Q

quassinoids: subclass of triterpenoids (nortriterpenoid) composed of 19-20 carbon atoms.

Quassinoid base.

Simarolide, C27 H36 O9.

quercetin: a common flavonol.

Quercetin, C15 H10 O7.

quincuncial: of aestivation in a flower, a variant of imbricate, such that two sepals (e.g.) have one edge outside the adjacent sepal and the other inside, one sepal has both edges inside, and two sepals have both edges outside, cf. cochleate, contorted, contortiplicate, crumpled, decussate.

quinolizidines: alkaloids derived from lysine and with two fused 6-membered rings that share a nitrogen.

Quinolizidine, C9 H17 N.	Cystisine, C19 H31 N2 O4 P.
Lupinine, C10 H19 N O.

quinones: the general name for aromatic compounds that have two atoms of hydrogen replaced by two atoms of oxygen, usually yellow, red, or orange, see anthraquinones, benzoquinones, hydroquinones, naphthoquinones.

quinque- (prefix) = five of whatever is qualified by the prefix.

R

raceme: an indeterminate inflorescence, the axis producing a series of flowers on lateral pedicels, the oldest at the base and the youngest at the top, adj. racemose, for variants, see botryoid, corymb, fascicle, raceme, spadix, spike, thyrse, umbel, cf. cyme.

rachis: that part of the axis of a pinnate or more highly compound leaf that bears leaflets or branches of the axis, pl. r(h)achises, cf. petiole.

rachis (rhachis), more specifically, inflorescence rachis = inflorescence axis, cf. also pedicel, peduncle, rachilla.

rachilla (rhachilla): especially of palms, the lateral or secondary branches of the inflorescence, and of a grass spikelet, the axis above the glumes, cf. inflorescence axis, pedicel, peduncle.

radially symmetrical = polysymmetrical.

radical: of leaves, clustered at the base of the stem, see basal, rosette, cf. cauline.

radicle: the basal continuation of the hypocotyl of an embryo or seedling that gives rise to the root system of the adult plant (see taproot), sometimes more or less abortive, cf. coleoptile, coleorhiza, collet, cotyledon, eophyll, epiblast, epicotyl, mesocotyl, plumule, primary leaf, scutellum.

raffinose: an oligosaccharide made up of three sugar units, galactose, fructose and glucose, serially linked, cf. stachyose.

ramiflorous: borne below the current leaves on recently formed woody branches, commonly used to describe general inflorescence position, cf. axillary, cauliflorous, terminal.

rank: used when organs such as leaves are arranged in vertical series (distichous = two-ranked, etc.); also used to refer to the degree of branching.

rank: in the taxonomic hierarchy, one of the levels assigned to plant groups; these denote relative inclusion relationships, e.g. a family will include a genus or genera, but not vice versa; members of the one rank are not equivalent other than - one hopes - all being monophyletic and are therefore not really comparable; for the main ranks mentioned here, see class, order, family, genus, species (which may well not be monophyletic...).

ranunculaceous (of stomata) = anomocytic.

raphe: where the funicle is adnate to the body of the ovule, see also antiraphe, chalaza, embryo sac, integument, lagenostome, megaspore, micropyle, nucellus, pollen chamber, obturator.

raphides: needle-like crystals of calcium oxalate that occur in bundles in the vacuoles of some plant cells, see biforines, cf. druses, styloids, sand.

ray: (anatomy) in xylem or phloem, a vertically elongated band of often radially elongated parenchymatous cells traversing the conducting elements, see tile cells, also heterogeneous, homogeneous and heterocellular, homocellular.

ray (inflorescence): of a compound umbel, one of the first series of branches of the inflorescence axis.

ray floret: a monosymmetric flower towards the periphery of a capitulum, esp. in Asteraceae, ligulate, with a split monosymmetric corolla, cf. disc floret.

ray initials: a kind of cambial initial in the vascular cambium, vertical series of low cells the division and subsequent differentiation of which that produce the rays, cf. fusiform initials.

ray parenchyma: radially orientated xylem parenchyma in the wood, see ray type, cf. axial parenchyma.

reaction wood: wood often with a distinctive anatomy and position formed where a branch joins the stem, see compression and tension wood.

recalcitrant: of germination, the seed needing to remain hydrated if germination is to occur, cf. after-ripening.

recaulescent: of axillary branching, a kind of metatopic growth when the bud is as it were shifted onto the subtending leaf, forming a "stalk" on which bud and leaf are borne, cf. concaulescent.

receptacle: the axis of a flower on which the perianth, androecium and gynoecium are borne; in Asteraceae, used to refer to the often swollen and apically flattened part of the stem bearing the flowers and inflorescence bracts.

receptacular epigyny: of epigyny, when the floral apex is initially convex, but after gynoecial initiation the periphery of the floral apex expands and raises, forming a basin in the center of which the carpels are borne and on the periphery of which the perianth members and androecium are borne, i.e. epigyny is due to development of axial tissues (Kuzoff et al. 2001), cf. appendicular epigyny.

receptacular nectary: a nectary in the flower supplied by branches of the receptacular or androecial vasculature, cf. gynoecial nectary.

recurved: curved or curled downwards or backwards, cf. incurved.

reduced: 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 the tapetum only, cf. basic, dicotyledonous, monocotyledonous, reduced.

reduplicate: of aestivation, valvate, the edges meeting, and although not overlapping, they are recurved, cf. crumpled, decussate, induplicate, open.

