page_title: Glossary of botanical terms
section_title: V
hierarchical_section_title: Glossary of botanical terms / V
caption_attribution_description: English: Cross section of dicotyledonous vascular bundle in stem of Rumex, with labels attached A: Phloem B: Cambium C: Xylem D: Fibrous sheath of the vascular bundle
context_page_description: This glossary of botanical terms is a list of definitions of terms and concepts relevant to botany and plants in general. Terms of plant morphology are included here as well as at the more specific Glossary of plant morphology and Glossary of leaf morphology.
context_section_description: vallecular canal
  A resin canal coinciding with a longitudinal groove in the seeds of Asteraceae.  A longitudinal cavity in the cortex of the stems of Equisetum, coinciding with a groove in the stem surface.
  valvate
  (of sepals and petals in bud) Meeting edge-to-edge but not overlapping.
  valve
  A portion of an organ that fragments or splits open, e.g. the teeth-like portions of a pericarp in a split (dehisced) capsule or pod when ripe.
  var.
  An abbreviation of varietas.
  variant
  A plant or group of plants showing some measure of difference from the characteristics associated with a particular taxon.
  variegated
  Irregularly marked with blotches or patches of another colour.
  varietas
   A taxonomic rank below that of species and between the ranks of subspecies and form.
  vascular
  Referring to the conducting tissues (xylem and phloem) of vascular plants.
  vascular bundle
  A bundle of vascular tissue in the primary stems of vascular plants, consisting of specialised conducting cells for the transport of water (xylem) and assimilate (phloem).
  vasculum
  A container used by botanists for collecting field specimens.
  vein
  A strand of  tissue, e.g. in the leaves of vascular plants.
  veinlet
  A small vein; the ultimate (visible) division of a vein.
  velamen
  A spongy tissue covering the aerial roots of orchids and some other epiphytes.
  velutinous
  See velvety.
  velvety
  Densely covered with fine, short, soft, erect hairs.
  venation
  The arrangement of veins in a leaf.
  ventral
  From Latin venter, meaning "belly". The opposite of dorsal. Partly because the term originally referred to animals rather than plants, usage in botany is arbitrary according to context and source. In general "ventral" refers to "the belly or lower part", but in botanical usage such concepts are not always clearly defined and may be contradictory. For example:
  facing towards the axis (adaxial) in referring to a lateral organ of an erect plant
  facing towards the substrate in any part of an erect plant, for example the lower surface of a more or less horizontal leaf (abaxial)
  facing towards the substrate in a prostrate or climbing plant.
  
  For more detail see dorsal.
  vernation
  The arrangement of unexpanded leaves in a bud; the order in which leaves unfold from a bud.
  vernonioid
  In the Compositae, style with sweeping hairs borne on abaxial surfaces of style branches.
  verruciform
  Wart-like in form.
  verrucose
  Having warts.
  verruculose
  Minutely verrucose; minutely warty.
  versatile
  (of anthers) Swinging freely about the point of attachment to the filament.
  verticillate
  Arranged in one or more whorls, i.e. several similar parts arranged at the same point of the axis, e.g. leaf arrangement. Compare pseudoverticillate (appearing whorled or verticillate but not actually so).
  verticillaster
  A type of pseudoverticillate inflorescence, typical of the Lamiaceae, in which pseudo-whorls are formed from pairs of opposite cymes.
  vesicular
  (of hairs) Bladder-like; vesciculous, bearing such hairs.
  vessel
  A capillary tube formed from a series of open-ended cells in the water-conducting tissue of a plant.
  vestigial
  Reduced in form and function from the normal or ancestral condition.
  villous
  Abounding in or covered with long, soft, straight hairs; shaggy with soft hairs.
  vine
  1.  Scandent plants climbing by means of trailing or twining stems or runners.
  2.  Such a stem or runner.
  3.  A member of the genus Vitis.
  virgate
   
  Wand-shaped, twiggy, especially referring to erect, straight stems. In mycology, referring to a pileus with radiating ribs or lines.
  Viridiplantae
  A clade of autotrophic organisms that includes the green algae, Charophyta and land plants, all of which have cellulose in their cell walls, chloroplasts derived from primary endosymbiosis with Cyanobacteria that contain chlorophylls a and b and lack phycobilins.
  viscid
  Sticky; coated with a thick, syrupy secretion.
  viviparous
  1.  Referring to seeds or fruits which germinate before being shed from the parent plant.
  2.  The development of plantlets on non-floral organs, e.g. leaves.
caption: Photomicrograph of cross section of vascular bundle in the stem of a typical herbaceous dicotyledon. A: Phloem  
  B: Cambium 
   C: Xylem
   D: Fibrous sheath of vascular bundle
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