quincuncial: of the arrangement of corolla lobes in a bud, a variant of imbricate aestivation.
Back to Glossary Index
raceme: an indeterminate inflorescence in which a main axis produces a series of flowers on lateral stalks, the oldest at the base and the youngest at the top. adj. racemose. cf. cyme.
racemule: secondary raceme in a compound raceme or umbellate inflorescence.
rachilla (= rhachilla): of palms and woody monocotyledons, the lateral or secondary branches of the inflorescence; of a grass spikelet, the axis above the glumes.
rachis (= rhachis): the axis of an inflorescence or a pinnate leaf; pl. rachises. secondary rachis: the axis of a pinna in a bipinnate leaf, or of a branch in a branched inflorescence.
radical: of leaves, clustered at the base of the stem.
radicle: the portion of an embryo that gives rise to the root system of a plant. cf. plumule.
ramiflorous: of flowers and fruits, borne below the current leaves on recently formed woody branches. cf. cauliflorous.
raphe: the part of the stalk of an anatropous ovule that is fused along the side of the ovule.
raphides: needle-like crystals that occur in bundles in the vacuoles of some plant cells.
ray: in woody stems, a radial band of cells traversing the conducting elements; of a compound umbel, one of the first (lower) series of branches of the inflorescence axis.
ray floret: a zygomorphic flower in Asteraceae. cf. disc floret.
receptacle: the axis of a flower (= torus); in ferns, an axis on which sporangia arise.
recurved: curved or curled downwards or backwards.
reflexed: bent sharply downwards or backwards.
regular: see actinomorphic.
replum: a longitudinal partition in an ovary, formed between parietal placentas.
resupinate: twisted through 180 degrees, e.g. as with the ovary of most Orchidaceae.
reticulate: forming a network.
retinaculum: a hook-like structure to which another structure is tethered; in Orchidaceae and Asclepiadaceae, the structure to which pollen masses are attached; in Acanthaceae, the persistent stalk of an ovule.
retrorse: bent, and pointing away from the apex. cf. antrorse.
retuse: with a very blunt and slightly notched apex.
revolute: rolled downwards or backwards; of a leaf, with the margins rolled towards the abaxial surface. cf. involute.
rhachilla: see rachilla.
rhachis: see rachis.
rhipidium: a compound cyme with the lateral branches developed alternately on one side and then the other.
rhizoid: a thread-like, unicellular absorbing structure occurring in the vascular plants, in gametophytes of ferns and some related plants.
rhizome: an underground stem, usually growing horizontally. cf. runner, stolon.
rhizophore: in Selaginella, a leafless stem that produces roots.
rhomboid: quadrangular, with the lateral angles obtuse.
root: unit of the axial system of a plant which is usually underground, does not bear leaves, tends to grow downwards and is typically derived from the radicle of the embryo. cf. adventitious.
rootstock: a short, erect, swollen structure at the junction of the root and shoot systems of a plant (loosely: the root system).
rostellum: in Orchidaceae, a beak-like upward extension of the stigma.
rosulate: clustered into a rosette, e.g. of basal leaves of some annual and biennial forbs.
rotate: circular and flattened, e.g. of a corolla with a very short tube and spreading lobes.
rudimentary: poorly developed and not functional. cf. vestigial, obsolete.
rugose: deeply wrinkled.
rugulose: covered with minute wrinkles.
ruminate: mottled in appearance, e.g. of bark, or of the food reserves in a seed.
runcinate: deeply lobed and with the lobes slanted away from the apex.
runner: a slender, prostrate or trailing stem which produces roots and sometimes erect shoots at its nodes. cf. rhizome, stolon.
Back to Glossary Index
This work is copyright. Apart from any use as permitted under the Copyright Act 1968, no part may be reproduced by any process without prior written permission from Australian Biological Resources Study. Requests and inquiries concerning reproduction and rights should be addressed in the first instance to the Executive Editor - Flora. These pages may not be displayed on, or downloaded to, any other server without the express permission of ABRS.
Last updated on 13 May 1999.