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

reflexed: bent sharply downwards or backwards, cf. inflexed.

regular (of floral symmetry) = polysymmetric.

reiteration: of plant architecture, when the characteristic construction of the individual is repeated by branch systems that develop on a plant after damage, or sometimes as the result of natural causes.

reniform = kidney-shaped.

repand = undulate.

reparatory strand: a strand of vascular tissue that fills ("repairs") the leaf gap left by the outgoing leaf trace, a branch of the sympodial units making up the central stele of seed plants.

replum: when placentation is parietal, a "false" septum joining the placentae.

repent: a general term, see ascending, decumbent, erect, procumbent.

reproduction: the general process by which new plants are formed, in particular cf. apomixis, amphimixis.

reproductive nectary: a nectary that is found on the inflorescence or flower or associated structures - a positional definition - cf. extrareproductive nectary.

resins: lipid-soluble terpenes or phenols, cf. gums, mucilages, latex, oils, waxes.

resupinate: of floral symmetry, twisted through 180^o, e.g. as with the ovary of many Orchidaceae.

resurrection plant: a plant whose leaves can dry out and remain dry for years, and then take in water and function normally when there is rain, cf. anhydrobiosis, diallagy.

reticulate: forming a network.

reticulate: a term used to describe the surface of a pollen grain, a network-like pattern consisting of lumina or other spaces wider than 1µm bordered by elements narrower than the lumina, whether pilae (retipilate) or muri, cf. baculate, echinate, fossulate, gemmate, foveolate, pilate, lophate, psilate, rugulate, scabrate, striate, verrucose.

reticulate-veined: a rather loose term describing leaves where reticulation and anastomosis predominate in the venation, cf. parallel-veined.

reticulodromous: of leaf venation, pinnate venation (camptodromous in particular), in which the secondary veins lose their identities towards the margin as they branch repeatedly, cf. brochidodromous, eucamptodromous in particular, also cf. acrodromous, actinodromous, campylodromous, craspedodromous, dichotomous, flabellate, parallelodromous, semicraspedodromous, simple-craspedodromous.

retinaculum/retinacle = corpusculum (flowers of Orchidaceae, Apocynaceae-Asclepiadoideae), cf. staminal retinaculum.

retinaculumAc = jaculator (fruits in Acanthaceae).

retipilate: referring to the surface of a pollen grain whose sculpturing is made up of pilae arranged in a reticulate pattern, cf. baculate, echinate, fossulate, gemmate, foveolate, pilate, lophate, psilate, reticulate, rugulate, scabrate, striate, verrucose.

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

retuse: of the apex of any laminar structure, e.g., petal, leaf blade, very blunt, slightly notched and divided less than 5% the length of the structure, cf. emarginate, lobed in particular, cf. also acute, attenuate, acumen, apiculum, arista, awn, cuneate, caudate, cuspidate, mucronate, muticous, obtuse, rounded, truncate, cf. also cordate, hastate, oblique, runcinate, sagittate (esp. of lamina base).

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

rhachilla, rhachis: see rachilla, rachis.

rheophyte: a narrow-leaves plant, usually a shrub, growing in or by rivers and periodically subject to immersion in fast-flowing waters, cf. acaulescent, arborescent, dendroid, frutescent, fruticose, herb, liane, suffrutescent, schopfbaum, shrub, subshrub, tree, vine, see also life forms.

rhexigenous: an intercellular space caused by the rupture of the cells there, cf. expansigenous, lysigenous, schizogenous.

rhinanthoid (of a floral aestivation) = ascending cochleate.

rhipidium: of a monochasial cymose inflorescence of some monocots, flowers arising successively from the adaxial prophylls, thus alternating from one side of the axis to the other side, and all being in a single plane, the whole inflorescence often appearing corymbose from a lateral view, cf. drepanium, helicoid cyme, scorpioid cyme.

rhizodermis: the surface layer of the root, originating from the outermost layers of the cortex or having a common origin with cells of the root cap, continuous with the epidermis of the stem.

rhizoid: a thread-like, uniseriate (unicellular) absorbing structure in the gametophytes (and sometimes sporophytes) of ferns, etc., cf. root.

rhizoid: unicellular trichomes on the collar in seedlings, especially those of monocots; basically precocious roothairs, but longer, denser, and/or living longer, but of course also different in position.

rhizome: a slender to much swollen underground stem that grows more or less horizontally, cf. bulb, bulbil, caudex, corm, lignotuber, pseudobulb, stolon, tuber, turion.

rhombic: a term used for outlines and plane shapes, with length:breadth ratio 2:1 - 3:2, widest and more or less angled at the middle, pointed at the apex and base, see broadly, broad-transverse, narrowly, transverse, cf. elliptic, obovate, ovate, triangular, trullate.

rhytidome: cork cambium and the tissues it isolates, since such cambia are often formed successively deeper and deeper in the stem, there may be pockets of cortical or phloem tissue in with the cork.

ribose: a sugar.

rind: a vague and imprecise term, often applied to the outer part of a fruit that differs in texture (harder, tougher) from the inner part.

ringent (of monosymmetric flowers) = personate.

ring porous: of porous wood, with vessels in more or less distinct rings, usually only at the beginning of the season's growth, cf. diffuse porous.

