Glossary - general

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Idioblast – isolated specialized cells containing non-living substances, such as reserve nutrients, excretory materials, pigments, minerals, oil, latex, gum, resin, tannin, crystals (of calcium oxalate, carbonate or silica)

Imbricate aestivation – when the adjacent sepals/petals partly overlap like tiles

Imbricate-quincuncial aestivation – a type of imbricate aestivation, where two sepals/petals are completely external, two completely internal, and one with one margin overlapping and the other overlapped

Immersed – sunk completely into

Imparipinnate leaf – unevenly or odd-pinnate, i.e. pinnate with a single terminal leaflet

Imperfect flowers – with one set of the sexual parts normally present, the other set (e.g. stamens) absent

Imperforate tracheary element – common term of tracheids, fibre tracheids and libriform fibres

Imperforate tectum (of pollen grains) – absence of holes in the tectum

Impervious – impassable to fluid

Inaperturate pollen grain – omniaperturate pollen grain; pollen grain without any opening or aperture; the pollen tube germinates through any part of the pollen wall (usually the side adjacent to the stigmatic receptive surface)

Inappendiculate – without appendage

Incipient – beginning

Incised – cut rather deeply; this term is intermediate between toothed and lobed

Included – not protruding from the surrounding structure or organ – Opposite: exserted

Included phloem – phloem islands surrounded by xylem in the secondary vascular tissue; cambium present between phloem and xylem

Incompletely tenuinucellar ovule – the ovule has a megasporangium in which the meiocyte is covered at the apex only by the epidermis but, in addition, by subepidermal tissue at its flanks and/or by more tissue at the megasporangium base

Incrassate – thick, stout

Incrassated – made stout

Incrustation – coating of mineral (non-organic) matter

Incubously – inserted obliquely, so that the distal part covers the base of the next one up (e.g. of leaves on a stem)

Incumbent anther – bent adaxially-inwards 90o

Incumbent embryo – with the cotyledons situated face to face and folded sideways so that the radicula lies against the face of one of the cotyledons; ‘in embryos derived from curved ovules the cotyledons are incumbent when they are at right angles to the plane formed by the long axis of the seed plus chalaza’

Incurved – bending inwards

Indefinite shoot growth – continuous

Indehiscent fruit – not splitting open

Indented – marked with a dent, a sharp impression

Indeterminate – (1) (of shoot) capable of more or less indefinite extension; (2) (of inflorescence) with the lower or outer flowers opening before the upper or inner ones, and with the floral axis continuing to grow indefinitely

Indument(um) – any covering consisting of hairs or scales

Induplicate – (Arecaceae) V-shaped in cross-section

Induplicate aestivation – the margins of adjacent sepals/petals incurved (folded inwards) but not overlapping

Induplicate ptyxis – opening along adaxial folds

Indurated – hardened

Induration – hardened part

Indurescent – becoming hardened

Indusium (of flower) – a cup covering the stigma (i.a. in Goodeniaceae)

Inferior ovary – where the calyx is above the ovary; rarely of other flower parts, if inserted below the ovary (not recommended); the flower apex becomes concave during or after formation of the perianth so that the lower part of the gynoecium appears to be sunken into the floral base at anthesis

Inflated – blown up

Inflexed – bent or curved inwards

Inflorescence – the part of the plant that bears the flowers, including all its bracts, branches and flowers, but excluding unmodified leaves

Infra- – below, beneath

Infralocular – positioned below or beneath the ovary locules

Infratectum – part of the ectexine present between the tectum and the foot layer, and including columellae and/or granules

Infructescence – the part of the plant that bears the fruits, including all its bracts, branches and fruits, but excluding unmodified leaves

Infundibuliform – funnel-shaped, i.e. abruptly widening from a narrow cylindrical part to a wider distal part

Innovation – (1) new shoot, which eventually becomes separate from the parent as its lower part dies; (2) (Poaceae) a new shoot which carries on further growth of the plant without becoming detached

Inrolled leaf or petal – with the margins rolled inwards (involute)

Insectivorous – plants deriving (part of) their nutrition from insects they have captured; antiquated term now replaced by ‘carnivorous’, indicating that these plants do not only capture insects, but other animals as well

Inserted – placed in

Intectate pollen grain – without a tectum yet with sculpturing

Integument – the covering of an organ; the outer envelope of an ovule

Integumental tapetum – endothelium; one or several layers of radially elongated and metabolically very active cells in the inner epidermis of the inner (or single) integument; the integumental tapetum is separated from the adjacent megasporangium and megagametophyte by cuticular layers

Inter- – between

Intercalated – inserted, placed between

Intercarinal – between keels or ridges

Intercolpate (of pollen grains) – present between colpi

Intercolpium – see Mesocolpium

Interfascicular cambium – present between the vascular bundles; together with the fascicular cambium developing into an annular cambium during the growth of the stem; the annular cambium produces a cylinder of secondary phloem towards the cortex and secondary xylem inwards

