vacuolar adj. See vacuole.

vacuolate (L. vacuus: empty) adj. Having a vacuole or vacuoles. Also vacuolated.

vacuolated See vacuolate.

vacuole (L. vacuus: empty) n. One of a number of different types of membrane-bound organelles in cells. Plant cells are typically characterized by having a large vacuole that may occupy over 90% of the cell's volume and contributes to the cell's turgor. The vacuole is also a site for the storage of various metabolites or pigments (as in beetroot cells). Vacuoles may be present in animal cells where they have a number of storage or metabolic functions including the 'food vacuoles' of phagocytes.

vagina (L. vagina: sheath) n. A sheath, as the sheathing petiole in grasses.

vaginate (L. vagina: sheath) adj. Sheathed; having a vagin or sheath.

vaginiferous (L. vagina: sheath; ferre: to carry) adj. Bearing sheaths.

vaginula n. (pl. vaginulae) A ring or sheath enveloping the base of the seta, derived from the base of the archegonium and surrounding stem tissue and remaining after the separation of the calyptra. Cf. ochrea, epigonium.

vaginulae Srr vaginula.

vallecula (L. vallecula: small valley) n. (pl. valleculae) A furrow, groove or depression in an organ or other part.

valleculae See vallecula.

vallecular (L. vallecula: small valley) adj. Of or pertaining to the valleculae.

vallecular canal Air-filled canals in the cortical (cortex) tissue of some sphenophytes that alternate with the vascular bundles.

valleculate (L. vallecula: small valley) adj. Having a vallecula or valleculae.

valvate (L. valvatus: with doors) adj. Meeting at the edges. e.g. a flower with the petals or sepals edge to edge along their entire length, without overlapping; opening as if by doors or valves, as in many dehiscent fruits.

valve (L. valvę: door) n. One of the segments of a dehiscent fruit, separating from other such segments at maturity; one of the parts or partially detached flap of tissue into which the capsule of most liverworts and hornworts separates upon dehiscence; e.g. Andreaea.

valved adj. With valves.

valvular (L. valvę: door) adj. Of or pertaining to valves; anther dehiscence through flap-covered pores.

var. See variety.

varicose (L. varicosus: with varices) adj. Swollen or enlarged in places.

variegated (L. variegatus: varied, shaded, nuanced) adj. Marked, striped, or blotched with some color in addition to the plant's general overall color.

variety (L. varietas: diversity, variety) n. The rank of taxa below subspecies but above forma; a plant which retains most of the characteristics of the species, but differs in some way such as flower or leaf color, size of mature plant, etc. A variety is added to the specific binomial and preceded by `var'., such as saxatilisi in the epithet Juniperus communis var. saxatilis. The variety is now largely abandoned as a botanical confusion with horticultural varieties.

vascular (L. vasculum: small vase) adj. Specialised for conduction of fluids. Refers to the xylem and phloem tissues, which conduct water and nutrients through the plant body.

vascular bundle n. A long continuous strand of conducting (vascular) tissue in tracheophyte plants that extends from the roots through the stem and into the leaves. It consists of xylem and phloem, which are separated by a cambium in plants that undergo secondary thickening. Syn. fascicle. See vascular tissue.

vascular cambium Lateral meristem that forms the secondary tissue and is located between the xylem and phloem.

vascular parasite Non-green plant growing on living, green plants. Indian-pipe (Monotropa uniflora) is a good example of a vascular parasite.

vascular plant The familiar woody and herbaceous plants, (Tracheata), are distinguished from the non vascular plants, mosses (Bryophyta), liverworts (Hepatophyta) and hornworts (Anthocerophyta), by their vascular system, lignified conducting tissues called xylem and phloem.

vascular ray A radiate band of parenchyma in the secondary xylem extending into the secondary phloem of the stems of certain vascular plants, formed by the cambium and serving for the storage of food and the conduction of nutriments.

vascular semi-parasite Green plant growing attached to other living, green plants. Many plants, such as eastern North American native gerardia (Agalinis purpurea), photosynthesize but also supplement their nutrients by parasitizing other plants.

vascular system A transport system in organisms. Examples are the blood system of animals, and the xylem and phloem (vascular bundles) of some plants. The system of vascular tissue in plants.