root: commonly thought of as one of the three basic parts of the seed plant body, that part of the axial system which is usually underground and more or less positively geotropic, does not bear leaves and only rarely shoots, is endogenous in origin, indeterminate in growth and often with secondary thickening, see root cap, root tip and root hair, see also fibrous root, tap root, cf. leaf and stem (the other main parts of the seed plant body), cf. also rhizoid.

root apical meristem (RAM): a group of pluripotent cells at the apex of a root from which tissues of the root differentiate, see closed meristem, open meristem.

root cap: a group of cells at the tip of the root that covers the apical meristem and protects it, made up of border cells, columella, peripheral root cap, and protoderm.

root hair: a projection from an epidermal cell of the root.

root tip: the apical part of the root including the apical meristem and root cap.

rootstock: a short, erect, more or less swollen structure at the junction of the root and shoot systems of a plant, cf. xylopodium.

rosette leaves: the leaves at the base of the stem when these are separated by very short internodes and lie more or less flat on the ground, so forming a circle, see also basal and radical leaves, cf. cauline.

rosmarinic acid: type of phenylpropanoid involving cinnamic acid derivatives; a depside of caffeic acid linked to dihydroxyphenyllactic acic, cf. chlorogenic acid.

rosoid: a leaf tooth in which the central vein terminates subapically and there is a large clear glandular foramen, two straight higher-order secondary veins also terminate in the foramen, cf. begonioid, chloranthoid, cucurbitoid, cunonioid, dillenioid, malvoid, monimioid, platanoid, salicoid, spinose, theoid, urticoid, violoid.

rostellum: in orchids, the (as stipes [hamulus, tegula], viscidium) apical portion of the median stigmatic lobe, sometimes used to refer only to the modified non-receptive part (see Rasmussen 1982), for other commonly-used terms specific to orchid flowers, see caudicula, column, incumbent, labellum, sectile, and stipes, also epichile, hypochile.

rostrum (rostrate) = beak (beaked).

rosulate: clustered into a rosette, e.g. of basal leaves of some annuals and biennials.

rotate: circular and flattened, e.g. of a polysymmetric corolla with a very short tube and spreading lobes, cf. campanulate, infundibular, salverform, tubular, urceolate.

rotenoids: flavonoids, derived from isoflavones, with an extra carbon atom from S-adenosyl methionine and incorporating a prenyl group into the isoflavone structure.

Gliricidol, C17 H14 O6.

Rotenone, C23 H22 O6.

rounded: of the shape of the apex or base in particular, without any angles and generally convex in apperance, cf. acute, attenuate, acumen, apiculum, arista, awn, cuneate, caudate, cuspidate, emarginate, mucronate, muticous, obtuse, retuse, truncate, cf. also cordate, hastate, oblique, runcinate, sagittate (esp. of lamina base).

route I: a kind of iridoid, derived from deoxyloganicacid, the normal route I iridoid not undergoing oxidation, see also secoiridoids, cf. route II.

Loganin, C17 H26 O10.

route II: a kind of iridoid derived from epi-deoxyloganicacid, see carboxylated (normal) iridoids, decarboxylated iridoids, cf. route I.

rubber: a component of latex, made up of isoprene units, cis 1,4-polyisoprene, cf. gutta, gutta percha.

rubiaceous (of stomata) = paracytic.

rudimentary: poorly developed and not functional, cf. obsolescent, vestigial, obsolete.

rugate = colpate, also, of pollen apertures with elongated or furrow-like apertures that are globally distributed, may be six or fewer in number?

rugose: deeply wrinkled, dim. rugulose, with minute wrinkles.

rugulate: a term used to describe the pollen surface, with elongated sexine elements more than 1µm long arranged in an irregular pattern intermediate between reticulate, retipilate and striate, cf. also baculate, echinate, fossulate, gemmate, foveolate, pilate, lophate, psilate, scabrate, verrucose.

ruminate: commonly used of endosperm, inpushings of the seed coat that more or less give the appearance of the villi of the rumen or intestine to the cut surface of the seed, cf. condyle.

runcinate: deeply lobed and with the lobes slanted away from the apex, cf. acute, attenuate, acumen, apiculum, arista, awn, cuneate, caudate, cuspidate, emarginate, mucronate, muticous, obtuse, retuse, rounded, truncate, cf. also cordate, hastate, oblique, sagittate (esp. of lamina base).

runner: rather vague, often used to refer to some kind of slender stolon.

ruspolinone: a pyrrolidine alkaloid.

S

saccate = pouched.

saccharose = sucrose.

saccus/sacci: wing- or bladder-like extension(s) of the pollen exine at leat partly filled with alveolate material.

sagittate: shaped like an arrow-head, cf. acute, attenuate, acumen, apiculum, arista, awn, cuneate, caudate, cuspidate, emarginate, mucronate, muticous, obtuse, retuse, rounded, truncate, cf. also cordate, hastate, oblique, runcinate (esp. of lamina base).

salicoid: a leaf tooth in which the medial vein ends in dark but not opaque persistent spherical callosity, no laterals are involved, perhaps close to a theoid tooth, cf. also begonioid, chloranthoid, cucurbitoid, cunonioid, dillenioid, malvoid, monimioid, platanoid, rosoid, spinose, urticoid, violoid.

salicylic acid: orthohydroxybenzoic acid, obtained from the bark of the white willow and wintergreen leaves, its salts are the salicylates.

