raceme (37 images): a more or less elongate inflorescence with pedicellate flowers arising from the bottom upward on an unbranched axis.

racemiform: having the form of a raceme.

racemose (1 image): an inflorescence characterized by flower in acropetal sequence.

rachilla: diminutive of rachis; the axis of the spikelet in the grasses and sedges.

rachis (3 images): a main axis, such as that of a compound leaf.

radiate (6 images): in the Asteraceae, having the marginal flowers of the head ligulate and the central ones tubular.

radicle: part of a plant embryo that develops into the primary root.

ramentum: thin, elongate scales of the epidermis.

ray (7 images): the ligule or ligulate flower in the Asteraceae; one of the branches of an umbel.

receptacle (8 images): the end of the stem (pedicel) to which the other flower parts are attached; in the Asteraceae, the end of the peduncle, to which the flowers of the head are attached.

recurved (5 images): curved backward.

reflexed (7 images): bent backward.

regular flower: a flower in which the members of each circle of parts (or at least the sepals and petals) are similar in size, shape, and orientation.

reniform: kidney-shaped.

repand: with a shallowly sinuate or slightly wavy margin.

repent: creeping.

replum (6 images): a persistent, septum-like or frame-like placenta that bears ovules on the margins.

resupinate: upside down, inverted by the twisting of the pedicel, as in orchid flowers.

reticulate: forming a network, as the veins of a leaf.

retrorse (2 images): directed backward or downward.

retuse (2 images): with a small terminal notch in an otherwise rounded or blunt tip.

revolute (4 images): rolled back from the margin.

rhizoid: a structure of rootlike form and function, but lacking xylem and phloem.

rhizomatous (1 image): bearing rhizomes.

rhizome (5 images): a creeping underground stem.

rhizophore: leafless branch in ferns and fern-like plants that grows downward, producing roots at its tip when it reaches the soil.

rib (1 image): one of the main longitudinal veins of a leaf or other organ.

rootstock: same as rhizome.

rosette (31 images): a cluster of leaves or other organs arranged in a circle or disk, often in basal position.

rostellate: diminutive of rostrate.

rostrate: beaked.

rotate: flat and circular in outline, saucer-shaped.

rotund: round or rounded.

ruderal: weedy, growing in waste places.

rudimentary: imperfectly developed, but reflecting an early evolutionary stage rather than evolutionary reduction.

rugose (1 image): wrinkled.

rugulose: diminutive of rugose.

runcinate: sharply cleft or pinnatifid, with backward-pointing segments.

runner: a slender stolon.