North American Orchid Conservation Center

Glossary: R

raceme raceme
A long array of flowers (inflorescence) with stalks (pedicles), each of which grows directly from the main axis (rachis) of the inflorescence.
rachilla rachilla
The main axis of the spikelet in grasses (Poaceae), which bears the spikes.
rachis rachis
The central axis of the frond that bears the pinnae in ferns.
rame rame
A long inflorescence containing both sessile and stalked flowers (as in Poaceae).
ramentum ramentum
The scales on a plant (usually used with a fern rachis).
rank
Assessment of a species' current level of security, taking into account rarity, number of individuals and sightings, ecological vulnerability, and threats to its existence. Ranks are meant to be an objective assessment of species' rarity and to aid in policy decisions but carry no legal protections. .
rare
A species with low population levels, at risk of becoming threatened.
ray floret ray floret
Flower with a single, long strap-like "ray" petal that forms the outer ring of a composite head (i.e., the "petals" of a daisy).
receptacle receptacle
The base of a flower, comprised of the enlarged top of the stalk, which holds some or all of the flower parts. In the Asteraceae (aster family), the receptacle is formed from the enlarged top of the peduncle that holds many small flowers (florets).
recurved recurved
Bent or curved downward.
reduced reduced
Lower or smaller than normal.
reflexed reflexed
Abruptly bent backward or downward.
remote remote
Separated from others of same form (as in a flower produced at a distance from other flowers on the same stem).
reniform reniform
Kidney-shaped.
replum replum
Placenta that forms the partition between separating valves of a silique (in Brassicaceae).
resupinate resupinate
Common condition in orchids that describes flowers that appear upside-down because of twisting of the pedicel- the lip is located on the bottom.
reticulate reticulate
Net-veined or with ribs that inter-connect to form a honeycomb pattern.
retrorse retrorse
Pointing downward or inward toward the basal end.
retuse retuse
With a terminal notch in an otherwise blunt or rounded apex.
revolute revolute
Rolled under, toward the abaxial surface.
rhizoids rhizoids
Epidermal hairs that anchor the protocorm and absorb water and nutrients from the environment.
rhizomatous rhizomatous
Proliferating by means of underground, horizontal stems (rhizomes).
rhizome rhizome
Underground, horizontal stem.
rhombic rhombic
Diamond-shaped.
root root
The underground part of a plant that anchors the plant to the ground and absorbs nutrients and water.
rosette rosette
A circle of tightly packed leaves, usually at ground level.
rostellum rostellum
A slender projection like a bird beak; on orchids, an outgrowth of the column that keeps the stigma lobe separate from the anthers to avoid self-pollination.
rounded rounded
With a gently curving outline.
Rubrica nasuta Rubrica nasuta
Sand Wasp, photo ©Gustavo Fernando Durán.
rudimentary
Small and arrested early in development.
rugose rugose
Rough or wrinkled.
rugulate rugulate
Covered with low, mounded ridges or wrinkles, not forming a honeycomb pattern; usually refers to the texture of a quillwort (Isoetes) megasphore.
runner runner
The ultimate branch of a stolon or rhizome.