vascular tissue The tissue that conducts water and nutrients through the plant body in higher plants (tracheophytes). It consists of xylem and phloem. Since the xylem and phloem tissues are always in close proximity to each other, distinct regions of vascular tissue can be identified (see vascular bundle). The possession of vascular tissue has enabled the higher plants to attain a considerable size and dominate most terrestrial habitats.

vasculate (L. vasculum: small vase) adj. Vase-shaped.

vasculum (L. vasculum: small vase) n. (pl. vascula, vasculums) A kind of case or box used by botanists for carrying specimens as they are collected.

vasoconstrictive adj. See vasoconstrictor.

vasoconstrictor adj., n. Causing vasoconstriction. A drug, agent, or nerve that causes narrowing (vasoconstriction) of the walls of blood vessels. Also vasoconstrictive.

vasodilator adj., n. Causing vasodilation. A drug, agent, or nerve that can cause dilation (vasodilation) of the walls of blood vessels.

vegetative adj. Of or pertaining to the non-floral parts of a plant; relating to growth and nutrition rather than to reproduction.

vegetative cell The larger cell of the male gametophyte of angiosperms that does not divide further.

vegetative growth Growth of a plant by division of cells, without sexual reproduction.

vegetative propagation A form of asexual reproduction in plants whereby new individuals develop from specialized multicellular structures (e.g. tubers, bulbs) that become detached from the parent plant. Examples are the production of strawberry plants from runners and of gladioli from daughter corms. Artificial methods of vegetative propagation include grafting (see graft), budding, and making cuttings.

vegetative reproduction See vegetative propagation.

vein (L. vena: vein) n. A vascular bundle, usually visible externally, as in leaves. A strand of vascular tissue.

veined adj. With vein.

veinlet (diminutive of L. vena: vein) n. A small vein. Aussi venule.

vela See velum.

velamen (L. velamen, velaminis: covering) n. (pl. velamina) A membrane; a water-storing tissue in the outer layer of some roots; a water-retaining outer layer of the aerial roots of some epiphytes, especially orchids. Syn. velamentum

velamenta See velamentum.

velamentum (L. velamentum: covering) n. (pl. velamenta) See velamen.

velamina See velamen.

veld n. The open country, bearing grass, bushes, or shrubs, or thinly forested, characteristic of parts of southern Africa.

velum (L. velum: veil, curtain, drape) n. (pl. vela) A membranous covering; a veil. The membranous flap of tissue partially covering the sporangium of Isoėtes. A ragged ring of tissue that remains on the stalk of a mushroom or toadstool, formed from the ruptured membrane that originally covered the lower surface of the cap.

velutinous adj. Clothed with velvety indumentum comprised of erect straight dense moderately firm hairs.

venation (L. vena: vein) n. The arrangement and pattern of veins in a leaf.

venenose (L. venenosus: poisonous) adj. poisonous.

venomous (L. venenum: any kind of drug, poison) adj. Poisonous.

venose (L. venosus: full of veins, venous) adj. Veiny; venous.

venous (L. venosus: full of veins, venous) adj. Of or pertaining to veins; vein-like.

venter n. (pl. ventri, venters) The wollen basal portion of an archegonium, containing the ovum. Cf. epigonium, calyptra.

ventral (L. venter, ventris: belly) adj. Belonging to the anterior or inner face of an organ; the opposite of dorsal; adaxial.

ventri See venter.

ventricose (L. venter, ventris: belly) adj. Inflated or swollen on one side only, as in some corollas, especially in the genus Penstemon.

venulation (L. venula: small vein) n. Diminutive of venation, referring to the pattern of veinlets on a leaf.

venule (L. venula: small vein) See veinlet.

venulose (L. venula: small vein) adj. With veinlets. Also venulous.

venulous (L. venula: small vein) adj. See venulose.

vermicidal adj. See vermicide.

vermicide n. Any substance used to kill worms.

vermicular (L. vermiculus: small worm) adj. Consisting of or characterized by sinuous or wavy outlines or markings resembling the forms or tracks of a worm. Also vermiculate.

vermiculate (L. vermiculus: small worm) adj. See vermicular.

vermiform (L. vermis: worm; forma: shape) adj. Worm-shaped. Also vermiformous.

vermiformous (L. vermis: worm; forma: shape) adj. See vermiform.

vernacular n. The everyday language spoken by a people as distinguished from the literary or scientific language. The common, nonscientific name of a plant or animal. adj. Relating to or designating the common, nonscientific name of a plant or animal.

