Quadrate.   Nearly square to form
Quadrifid.   Cut or divided into four lobes or parts


Quincuncial.   Having five structures, two of which are exterior, two interior, and a fifth with one margin covering interior structure and other margin covered by that of one of the exterior structures


Raceme.   Unbranched, indeterminate inflorescence with pedicelled flowers


Rachilla.   Secondary axis of compound leaf; central axis of a grass or sedge spikelet


Rachis.   The main axis of a pinnately compound leaf; major axis within an inflorescence; axis of a compound fern blade


Radical.   Leaves basal, near ground, usually from caudex or rootstock


Radicle.   Basal end of embryo axis that gives rise to root system


Rameal Sheath.   Leaf sheath on the stem joints, as in Equisetum


Ramentaceous.   Having many thin scales, as on the epidermis of some ferns


Ramose.   Branched


Raphe.   Ridge on seed coat formed from adnate funiculus


Ray.   Secondary axis in a compound inflorescence


Receptacle or Torus.   The region at end of pedicel or on axis to which flower is attached; point on a leaf where sporangia are attached


Receptaculum.   A fleshy structure below the seed formed from the bases of bracts and the swollen receptacle or cone axis; e. g., Acmopyle, and some Podocarpus spp


Reclinate.   Bent down upon the axis, no angle of divergence


Reclined.   Descending at 106-135° angle of divergence


Rectangular.   Box-shaped, longer than wide


Recurved.   Curved outward or downward


Reduced.   Decreased in size


Reflexed.   Bent or turned downward


Regular.   With floral parts within a whorl similar in shape and size


Reniform.   Kidney-shaped, with shallow sinus and widely rounded margins


Repand.   Sinuate with indentions less than 1/16 distance to midrib or midvein


Repent.   Creeping or lying flat and rooting at the nodes


Replicate.   With lamina folded once abaxially along midrib or midvein


Replum.   Persistent septum after dehiscence of fruits, as in the Brassicaceae


Resinous.   Having a yellowish, sticky, exudate


Resupinate.   Inverted or twisted 180°, as in pedicels in the Orchidaceae


Reticulate.   Netted; with veins forming a network


Reticulodromous.   With a single primary vein, the secondary veins not terminating at the margin and losing their identities near the margin by repeated branching, yielding a dense reticulum


Retinaculum, Jaculator or Echma.   A persistent indurated, hook-like funiculus in the fruits of Acanthaceae


Retrorse.   Bent or directed downward. Retrorsely Crenate - Rounded teeth directed toward base. Retrorsely Serrate - Sharp or pointed teeth directed toward base


Retuse.   Lobe rounded; sinus depth to 1/16 distance to midpoint of blade; margins convex


Revolute.   Margins or outer portion of sides rolled outward or downward over lower or dorsal surface


Rhizocarpic.   Plants having the roots living for many years with the stems dying annually


Rhizoid.   A hair-like absorptive organ on gametophytes and rarely on sporophytes


Rhizome.   A horizontal underground stem


Rhizotaxis.   Arrangement of roots


Rhombic.   With widest axis at midpoint of structure, and with straight margins; elliptic but margins straight and middle angled


Ribbed.   With longitudinal nerves


Ringed.   With old bud scale scar rings


Robust.   Large


Rolled.   Sides enrolled, usually loosely, over upper or lower surfaces


Root.   An absorbing and anchoring organ, usually initially developed from the radicle and growing downward. Root Cap - Parenchymatous, protective apex of root. Root Hair - Lateral, absorbing outgrowth of the epidermal cell


Secondary Root.   Lateral root with root cap and hairs, derived from the pericycle


Rootstock.   A term applied to miscellaneous types of underground stems or parts


Roridulate or Dewy.   Covered with waxy platelets, appearing dewy


Rostellum or Beak.   Persistent stylar base on fruit


Rosulate.   Leaves in a rosette


Rotate.   Wheel-shaped, with short tube and wide limb at right angles to tube


Rounded.   Margins and apex forming a smooth arc


Rudimentary.   Basal, small nonperipheral embryo in small to large seed; relatively undifferentiated; endosperm copious


Rugose.   Covered with coarse reticulate lines


Ruminate.   Coarsely wrinkled, appearing as chewed


Runcinate.   Oblanceolate with lacerate to parted margins


Runner or Stolon.   An indeterminate, elongate, above ground propagative stem, with long internodes, rooting at the tip forming new plants