Salicylic acid, C7 H6 O3.

salverform: e.g. of a polysymmetric corolla, salver- or trumpet-shaped, like the corolla of Primula with a long, slender tube and abruptly expanded flat, spreading limb (rotate in one sense), cf. campanulate, rotate, infundibular, tubular, urceolate.

samara: a dry, indehiscent fruit with its wall expanded into a wing or wings, a variant of an achene or a mericarp of a schizocarp.

sand: a microcrystalline form of calcium oxalate, or some other crystalline inclusion, forming a granular mass, cf. druse, raphide, styloid.

Sanio: see Bars of Sanio.

saponins: water-soluble and sometimes toxic glycosides based on steroid or terpenoid alcohols, become a foam when in solution and then shaken.

Glycyrrhizin, C42 H62 O16.

sapromyophilous: a kind of entomophilous pollination, flowers pollinated by flies and with a distinctive syndrome (e.g. purplish color, the odour of carrion or of decay in general), cf. cantharophilous, melittophilous , myophilous, myophilous, sphigophilous.

saprophyte: a heterotroph obtaining complex nutrients from the decay of other organisms, usually lacking chlorophyll, cf. hemiparasite, parasite, hyperparasite, myco-heterotroph.

sapwood: the outer and still functional portion of the wood of a trunk or large root, cf. heartwood.

sarcotesta: a fleshy testa, or a fleshy layer of the testa (mesotesta), outside the sclerotesta, when the latter is present, cf. also aril, arillode, caruncle, elaiosome.

sarmentose = stoloniferous.

saturated: e.g. of fatty acids, lacking double bonds, cf. unsaturated.

Palmitic acid, C16 H32 O2.

Lauric acid, C12 H24 O2.

Myristic acid, C14 H28 O2.

saxicolous: of a plant growing on rock, see epilithic.

scabrate: a term used to describe the pollen surface, ornamented in any way with elements less than 1µm in all directions, cf. baculate, echinate, fossulate, gemmate, foveolate, pilate, lophate, psilate, reticulate, retipilate, rugulate, striate, verrucose.

scabrous (= scabrid): rough to the touch, dim. scaberulous, slightly or minutely rough to the touch, minutely scabrous.

scalariform: having a ladder-like pattern; of a vessel, the end walls having one to many bars across them, cf. simple; of pits, elongated in outline, cf. bordered, simple, vestured.

scale: a rather vague term, usually a thin flap of tissue of epidermal origin, e.g. at the base of a stamen in Simaroubaceae.

scale leaf: a reduced leaf, often ± dry, non-photosynthetic, and protective, e.g. surrounding a dormant bud, a budscale (see perulate bud).

scale: a thin, more or less scarious trichome which is flattened and variously shaped, cf. hair.

scandent: climbing, see liane or vine.

scape: the stem-like peduncle of a plant with radical or rosette leaves that lacks leaves along its length, cf. inflorescence axis.

scarious: dry and membranous in texture, cf. chaffy, chartaceous, coriaceous, papyraceous.

Schisandra: an embryo sac type, the types based on variation in megasporogensis and megagametogenesis, unisporic (from the chalazal cell), 4-celled, all cells haploid, cf. Adoxa, Allium, Drusa, Endymion, Fritillaria, Oenothera, Penaea, Peperomia, Plumbagella, Plumbago, Polygonum, Schisandra.

schizo- (prefix): split.

schizocarp: a dry, dehiscent fruit formed from more than one carpel and breaking apart septicidally into 1-carpellate units (mericarps) when ripe, these containing one (or more) seeds, cf. capsule, follicle, lomentum.

schizogenous: of cavities in plants, formed by the separation of cells down their middle lamellae, cf. expansigenous, lysigenous, rhexigenous.

schopfbaum: of habit, an unbranched woody plant less than about 10 m tall and often with a rather stout trunk and a tuft of large leaves at the top, cf. acaulescent, arborescent, dendroid, frutescent, fruticose, herb, liane, rheophyte, shrub, subshrub, suffrutescent, tree, vine, see also life forms.

scion: in grafting, the stem of one plant that is variously attached or inserted onto or into the stock.

sclereid: a dead cell that is a component of sclerenchyma, variously shaped but usually at most only moderately elongated and with a strongly lignified wall, cf. fibre, see astrosclereid, brachysclereid, macrosclereid, trichosclereid.

sclerenchyma: mechanical tissue made up of fibres and/or sclereids, cf. aerenchyma, collenchyma, parenchyma.

sclerophyll: with stiff, hard leaves usually with much sclerenchyma, cf. mesophyll.

scleromorphic: referring to hardness or toughness, especially of leaves (sclerophyll above), whether in respoinse to dry climate or nutrient-poor conditions, cf. xeromorphic.

sclerotesta: a stony, sclerenchymatous layer of the testa, usually mesotestal in origin and inside the sarcotesta.

scopoletin: a coumarin.

scorpioid cyme: a monochasial cymose inflorescence branching alternately from a bracteole/prophyll on one side of a pedicel and then from one on the other side, the flowers being borne in two rows, the whole more or less zig-zag but also coiled like the tail of a scorpion, cf. drepanium, helicoid cyme, rhipidium. (bottom left hand image).

sculpture elements: making up the supractectal structures of the ektexine of a pollen grain.

scutellum: a special term applied to the more or less shield-shaped and absorbtive haustorium at the end of the cotyledonary hyperphyll in the embryo or seedling of grasses (i.e. the term haustorium itself would really do), of a monocot seedling, see also < href="glossaryi_p.html#mesocotyl">mesocotyl, coleorhiza, hyperphyll (apocole, /scutellum, phanomer), hypophyll (cotyledonary sheath, coleoptile), collar (epiblast, periblast).

secoiridoid: a class of route I iridoid derived from deoxyloganic acid via oxidation to carboxyl at C₁₁.

