page_title: Glossary of botanical terms
section_title: R
hierarchical_section_title: Glossary of botanical terms / R
caption_attribution_description: Slika 431. Regrat. (Leóntodon Taráxacum [sic!].)
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: raceme
   An indeterminate inflorescence in which the main axis produces a series of flowers on lateral stalks, the oldest at the base and the youngest at the top. Compare spike. Also racemiform or racemoid - having the form of a raceme
  rachilla (rhachilla)
  the axis of a grass spikelet, above the glumes.
  rachis
   
  The axis of an inflorescence or a pinnate leaf; for example ferns; secondary rachis is the axis of a pinna in a bipinnate leaf distal to and including the lowermost pedicel attachment.
  radial
  With structures radiating from a central point as spokes on a wheel (e.g. the lateral spines of a cactus).
  radiate
  (of daisies, of a capitulum) With ray florets surrounding disc florets.
  radical
  Springing from the root; clustered at base of stem.
  radicle
  The part of an embryo giving rise to the root system of a plant. Compare plumule.
  rainforest
  A moist temperate or tropical forest dominated by broad-leaved trees that form a continuous canopy.
  ramet
  An individual member of a clone.
  ramicaul
  a single-leafed stem, as in Pleurothallis orchids.
  ray
  1.  zygomorphic (ligulate) flowers in a radiate flowerhead, that is, ray-florets/flowers, for example Asteraceae.
  2.  each of the branches of an umbel.
  receptacle
  the axis of a flower, in other words, floral axis; torus; for example in Asteraceae, the floral base or receptacle is the expanded tip of the peduncle on which the flowers are inserted.
  recumbent
  bent back towards or below the horizontal.
  recurved
  bent or curved backwards or downwards.
  reduplicate
  folded outwards, or with the two abaxial surfaces together.
  reflexed
  bent sharply back or down.
  registered name
  a cultivar name accepted by the relevant International Cultivar Registration Authority.
  registration
  1.  the act of recording a new cultivar name with an International Cultivar Registration Authority.
  2.  recording a new cultivar name with a statutory authority like the Plant Breeder’s Rights Office.
  3.  recording a trademark with a trade marks office.
  regular
  See actinomorphic.
  reniform
  Kidney-shaped.
  replum
  a framework-like placenta to which the seeds attach, and which remains after each valve drops away.
  resupinate
  1.  In botany, describing leaves or flowers that are in an inverted position because the petiole or pedicel, respectively, is twisted 180 degrees. compare: #hyper-resupinate
  2.  In lichenology, referring to either having or being a fruiting body that lies flat on the substrate, with the hymenium either over the whole surface or at the periphery.
  reticulate
  forming a network (or reticulum), e.g. veins that join one another at more than one point.
  retrorse
  Bent backwards or downwards. Compare antrorse.
  retuse
  Having a blunt (obtuse) and slightly notched apex.
  revision
  an account of a particular plant group, like an abbreviated or simplified monograph.  Sometimes confined to the plants of a particular region.  Similar to a monograph in clearly distinguishing the taxa and providing a means for their identification. Compare monograph.
  revolute
  rolled under (downwards or backwards), for example when the edges of leaves are rolled under towards the midrib. Compare involute.
  rhachis
  See rachis.
  rhizine
  The "root" or "trunk" projection of a foliose lichen that attaches the lichen to the substrate (what the lichen is growing on)
  rhizodermis
  the root epidermis, the outermost primary cell layer of the root
  rhizome
  a perennial underground stem usually growing horizontally.  See also stolon. Abbreviation: rhiz.
  rhizomatous
  adj. a plant whose above ground stem is derived from a below ground stem (rhizome). cf. arhizomatous (arhizomatic)
  rhizosphere
  the below-ground surface of plants and adjacent soil as a habitat for microorganisms.
  rhytidome
  the dead region of the bark that lies outside the periderm.
  rhombic
  like a rhombus: an oblique figure with four equal sides. Compare trapeziform, trullate.
  rhomboid
  a four-sided figure with opposite sides parallel but with adjacent sides an unequal length (like an oblique rectangle); see also rhombic.
  rhomboidal
  a shape, for instance of a leaf, that is roughly diamond-shaped with lengt
caption: The runcinate lobes of a Taraxacum officinale leaf point downwards, i.e. towards the stem
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