Interfascicular wood rays – present between the vascular bundles

Interlocular – in between the locules of the ovary

Internal phloem – primary phloem present adaxially or internally to the xylem

Internode – the part of the stem between two nodes

Interpetiolar – present between the petioles of opposite leaves; characteristic of stipules in, e.g., Rubiaceae

Interpetiolar stipules – present between the petioles of opposite leaves

Interphyll – (Zingiberales); scale-like and sometimes membranous blade-less leaf (leaf-sheath) usually present on the second node of a unit branch of the shoots in, e.g., Marantaceae

Interspersed – scattered amongst

Interstaminal – present between the stamens

Interstice – (1) part, interval; usually referring to small air spaces; (2) (Araceae) a flowerless part on the spadix

Intertracheary pits (of vessel elements) – bordered or unbordered lateral pits present on the radial vessel walls, forming vessel-to-vessel contacts and often occurring in serial arrangement; intertracheary pits may be opposite, scalariform or alternating

Interxylary phloem – formed by a single internal cambium; the strands of interxylary phloem are intercalated into secondary xylem that has a distribution of vessels not related to the phloem

Intine (of pollen grains) – the innermost of the major layers of the pollen grain wall underlying the exine and bordering the surface of the cytoplasm

Intra- – on the inside of, within

Intracauline – arising from the cortical part of the stem (e.g. adventitious roots in Bromeliaceae)

Intragynoecial compitum – a tract of transmission tissue in the gynoecium which is common to all the carpels of the one flower and that allows pollen grains landing on any one stigma or part of a stigma to fertilize ovules in any carpel

Intrajugal vittae – (Apiaceae) intrajugal secretory canals, intrajugal oil ducts present in the primary ribs above the vascular bundles in the pericarp

Intraluminal columellae (of pollen grains) – columellae present within lumina in a semitectate exine

Intramarginal – within or near the margin

Intramarginal veins – veins present within or close to the leaf margin

Intrapetiolar – present between the petiole and the stem

Intrapetiolar stipules – stipules inserted between the petiole and the stem, i.a. in some Melianthaceae and Erythroxylaceae

Intrastaminal – inserted between stamens and ovary, or within the stamens

Intravaginal squamules (intravaginal scales) – (Alismatales) squamulae intravaginales, squamulae intraaxillares; two to numerous scale-, gland- or colleter-like non-vascularized trichomes present on the adaxial side of the leaf base (leaf axil); intravaginal squamules consist of usually two (sometimes more) layers and numerous cells, and secrete a protective mucilage

Intraxylary phloem – phloem present within the xylem/wood vessel bundle; formed at the margin between pith and primary xylem

Intricate branching – dense, tangled

Introrse anther – opening inwards, towards the centre of the flower

Intrusive – pushing or projecting into another organ

Intrusively parietal placentation – the placenta projects (sometimes deeply) into the ovary locule

Invaginated – enclosed in a sheath

Invagination – enclosing in a sheath

Invasive tapetum – the microsporocytes are in the centre of the anther locule and surrounded by layers of tapetal cells; the tapetal cells may invade the anther locule yet do not fuse; plasmodesmata do not develop at the microsporocyte stage (cf. amoeboid-periplasmodial tapetum); instead the cell walls break down successively in the tapetal cell layers and discharge protoplasm into the anther locule; the tapetum is not enclosed by a perispore membrane; the free microspores are surrounded by the tapetal protoplasm, which degenerates

Inverted vascular bundle – with the xylem outside and the phloem inside

Invested in – clothed in

Involucel – a secondary involucre around the parts of an inflorescence

Involucrate – with an involucre (a cluster of bracts)

Involucral bract – see Involucre

Involucre – a series of bracts, usually inserted close together and appressed, below or around a compact head of flowers (e.g. in Asteraceae)

Involute ptyxis – leaf margins rolled inwards and upwards towards the adaxial surface; frequently occurring in water plants having floating peltate or cordate lamina – Opposite: revolute

Iridaceous – shaped like an Iris leaf, i.e. sword-shaped (ensiform), narrow and acute

Iridescent – many-coloured, with rainbow sheen

Iridiform leaf – resembling an Iris, with a flat leaf the two folded halves of which are fused so that the vascular bundles point both ways

Irregular flower – the parts of the calyx or corolla are dissimilar in size or shape (i.e. asymmetrical or zygomorphic flowers)

Isobifacial leaf – with similar upper and lower surfaces

Isobilateral leaf – a flat leaf without any upper or lower surface

Isodiametric (i.a. of venation) – with an equal diameter in all directions

Isomerous – with the numbers of successive floral organs equal, such as sepals, petals and stamens

Isomorphic leaves – with all leaves on the plant of the same type – Opposite: anisomorphic leaves

Isostylous – see Homostylous

Isthmus – narrowed part connecting two wider parts