Secoiridoid base.	Deutzioside, C15 H22 O9.
Patrinoside, C21 H34 O11.	Secologanin, C17 H24 O10.

secondary: in pollination, where pollen is presented to the pollinator elsewhere than directly on the anther, see brush presentation, pollen presenter, pump presentation.

secondary growth: growth in width caused by the elongation, differentiation and maturation of cells derived from the lateral meristems, cf. primary growth.

secondary meristem, loosely, = lateral meristem.

secondary metabolite: a rather misleading term referring to compounds not involved in photosynthesis, respiration and other basic metabolic activities of the cells.

secondary thickening: increase in diameter of the stem because of the activity of the lateral meristems.

secondary tissue: the differentiated products of lateral meristems.

secondary wall: that part of the cell wall deposited during late expansion growth of the cells with strengthening, etc., functions, and made up of cellulose fibrils, lignin, etc., cf. middle lamella, plasmodesmata, primary wall.

secretory (of tapetum) = glandular.

sectile: in Orchidaceae, refering to the soft and friable - "mealy" - texture of some pollinia made up of massulae - for other commonly-used terms specific to orchid flowers, see caudicula, column, hamulus, incumbent, labellum, rostellum, stipes, tegula, viscidium, also epichile, hypochile.

secund: with all the parts grouped on one side or turned to one side, applied especially how flowers are held in an inflorescence or stamens in a flower, cf. diffuse, divaricate.

seed: a propagating organ formed in the reproductive cycle of gymnosperms and angiosperms, derived from the ovule and usually consisting of a protective seed coat (rarely absent) formed from the integument or integuments (see hilum, micropyle, linea fissura) and enclosing an embryo and often also food reserves (endosperm, primary endosperm or perisperm), see also aril, arillode, caruncle, coma, elaiosome ("appendages").

seed coat: covering of seed derived from ovular - mainly integumentary - tissue, but to be used only when not specified more precisely, for which see tegmen and testa.

seed leaf = cotyledon.

seedling: the young plant that results from germination of the seed, see apical hook, collet, cotyledon, eophyll, epicotyl, hypocotyl, plumule, primary leaf, radicle, of a monocot seedling, see also mesocotyl, coleorhiza, hyperphyll (apocole, haustorium/scutellum, phanomer), hypophyll (cotyledonary sheath, coleoptile), collar (epiblast, periblast).

segment: a part or sub-division of a structure.

self pollination: pollination of a flower by pollen from the same plant, cf. autogamy, geitonogamy, cf. also allogamy, cross pollination.

semaphyll: any structure, bract, sepal (when the rest of the perianth is inconspicuous), etc., that is modified and forms the part of the flower that attracts the pollinator.

semelparous: of reproduction, when there is just a single episode of flowering in the life of an individual, cf. iteroparous, cf. more from the point of view of meristem persistence hapaxanthic, monocarpic, pleonanthic, and of plant duration, annual, biennial, ephemeral, perennial.

semicraspedodromous: pinnate venation, craspedodromous in particular, in which the secondary veins branch just inside the margin, one of the branches terminating at the margin, the other joining the superadjacent secondary vein, cf. simple craspedodromous in particular, also cf. acrodromous, brochidodromous, campylodromous, eucamptodromous.

semitectate: pollen in which the sexine forms a incomplete roof over the columellae, granules or other infratectal elements, the tectum in outer view often forming a reticulate pattern, cf. atectate, tectate.

senecionine: a pyrrolizidine alkaloid.

senescence: age-related processes that signal the beginning of the death of a plant or plant part.

sensu lato: after a name, meaning that the name is to be taken with a broad circumscription, often s. lat., cf. sensu stricto.

sensu stricto: after a name, meaning that the name is to be taken with a narrow circumscription, often s. str., cf. sensu lato.

sepal: a member of the (usually green) outer whorl of non-fertile parts surrounding the fertile organs of a flower, cf. epicalyx, petal, tepal.

sepaloid: looking like sepals, e.g. of bracts, when green and arranged in a ring beneath a flower.

septal nectary: a nectary consisting of a more or less complexly organised epithelial surface in the septum or septal radius of the ovary in angiosperms, so far known only from monocots.

septate, see septum.

septicidal: of the dehiscence of a capsule (including schizocarps), separating down the middle of the septae or partitions between the loculi, cf. circumscissile, loculicidal, poricidal, septifragal.

septifragal: of the dehiscence of a capsule (including schizocarps), with the valves or backs of the carpels breaking away leaving the septae intact, cf. circumscissile, loculicidal, poricidal, septicidal.

septum: a thin partition or membrane that divides cavities or soft masses of tissues, e.g. the ovary loculus, anther sporangia, etc., pl. septa, when qualifying pith, = chambered pith.