vernal (L. vernalis: relative to spring) adj. Belonging to the spring; appearing or occurring in spring; of the spring season, appropriate to spring. (e.g. vernal equinox).

vernally adv. See vernal.

vernation (L. vernare: to be in the spring) n. The arrangement of unexpanded leaves in a bud. Cf. aestivation.

vernicose adj. Shiny; with a varnished appearance and texture.

verrucose (L. verrucosus: bearing a wart) adj. Warty; having little warts or wartlike growth on the surface.

verruculose (diminutive of L. verrucosus: bearing a wart) adj. Covered with very small wart-like elevations.

versatile (L. versatillis: mobile, that turns easily) adj. Turning freely on its support, attached near the middle rather that at one end, as an anther attached near the middle and capable of swinging freely on the filament. Cf. basifixed and dorsifixed.

versicolor (L. versicolor; with changing colors, with many hues) adj. Of various colors; changeable in color.

vertebrate n. Any animal that has a spinal column containing bone marrow. Current vertebrates mainly consist of fish, reptiles (two truncated lines of descent), batrachians, birds and mammals (three clades).

vertical (L. verticalis: vertical) adj. Positioned lengthwise, in the same direction as the axis; leaves positioned with the blade perpendicular, so that neither surface is obviously the upper or lower.

verticil (L. vertex, verticis: whirl) n. An arrangement of leaves, flowers, inflorescences, or other structures which surround the stem in a circle upon the same plane about the same point on the axis.

verticillaster n. A cymose inflorescence resembling a whorl but actually arising in the axils of opposite bracts, as in most mints.

verticillastrate adj. See verticillaster.

verticillate (L. vertex, verticis: whirl) adj. Growing in a whorl or arranged on the same plane around an axis, as flowers, leaves, branches, etc.; arranged in verticils, whorled.

vesicant adj., n. See vesicatory.

vesicate v. To blister or become blistered.

vesication n. A blister. The formation of a blister.

vesicatory adj., n. Causing blisters. A chemical agent that causes blistering. Syn: vesicant.

vesicle (L. vesicula: bladder, pod) n. Any small bladder-like structure, cavity, sac, or cyst; a small bladderlike sac filled with air.

vesicular See vesiculose.

vesiculose adj. Inflated, bladderlike; of or relating to vesicles; having the form of a vesicle; composed of or containing vesicles. Also vesicular.

vespertine adj. Opening or functioning in the evening.

vessel n. A capillary tube formed from a series of open-ended cells in the water conducting tissue of a plant. A tube-like xylem structure composed of vessel elements attached end to end.

vessel element A type of cell occurring within the xylem of flowering plants, many of which, end to end, form water-conducting vessels. Vessel elements are frequently very broad and have side walls thickened by deposits of lignin over most of the surface area. However, the end walls are broken down to provide connections with the cells both above and below them. Cf. tracheid.

vestigial (L. vestigium: footprint, trace) adj. An organ or structure which is much reduced rom the ancestral condition and likely nonfunctional, though believed at one time to have been more perfectly formed. Cf. rudimentary.

vestiture (L. vestitus: clothings) n. The epidermal coverings of a plant, collectively. Also vesture.

vesture (L. vestis: clothings) See vestiture.

vestured adj. Said of pits, bordered in particular, and more or less lined with small projections or vestures that are branched or not.

vexilla See vexillum.

vexillum (L. vexillum: flag) n. (pl. vexilla) The upper and usually largest petal of a papilionaceous flower, as in peas and sweet peas.

viatical adj. Growing by roadsides or paths.

vicariance (L. vicarius: substitute) n. Speciation which occurs as a result of the geographical separation and subsequent isolation of portions of an original population, so that two closely related species or a species pair result, one species being the geographical counterpart of the other. Also vicariation.

vicariation See vicariance.

vicarious adj. Phylogenetically closely related taxa replacing each other ecologically in different areas. See vicariance.

villi See villus.

villose See villous.

villosulous (diminutive of L. villosus: hairy) adj. Diminutive of villous.

villous (L. villosus: hairy) n. Pubescent; shaggy; covered with fine long hairs, but the hairs not matted, not interwoven. Cf. hirsute. Also villose.

villus (L. villus: hair) n. (pl. villi). A long, soft, shaggy hair, covering the fruit, flowers, and other parts of certains plants.

vimen (L. vimen, viminis: any flexible wood) n. (pl. vimina) A long, flexible shoot of a plant.

vimina See vimen.

