblate, spherical.
proliferation: sometimes used of an inflorescence which returns to vegetative growth, and bearing a series of congested shoots, or, more generally (see Bell & Bryan 2008) a condensed branching system with very little internode elongation, and so including short shoots, fascicles, verticillasters, etc.
proliferation tissue: [add definition and links].
proliferous: able to reproduce vegetatively from the shoot system, e.g. by stems rooting at the nodes, by plantlets developing on leaves or fronds or in the inflorescence, etc.
prominent: more or less raised and standing out from the surrounding surface, i.e. not simply obvious or conspicuous.
propagule: any structure with the capacity to give rise to a new plant, e.g. a seed, a spore, or part of the vegetative body capable of independent growth if detached from the parent.
prophyll: the first leaf or two leaves formed along an axillary shoot, often smaller and/or in a distinctively different position from those formed subsequently, often called bracteole(s) when borne on a pedicel, cf. pherophyll. ("The prophyll is the first leaf on the branch and nothing more" [Blaser 1944, p. 62].)
protocorm: a small cormous structure developed early in germination of an orchid seedling but already exhibiting a mycorrhizal association.
protoderm: primary meristem of stem or root, located at the apex, giving rise to the epidermis, cf. ground meristem, intercalary meristem, primary thickening meristem and procambium (all of stem) and columella and peripheral root cap initials (root).
protoplast: a unit bounded by a plasma membrane, generally containing a single nucleus, the product of enzymatic digestion of the wall, but incapable of dividing until it forms a wall (this term is not found in animal literature; apart from the origin of this structure, it is identical to the broad definition of cell, which see), cf. also. organ, tissue.
proximal: near to the point of origin or attachment, e.g. the inner walls of a pollen tetrad that are adjacent to the walls of the other members of the tetrad, but sometimes it is difficult to understand exactly what is meant by the term, cf. distal.
pseudanthium: a compact inflorescence of several to many small flowers which simulates a single flower, used here only when the identity of the individual flowers is more or less lost, the other extreme from meranthium, cf. also euanthium.
pseudo- (prefix): false, apparent, not genuine.
pseudobulb: a rounded and thus "bulb-like" swelling of the stem, as in some Orchidaceae, cf. bulb, bulbil, caudex, corm, creeping stem, dropper, lignotuber, rhizome, runner, stolon, tuber, tiller, turion.
pseudocarp: a structure made up of the fruit sensu stricto plus another part of the plant, includes everything from rose hips and strawberries to pineapples, figs, and the dispersal units of a dandelion, hardly a term of much value.
pseudopetiole: often used when describing monocot leaves which appear to have a petiole.
pseudoverticillate: of leaf arrangement, where spirally-arranged leaves are congested at the end of each innovation and appear to form a whorl, cf. also alternate, bijugate, decussate, distichous, opposite, pilate, spiral, spiromonistichous, tristichous, whorled.
psilate: a term used to describe the pollen surface, lacking sculpturing, cf. baculate, echinate, fossulate, gemmate, foveolate, lophate, reticulate, retipilate, rugulate, scabrate, striate, verrucose.
psychophilous: of entomophilous flowers pollinated by butterflies, often with a distinctive syndrome (long, more or less spreading lobes, bright color, scent, etc.), cf. cantharophilous, melittophilous , myophilous, sapromyophilous, sphigophilous.
ptyxis: pattern of folding and rolling of an individual leaf during early development, see circinate, conduplicate, conduplicate-flat, conduplicate-involute, conduplicate-plicate, curved, flat, involute, plicate, revolute, supervolute, supervolute-curved, supervolute-involute, cf. aestivation, see also vernation.
ptyophagy: an uncommon condition in orchidaceous endomycorrhizae where deformation and lysis of fungal hyphae occurs ± oustide the host cell plasmalemma, before the formation of pelotons, etc., cf. tolypophagy.
puberulous: covered with minute, soft, erect hairs, cf. arachnoid, arbuscular, canescent, hirsute, hispid, lepidote, pubescent, sericeous, stellate, strigose, tomentose, T-shaped, villous, see also glabrescent and glabrate, which refer to stages in the loss of these hairs.
pubescent: covered with short, soft, erect hairs, cf. arachnoid, arbuscular, canescent, hirsute, hispid, lepidote, puberulous, sericeous, stellate, strigose, tomentose, T-shaped, villous, see also glabrescent and glabrate, which refer to stages in the loss of these hairs. Pubescent is not a synonym of indumentum (Rickett 1954a).
pulverulent: appearing as though dusted over with powder.
pulvinus: a more or less abrupt swelling, especially at the apex or base of a petiole or leaf sheath, often glandular and/or being the place where a plant responds to touch, gravity or light, in panicoid grasses a swollen region in the stem above the intercalary meristem - such a definition would also include stems of Chloranthaceae, Acanthaceae, Caryophyllaceae, Amaranthaceae, etc., cf. articulation.
pump presentation: a type of secondary pollen presentation in which the pollen is presented to the pollinator as it is extruded from or pumped out of a tube formed by the anthers by the action of the stigma-style, cf. brush presentation.
pungent: ending in a stiff, sharp point; having an acrid taste or smell.
pustulate: covered with small pustule- or blister-like elevations.
pyranochromones: class of chromones which are isomers of pyranocoumarins (can't find much of substance on this one).