seriate: in rows or whorls, often used as a suffix, as in 2-seriate, biseriate, etc.

sericeous: of indumentum, silky in appearance, covered with silky hairs, cf. arachnoid, arbuscular, canescent, hirsute, hispid, lepidote, puberulous, pubescent, tomentose, T-shaped, villous, see also glabrescent and glabrate, which refer to stages in the loss of these hairs.

serotinous: of fruits/cones retaining mature seeds for more than a year, often associated with bradyspory.

serrate: of margins, toothed, with asymmetrical forwardly-pointing teeth, cf. biserrate, crenate, dentate, entire, undulate.

serrulate: finely serrate.

sesamin: a lignan.

sesquiterpene lactones: lactones, subclass of C15 terpenoids (= sesquiterpenoids, sesquiterpenes), bitter-tasting and toxic, derived via the mevalonate pathway from three C5 isopentenyl pyrophosphate units.

Xanthinin, C17 H22 O5.	Ambrosanolide, C17 H24 O5.
Eremophilanolide, C15 H22 O2.

sessile: without a stalk, e.g. a flower without a pedicel, as in a spike, or when applied to a stigma, indicates that the style is absent, the stigma sitting directly on the ovary.

seta: a bristle or stiff hair, setaceous, setiferous (bearing setae), setose, dim. setulose.

sexine (Erdtman term): the outer, sculptured layer of the exine, which lies above the nexine, sometimes up to sexine 5, although the three layers below are the commonest ones, cf. also perine.

sexine 1 = columellae.

sexine 2 = tectum.

sexine 3 = sculpture elements.

sexual: of reproduction, a plant that produces viable offspring only via fertilisation, see oogamy, cf. apomixis, asexual reproduction, vegetative reproduction.

sheath: especially of the lower part of a monocot leaf, closely and completely surrounding the stem, see closed, open.

sheathing: of a stipule that entirely surrounds the stem, "ochreate" in the image, cf. interpetiolar, intrapetiolar.

shikimic acid: an aromatic carboxylic acid that is a precursor in the biosynthesis of alkaloids and flavonoids.

Shikimic acid, C7 H10 O5.

shoot apical meristem (SAM): a group of pluripotent cells at the apex of a stem from which stems, leaves and reproductive structures differentiate, see corpus, tunica (a histological zonation in angiosperms and Gnetales).

short-day: of a photoperiodic response, where short periods of light alternating with long periods of dark are neeeded for flowering to occur (more accurately, a long uninterrupted period of dark), cf. long-day.

short shoot: a shoot in which the internodes elongate little or at all, bearing reproductive structures and/or leaves, when well developed, as in Ginkgo and some apples, rather spur-like, cf. long shoot; the comparison is often made between axillary shoots.

shrub: of habit, a woody plant less than five metres high, either without a distinct main axis, or with branches persisting on the main axis almost to its base, cf. acaulescent, arborescent, dendroid, frutescent, fruticose, herb, liane, rheophyte, schopfbaum, subshrub, suffrutescent, tree, vine, see also life forms.

sieve cell: a conducting cell in phloem tissue of gymnosperms, elongated, nucleate, and not necessarily derived from the same mother cell that produces the closely associated Strasburger cell, the sieve areas being relatively unspecialised and the pores apparently filled with membranes that are continuous with smooth endoplasmic reticulum in the adjacent cytoplasm, there also being a central cavity in the area of the middle lamella, cf. sieve element and sieve plate.

sieve element: a cell in phloem tissue of angiosperms, that is elongated, enucleate, with P[phloem]-protein, sieve tube plastids, and a sieve plate; derived from the same mother cell that produces the closely associated companion cell, cf. sieve cell, see sieve tube.

sieve plate: an area of the end wall of a sieve element; it has has larger pores than are found elsewhere on the wall, the pores being open channels.

sieve tube: a conducting tube in the phloem made up of a number of sieve elements attached end to end.

sieve element/cell plastid: a plastid in the sieve tube or sieve element usually with starchy and/or proteinaceous inclusions, cf. chloroplast, leucoplast.

sigmoid: doubly curved in opposite directions like the letter S.

siliceous: containing silica (SiO₂).

silicula, siliqua, silique (etc.): a series of terms applied to the septifragal capsules esp. of Brassicaceae, confusing and of no value here.

simaroubolide: quassinoids, e.g. simarolide, occurring in Simaroubaceae.

simple aperture: of pollen where the aperture consists of a single component in one layer of the wall, cf. compound aperture, see colpate, porate, sulcate, sulculate, trichotomosulcate, ulcerate and zona-aperturate, also heterocolpate, a mixture of the two!

simple-craspedodromous: of pinnate venation, a variant of craspedodromous in which the secondary veins and their branches terminate at the margins, often as teeth, cf. semicraspedodromous in particular, also cf. acrodromous, actinodromous, brochidodromous, eucamptodromous, reticulodromous.

simple fruit: a fruit that is made up of two or more connate carpels or from a single carpel, e.g. as in Fabaceae, Asteraceae, etc., etc., i.e., fruit made up of a single unit (although this seems a singularly unhelpful definition, even by the standards of fruit terminology), cf. accessory fruit, aggregate fruit, multiple fruit.