vimineous (L. vimineus: made of folding wood) adj. With long, flexible twigs; composed of twigs; twig-like.

vinaceous (L. vinaceus: grape skin) adj. Of the color of red wine; Of, pertaining to, or resembling wine or grapes.

vine (L. vinea: vine) n. A plant with the stem not self-supporting, but climbing or trailing on some support.

vinicolor (L. vinum, vini: wine; color; color) adj. See vinaceous.

viny adj. Of, pertaining to, of the nature of, or resembling vines.

violaceous (L. violaceus: violet-colored) adj. Bluish-purple; violet-colored; of or pertaining to the Violaceae.

violoid adj. Said of a leaf tooth in which the medial vein ends in opaque persistent glanduar termination, no laterals are involved.

virescence (L. virescere: to become green) n. The state of becoming somewhat, though usually not totally, green, due to the abnormal presence of chlororphyll.

virescent (L. virescere: to become green) adj. Becoming green; greenish. Also viridescent.

virgate (L. virga: rod, stick) adj. Wand-like; straight, slender, slim and erect.

Virgilian n. The final series in the Pennsylvanian of N. America, underlain by the Missourian, overlain by the Wolfcampian (Permian), and roughly contemporaneous with the upper Chamnovnicheskian and Dorogomilovskian Stages of the Kasimovian Series plus the Gzelian Series.

viridescent (L. viridescere: to become green) adj. See virescent.

viscid (L. viscidus: viscous, sticky) adj. Thick, sirupy, and sticky, viscous; covered with a viscid substance as of leaves; gummy.

viscidia See viscidium.

viscidium (L. viscidus: viscous, sticky) n. (pl.viscidia) A sticky structure on the pollinia of the Orchidaceae which attaches to a pollinator.

viscidulous (diminutive of L. viscidus: viscous, sticky) adj. Slightly sticky.

viscin n. A clear, viscous, tasteless substance extracted from the mucilaginous sap of the mistletoe (Viscum album), holly, etc., and constituting an essential ingredient of birdlime.

Visean 1. An epoch in the Mississippian, comprising the Chadian, Arundian, Holkerian, Asbian, and Brigantian Ages (these are also stage names in western European stratigraphy). The Visean is preceded by the Tournaisian, followed by the Serpukhovian, and dated at 349.5 to 332.9 million years ago. 2. The name of the corresponding European series which has its lower boundary at the base of the Chadian Stage near Clitheroe, Lancashire, England. It is roughly contemporaneous with the upper Carboniferous Limestone Series (Britain), and the upper Osagean, Meramecian, and lower Chesterian (N. America). See also Dinantian.

vitamin A A fat-soluble vitamin and an essential constituent of the visual pigments of the eyes. It also functions in the maintenance of healthy mucous membranes. Vitamin A deficiency leads to dryness of membranes lining the mouth and respiratory tract, blindness, and defective growth. Sources include liver, fish-liver oils, and egg yolk, while precursors of vitamin A, such as beta-carotene, occur in green plants and vegetables (e.g. carrots). Syn. retinol.

vitiligo n. An idiopathic, probably autoimmune, condition characterized by destruction of melanocytes in small or large circumscribed areas of the skin, resulting in patches of depigmentation often having a hyperpigmented border, and often enlarging slowly.

vitreous (L. vitreus: in glass, of glass) adj. Transparent.

vitta (L. vitta: link, ribbon) n. (pl. vittae) An oil tube in fruit (the carpel walls) of some plants, as of the fruits of the Umbelliferae (Apiaceae). A streak or stripe, as of color. A band or ribbon. In liverworts the longitudinal stripe of longer, often thicker-walled cells in a leaf lamina resembling a nerve but only one cell layer thick; e.g. Herbertus. Cf. costa.

vittae See vitta.

Vittariaceae n. A family of the phylum Filicinophyta.

vittate (L. vittatus: ornate with ribbon) adj. Having vittae; striped longitudinally.

viviparous (L. viviparus: viviparous) adj. Of seeds or fruits, germinating before being shed from the parent plant. Sprouting on the parent plant, as the bulblets forming in some inflorescences.

volute (L. voluta: volute) adj. Rolled up. Also voluted.

voluted See volute.

voucher n. A specimen preserved from nature to serve for future reference, especially for comparative evidence in experimental and chemical studies,

vulnerary adj., n. Used in the healing or treating of wounds. A remedy used in healing or treating wounds.