simple leaf: of a leaf, not divided into leaflets, cf. compound; of a hair or an inflorescence, not branched;

simple perforation: of a vessel element, the end walls having completely broken down and so leaving a single aperture, cf. scalariform.

simple pit: of vascular pits, with the opening the same width as the base, cf. bordered, scalariform, vestured.

simple polyembryony: where there is more than one embryo per ovule because of the development of more than one fertilised egg, cf. adventitious (poly)embryony, cleavage polyembryony.

simultaneous: of microsporogenesis where cell wall formation occurs only at the second meiotic division, the resultant tetrads being tetrahedral, sometimes associated with trichotomosulcate pollen, cf. successive.

sinapic acid: a monosaccharide ester of a hydroxycinnamic acid, cf. caffeic acid, ferulic acid, p-coumaric acid.

sinapine, sinigrine: methyl glucosinolates.

Sinapine, C16 H24 N O5.

sinistrorse = counterclockwise, cf. dextrorse or clockwise.

sinuate, sinuous: with horizontal, wave-like depressions, e.g. along a margin, not necessarily with teeth, cf. biserrate, crenate, dentate, entire, serrate, undulate.

siphonogamy: the process of fertilisation in which an elongated pollen tube delivers the non-flagellated gametes directly to the egg apparatus, cf. zooidogamous.

siphonostele: a variant of a stele in which the central vascular column is medullated, i.e. has pith, see amphiphloic, ectophloic, cf. atactostele, eustele, dictyostele (this is a dissected amphiphloic siphonostele!), protostele.

sister group: a clade that joins the tree immediately adjacent to a clade just mentioned, cf. in group, outgroup.

skotophilic: lit. "dark loving".

slime (in phloem sieve elements) = P-protein.

slit: an elongated opening through which pollen escapes from an anther, cf. pore, valve.

slit-monosymmetric: of a monosymmetric flower in which it is as if the corolla has been slit down one side and more or less spread open, cf. bilabiate, papilionoid, personate.

snail gland: cf. colleter, collar rhizoid, dendritic, malpighiaceous, pearl gland, root hair, stellate, T-shaped hair.

softwood: wood of a gymnosperm, usually softer than that from a broad-leaved angiosperm because of the fewer fibers, etc., cf. hardwood.

sole = foot layer.

solenostele = amphiphloic siphonostele.

solitary: of flowers, borne singly, not grouped in an inflorescence.

somatic embryo: an embryo developing from previously differentiated somatic cells, not from a zygote, a term usually used in tissue culture.

sorbitol: a straight-chained hexitol formed by reduction of the carbonyl group of glucose, cf. arabitol, dulcitol, mannitol, and sorbitol.

Sorbitol, C6 H14 O6.

sorus: in ferns, a discrete group of separate sporangia, pl. sori, cf. synangia.

spadix: a spicate inflorescence with congested flowers and a stout, often succulent axis, often more or less surrounded by a spathe, cf. see botryoid, corymb, fascicle, raceme, raceme, thyrse, umbel.

spathe: a large inflorescence bract ensheathing an inflorescence, cf. spadix; spathaceous, like a spathe, with a spathe.

spathella: as in some Podostemaceae, a small, closed membranous sac which envelopes the immature flower, rupturing irregularly as the pedicel elongates at anthesis.

spathulate (= spatulate): spoon-shaped; broad at the tip and narrowed towards the base.

species: a taxon comprising one or more populations of individuals capable of interbreeding to produce fertile offspring and not so interbreeding with other species, or a group of organisms phenetically distinguishable from other such groups, or...., the lowest major rank of the taxonomic hierarchy, cf. class, family, genus, order.

sperm: in general, male gametes, whether motile or not, in angiosperms, the two cells of the male gametophyte that are produced from the generative cell, cf. vegetative cell.

spherical: a general pollen shape descriptor, a radially symmetrical grain in which the polar axis and equatorial diameter are about the same, cf. boat-shaped, globose, oblate, prolate.

sphingophilous: of entomophilous flowers pollinated by hawk moths, often with a distinctive syndrome (long tube, spreading lobes, whitish color, sweet scent, etc.), cf. cantharophilous, melittophilous, myophilous, psychophilous, sapromyophilous.

spike: a racemose inflorescence, unbranched, the flowers sessile, adj. spicate, cf. botryoid, corymb, fascicle, raceme, spadix, thyrse, umbel. Note that the inflorescence of grasses like barley (Hordeum), etc. are not spikes in the strict sense, since the flowers are borne on congested lateral branches.

spikelet: a unit of the inflorescence, especially in grasses, sedges and some other monocotyledons, a racemose unit consisting of one to many closely-packed flowers and associated glumes, etc.

spine: a stiff, vascularised, sharp-pointed structure, formed from a leaf or part of a leaf such as a stipule, leaf tooth, etc., cf. prickle, thorn.

spinose: a leaf tooth in which the principal vein projects beyond the non-glandular apex, cf. begonioid, chloranthoid, cucurbitoid, cunonioid, dillenioid, malvoid, monimioid, platanoid, rosoid, salicoid, theoid, urticoid, violoid.

spinose: of pollen, = echinate.

spiral: of leaves or floral organs, borne singly at different levels on the axis, the insertion points of successively initiated structures forming a spiral, cf. alternate, bijugate, decussate, distichous, opposite, pseudoverticillate, spiromonistichous, tristichous, whorled.

spiromonistichous: of leaves or floral organs, borne in a single rank in a spiral along the axis, cf. alternate, bijugate, decussate, distichous, opposite, pseudoverticillate,spiral, tristichous, whorled.

split lateral: of the nodal anatomy of some plants with opposite leaves, where traces departing from the central vascular cylinder at the midpoints between the two leaves divide into two, one part proceeding to each of the leaves, cf. multilacunar, trilacunar, unilacunar, see also flank bridges.

spodogram: literally "ash letter", the mineral cystoliths, etc., remaining after calcining a leaf.

spongy: especially of leaf mesophyll, but of tissues in general, where the cells are little elongated and not closely packed, there being large intercellular spaces, cf. palisade.

sporangium: a structure within which spores are formed, pl. sporangia, in seed plants, see anther and its thecae (really synangia) in turn made up of endothecium, exothecium, placentoid, and tapetum, all of a microsporangium, and also the nucellus + megaspore(s), both of a megasporangium, part of an ovule; for vascular plants in general, see the two basic kinds, eusporangium/giate and leptosporangium/giate.

spore: a haploid reproductive structure produced after meiosis marking the end of the sporophytic phase of the life cycle, germinating to produce the gametophyte, see megaspore and microspore/pollen (kinds of spores) and endosporic and exosporic (development of spores).

sporocarp: in aquatic ferns, the hard, protective structure enclosing the megasporangia and microsporangia.

sporocyte: a cell that undergoes meiosis and produces spores, see megasporocyte, microsporocyte.

sporoderm: the entire wall of a pollen grain or spore, i.e. perine + exine + intine, or perispore + exospore + endospore.

sporogenous: spore-generating.

sporophore: a structure bearing sporangia alone, cf. tropophore.

sporophyll: a more or less leaf-like organ on which one or more sporangia are borne, see megasporophyll (carpel), microsporophyll (stamen), and strobilus, cf. tropophyll.

sporophyte: the diploid phase of the life cycle of a land plant (alternation of generations), a plant that bears spores formed by meiotic events, cf. gametophyte.

sporopollenin: the most highly decay- and chemical-resistant biopolymer known, made up of cross-linked phenolics and hydrocarbons that covers pollen grains in particular and embryophyte spores in general (but not the megaspore in flowering plants).

sport = mutant.

spring wood = early wood.

spur: a tubular pouch at the base of a perianth part, often containing nectar

spur shoot = short shoot.

stachyose: an oligosaccharides made up of four sugar units, two galactose, one glucose, and one fructose, serially linked, cf. raffinose.

stachysporous: of sporangia borne directly on a stem, cf. phyllosporous.

stamen: a microsporophyll, a member of the androecium, made up of anther, connective, and filament, and variously fused, see diadelphous, fascicle, monadelphous, phalangiate, syngenesious.

staminal corona: in Apocynaceae-Asclepiadoideae, fleshy outgrowths of tissue, attached abaxially to the staminal column at the bases of the filaments or on the backs of the anthers, see gynostegial corona.

staminal retinaculum: in Apocynaceae-"Apocynoideae", connective tissue between the the anther thecae and the top of the filament, involved in the adnation of the anthers to the stigmatic head.

staminate: (of a flower) with functional stamens only, cf. carpellate, neuter, perfect.

staminode: a sterile stamen, minute and practically invisible to large and petaloid, sometimes bearing an antherode.

standard: a relatively large adaxial petal (or petals) in a papilionoid flower, cf. keel, wings.

stapetalum: referring to the length of corolla tube with fused/adnate stamens (the term synstapetalum may be used instead), cf. apostapetalum, cf. also hypanthium, stemonozone.

starch: a more or less coiled-chain polysaccharide made up of alpha glucose units, see amylose and amylopectin, and staining black with an iodine/potassium iodide solution, cf. amyloid, callose, cellulose, hemicellulose, inulin, pectin, polyol.

starch grain: alternating layers of amylose and amylopectin (starch laid down aroun a more or less central point or hilum; the grains may be either simple or compound.

starch sheath: the outer and starch-containing layer of cells of a two-layered bundle sheath surrounding a vascular bundle, cf. mestome sheath, parenchyma sheath.

staurocytic: of stomata, with four (three to five) subsidiary cells each oblique to the long axis of the guard cells, cf. actinocytic, allelocytic, anisocytic, anomocytic, cyclocytic, diacytic, helicocytic, laterocytic, paracytic, parallelocytic, stephanocytic, tetracytic.

stegmata: SiO₂-containing cells usu. adjacent to vascular tissue, the wall adjacent to the underlying sclerenchyma thick, the anticlinal walls thinner, and the outer periclinal wall thinnest; the term rarely used when the cells are epidermal.

stele: a column of primary vascular tissue in the root and stem and any tissue that it surrounds, cf. cortex, epidermis, see atactostele, eustele, protostele (of which actinostele, haplostele, and plectostele are variants), siphonostele (of which a dictyostele, amphiphloic siphonostele and ectophloic siphonostele are variants), also polystely.

stellate: star-shaped, e.g. of a hair, cf. colleter, collar rhizoid, dendritic, malpighiaceous, pearl gland, root hair, snail gland, T-shaped hair, also used to describe indumentum, cf. arachnoid, arbuscular, canescent, glabrescent, <